The DOI matches its Crossref record; 95 of the 95 references it cites were found in a registry or an index; 19 of the 152 sources its claims cite were checked for support.
Evolution of indirect reciprocity
Open accessAbstract
Natural selection is conventionally assumed to favour the strong and selfish who maximize their own resources at the expense of others. But many biological systems, and especially human societies, are organized around altruistic, cooperative interactions. How can natural selection promote unselfish behaviour? Various mechanisms have been proposed, and a rich analysis of indirect reciprocity has recently emerged: I help you and somebody else helps me. The evolution of cooperation by indirect reciprocity leads to reputation building, morality judgement and complex social interactions with ever-increasing cognitive demands.
Overview
AI snapshot
Written from the paper’s full text.
TL;DR
This review argues that indirect reciprocity—helping others to build a reputation that leads third parties to help you—can sustain cooperation when the cost-to-benefit ratio is low and social information is sufficient. It synthesizes evolutionary game theory and experimental economics, emphasizing reputation, moral judgment, and increasing cognitive demands.
Key findings
- Direct reciprocity is repeated Prisoner’s Dilemma between the same two individuals; indirect reciprocity assumes any two players interact at most once and relies on reputation and community enforcement, so help is channelled towards those who help.
- In binary-assessment models, first-order assessment has 4 rules, second-order 16, third-order 256, and combining action and assessment yields 4096 strategies; Ohtsuki & Iwasa proved only 8 (“leading eight”) are evolutionarily stable under certain conditions, all distinguishing justified from unjustified defection. STANDING and JUDGING belong to the leading eight; SCORING and SHUNNING do not.
- Experiments show substantial donations, image score correlates with receiving money, more information enhances cooperation, donations are more frequent in earlier rounds, and the propensity to donate more than doubles if players know their action will be communicated. In one public-goods experiment, contributions do not deteriorate when indirect reciprocity rounds are sandwiched between public-goods rounds, and donations reward high contributors.
- Indirect reciprocity requires the probability \(q\) of knowing another’s social score to exceed the cost-to-benefit ratio \(c/b\), analogous to Hamilton’s rule; simulations often use population sizes of 50 to 100 individuals, and language and cognition likely coevolved with indirect reciprocity.
Methods
- Review/synthesis, not a primary empirical study; no new data are presented.
- Draws on evolutionary game theory (repeated Prisoner’s Dilemma, indirect reciprocity models, replicator dynamics, individual-based simulations) and experimental economics/psychology (donation/helping games, public goods, trust games).
- Main analysis is conceptual and comparative, citing models and experiments; no formal meta-analysis or systematic search is reported.
Limitations
- The paper states that private reputation lists and errors in perception can undermine cooperation; gossip may spread false rumours; the coevolution of language and indirect reciprocity is “fascinating and yet unexplored”; population structure is debated; strategies depending on both donor payoff and recipient score “have not been analysed so far”; and group selection should not be confused with indirect reciprocity.
- Evident from the text: as a review, it does not present new experiments or a systematic quantitative synthesis, and many cited experiments are described only briefly, with some references listed as working papers or in press.
Model-written summary. Check it against the paper before relying on it.
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Verification
Claims the paper makes
55 No full text of the sources · 55 Own interpretation · 49 No basis given · 12 Not checked yet · 6 Couldn’t confirm · 3 Partly supported · 3 Own method · 2 Supported so far · 2 Not supported · 1 Supported · 1 Sources not found · 1 Own result · accuracy not yet measured
At least one cited source doesn’t support this claim or points to a different paper, and none confirmed it — see the verdicts below.
In the paper
“After a couple of rounds the personal experience obtained with the given co-player becomes more decisive 62 .”
What the sources say
- Disputedcites [62] Bolton, G. E., Katok, E. & Ockenfels, A. Cooperation among strangers with limited information about reputation. J. Public Econ. 89, 1457–1468 (2005) sourceExperimental — accuracy not yet measured
The Design of the experiment section (page unavailable) says that no two subjects were paired more than once and that subjects knew this. Its design therefore rules out gaining experience with a given co-player over several rounds; the paper instead studies decisions based on information about a new partner’s past actions. (LLM, conf=0.89)
Checked by a reasoning model — may be wrong.
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
- Disputed
The sources with a verdict support this claim; the rest weren’t checked yet, have no full text we could read, or their verdicts aren’t rated yet.
In the paper
“In this sense, the step from direct to indirect reciprocity corresponds simply to the step from personal enforcement to community enforcement 26-29 .”
What the sources say
- Not checked — no full text of the sourcecites [26] Binmore, K. Fun and Games: A Text on Game Theory (Heath, Lexington, Massachusetts, 1992)
- Not checked — no full text of the sourcecites [27] Rosenthal, R. W. Sequences of games with varying opponents. Econometrica 47, 1353–1366 (1979) source
- Supportedcites [28] Kandori, M. Social norms and community enforcement. Rev. Econ. Stud. 59, 63–80 (1992) source
The Introduction (page not provided) defines personal enforcement as retaliation by the victim and community enforcement as sanctions by other members after dishonesty toward a partner. That distinction supports the claimed correspondence between direct and indirect reciprocity. (LLM, conf=0.92)
- Supportedcites [29] Ellison, G. Cooperation in the prisoner's dilemma with anonymous random matching. Rev. Econ. Stud. 61, 567–588 (1994) source
The Introduction contrasts cooperation sustained by personal retaliation between the same two players with cooperation sustained by contagious punishments that spread through an anonymously matched population. This supports the claimed correspondence between direct versus indirect responses and personal versus community enforcement, although the paper uses different terminology. (LLM, conf=0.85)
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
The sources with a verdict support this claim; the rest weren’t checked yet, have no full text we could read, or their verdicts aren’t rated yet.
In the paper
“The growth of e-auctions and other forms of e-commerce is based, to a considerable degree, on reputation and trust 5-10 .”
What the sources say
- Supportedcites [5] Bolton, G. E., Katok, E. & Ockenfels, A. How effective are electronic reputation mechanisms? An experimental investigation. Manage. Sci. 50, 1587–1602 (2004) source
The Introduction says many online markets rely on electronic reputation systems to promote trust in transactions. It also describes feedback systems used by eBay and other platforms, supporting the claim's broad point about e-auctions and e-commerce. (LLM, conf=0.88)
- Supportedcites [6] Keser, C. Trust and reputation building in e-commerce. IBM Watson Research Center, CIRANO working paper no. 2002s-75 http://www.cirano.qc.ca/en/publication_detail.php?id=2002s-75 (2002).
The Introduction says trust may play a critical role in developing the Internet as a marketplace. It also describes reputation systems used by online markets to increase trust between trading partners, including in e-auctions. This supports the claim's broad characterization without asserting a measured contribution to growth. (LLM, conf=0.90)
- Not checked — no full text of the sourcecites [7] Dellarocas, C. Sanctioning reputation mechanisms in online trading environments with moral hazard. MIT Sloan School of Management working paper no. 4297–03 http://ssrn.com/abstract=393043 (2003). source
- Not checked — no full text of the sourcecites [8] Bolton, G., Katok, E. & Ockenfels, A. in Applications of Supply Chain Management and e-Commerce Research (eds Geunes, J., Akcali, E., Pardalos, P. M., Romeijn, H. E. & Shen, Z.-J.) 195–216 (Springer, Dordrecht, 2005) source
- Supportedcites [9] Resnick, P., Zeckhauser, R., Friedman, E. & Kuwabara, K. Reputation systems. Commun. ACM 43, 45–48 (2000) source
In the section labeled “MARC MONGEAU” (page not provided), the paper says reputation systems help people decide whom to trust online and describes eBay’s high rate of successful transactions despite substantial risks. It also describes reputation systems used by online retailers beyond auction sites, supporting the broad claim that reputation and trust underpin these forms of e-commerce. (LLM, conf=0.84)
- Not matchedcites [10] Lucking-Reiley, D., Bryan, D., Prasad, N. & Reeves, D. Pennies from eBay: The Determinants of Price in Online Auctions. Vanderbilt Univ., Univ. Arizona working paper (1999).
Couldn’t be matched to a paper in Crossref, so it can’t be checked.
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
- Supported
The cited sources support only part of this claim — read each source’s verdict below.
In the paper
“A more sophisticated assessment rule should distinguish between justified and unjustified defection, and thus take into account the score of the receiver: someone withholding help from a 'bad' player should not pay with a reduced score 35,38,39,47 .”
What the sources say
- Not checked — no full text of the sourcecites [35] Nowak, M. A. & Sigmund, K. A strategy of win-stay, lose-shift that outperforms tit-for-tat in the prisoner's dilemma game. Nature 364, 56–58 (1993) source
- Not checked — no full text of the sourcecites [38] Ferrière, R. Help and you shall be helped. Nature 393, 517–519 (1998) source
- Not checked — no full text of the sourcecites [39] Leimar, O. & Hammerstein, P. Evolution of cooperation through indirect reciprocation. Proc. R. Soc. Lond. B 268, 745–753 (2001) source
- Partly supportedcites [47] Sigmund, K., Hauert, C. & Nowak, M. A. Reward and punishment. Proc. Natl Acad. Sci. USA 98, 10757–10762 (2001) sourceExperimental — accuracy not yet measured
In “Bifurcation Through Reputation” (page unavailable), the paper models cooperators defecting against known nonpunishers, so a coplayer’s reputation can affect the decision to help. It does not describe an assessment rule that distinguishes justified from unjustified defection or say that withholding help from a bad player leaves the donor’s score unchanged. (LLM, conf=0.78)
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: unclear — It is unclear whether it could be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
The cited sources that could be checked couldn’t confirm or dispute this claim.
In the paper
“A stable mix of discriminating and undiscriminating altruists which cannot be invaded by defectors, is also obtained by assuming that as players grow older, their social network grows, and with it their information about their co-players' past 54,55 .”
What the sources say
- Could not verifycites [54] Brandt, H. & Sigmund, K. The logic of reprobation: Assessment and action rules for indirect reciprocity. J. Theor. Biol. 231, 475–486 (2004) sourceExperimental — accuracy not yet measured
Split into 2 atoms — 0 confirmed, 0 partially supported, 0 disputed, 0 misattributed, 2 unverifiable. Expand the claim to see per-atom verdicts.
- Not checked — no full text of the sourcecites [55] Mohtashemi, M. & Mui, L. Evolution of indirect reciprocity by social information: The role of trust and reputation in evolution of altruism. J. Theor. Biol. 223, 523–531 (2003) source
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
- Could not verify
Every source the paper cites for this claim was checked and supports it.
In the paper
“But if players have different views about the reputation of others, then errors in perception can undermine cooperation 56 .”
What the sources say
- Supportedcites [56] Brandt, H. & Sigmund, K. Indirect reciprocity, image scoring, and moral hazard. Proc. Natl Acad. Sci. USA 102, 2666–2670 (2005) source
In Results and Discussion (p. 4), the paper explains that incomplete information and misperception make reputation-based standing strategies difficult to use. It also reports that a standing strategy performed much less well under errors of perception, supporting the claim that differing information about reputations can undermine cooperation. (LLM, conf=0.87)
plainconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
- Supported
The cited sources that could be checked couldn’t confirm or dispute this claim.
In the paper
“Such a population structure, however, facilitates the evolution of altruism via group selection 56 .”
What the sources say
- Could not verifycites [56] Brandt, H. & Sigmund, K. Indirect reciprocity, image scoring, and moral hazard. Proc. Natl Acad. Sci. USA 102, 2666–2670 (2005) sourceExperimental — accuracy not yet measured
The Continuous-Entry Model for Indirect Reciprocity (pp. 2–3) analyzes reputation and information within a population, not group selection. Searches for separate groups, exchange, and migration found no passage addressing whether that population structure facilitates altruism. (LLM, conf=0.73)
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
- Could not verify
The cited sources that could be checked couldn’t confirm or dispute this claim.
In the paper
“A good strategy for the latter is Observer Tit For Tat 35,68 .”
What the sources say
- Not checked — no full text of the sourcecites [35] Nowak, M. A. & Sigmund, K. A strategy of win-stay, lose-shift that outperforms tit-for-tat in the prisoner's dilemma game. Nature 364, 56–58 (1993) source
- Could not verifycites [68] Güth, W., Königstein, M., Marchand, N. & Nehring, K. Trust and reciprocity in the investment game with indirect reward. Homo Oecon. 18, 241–262 (2001) sourceExperimental — accuracy not yet measured
The Introduction describes a third person observing an investment and potentially rewarding the investor, while the Discussion compares indirect with direct reward. Neither passage evaluates a strategy for interested audiences. Searches for “Observer Tit For Tat” and an observing-and-reciprocating strategy found no passage addressing that claim. (LLM, conf=0.72)
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
The cited sources that could be checked couldn’t confirm or dispute this claim.
In the paper
“For example, donors are more generous if they learn that the recipient has recently made a donation to a charitable institution 72 .”
What the sources say
- Could not verifycites [72] Fehr, E. & Fischbacher, U. Third party punishment and social norms. Evol. Hum. Behav. 25, 63–87 (2004) sourceExperimental — accuracy not yet measured
The Results and dictator-game passages report transfers and punishment, but do not say whether recipients had previously donated to charity or whether donors learned of such donations. Searches for “donation to a charitable institution” and “recipient donated charity” found no passage addressing the claimed effect. (LLM, conf=0.76)
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
- Could not verify
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Random fluctuations, however, make their frequencies drift up and down.”
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
- It may state two separate claims as one. 52
- Probably not a substantial claim. 71
At least one cited source doesn’t support this claim or points to a different paper, and none confirmed it — see the verdicts below.
In the paper
“In another experiment 62 , however, those who give often end up with the highest payoff, so that there is a strategic advantage to generosity.”
What the sources say
- Disputedcites [62] Bolton, G. E., Katok, E. & Ockenfels, A. Cooperation among strangers with limited information about reputation. J. Public Econ. 89, 1457–1468 (2005) sourceExperimental — accuracy not yet measured
The Conclusions (section 6; page not provided) report the opposite individual-level pattern: in every treatment, giving more gifts was negatively correlated with total payoff. Although giving raised the chance of receiving a gift, the paper says an additional gift cost the giver about 9 cents on average, rather than conferring the claimed payoff advantage. (LLM, conf=0.90)
Checked by a reasoning model — may be wrong.
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
- Disputed
The cited sources support only part of this claim — read each source’s verdict below.
In the paper
“The fact that costly punishment plays an undisputed role in other contexts, such as public goods games, ultimatum games and trust games 43-46 , shows that this form of discrimination is highly plausible.”
What the sources say
- Not checked — no full text of the sourcecites [43] Dawes, R. M. Social dilemmas. Annu. Rev. Psychol. 31, 169–193 (1980) source
- Supportedcites [44] Fehr, E. & Gächter, S. Cooperation and punishment in public goods experiments. Am. Econ. Rev. 90, 980–994 (2000) source
The cited paper supports the public-goods-games example in the multi-citation sentence. Its Concluding Remarks report that participants punished free riders even when doing so was costly and offered little or no private benefit. The inference about the plausibility of discrimination is the citing authors’ own conclusion. (LLM, conf=0.90)
- Partly supportedcites [45] Fehr, E. & Gächter, S. Altruistic punishment in humans. Nature 415, 137–140 (2002) sourceExperimental — accuracy not yet measured
The public-goods experiment (p. 1) documents punishment that cost the punisher money, and “Altruistic punishment and cooperation” (p. 1) reports that it occurred frequently. The paper does not establish the cited point for ultimatum or trust games; those examples are not supported by this source. (LLM, conf=0.86)
- Partly supportedcites [46] Fehr, E. & Fischbacher, U. The nature of human altruism. Nature 425, 785–791 (2003) sourceExperimental — accuracy not yet measured
The Altruistic punishment section (p. 1) describes people punishing unfair offers in ultimatum games at a cost to themselves, and Strong reciprocity and multilateral cooperation (p. 3) discusses punishment of non-cooperators. But the paper’s discussion of trust games is in Altruistic rewarding (p. 2); it does not establish costly punishment in trust games. The inference about discrimination is the citing authors’ own conclusion. (LLM, conf=0.85)
boosted- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
The cited sources that could be checked couldn’t confirm or dispute this claim.
In the paper
“Observer Tit For Tat relies on reputation in the first round and on personal experience in all further rounds against the same co-player.”
What the sources say
- Not checked — no full text of the sourcecites [35] Nowak, M. A. & Sigmund, K. A strategy of win-stay, lose-shift that outperforms tit-for-tat in the prisoner's dilemma game. Nature 364, 56–58 (1993) source
- Could not verifycites [68] Güth, W., Königstein, M., Marchand, N. & Nehring, K. Trust and reciprocity in the investment game with indirect reward. Homo Oecon. 18, 241–262 (2001) sourceExperimental — accuracy not yet measured
The Introduction (page unavailable) discusses direct and indirect rewards in investment games, but does not describe an Observer Tit For Tat strategy. Searches for the strategy name and for first-round reputation versus later personal experience found no passage addressing that distinction. (LLM, conf=0.76)
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
The cited sources support only part of this claim — read each source’s verdict below.
In the paper
“Yet it emerges as the winner in a computer tournament, if errors in perception are included and if there are only a few rounds in the game 56 .”
What the sources say
- Partly supportedcites [56] Brandt, H. & Sigmund, K. Indirect reciprocity, image scoring, and moral hazard. Proc. Natl Acad. Sci. USA 102, 2666–2670 (2005) sourceExperimental — accuracy not yet measured
The Results and Discussion (p. 4) report that, in simulations with errors of perception, a strategy that assigns a Bad score to anyone meeting a Bad coplayer did much better than standing. The passage does not say it won the tournament or that this result depended on there being only a few rounds. (LLM, conf=0.84)
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
- Partly supported
The cited sources that could be checked couldn’t confirm or dispute this claim.
In the paper
“Reputation mechanisms have also played an important role in the emergence of medieval trade 78 .”
What the sources say
- Could not verifycites [78] Pfeiffer, T., Rutte, C., Killingback, T., Taborsky, M. & Bonhoeffer, S. Evolution of cooperation by generalized reciprocity. Proc. R. Soc. B 272, 1115–1120 (2005) sourceExperimental — accuracy not yet measured
The Introduction discusses generalized reciprocity and briefly notes related work in economics; the Conclusions and discussion describe simulations of cooperation in small groups. Neither section addresses reputation mechanisms or the emergence of medieval trade (searched: medieval trade, reputation, merchants, and historical trade). (LLM, conf=0.76)
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
- Could not verify
In the paper
“No player has an incentive to deviate if all other players adopt this strategy, and the effect of an error will be overcome after T rounds.”
What the sources say
- Not checked — no full text of the sourcecites [27] Rosenthal, R. W. Sequences of games with varying opponents. Econometrica 47, 1353–1366 (1979) source
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“However, in the case of direct reciprocity, the frequencies oscillate periodically, whereas in the case of indirect reciprocity, they converge to an equilibrium.”
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“Both STANDING and JUDGING belong to the leading eight, but neither SCORING nor SHUNNING.”
What the sources say
- Not checked — no full text of the sourcecites [41] Nowak, M. A. & Sigmund, K. The dynamics of indirect reciprocity. J. Theor. Biol. 194, 561–574 (1998) source
- Not checked yetcites [48] Sugden, R. The Economics of Rights, Cooperation and Welfare (Blackwell, Oxford, 1986)
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“In real experiments, many donors transfer substantial amounts, and some obtain large returns, so that both players win.”
What the sources say
- Not matchedcites [79] Brandt, H. & Sigmund, K. The good, the bad and the discriminator. J. Theor. Biol. (in the press)
Couldn’t be matched to a paper in Crossref, so it can’t be checked.
- Not checked — no full text of the sourcecites [80] Imhof, L., Fudenberg, D. & Nowak, M. A. Evolutionary cycles of cooperation and defection. Proc. Natl Acad. Sci. USA 102, 10797–10800 (2005) source
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
- Not matched
None of the sources cited for this claim have been checked yet.
In the paper
“In real experiments, however, many players contribute.”
What the sources say
- Not matchedcites [79] Brandt, H. & Sigmund, K. The good, the bad and the discriminator. J. Theor. Biol. (in the press)
Couldn’t be matched to a paper in Crossref, so it can’t be checked.
- Not checked — no full text of the sourcecites [80] Imhof, L., Fudenberg, D. & Nowak, M. A. Evolutionary cycles of cooperation and defection. Proc. Natl Acad. Sci. USA 102, 10797–10800 (2005) source
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
- Not matched
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In both cases a lot of innocents would be punished, and errors cause havoc.”
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A claim is checked only against the cited paper’s full text, never its abstract, and none is available for its sources.
In the paper
“For direct reciprocity, game theoretical analysis and individual-based simulations have shown that a population of defectors can be invaded by a small cluster of retaliators 31 or even by a single retaliator 32 .”
What the sources say
- Not checked — no full text of the sourcecites [31] Nowak, M. A. & Sigmund, K. Evolutionary dynamics of biological games. Science 303, 793–799 (2004) source
- Not checked — no full text of the sourcecites [32] Nowak, M. A. & Sigmund, K. Tit for tat in heterogeneous populations. Nature 355, 250–253 (1992) source
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“In contrast to other eusocial species, such as bees, ants or termites, humans display a large amount of cooperation between non-relatives 12-14 .”
What the sources say
- Not checked yetcites [12] Wilson, E. O. Sociobiology (Harvard Univ. Press, Cambridge, Massachusetts, 1975)
- Not checked yetcites [13] Trivers, R. Social Evolution (Benjamin Cummings, Menlo Park, 1985)
- Not checked — no full text of the sourcecites [14] Hamilton, W. D. Narrow Roads of Gene Land Vol. 1 (Freeman, New York, 1996) source
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“If both players cooperate, each receives b-c , which is better than what they would obtain by defecting, namely 0.”
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim.
- The authors state this as an assumption: The cost of an altruistic act is smaller than the benefit.
A claim is checked only against the cited paper’s full text, never its abstract, and none is available for its sources.
In the paper
“Neuro-economic experiments show that these emotions have a physiological basis 15-17 .”
What the sources say
- Not checked — no full text of the sourcecites [15] Sanfey, A. G., Rilling, J. K., Aronson, J. A., Nystrom, L. E. & Cohen, J. D. The neural basis of economic decision-making in the ultimatum game. Science 300, 1755–1758 (2003) source
- Not checked — no full text of the sourcecites [16] Rilling, J. K. et al. A neural basis for social cooperation. Neuron 35, 395–405 (2002) source
- Not checked — no full text of the sourcecites [17] Fehr, E. The neural basis of altruistic punishment. Science 305, 1254–1258 (2004) source
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Indirect reciprocity, in this view, is based on reputation.”
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
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Probably not a substantial claim.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“But a unilateral defector would earn b , which is the highest payoff, and the exploited co-operator would pay the cost c without receiving any benefit.”
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. It may state two separate claims as one.
- The authors state this as an assumption: The cost of an altruistic act is smaller than the benefit.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The same terms 'good' and 'bad' which are applied to pleasure and pain are also used for moral judgements: this linguistic quirk reveals an astonishing degree of empathy, and reflects highly developed faculties for cognition and abstraction.”
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: fails — It may be too vague to check against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. It may be too vague to check against evidence. The paper’s conclusions may not depend on it. The paper may give no reason why it holds. It may state two separate claims as one.
In the paper
“Game theory shows that even if information is transmitted only locally and errors occur occasionally, cooperation can be sustained: there exist strategies such that no rational player has an interest to deviate unilaterally 27 .”
What the sources say
- Not checked — no full text of the sourcecites [27] Rosenthal, R. W. Sequences of games with varying opponents. Econometrica 47, 1353–1366 (1979) source
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The step from there to judging, as 'good' or 'bad', actions between third parties, is not obvious.”
plain- Asserted: passes — The authors put it forward as true.
- Checkable: fails — It may be too vague to check against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. It may be too vague to check against evidence. The paper’s conclusions may not depend on it.
In the paper
“but the capacity for moral norms appears to be a human universal for which there is little evidence in other species 19 .”
What the sources say
- Not checked yetcites [19] Brown, D. E. Human Universals (McGraw-Hill, New York, 1991)
hedged- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The evolution of cooperation by indirect reciprocity leads to reputation building, morality judgement and complex social interactions with ever increasing cognitive demands.”
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“But a trigger strategy prescribing each person to cooperate until the first defection is personally experienced, and thenceforth to defect, hurts the original wrong-doer only after many rounds. A strategy triggered by the first defection in the population leaves cooperation at the mercy of the first wrong move.”
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
In the paper
“The so-called folk theorem on repeated games states that if the probability for future rounds is sufficiently high, cooperation can be sustained by so-called trigger strategies, which switch to relentless defection as soon as the co-player defects once 25 .”
What the sources say
- Not checked — no full text of the sourcecites [25] Fudenberg, D. & Maskin, E. The folk theorem in repeated games with discounting or with incomplete information. Econometrica 50, 533–554 (1986) source
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A claim is checked only against the cited paper’s full text, never its abstract, and none is available for its sources.
In the paper
“In order to analyse these questions, an even simpler model was proposed, based on a binary score, taking only the values 'good' or 'bad', depending on what the co-player did when last observed 39-41 .”
What the sources say
- Not checked — no full text of the sourcecites [39] Leimar, O. & Hammerstein, P. Evolution of cooperation through indirect reciprocation. Proc. R. Soc. Lond. B 268, 745–753 (2001) source
- Not checked — no full text of the sourcecites [40] Panchanathan, K. & Boyd, R. A tale of two defectors: The importance of standing for evolution of indirect reciprocity. J. Theor. Biol. 224, 115–126 (2003) source
- Not checked — no full text of the sourcecites [41] Nowak, M. A. & Sigmund, K. The dynamics of indirect reciprocity. J. Theor. Biol. 194, 561–574 (1998) source
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim.
In the paper
“Such a form of altruistic punishment is good for the community, but costly for the punisher, and thus can be viewed as a social dilemma 42 .”
What the sources say
- Not checked — no full text of the sourcecites [42] Ohtsuki, H. & Iwasa, Y. How should we define goodness? Reputation dynamics in indirect reciprocity. J. Theor. Biol. 231, 107–120 (2004) source
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
In the paper
“Alternatively, if the discriminating strategy distinguishes between justified and unjustified defection, the population can converge to discriminators only, which cannot be invaded by unconditional strategies 39 .”
What the sources say
- Not checked — no full text of the sourcecites [39] Leimar, O. & Hammerstein, P. Evolution of cooperation through indirect reciprocation. Proc. R. Soc. Lond. B 268, 745–753 (2001) source
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A claim is checked only against the cited paper’s full text, never its abstract, and none is available for its sources.
In the paper
“In this scenario, a population consisting only of conditional and unconditional altruists is not subject to random drift, but selection leads to a well defined, stable mix of the two types.”
What the sources say
- Not checked — no full text of the sourcecites [39] Leimar, O. & Hammerstein, P. Evolution of cooperation through indirect reciprocation. Proc. R. Soc. Lond. B 268, 745–753 (2001) source
- Not checked — no full text of the sourcecites [49] Ohtsuki, H. & Iwasa, Y. The leading eight: social norms that can maintain cooperation by indirect reciprocity. J. Theor. Biol.(in the press) source
- Not checked — no full text of the sourcecites [50] Lotem, A., Fishman, M. A. & Stone, L. Evolution of cooperation between individuals. Nature 400, 226–227 (1999) source
- Not checked — no full text of the sourcecites [51] Lotem, A., Fishman, M. A. & Stone, L. Evolution of unconditional altruism through signalling benefits. Proc. R. Soc. Lond. B 270, 199–205 (2002) source
- Not checked — no full text of the sourcecites [52] Fishman, M. A., Lotem, A. & Stone, L. Heterogeneity stabilises reciprocal altruism interaction. J. Theor. Biol. 209, 87–95 (2001) source
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“A discriminating donor using this assessment rule refuses help to a 'bad' recipient, and therefore becomes 'bad', which reduces the chance of being helped in turn.”
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“This can be viewed as a basic system of moral assessment.”
plain- Asserted: passes — The authors put it forward as true.
- Checkable: fails — It may be too vague to check against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. It may be too vague to check against evidence. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Therefore, both the lack of information and the prevalence of unconditional altruists may, surprisingly, stabilise cooperation.”
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Punishing a player with a bad score creates another player with a bad score; but this 'passing the buck along' can stop in two ways, by encountering either a discriminator who is uninformed, or an undiscriminating altruist.”
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A claim is checked only against the cited paper’s full text, never its abstract, and none is available for its sources.
In the paper
“In a population consisting entirely of discriminators, undiscriminating co-operators fare just as well and thus spread by neutral drift.”
What the sources say
- Not checked — no full text of the sourcecites [39] Leimar, O. & Hammerstein, P. Evolution of cooperation through indirect reciprocation. Proc. R. Soc. Lond. B 268, 745–753 (2001) source
- Not checked — no full text of the sourcecites [49] Ohtsuki, H. & Iwasa, Y. The leading eight: social norms that can maintain cooperation by indirect reciprocity. J. Theor. Biol.(in the press) source
- Not checked — no full text of the sourcecites [50] Lotem, A., Fishman, M. A. & Stone, L. Evolution of cooperation between individuals. Nature 400, 226–227 (1999) source
- Not checked — no full text of the sourcecites [51] Lotem, A., Fishman, M. A. & Stone, L. Evolution of unconditional altruism through signalling benefits. Proc. R. Soc. Lond. B 270, 199–205 (2002) source
- Not checked — no full text of the sourcecites [52] Fishman, M. A., Lotem, A. & Stone, L. Heterogeneity stabilises reciprocal altruism interaction. J. Theor. Biol. 209, 87–95 (2001) source
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A claim is checked only against the cited paper’s full text, never its abstract, and none is available for its sources.
In the paper
“Various assumptions on the distribution of the number of rounds lead to a bi-stable system, where depending on the initial state, the population converges either to the fixation of defectors, or to a stable mix of altruists which cannot be invaded by defectors 52,53 .”
What the sources say
- Not checked — no full text of the sourcecites [52] Fishman, M. A., Lotem, A. & Stone, L. Heterogeneity stabilises reciprocal altruism interaction. J. Theor. Biol. 209, 87–95 (2001) source
- Not checked — no full text of the sourcecites [53] Fishman, M. A. Indirect reciprocity among imperfect individuals. J. Theor. Biol. 225, 285–292 (2003) source
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
In the paper
“Only eight of them lead to cooperation and, at the same time, are evolutionarily stable: a homogeneous population of players using such a strategy cannot be invaded by players using other strategies 41 .”
What the sources say
- Not checked — no full text of the sourcecites [41] Nowak, M. A. & Sigmund, K. The dynamics of indirect reciprocity. J. Theor. Biol. 194, 561–574 (1998) source
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“More generally, it seems that decisions often depend on both the donor's payoff and the recipient's score, but such strategies have not been analysed so far.”
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: fails — It may be too vague to check against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. It may be too vague to check against evidence. The paper’s conclusions may not depend on it. The paper may give no reason why it holds. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Indirect reciprocity is situated somewhere between direct reciprocity and public goods.”
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A claim is checked only against the cited paper’s full text, never its abstract, and none is available for its sources.
In the paper
“The widespread tendency to judge actions between third parties, and the readiness for cooperation combined with altruistic punishment (also known as strong reciprocity 69 ) has been neatly captured in an experiment involving three players 70,71 .”
What the sources say
- Not checked — no full text of the sourcecites [69] Pollock, G. B. & Dugatkin, L. A. Reciprocity and the evolution of reputation. J. Theor. Biol. 159, 25–37 (1992) source
- Not checked — no full text of the sourcecites [70] Gintis, H. Game Theory Evolving: A Problem-Centered Introduction to Modeling Stategic Interaction (Princeton Univ. Press, Princeton, 2000)
- Not checked — no full text of the sourcecites [71] Fehr, E. & Fischbacher, U. Social norms and human cooperation. Trends Cogn. Sci. 8, 185–190 (2004) source
boosted- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“In order to eliminate confounding effects, players usually do not interact face-to-face, but they are given some information about the past actions of their potential recipients.”
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Gossip might be a way of achieving consensus, but can also be used for spreading false rumours and manipulating co-players.”
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds. It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Many experiments have shown that players who have just received a donation are more likely to give a donation in turn.”
boostedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“They know that their recipients will never be their donors on future occasions, and thus that there is no scope for direct reciprocity.”
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. It may state two separate claims as one.
In the paper
“Richard Alexander claimed that indirect reciprocity originates from direct reciprocity in the presence of interested audiences 2 .”
What the sources say
- Not checked yetcites [2] Alexander, R. D. The Biology of Moral Systems (Aldine de Gruyter, New York, 1987)
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“This indicates that they expect their refusal to lower their score in the co-players' eyes, and that they do not rely on the community's understanding.”
hedged- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“In this series of experiments, there is a significant positive correlation between the number of gifts given and received, but a slightly negative correlation between the number of gifts given and the total payoff obtained.”
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
In the paper
“Often there is evidence for a dual motivation players give donations if the recipient's score is high or their own score is low 35 .”
What the sources say
- Not checked — no full text of the sourcecites [35] Nowak, M. A. & Sigmund, K. A strategy of win-stay, lose-shift that outperforms tit-for-tat in the prisoner's dilemma game. Nature 364, 56–58 (1993) source
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“As expected, donations occur more frequently if the cost-to-benefit ratio is lower, or the starting account higher.”
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In such small populations, random drift can strongly affect evolution.”
boosteddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The discrepancy could be due to the larger number of rounds - the advantage showed up only after a dozen of rounds - or to the fact that players were informed not only about the recipients' last move but their whole history of giving.”
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“The interactions both with the co-players and with the experimenters are kept as anonymous as possible, usually under double-blind conditions.”
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
In the paper
“Players faced with a full history of all previous rounds take in general a longer time to reach their decision, suggesting that they attempt to take into account, not only their recipient's last move, but also that of their recipient's recipient.”
What the sources say
- Not checked — no full text of the sourcecites [64] Engelmann, D. & Fischbacher, U. Indirect reciprocity and strategic reputation building in an experimental helping game. Univ. Zürich working paper no. 132 http://www.iew.unizh.ch/wp/iewwp132.pdf (2002). source
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
In the paper
“There is evidence for 'upstream' indirect reciprocity in cyclical networks: as expected, short loops and a high benefit-to-cost ratio favour cooperation 65 .”
What the sources say
- Not checked — no full text of the sourcecites [65] Milinski, M., Semmann, D., Bakker, T. C. M. & Krambeck, H. J. Cooperation through indirect reciprocity: Image scoring or standing strategy? Proc. R. Soc. Lond. B 268, 2495–2501 (2001) source
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
In the paper
“It could be that co-operators fare less well than defectors within each group, but that groups of co-operators fare better than groups of defectors 57 .”
What the sources say
- Not matchedcites [57] Takahashi, N. & Mashima, R. The emergence of indirect reciprocity: Is the standing strategy the answer? Hokkaido Univ. working paper no. 29 http://lynx.let.hokudai.ac.jp/COE21/pdf/029.zip (2003).
Couldn’t be matched to a paper in Crossref, so it can’t be checked.
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
- Not matched
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“On one hand, it is a game between two players only, the donor and the recipient, but on the other hand it has to be played within a larger group.”
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Both strategies are not evolutionary stable, but their ability to catalyze cooperation in adverse scenarios and their simplicity constitute their strength.”
plaindirect- Asserted: passes — The authors put it forward as true.
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It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“There are 16 second order rules.”
plain- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“In the Trust Game, donors who trust their responder will expect to gain from transferring money.”
plainconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
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Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“We expect, however, that SCORING plays a similar role in indirect reciprocity as Tit-for-tat in direct reciprocity.”
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
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Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In each case, there are many other discriminating strategies, which are likely to take over eventually.”
hedgeddirect- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Hence, there are 2 3 =8 different assessment rules.”
plain- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“It is very likely that games of indirect reciprocity provided the selective scenario that led to cerebral expansion in human evolution.”
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: fails — It may be too vague to check against evidence.
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Probably not a substantial claim. It may be too vague to check against evidence. The paper may give no reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“A responder with an income-maximising strategy should send nothing back.”
plaindirect- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Any donor expecting this should therefore transfer nothing.”
plaindirect- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it.
In the paper
“Trust, 'a lubricant of social life' 77 , plays an essential part in many types of economic transactions.”
What the sources say
- Not checked — no full text of the sourcecites [77] Boyd, R. & Richerson, P. J. The evolution of indirect reciprocity. Soc. Networks 11, 213–236 (1989) source
plain- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“If all do, they multiply their endowment by the factor r.”
plaindirect- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Indirect reciprocity based on reputation serves as a link between diverse forms of cooperative interaction.”
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
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Probably not a substantial claim. The paper may give no reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“In contrast, donors in the Indirect Reciprocity game know that they can expect no direct return, even if their recipient is trustworthy.”
plain- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The reputation of players may not only be determined by their own actions, but also by their associations with others.”
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
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Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“There are 16 action rules.”
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
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Probably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“In a world of binary moral judgements, there are four ways of assessing donors in terms of 'first order assessment': always consider them as good, always consider them as bad, consider them as good if they refuse to give, or consider them as good if they give.”
plain- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“If we view a strategy as the combination of an action rule and an assessment rule, we obtain 4096 strategies.”
plain- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In extended versions of indirect reciprocity, where donors can sometimes deceive others about the reputation of the recipient, SCORING is the 'fool-proof' concept of 'I believe what I see'.”
plain- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In human evolution, there was a tendency from the simple cooperation promoted by kin or group selection to the strategic subtleties of direct and indirect reciprocity.”
plaincorrelational- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“There are 256 third order assessment rules.”
plain- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“SCORING judges the action and ignores the stories.”
plain- Asserted: passes — The authors put it forward as true.
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- Load-bearing: fails — The paper’s conclusions may not depend on it.
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Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Indirect reciprocity, in addition, has to monitor interactions among other people, possibly judge the intentions that occur in such interactions, and keep up with the ever changing social network of the group.”
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
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Probably not a substantial claim. The paper may give no reason why it holds. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The donations in the indirect reciprocity game, which are channelled towards those who contributed much to the public goods, can be viewed as rewards.”
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
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Probably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“It is known that many players show an initial willingness to contribute to the public goods a substantial amount of their endowment, but this willingness often vanishes within a few rounds.”
boosted- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
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Probably not a substantial claim. It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Since each player receives, in return for the own contribution, only the fraction r/N , the incomemaximising strategy is to contribute nothing.”
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
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Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“But settling on this strategy, for instance, on the specific number T, seems to require an institution able to guarantee honest labelling.”
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
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Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The moralistic assessment of the other members in the population, even if they are only observed at a distance, provides a powerful tool for channelling support toward those who collaborate, and thus an incentive to join group efforts.”
boosteddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
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Probably not a substantial claim. The paper may give no reason why it holds. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“This very crude form of assessment seems to suffice for the purpose of reputation-building, and seems to be reasonably proof against manipulation.”
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
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Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“All they can gain from the transfer is an increased reputation for altruism and trustworthiness.”
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
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Probably not a substantial claim.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Direct reciprocity requires precise recognition of individual people, a memory of the various interactions one had with them in the past, and enough brain to conduct multiple repeated games simultaneously.”
plaindirect- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds. It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Helping another individual is costly but buys the reputation of being helpful.”
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
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Probably not a substantial claim. The paper may give no reason why it holds. It may state two separate claims as one.
In the paper
“Altruism toward genetic relatives can evolve by kin selection provided Hamilton's rule 14 holds: the coefficient of relatedness, r , between the donor and the recipient has to exceed the cost to benefit ratio of the altruistic act,”
What the sources say
- Not checked — no full text of the sourcecites [14] Hamilton, W. D. Narrow Roads of Gene Land Vol. 1 (Freeman, New York, 1996) source
plaindirect- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it.
In the paper
“While language might help to compare and synchronize these lists 41 , ultimately reputation is in the eyes of the beholder.”
What the sources say
- Not checked — no full text of the sourcecites [41] Nowak, M. A. & Sigmund, K. The dynamics of indirect reciprocity. J. Theor. Biol. 194, 561–574 (1998) source
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: fails — It may be too vague to check against evidence.
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Probably not a substantial claim. It may be too vague to check against evidence. The paper’s conclusions may not depend on it. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Kin selection works in 'viscous' populations where chances are high that neighbours are genetic relatives.”
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“The observers, the donor and the recipient can inform others about what has happened.”
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Indirect reciprocity, in contrast, is built on reputation.”
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“The Public Goods game for N =2 players has the structure of a Prisoner's Dilemma.”
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
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Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Two players who cooperate earn more than two players who defect; but a defector cheating on a cooperator earns the highest payoff, and the exploited cooperator earns the lowest.”
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Direct reciprocity is captured in the framework of the repeated Prisoner's Dilemma.”
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
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Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“An individual who has been at the receiving end of a donation may feel motivated to donate in turn.”
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper may give no reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“An entirely different approach to indirect reciprocity is based, not on the reputation of the recipient, but on the experience of the donor.”
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“If two players, in a trust game, are simultaneously in the role of the donor, and then simultaneously in the role of the responder, they play two rounds of a Prisoner's Dilemma.”
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
In the paper
“In a natural extension of the basic model of indirect reciprocity, an action between a donor, A, and a recipient, B, is observed by a subset of the population 35 .”
What the sources say
- Not checked — no full text of the sourcecites [35] Nowak, M. A. & Sigmund, K. A strategy of win-stay, lose-shift that outperforms tit-for-tat in the prisoner's dilemma game. Nature 364, 56–58 (1993) source
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Therefore, the reputation of a person is not simply a label that is visible to all others, but instead each person has a private list of the reputation of others.”
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“There are many possibilities of error: the action or the intention of the donor can interpreted differently by different people, some individuals may receive conflicting information from different sources, some individuals may not receive any information at all.”
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“The probability that brothers share a 'selfish gene' is ½; the same probability for cousins is 1/8.”
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In both cases, the decision to give help can be interpreted as a misdirected act of gratitude.”
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
The paper relies on this without support.
Natural selection favours selfish individuals who maximize their own resources at the expense of others.
“Natural selection favours the strong and selfish who maximize their own resources at the expense of others.”
The paper relies on this without support.
Many biological systems, and especially human societies, are organized around altruistic, cooperative interactions.
“But many biological systems, and especially human societies, are organized around altruistic, cooperative interactions.”
The authors state this as an assumption.
The cost of an altruistic act is smaller than the benefit.
“We shall always assume that the cost is smaller than the benefit, so that if the act is returned, both individuals experience a gain.”
The authors state this as an assumption.
In each round both players decide simultaneously.
“For simplicity, we shall assume that in each round both players decide simultaneously.”
The authors state this as an assumption.
In indirect reciprocity, any two players interact at most once with each other.
“In the context of indirect reciprocity, any two players are supposed to interact at most once with each other.”
The authors state this as an assumption.
Each player can experience many rounds, but never with the same partner twice.
“Each player can experience many rounds, but never with the same partner twice.”
The authors state this as an assumption.
In the indirect reciprocity model, within a well-mixed population, individuals meet randomly, one as donor, one as recipient.
“A similar model of indirect reciprocity assumes that within a well-mixed population, individuals meet randomly, one in the role of the potential donor, the other as potential recipient (Fig 2).”
The authors state this as an assumption.
Each individual experiences several rounds of this interaction in both roles, but never with the same partner twice.
“Each individual experiences several rounds of this interaction in both roles, but never with the same partner twice.”
The authors state this as an assumption.
All that counts is the total payoff.
“Again, all that counts is the total payoff.”
The authors state this as an assumption.
Typically, one considers a well-mixed population where individuals meet randomly and play a series of Prisoner's Dilemma games with each other.
“Typically, one considers a well-mixed population where individuals meet randomly and play a series of Prisoner's Dilemma games with each other.”
The authors state this as an assumption.
What counts is the total payoff.
“What counts is the total payoff.”
The authors state this as an assumption.
In the binary score model, a player's score is 0 at birth, increases whenever that player helps and decreases whenever the player withholds help.
“A player's score is 0 at birth, increases whenever that player helps and decreases whenever the player withholds help.”
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“costly-signaling accounts interpret helping as the advertisement of desirable qualities (41)”
From Volunteerism as a multidimensional form of human prosocial engagement (2026) · cites this paper as [41]
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“Evolutionary biology has also developed theories about reputation and gossip: indirect reciprocity and biological markets are formal theories describing how animals should behave given that reputations exist (Noë and Hammerstein, 1995; Nowak and Sigmund, 2005; Barclay, 2013).”
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“There are many well-known theories that explain altruism, including kin selection [8] and reciprocal altruism based on direct reciprocity [9–11] or indirect reciprocity [12, 13].”
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“Consistent with earlier research, we identified both direct reciprocity in repeated dyadic/group interactions (Studies 3 and 4) and indirect reciprocity in interactions with multiple anonymous others (Studies 1 and 2; Kelley & Stahelski, 1970b; Nowak & Sigmund, 2005; Romano, Saral, & Wu, 2022).”
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“Thus, reputation promotes cooperation in humans (Nowak & Sigmund, 2005; Rand & Nowak, 2013;Wedekind & Milinski, 2000).”
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“As theoretical studies in mathematical biology explain the evolution of cooperation through indirect reciprocity (Nowak and Sigmund, 2005), especially through group structured (Masuda, 2012; Nax et al.”
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“Another possible reason is that helping other humans can enhance the helpers’ social reputation, making the public more willing to cooperate with the helpers and ofer help to them, a phenomenon known as indirect reciprocity [51].”
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“It is possible that such donors were motivated by indirect reciprocity (37), a desire to “pay it forward” for other donors by supporting the matching fund after receiving matching funds.”
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“…personal disaster situation, employees are more likely to pursue self-interest or immediate rewards (Hommelhoff et al., 2018; Li et al., 2018; Nowak & Sigmund, 2005) as well as to have a present, rather than future, time perspective regarding their tenure in the organization (cf. Hommelhoff…”
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“cial mechanisms behind it has been the focus of research attention for decades [3]. Specifically, research identified several factors influencing pro-social behavior, including direct [4, 5] andindirect [6, 7]reciprocity, multilevelcooperation[8, 9], kin-selection[10], and social network structure [11, 12]. These mechani…”
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“…1982), the punishment of defectors via both reciprocal altruism (direct reciprocity) (Trivers 1971) and social reputations (indirect reciprocity) (Nowak and Sigmund 2005; Ohtsuki and Iwasa 2006), and embedding evolutionary game dynamics in space or on social networks (Durrett and Levin 1994;…”
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“…within cultural groups so as to not be undermined by defectors (see e.g., Trivers, 1971; Van Veelen, Garc ıa, Rand, & Nowak, 2012; Sugden, 1986; Nowak & Sigmund, 2005; Panchanathan & Boyd, 2004, 2005; Boyd & Mathew, 2021; Richerson & Boyd, 2005), pointing to the importance of enforcing shared…”
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“…like direct or indirect reciprocity, showing how strategies such as tit-for-tat (under direct reciprocity) (Imhof et al. 2005) or stern judging (under indirect reciprocity) (Nowak and Sigmund 2005; Pacheco et al. 2006) can help promote the persistence of cooperation via multilevel selection.”
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“…prosocial behavior that is driven by the desire to benefit others and therefore (often implicitly) views gossip as trustworthy, useful, and reliable (Beersma et al., 2019; Feinberg et al., 2012, 2014; Giardini et al., 2022; Lee & Barnes, 2021; Nowak & Sigmund, 2005; Sommerfeld et al., 2007).”
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Metadata
- Authors
- Nowak, M. A., & Sigmund, K.
- Affiliations
- Harvard University (US)
- University of Vienna (AT)
- Corresponding author
- Sigmund, Karl
- Venue
- Nature
- Published
- 2005-10
- Volume
- 437
- Issue
- 7063
- Pages
- 1291-1298
- ISSN
- 0028-0836 (ISSN-L)
- 1476-4687
- OpenAlex
- W2157592153
- Semantic Scholar
- 9f4a89877e0d7513834801bfe2c71823632d213f
- Cited by
- 2,762
- References
- 90
- Citations by year
- 2026: 137 · 2025: 151 · 2024: 162 · 2023: 170 · 2022: 126 · 2021: 170 · 2020: 159 · 2019: 135 · 2018: 158 · 2017: 120 · 2016: 166 · 2015: 130 · 2014: 142 · 2013: 132 · 2012: 140
- FWCI
- 224.45
- Type
- journal article
- Language
- en
- Open access
- green
- pure.iiasa.ac.at
- Licence
- www.springer.com/tdm (tdm)
- Locations
- Nature (publishedVersion)
- PubMed (publishedVersion)
- IIASA PURE (International Institute of Applied Systems Analysis) (submittedVersion)
- RePEc: Research Papers in Economics (submittedVersion)
- Funders
- John Templeton Foundation
- Harvard University
- Topics
- Social Sciences › Sociology and Political Science › Evolutionary Game Theory and Cooperation
- Social Sciences › Psychology › Experimental and Cognitive Psychology › Evolutionary Psychology and Human Behavior
- Life Sciences › Agricultural and Biological Sciences › Ecology, Evolution, Behavior and Systematics › Animal Behavior and Reproduction
- Keywords
- indirect reciprocity, evolution of cooperation, altruism, reputation, morality, social evolution, natural selection, human social behavior
- MeSH terms
- Altruism, Cooperative Behavior, Biological Evolution, Humans, Models, Biological, Morals, Trust
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
A language model drew the claims from the paper on 2026-10-23, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).
A second model labelled each claim on 2026-10-23 (model jev-1.13-20260917, definition revision gold-guideline-v0.2).
Cited sources are checked with a language model’s help (gpt-6-sol).
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
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