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Cited by 415Evolutionary Psychology and Human BehaviorAttachment and Relationship DynamicsSocial Power and Status Dynamics

Relationships and the social brain: Integrating psychological and evolutionary perspectives

Sutcliffe, Alistair, Dunbar, Robin, Binder, Jens, Arrow, Holly·2012·British Journal of Psychology
DOI 10.1111/j.2044-8295.2011.02061.x
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Abstract

Psychological studies of relationships tend to focus on specific types of close personal relationships (romantic, parent–offspring, friendship) and examine characteristics of both the individuals and the dyad. This paper looks more broadly at the wider range of relationships that constitute an individual's personal social world. Recent work on the composition of personal social networks suggests that they consist of a series of layers that differ in the quality and quantity of relationships involved. Each layer increases relationship numbers by an approximate multiple of 3 (5–15‐50–150) but decreasing levels of intimacy (strong, medium, and weak ties) and frequency of interaction. To account for these regularities, we draw on both social and evolutionary psychology to argue that relationships at different layers serve different functions and have different cost‐benefit profiles. At each layer, the benefits are asymptotic but the costs of maintaining a relationship at that level (most obviously, the time that has to be invested in servicing it) are roughly linear with the number of relationships. The trade‐off between costs and benefits at a given level, and across the different types of demands and resources typical of different levels, gives rise to a distribution of social effort that generates and maintains a hierarchy of layered sets of relationships within social networks. We suggest that, psychologically, these trade‐offs are related to the level of trust in a relationship, and that this is itself a function of the time invested in the relationship.

AI snapshot

Written from the paper’s full text.

TL;DR

This integrative review argues that human personal social networks are structured in hierarchically inclusive layers of about 5, 15, 50, and 150 relationships, differing in intimacy, contact frequency, and function. It proposes that time-investment costs and trust formation, combined with asymptotic benefits and linear maintenance costs, generate these layered relationship types.

Key findings

  • Personal social networks show consistent layered scaling by an approximate multiple of 3: support clique of 4–5, sympathy group of 12–15, affinity group/band of around 50, and active network/clan of 150.
  • Layers differ in emotional closeness and contact frequency. In data from 295 women in the UK and Belgium, mean emotional closeness differed significantly across layers (F₄,₁₈₅₃₈ = 2002.4, p < .0001), with each layer differing from all others (Scheffé tests: p < .001 in each case); contact frequency declined as a steep negative exponential function of network layer.
  • The paper models relationship maintenance as a cost-benefit trade-off: benefits are asymptotic while maintenance costs rise roughly linearly with number of relationships, yielding separate optimal group sizes at Nash equilibria. Assuming 30-min average interactions and reported contact rates, social interaction totals 2.25 h/day, within the 3.5 h/day reported in diary/time-budget studies; if every layer required support-clique intensity, the total would be 39.4 h/day.
  • Trust is proposed to develop with interaction frequency and stabilize at plateaus corresponding to network layers, with an “affect buffer” making strong ties more resilient. In one cited longitudinal study, 29.7% of kin Alters moved from inner layers (5–15) to outer layers (50–150) over 18 months, compared with 51.4% of non-kin Alters.

Methods

  • Design: conceptual and integrative theoretical paper combining psychological and evolutionary perspectives, including the social brain hypothesis, selective investment theory, and a trust-based model of relationship maintenance.
  • Data/sample: draws on existing primate and human sociality literature and egocentric network data, including a sample of ∼300 complete personal social networks and Figure 2 data from 295 women in the UK and Belgium.
  • Analysis: qualitative synthesis plus an optimality model in which linear time-investment costs intersect with asymptotic benefit curves to define Nash equilibria and optimal numbers of relationships at different layers.

Limitations

  • The paper states that the outer layers at 50 and 150 are not equally well understood and that their functions are conjectural; it also states that at least three deep causal explanations remain open, including social-cognitive capacity limits, belonging/security motivations, and evolutionary predispositions.
  • The paper states that it is unclear whether network layers reflect functional task demands and group dynamics or are more directly derivative of evolved cognition, and that the strong version of the “signatures” hypothesis would require discrete step functions that are not yet established.
  • Evident from the text: this is a theoretical integration rather than a new empirical test of the proposed trust and relationship-signature predictions; several empirical claims rely on secondary data, and the Figure 2 sample is limited to 295 women in the UK and Belgium.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1111/j.2044-8295.2011.02061.x

Cites

113 of 113 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 66 cited sources checked · 0 supported · 0 flagged

  • Findingcitation
    § Discussion · p. 14

    Both strong and medium friendship (but not kinship) ties wane if they are not regularly serviced during the transition from school to university.

    “In partial support of this, we have found that both strong and medium friendship (but not kinship) ties wane if they are not regularly serviced during the transition from school to university (Roberts &amp; Dunbar, in press).”
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    • cites Roberts & Dunbar, in press

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  • Interpretationreasoning
    § Relationships, group size, and the structure of social networks · p. 4

    Personal social networks of friends who both belong to the same large group of 150 overlap at best incompletely.

    “So, the personal social networks of friends who both belong to the same large group of 150 overlap at best incompletely, even though each has an active network of about the same size.”
    Quote in the paperSubstantial claim
  • Premisecitation
    § Relationships and the social brain: Integrating psychological and evolutionary perspectives · p. 1

    Personal social networks consist of a series of hierarchically inclusive layers that differ in the quality and quantity of relationships.

    “Recent work on the composition of personal social networks suggests that they consist of a series of layers that differ in the quality and quantity of relationships involved.”
    • Also stated in: § Relationships, group size, and the structure of social networks · p. 3 · hedged
      “Within the network as a whole, there are a series of 'circles of acquaintanceship' that seem to scale with a consistent ratio close to 3”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Hill & Dunbar, 2003

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    • cites Zhou et al., 2005

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  • Premisecitation
    § Relationships and the social brain: Integrating psychological and evolutionary perspectives · p. 1

    Relationship intimacy and frequency of interaction decrease across the layers from inner to outer.

    “but decreasing levels of intimacy (strong, medium, and weak ties) and frequency of interaction”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Hill & Dunbar, 2003

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    • cites Roberts et al., 2009

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  • Premisecitation
    § Relationships, group size, and the structure of social networks · p. 3

    The layering pattern holds for both the bottom-up structure of egocentric networks and the top-down structure of communities and their constituent subgroups.

    “This layering pattern holds for both the bottom-up structure of egocentric networks and the top-down structure of communities and their constituent subgroups”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Dunbar, 2010b

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  • May combine two claims. 27
  • Classified as probably not a substantial claim. 11

  • May combine two claims.

    Findingown data
    § Trade-offs and constraints · p. 7

    Data from the authors' sample of ~300 complete personal social networks show that humans invest much more time and effort in some relationships (especially the inner core of five intimates) than in others, with frequency of contact with Alters declining as a steep negative exponential function of network layer.

    “More importantly, the data from our sample of ∼ 300 complete personal social networks clearly demonstrate that humans invest much more time and effort in some relationships (especially those in the inner core of five intimates) than in others, with frequency of contact with Alters declining as a steep negative exponential function of network layer (Figure 3).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation
    § Relationships, group size, and the structure of social networks · p. 4

    The innermost two layers are the support clique of 4-5 and the sympathy group of 12-15; next are the affinity group of around 50 and the active network of 150.

    “In humans, the innermost two layers have been identified as the support clique of 4-5 and the sympathy group of 12-15”
    • Also stated in: § Relationships, group size, and the structure of social networks · p. 4 · plain
      “These are followed by the affinity group (or band in the ethnographic literature) of around 50 and the active network (clan in the ethnographic literature) of 150 individuals.”
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    • cites Dunbar & Spoors, 1995

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    • cites Stiller & Dunbar, 2007

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    Premisecitation
    § Relationships, group size, and the structure of social networks · p. 3

    The primate social brain hypothesis predicts an average human group/community size of around 150, a value documented across social, cultural, and historical circumstances.

    “Applied to humans, the primate SBH relationship predicts an average group (i.e., community) size of around 150, a value that has been documented in a wide range of social, cultural, and historical circumstances”
    • Also stated in: § Relationships, group size, and the structure of social networks · p. 3 · boosted
      “This convergence between whole group size and egocentric network size is striking”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Dunbar, 1993

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    • cites Hamilton et al., 2007

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    • cites Hill & Dunbar, 2003

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    Premisecitation
    § Relationships and the social brain: Integrating psychological and evolutionary perspectives · p. 1

    The layers scale by an approximate multiple of 3, with characteristic sizes around 5, 15, 50, and 150.

    “Each layer increases relationship numbers by an approximate multiple of 3 (5-15-50-150)”
    • Also stated in: § Relationships, group size, and the structure of social networks · p. 3 · plain
      “These layers (which are hierarchically inclusive) lie at around 5, 15, 50, and 150 individuals”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Hill & Dunbar, 2003

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    • cites Zhou et al., 2005

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    Premisecitation
    § Trust in social relationships · p. 11

    The maintenance of coherent, long-lasting relationships depends on at least two key constraints: the time required to establish and maintain a relationship and the cognitive demands of maintaining a functional mental database for social information.

    “The maintenance of coherent, long-lasting relationships seems likely to depend on at least two key constraints: the time required to establish and maintain a relationship and the cognitive demands of maintaining a functional mental database that can be used to manipulate information about one's social world (Dunbar, 2008).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Dunbar, 2008

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    Premisecitation
    § Trade-offs and constraints · p. 8

    Benefits are asymptotic for groups with tasks that require close coordination; larger task groups commonly fail to perform in proportion to their size due to free riding, loss of motivation, and process losses.

    “Research in the social psychology of group work confirms that benefits are asymptotic for groups with tasks that require close coordination. Larger task groups commonly fail to perform in proportion to their size (Steiner, 1972) for a number of reasons, including free riding and loss of motivation (Kerr, 1983), as well as process losses”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Steiner, 1972

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    • cites Kerr, 1983

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    • cites Diehl & Stroebe, 1991

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    Premisecitation
    § Trust in social relationships · p. 12

    Exchange relationships among non-kin necessarily rely on trust that other network members will cooperate or reciprocate when required and that none will deliberately undermine or abuse the relationship.

    “Many of the relationships we have discussed involve reciprocation of commitment or exchange relationships among non-kin that necessarily rely on trust - trust that (1) other members of one's network will cooperate or reciprocate when required to do so and (2) none will deliberately undermine or abuse that relationship (Dunbar, 1998a).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Dunbar, 1998a

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    Premisecitation
    § Trade-offs and constraints · p. 7

    Intimate relationships provide a level of emotional intensity that is crucial in creating close friendships, thereby facilitating close support coalitions.

    “we follow both Brown and Brown (2006) in arguing that intimate relationships provide a level of emotional intensity that is crucial in creating close friendships, thereby facilitating the formation of close support coalitions”
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    • cites Brown & Brown, 2006

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    Interpretationreasoning
    § Trade-offs and constraints · p. 11

    Selection pressures driving the emergence of a particular layer do not limit the functionality of that layer; selection acts on the psychological mechanisms that enable a group of a particular size to be realized.

    “It is worth emphasizing here that the selection pressures driving the emergence of a particular layer do not limit the functionality of that layer; rather, selection acts on the psychological mechanisms that enable a group of a particular size to be realized”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Trust in social relationships · p. 12

    Trust evolved to enhance collaboration through improved abilities to assess trustworthiness and detect deceit in social interactions.

    “McCabe (2002) argues that trust evolved to enhance collaboration through improved abilities to assess trustworthiness and detect deceit in social interactions.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites McCabe, 2002

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    Interpretationreasoning
    § Trade-offs and constraints · p. 9

    Some resource types (e.g., emotional support) have high fitness valency, asymptote at an absolutely higher level but earlier; other resources (generalized exchange) rise to a lower asymptote more slowly.

    “Some resource types (e.g., emotional support) have high fitness valency, and thus asymptote at an absolutely higher level, but reach that asymptote earlier because they impose comparatively high demands; in contrast, other resources (generalized exchange relationships for childcare and other reciprocated benefits) rise to a lower asymptote more slowly”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation
    § Trade-offs and constraints · p. 11

    Around 75% of introductions to future life partners come through the first three steps in the social network, probably equivalent to the 150 layer of egocentric networks.

    “Christakis and Fowler (2010) note that around 75% of introductions to future life partners come through the first three steps in the social network (i.e., the friends of friends of friends), which is probably equivalent to the 150 layer of egocentric networks.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Christakis & Fowler, 2010

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    Premisecitation
    § Relationships, group size, and the structure of social networks · p. 6

    Consistent behaviour differences have been reported for different levels of relationship intensity, with close/best friendships involving more interaction, emotional and informational support, and less dependence on contact opportunities than casual friendships.

    “In sum, consistent behaviour differences have been reported for different levels of relationship intensity.”
    • Also stated in: § Relationships, group size, and the structure of social networks · p. 5 · plain
      “Hays (1989) compared close and casual friendships and found that close friendships showed more interactions during the week, across a wider range of days, times, and locations than casual friendships. In terms of benefits received, close friends offered more emotional and informational support than casual ones.”
    • Also stated in: § Relationships, group size, and the structure of social networks · p. 5 · plain
      “Rose and Serafica (1986) found that casual friends required less emotional involvement than best or close friends, but were more dependent on opportunities for contact.”
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    • cites Hays, 1989

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    • cites Rose & Serafica, 1986

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    • cites Oswald et al., 2004

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    Premisereasoning
    § Trade-offs and constraints · p. 10

    Overnight camp groups depend on much weaker ties linking families or other clusters and are relatively unstable in hunter-gatherer societies, changing membership on a scale of months.

    “Overnight camp groups depend on much weaker ties (Figure 3) linking families or other clusters. As a result, these larger groups are relatively unstable in hunter-gatherer societies, and tend to change membership on a scale of months”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Interpretationreasoning
    § Trade-offs and constraints · p. 9

    The trade-off is between spreading oneself thinly to gain many potential allies and concentrating social time more conservatively to build a higher level of trust among a smaller number of allies.

    “The trade-off is between spreading oneself thinly to gain many potential allies, and concentrating social time more conservatively to build a higher level of trust among a smaller number of allies.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation
    § Trade-offs and constraints · p. 11

    Information exchange and access to resources may drive weak ties in the outer layer; the more people an individual knows and socializes with, the better their information flow and survival intelligence.

    “Another driver for forming weak ties in this outer layer may be information exchange and access to resources. The more people an individual knows and socializes with, the better that individual's information flow ( sensu Granovetter, 1973), and hence the better their survival intelligence”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Granovetter, 1973

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  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given
    § Trade-offs and constraints · p. 10

    The 150 layer is composed of individuals who are socially familiar with most other members of the larger collective, with clusters linked together in a 'small world' structure.

    “This layer is composed of individuals who are socially familiar with most other members of the larger collective, with clusters linked together in a 'small world' structure.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Interpretationnone given
    § Relationships, group size, and the structure of social networks · p. 6

    The layers of relationships are designed to deal with different kinds of functions and/or constraints.

    “One plausible explanation for the layering of relationships in human personal social networks is that the layers (i.e., the different relationship types) are designed to deal with different kinds of functions and/or constraints.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning
    § Trade-offs and constraints · p. 7

    Intimates provide close emotional support that allows fine-tuning of emotional well-being and stress reduction and interfacing with the wider social world.

    “Intimates identify a set of individuals who provide (and/or require) close emotional support that allows us to fine-tune emotional well-being and stress reduction as well as enabling us to interface with the wider social world.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation
    § Relationships, group size, and the structure of social networks · p. 5

    There is considerable support in the literature for at least the two inner layers, with studies reporting comparable network sizes (intimate ~5, active ~12.5; name-generation ~15).

    “there is considerable support in the literature for at least the two inner layers”
    • Also stated in: § Relationships, group size, and the structure of social networks · p. 5 · plain
      “Using an intimate (socially close) versus routine (actively maintained) classification, Wellman, Carrington, and Hall (1988) found a mean of 5.0 intimate ties and 12.5 active ties”
    • Also stated in: § Relationships, group size, and the structure of social networks · p. 5 · hedged
      “Name-generation studies of relationships, which elicit stronger ties by using a number of questions as cues give a fairly consistent mean network size of approximately 15 individuals”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Wellman et al., 1988

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    • cites Dunbar & Spoors, 1995

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    • cites Fischer, 1982

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  • May combine two claims.

    Interpretationreasoning
    § Trust in social relationships · p. 13

    Strong ties with non-kin in the inner circle of around 5 take longer to develop and have to rise to a higher level of trust than medium or weak ties (corresponding to the 50 and 150 outer layers).

    “Strong ties with non-kin in the inner circle of around 5 take longer to develop and have to rise to a higher level of trust than medium or weak ties (i.e., those corresponding to the 50 and 150 outer layers).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning
    § Trust in social relationships · p. 12

    Emotional engagement provides the basis for future commitment, and the level of pleasure in Alter's company can serve as an index of how much they can be relied on.

    “This emotional engagement then provides the basis for future commitmentwheneverthismightbeneeded,andthelevelofpleasureinAlter's company can serve as an index of how much they can be relied on.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given
    § Trust in social relationships · p. 13

    At the highest level of trust, an affect buffer comes into play and buffers the tie against isolated negative events.

    “At the highest level of trust, an affect buffer comes into play and buffers the tie against isolated negative events.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationreasoning
    § Discussion · p. 16

    The cost-benefit trade-offs could link to behaviour that enhances fitness and survival at the individual level, in the form of improved survival of offspring and parents through reciprocal social support.

    “The cost-benefit trade-offs could link to behaviour that enhances fitness and survival at the individual level, in the form of improved survival of offspring and parents through reciprocal social support.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning
    § Discussion · p. 14

    A set of cost-benefit trade-offs governs the distribution of individuals' social investment in others, and the cost-benefit profile differs for different layers.

    “we posit that a set of cost-benefit trade-offs governs the distribution of individuals' social investment in others, and that the cost-benefit profile differs for different layers.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationreasoning
    § Trust in social relationships · p. 13

    Weak ties are relatively immune to insults due to their low trust level.

    “Weak ties are relatively immune to such insults due to their low trust level.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation
    § Affective and cognitive correlates of tie strength · p. 14

    Stronger ties tend to be more stable over time, whereas weaker ties are more liable to change.

    “As would be expected by the steeper investment in the closest circles of support clique and sympathy group, stronger ties do tend to be more stable over time (e.g., Ledbetter, Griffin, &amp; Sparks, 2007), whereas weaker ties are more liable to change.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Ledbetter, Griffin, & Sparks, 2007

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  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Interpretationnone given
    § Trust in social relationships · p. 13

    Trust rises as a function of frequency of interaction, but there are a series of levels that trust naturally stabilizes at; trust can rise above these stable points only if significant additional social effort is invested in the relationship.

    “although trust rises (perhaps linearly) as a function of the frequency of interaction, there are a series of levels that trust naturally stabilizes at (represented by the plateaux); trust can rise above these stable points only if significant additional social effort is invested in the relationship.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: Increasing frequency of interaction results in increased levels of trust.

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationreasoning
    § Discussion · p. 14

    One underlying mechanism that governs the allocation of social investment in different layers may be the trust formation process, which creates an 'affect buffer' that makes strong ties less susceptible to decay.

    “One underlying mechanism that governs the allocation of social investment in different layers may be the trust formation process, which creates an 'affect buffer' that makes strong ties less susceptible to decay.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based).

    Interpretationreasoning
    § Discussion · p. 14

    This affect buffer might function to free up more social time for Ego to invest in other relationships.

    “This affect buffer might function to free up more social time for Ego to invest in other relationships.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation
    § Trust in social relationships · p. 12

    The degree of trust is closely related to emotional closeness; as a relationship becomes closer, affect reduces the need to consciously calculate trust, alleviating the cognitively costly theory of mind burden in tracking very close (support group) relationships.

    “The degree of trust is therefore closely related to emotional closeness; however, as a relationship becomes closer, affect reduces the need to consciously calculate trust, and hence alleviates the cognitively costly theory of mind burden (Powell, Lewis, Dunbar, Garc´ ıa-Fi˜ nana, &amp; Roberts, 2010) in tracking very close (support group) relationships.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Powell, Lewis, Dunbar, Garc´ ıa-Fi˜ nana, & Roberts, 2010

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  • May combine two claims.

    Interpretationreasoning
    § Affective and cognitive correlates of tie strength · p. 14

    Sympathy group relationships are more fluid and reflect individuals' different interests beyond the cluster; more broadly, relationships become increasingly diffuse and less well integrated as one moves out through the layers.

    “Sympathy group relationships should be more fluid and reflect individuals' different interests beyond the cluster; more broadly, relationships will become increasingly diffuse and less well integrated as one moves out through the layers.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning
    § Trust in social relationships · p. 13

    Medium ties are more sensitive to insults and exhibit an immediate decline in trust following an insult, after which trust may rebuild.

    “However, medium ties are more sensitive, and exhibit an immediate decline in trust following an insult, after which trust may rebuild.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationcitation
    § Discussion · p. 16

    Relationships and trust formation may reflect constraints imposed by social cognitive capacities such as theory of mind, in that memory for managing relationships is limited not only by absolute capacity but also by accuracy and recency.

    “First, relationships and, inter alia , trust formation may reflect constraints imposed by social cognitive capacities such as theory of mind (Stiller &amp; Dunbar, 2007) in that memory for managing relationships is limited not only by absolute capacity but also by accuracy and recency.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Stiller & Dunbar, 2007

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  • May combine two claims.

    Interpretationreasoning
    § Trust in social relationships · p. 13

    Strong ties exhibit more resilience to unfriendly interactions, giving intimate friends the benefit of the doubt, whereas sympathy group relationships are more susceptible to variation in trust in response to unfriendly interactions, reflecting a conscious, calculative mode.

    “Strong ties exhibit more resilience to unfriendly interactions, giving intimate friends the benefit of the doubt, whereas sympathy group relationships will be more susceptible to variation in trust in response to unfriendly interactions, reflecting a conscious, calculative mode.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning
    § Discussion · p. 15

    Both the online debate on numbers of friends and surveys of actual friends' listings on individual sites strongly conform to the predictions of the social brain model.

    “If anything, both the online debate on numbers of friends and surveys of actual friends' listings on individual sites strongly conform to the predictions of the social brain model.”
    Quote in the paperNot a substantial claim
36 of 36

  • The authors state this as an assumption.

    Costs rise more or less linearly with the number of relationships that have to be maintained, and do so more steeply for relationships that require more intense relationships, while the benefits themselves are asymptotic.

    “We assume that costs rise more or less linearly with the number of relationships that have to be maintained, and do so more steeply for relationships that require more intense relationships (high- vs. low-costs lines), while the benefits themselves are asymptotic”

  • The authors state this as an assumption.

    Increasing frequency of interaction results in increased levels of trust.

    “The model assumes that increasing frequency of interaction results in increased levels of trust.”
2 of 2

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Building close personal ties with individuals relies more on frequently repeated one-on-one (or small group) interactions in which individuals have the opportunity to talk and observe each other at close quarters to build up an idea of a potential social partner's trustworthiness and usefulness as a coalition partner.

    “By contrast, building close personal ties with individuals relies more on frequently repeated one-on-one (or small group) interactions in which individuals have the opportunity to talk and observe each other at close quarters to build up an idea of a potential social partner’s trustworthiness and usefulness as a coalition partner [15].”

    From The ice-breaker effect: Singing mediates fast social bonding (2015) · cites this paper as [15]

  • Creating and maintaining personal relationships requires sufficient time investment, but finite time budgets place a limit on the number of personal relationships that an individual can maintain through one-on-one interactions.

    “Creating and maintaining personal relationships requires sufficient time investment, but finite time budgets place a limit on the number of personal relationships that an individual can maintain through one-on-one interactions [15–17].”

    From The ice-breaker effect: Singing mediates fast social bonding (2015) · cites this paper as [15]

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • First network layer contains more Alters than the sample permits

    Minor

    The first layer contains at most five Alters per woman. Across 295 women, it could therefore contain at most 1,475 Alters, not the reported 4,770.

    Reported 4770 · recomputed 1475

  • Medium ties are assigned to different network layers

    Minor

    One passage assigns medium ties to the 50 layer, while the Figure 5 caption assigns them to the 15 layer.

2 of 2

Cites

Flagged first, then by citations

Research works printed but not linked: 14

  1. Binder J., 2009, Proceedings: CHI ’09 human factors in computing systems, Boston
  2. Christakis N., 2010, Connected: The surprising power of our social networks
  3. Crockford C., 2008, Hormones and Behavior, 254
  4. Curry O., 2011, Biology Letters
  5. Curry O., 2011, The strength of ties in social networks: Altruism is more closely related to emotional closeness among friends than among family
  6. Fredrickson B. L., 2004, 359B, 1367
  7. Hogan B., 2008, The handbook of online research methods
  8. Joinson A. N., 2008, Proceedings of the Twenty‐sixth Annual SIGCHI Conference on Human Factors in Computing Systems, CHI‐08
  9. Kayahara J., 2005, Canadians, culture and computers: Report to Heritage Canada
  10. Kelley H. H., 1983, Close relationships
  11. Machin A. J., Behaviour
  12. McCabe K. A., 2002, Trust and reciprocity: Interdisciplinary lessons from experimental research, 147
  13. Ostrom E., 2002, Trust and reciprocity: Interdisciplinary lessons from experimental research, 19
  14. Wellman B., 1988, Social structures: A network analysis, 130

Cited by

Sorted by citations

Related

Authors
Sutcliffe, A., Dunbar, R., Binder, J., & Arrow, H.
Affiliations
  • British Academy (GB)
  • University of Manchester (GB)
  • University of Oregon (US)
ORCID
Venue
British Journal of Psychology
Publisher
Wiley
Published
2011-07-25
Volume
103
Issue
2
Pages
149-168
ISSN
  • 0007-1269 (ISSN-L)
  • 2044-8295
DOI
10.1111/j.2044-8295.2011.02061.x
OpenAlex
W2115437174
Semantic Scholar
35f23da54656b096dcc341c2d1218add8252011f
Cited by
415
References
113
Citations by year
2026: 13 · 2025: 17 · 2024: 23 · 2023: 20 · 2022: 33 · 2021: 76 · 2020: 44 · 2019: 20 · 2018: 25 · 2017: 33 · 2016: 26 · 2015: 34 · 2014: 24 · 2013: 17 · 2012: 7
FWCI
2.14
Type
journal article
Language
en
Open access
closed
Licence
onlinelibrary.wiley.com/termsAndConditions#vor (vor)
Locations
  • British Journal of Psychology (publishedVersion)
  • PubMed (publishedVersion)
  • Nottingham Trent University's Institutional Repository (Nottingham Trent Repository) (submittedVersion)
  • Scholars' Bank (University of Oregon) (submittedVersion)
Funders
Engineering and Physical Sciences Research Council (EP/D05088X/1)
Topics
  • Social Sciences › Psychology › Experimental and Cognitive Psychology › Evolutionary Psychology and Human Behavior
  • Social Sciences › Psychology › Social Psychology › Attachment and Relationship Dynamics
  • Social Sciences › Sociology and Political Science › Social Power and Status Dynamics
Keywords
social networks, strong and weak ties, social brain, evolutionary psychology, social psychology of relationships, cost-benefit trade-off, trust, intimacy, personal networks, parent-offspring relationships, romantic relationships, friendship
MeSH terms
Brain, Cognition, Emotions, Biological Evolution, Family Relations, Group Processes, Humans, Interpersonal Relations, Object Attachment, Social Support, Friends, 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.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-09.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-09.

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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