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Cited by 244Primate Behavior and EcologyMemory Processes and InfluencesChild and Animal Learning Development

Keeping track of time: evidence for episodic-like memory in great apes

Open access
Martin-Ordas, Gema, Haun, Daniel, Colmenares, Fernando, Call, Josep·2010·Animal Cognition
DOI 10.1007/s10071-009-0282-4PMC PMC2822233
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Abstract

Episodic memory, as defined by Tulving, can be described in terms of behavioural elements (what, where and when information) but it is also accompanied by an awareness of one's past (chronesthesia) and a subjective conscious experience (autonoetic awareness). Recent experiments have shown that corvids and rodents recall the where, what and when of an event. This capability has been called episodic-like memory because it only fulfils the behavioural criteria for episodic memory. We tested seven chimpanzees, three orangutans and two bonobos of various ages by adapting two paradigms, originally developed by Clayton and colleagues to test scrub jays. In Experiment 1, subjects were fed preferred but perishable food (frozen juice) and less preferred but non-perishable food (grape). After the food items were hidden, subjects could choose one of them either after 5 min or 1 h. The frozen juice was still available after 5 min but melted after 1 h and became unobtainable. Apes chose the frozen juice significantly more after 5 min and the grape after 1 h. In Experiment 2, subjects faced two baiting events happening at different times, yet they formed an integrated memory for the location and time of the baiting event for particular food items. We also included a memory task that required no temporal encoding. Our results showed that apes remember in an integrated fashion what, where and when (i.e., how long ago) an event happened; that is, apes distinguished between different events in which the same food items were hidden in different places at different times. The temporal control of their choices was not dependent on the familiarity of the platforms where the food was hidden. Chimpanzees' and bonobos' performance in the temporal encoding task was age-dependent, following an inverted U-shaped distribution. The age had no effect on the performance of the subjects in the task that required no temporal encoding.

AI snapshot

Written from the paper’s full text.

TL;DR

Great apes remembered what, where, and when food was hidden in an integrated fashion, choosing perishable frozen juice more after 5 min and non-perishable grape after 1 h. Performance on this episodic-like memory task followed an inverted U-shaped age pattern, while a non-temporal memory task showed no age effect.

Key findings

  • In Experiment 1, apes chose frozen juice significantly more often after a 5-min retention interval than after 1 h (Wilcoxon: z = 2.55, p = 0.011, n = 12); 4 of 12 subjects showed this reversal individually.
  • In the pre-test requiring no temporal encoding, apes remembered food location above chance across delays (Wilcoxon: z = 3.12, p = 0.002, n = 12), with no age effect (r_s = 0.08, p = 0.41).
  • Experiment 1 www-memory performance showed an inverted U-shaped age trend (permutation test: c² = −0.142, p = 0.0682, n = 12); for chimpanzees and bonobos alone this was significant (c² = −0.026, p = 0.002, n = 9).
  • In Experiment 2, subjects chose frozen juice significantly more often from the platform baited last than from the platform baited first (Wilcoxon: z = 1.79, p = 0.037, one-tailed, n = 5), supporting integrated what–where–when memory.

Methods

  • Experiment 1 tested 7 chimpanzees, 3 orangutans, and 2 bonobos (12 total; ages 6–31 years) at the Wolfgang Köhler Primate Research Centre, using a platform with three possible baiting sites and two food types: preferred perishable frozen juice and less preferred non-perishable grape.
  • Subjects chose after 5-min or 1-h retention intervals; analyses used Wilcoxon tests, Pearson chi-square, and permutation-based quadratic models of age effects.
  • Experiment 2 tested 5 successful subjects (2 bonobos, 2 chimpanzees, 1 orangutan; ages 10–14 years) with two baiting events separated by 1 h and choice tests 5 min after the second event, analyzed with a one-tailed Wilcoxon test.

Limitations

  • The paper states that the reduced sample size did not allow more fine-grained analyses to distinguish differences between great ape species or developmental patterns.
  • The paper states that the data do not allow the conclusion that apes are actually recalling the baiting episode, and the mechanism used to keep track of time remains undetermined.
  • The paper notes that orangutan performance could reflect species differences or simply that the tested orangutans were too young or too old; more broadly, the study assesses behavioral criteria for episodic-like memory, not autonoetic awareness.

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

Integrity signals

Registry

Crossref · 10.1007/s10071-009-0282-4

Cites

69 of 69 references verified0 citation errors · 0 not checkable

Statistics

Claims the paper makes

0 of 47 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    Four out of 12 subjects chose the frozen juice significantly more often than the grape after the short retention interval and the grape after the long retention interval.

    “Individual analyses showed that 4 out of 12 subjects chose the frozen juice significantly more often than the grape after the short RI and the grape after the long RI (Table 1).”
    Quote in the paperSubstantial claim
  • Findingown data

    Performance on the what-where-when memory test revealed an inverted U-shaped trend as a function of age.

    “the performance on the www-memory test revealed an inverted U-shaped trend as a function of age (permutation test: c 2 = −0.142, p = 0.0682, n = 12, Fig. 1).”
    Quote in the paperNot a substantial claim
  • Findingown data

    Apes remembered the location of food above chance after each retention interval (2 min, 1 h, 2 h, 24 h) in the memory ability pre-test.

    “Overall apes remembered the location of the food after each RI above the chance levels in the memory ability pre-test (Wilcoxon test: z = 3.12, p = 0.002, n = 12 in all intervals, Fig. 1)”
    Quote in the paperSubstantial claim
  • Findingown data

    There was no change in performance across ages in the memory ability pre-test (task requiring no temporal encoding).

    “there was no change in performance across ages (r s=0.08, p = 0.41, n = 12).”
    • Also stated in: § Abstract · plain
      “The age had no effect on the performance of the subjects in the task that required no temporal encoding.”
    Quote in the paperNot a substantial claim
  • Findingnone given

    The temporal control of the apes' choices was not dependent on the familiarity of the platforms where the food was hidden.

    “The temporal control of their choices was not dependent on the familiarity of the platforms where the food was hidden.”
    Quote in the paperSubstantial claim
  • May combine two claims. 14
  • The quote only partly states this claim. 1
  • Classified as probably not a substantial claim. 30

  • May combine two claims.

    Findingown data

    Subjects' choices remained unchanged during testing in both the 5-min and 1-h conditions.

    “Their choices remained unchanged during testing (Friedman tests: 5-min—χ 2 = 0.16, n = 12, p = 0.92; 1-h—χ 2 = 0.42, n = 12, p = 0.8).”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    Subjects younger than 7 and older than 18 years of age showed much lower performance than adolescents and young adults on the what-where-when memory test.

    “Subjects younger than 7 and older than 18 years of age showed a much lower performance than adolescents and young adults.”
    Quote in the paperNot a substantial claim

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

    Premisecitation

    Clayton and colleagues have shown that scrub jays flexibly integrated memories for the what, where and when of an event.

    “Clayton and colleagues have shown that scrub jays flexibly integrated memories for the what, where and when of an event (Clayton and Dickinson 1998, 1999; Clayton et al. 2001, 2003b).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Clayton and Dickinson 1998 source

      Not checked in the free run.

    • cites Clayton et al. 2001 source

      Not checked in the free run.

    • cites Clayton et al. 2003b

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    The apes' choices of the less preferred food after the 1-h delay were not simply due to memory lapses, because they rarely selected the empty boxes in the pre-test and test.

    “Since subjects rarely selected the empty boxes in the pre-test and test (pre-test: less than 12% of the trials, test: less than 3% of the trials), this suggests that their choices of the less preferred food after 1-h delay were not simply due to memory lapses.”
    Quote in the paperSubstantial claim

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

    Interpretationcitation

    One weakness in Clayton's experimental approach is that it does not measure memory for unique experiences because they require training.

    “Therefore, one weakness in Clayton’s experimental approach is that it does not measure memory for unique experiences because they require training.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Zentall et al. 2001 source

      Not checked in the free run.

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

    Study design and conductnone given

    The apes did not have any previous experience with the frozen juice used in the experiment.

    “It is important to mention that the apes did not have any previous experience with the frozen juice that we used in our experiment.”
    Quote in the paperNot a substantial claim

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

    Study design and conductown data

    Subjects' general long-term memory was tested in a pre-test before the what-where-when memory test.

    “In the pre-test, we tested individuals’ general long-term memory.”
    Quote in the paperNot a substantial claim

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

    Study design and conductnone given

    In each round and for each trial different baiting places were used and the three possible sites were counterbalanced.

    “In each round and for each trial different baiting places were used and the three possible sites were counterbalanced.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    Hoffman et al.'s procedure is vulnerable to criticism because subjects were asked to remember what, where and when on separate occasions, raising doubts about the integration of the components.

    “However, their subjects were asked to remember these three elements in separate occasions, raising doubts about the integration of the components.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Hoffman et al. 2009

      Not checked in the free run.

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

    Study design and conductnone given

    The order in which subjects were presented in the 5-min and 1-h trials was counterbalanced.

    “The order in which subjects were presented in the two types of trials was counterbalanced.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Recent experimental studies have shown evidence for planning in chimpanzees, bonobos and orangutans.

    “recent experimental studies have shown evidence for planning in chimpanzees, bonobos and orangutans”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Mulcahy and Call 2006 source

      Not checked in the free run.

    • cites Dufour and Sterck 2008 source

      Not checked in the free run.

    • cites Osvath and Osvath 2008 source

      Not checked in the free run.

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

    Study design and conductreasoning

    To provide a unique baiting location on every trial within each round for each ape, the three baiting sites were covered with three different containers each, and these containers were different for each trial.

    “To provide a unique baiting location on every trial within each round for each ape, the three baiting sites were covered with three different containers each. Additionally, these containers were different for each trial.”
    Quote in the paperSubstantial claim

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

    Premisecitation

    Eacott et al. (2005) challenged the main role of the 'when' component in episodic-like memory, arguing that human episodic memory is poor in recalling timing and 'when' serves as a marker to distinguish events.

    “An alternative approach suggested by Eacott et al. (2005) challenged the main role of the “when” component in episodic-like memory.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Eacott et al. 2005 source

      Not checked in the free run.

    • cites Friedman 1993 source

      Not checked in the free run.

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

    Premisecitation

    Rats were sensitive not only to the location of objects but also to the temporal order in which they were presented, leading authors to conclude that rats integrated what, where and when an event happened.

    “The results from these experiments showed that rats were sensitive not only to the location of the objects, but also to the temporal order in which they were presented. These results led the authors to conclude that rats integrated what, where and when an event happened.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Kart-Teke et al. 2006 source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Study design and conductown data

    Food preference for the two food items was established prior to the experiment.

    “Prior to the experiment, we established the apes’ preference for two food items.”
    Quote in the paperSubstantial claim

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

    Premisecitation

    Other bird and mammal species have also been shown to possess episodic-like memory (what, where, when).

    “Other bird and mammal species have also been shown to possess such type of memory”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Babb and Crystal 2005 source

      Not checked in the free run.

    • cites Henderson et al. 2006 source

      Not checked in the free run.

    • cites Hampton et al. 2005 source

      Not checked in the free run.

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

    Premisecitation

    Longitudinal and cross-sectional studies in human memory have reported an inverted U-shaped curve as a function of age for episodic memory and no age effect for long-term memory.

    “Interestingly, longitudinal and cross-sectional studies in human memory have reported an inverted U-shaped curve as a function of age for episodic memory and no age effect for long-term memory (Bialystok and Craik 2006 for a review).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Bialystok and Craik 2006 source

      Not checked in the free run.

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

    Premisecitation

    Hoffman et al. (2009) found positive evidence for episodic-like memory in rhesus monkeys using a computer task.

    “Recently, Hoffman et al. 2009 examined working memory (Baddeley 2000) for what, where and when information in rhesus monkeys using a new paradigm based on a computer task and found positive evidence for episodic-like memory.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Hoffman et al. 2009

      Not checked in the free run.

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

    Premisecitation

    The trial-unique learning paradigm has been successfully implemented in rodents and birds.

    “The trial-unique learning paradigm has been successfully implemented in rodents (rats: Kart-Teke et al. 2006; mice: Dere et al. 2005) and birds (Zentall et al. 2001).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Kart-Teke et al. 2006 source

      Not checked in the free run.

    • cites Dere et al. 2005 source

      Not checked in the free run.

    • cites Zentall et al. 2001 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The unexpected question experiment by Zentall et al. (2001) only deals with short-time delays between encoding and question, whereas episodic memory is defined as a long-term memory system.

    “However, as pointed out by Crystal (2009), episodic memory is defined as a long-term memory system and the unexpected question experiment carried out by Zentall et al. (2001) only deals with short-time delays between the encoding event and the experimental question.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Crystal 2009 source

      Not checked in the free run.

    • cites Zentall et al. 2001 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing).

    Premisecitation

    Episodic memory and future planning depend on common processes.

    “It has also been argued that episodic memory and future planning depend on common processes”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Mulcahy and Call 2006 source

      Not checked in the free run.

    • cites Dufour and Sterck 2008 source

      Not checked in the free run.

    • cites Osvath and Osvath 2008 source

      Not checked in the free run.

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

    Premisecitation

    Pigeons were able to report which action they performed in the past in a delayed-matching to sample task.

    “The results from this experiment showed that pigeons were able to report which action they performed in the past.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Zentall et al. 2001 source

      Not checked in the free run.

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

    Premisenone given

    Compared to rodents and birds, non-human primates have received relatively little attention in episodic-like memory research.

    “Compared to rodents and birds, non-human primates have received relatively little attention in episodic-like memory research.”
    Quote in the paperNot a substantial claim

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

    Premisecitation

    Rats' success in Eacott et al.'s task allowed the authors to conclude that rats recollected the what, where and which of a past episode.

    “Rats’ success in this task allowed the authors to conclude that rats recollected the what, where and which of a past episode.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Eacott et al. 2005 source

      Not checked in the free run.

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

    Study design and conductown data

    Our reduced sample size does not allow us to carry out more fine-grained analyses to tell apart differences between the great ape species included in this study and the developmental patterns in this memory system.

    “It is precisely our reduced sample size that does not allow us to carry out more fine-grained analyses in order to tell apart differences between the great ape species included in this study and the developmental patterns in this memory system.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    Apes chose more often the frozen juice in the platform baited last because the frozen juice was hidden 5 min ago and was still edible.

    “Likewise, they chose more often the frozen juice in the platform baited last because the frozen juice was hidden 5 min ago and was, therefore, still edible.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Frozen juice hidden 1 h earlier had melted and was not edible, while frozen juice hidden 5 min earlier was still edible.

  • Classified as probably not a substantial claim.

    Premisecitation

    Familiarity is a recognition process that provides a temporal cue for knowing which food item will be available without actually recollecting the past event.

    “Familiarity is a recognition process that provides a temporal cue for knowing which food item will be available without actually recollecting the past event (Kort et al. 2005).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Kort et al. 2005 source

      Not checked in the free run.

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

    Study design and conductnone given

    The order of the 5 min and 1-h trials and the baited sites on the platform were counterbalanced across subjects.

    “The order of the 5 min and 1-h trials and the baited sites on the platform were counterbalanced across subjects.”
    Quote in the paperNot a substantial claim

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

    Premisereasoning

    An animal using a where-what-when representation would be unable to discriminate two episodes sharing the same 'what' because the 'where' and the 'when' components are not directly connected.

    “As a consequence, an animal using this representation would be unable to discriminate two episodes sharing the same “what” because the “where” and the “when” components are not directly connected.”
    Quote in the paperNot a substantial claim

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

    Premisenone given

    An inverted U-shape distribution is a feature of episodic memory in humans.

    “Second, an inverted U-shape distribution is a feature of episodic memory in humans.”
    Quote in the paperNot a substantial claim

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

    Premisecitation

    Friedman (1993) described three types of information that humans (but also animals) could process: temporal locations, temporal distances, and before-after relations or order of events.

    “Friedman (1993) described three types of information that humans (but also animals) could process: temporal locations, which refer to when an event took place within a time pattern; temporal distances, implying how long ago an event occurred and before–after relations or order of events.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Friedman 1993 source

      Not checked in the free run.

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

    Study design and conductreasoning

    The statistical test in Experiment 2 was one-tailed given that we had an a priori prediction.

    “The statistical test was one-tailed given that we had an a priori prediction.”
    Quote in the paperNot a substantial claim

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

    Study design and conductnone given

    The nature of Experiment 2 was confirmatory.

    “The nature of this experiment was confirmatory.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    The results of Experiment 2 confirmed the findings from the first experiment, that is, subjects' choices are mediated by the temporal information.

    “The results of this experiment confirmed the findings from the first experiment, that is, subjects’ choices are mediated by the temporal information.”
    Quote in the paperSubstantial claim

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

    Interpretationnone given

    The mechanism that apes used to keep track of time and the nature of the temporal representation of past events remains undetermined.

    “However, the mechanism that apes used to keep track of time and the nature of the temporal representation of the past events remains undetermined.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S1 (asserted), S4 (based).

    Premisenone given

    If the three components occurred in an integrated representation, interrogating any episodic memory for any feature of the event will retrieve the other two features.

    “If the three components occurred in an integrated representation, interrogating any episodic memory for any feature of the event will retrieve the other two features.”
    Quote in the paperNot a substantial claim

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

    Premisecitation

    Research on memory for past events in humans has shown that there is no evidence that events are coded by the times of their occurrence or that memory is temporally organised.

    “Research on memory for the past events in humans has shown that there is no evidence that events are coded by the times of their occurrence or that memory is temporally organised (Friedman 1993, 2004).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Friedman 1993 source

      Not checked in the free run.

    • cites Friedman 2004 source

      Not checked in the free run.

37 of 37

  • The paper relies on this without support.

    Frozen juice remains available/edible after 5 min but melts and becomes unobtainable after 1 h.

    “The frozen juice was still available after 5 min but melted after 1 h and became unobtainable.”
    “After 1 h, the frozen juice melted and became unobtainable, but it was still edible if chosen after 5 min.”

  • The paper relies on this without support.

    The grape is a non-perishable food.

    “less preferred but non-perishable food (grape)”

  • The paper relies on this without support.

    Chimpanzees, bonobos and orangutans represent our closest and most distant great ape relatives, respectively.

    “We tested chimpanzees, bonobos and orangutans because they represent our closest and most distant great ape relatives, respectively.”

  • The paper relies on this without support.

    Frozen juice hidden 1 h earlier had melted and was not edible, while frozen juice hidden 5 min earlier was still edible.

    “the frozen juice hidden in that platform was baited 1 h earlier and, therefore, had melted”
    “the frozen juice was hidden 5 min ago and was, therefore, still edible”

  • The paper relies on this without support.

    Apes prefer frozen juice over grapes when both are available.

    “they should preferentially choose the frozen juice in the table baited last but the grape in the table baited first”

  • The paper relies on this without support.

    The orangutan's significant reversal of choices in the last round of Experiment 1 indicates that her choices were based on how long ago the baiting event took place.

    “We included one of the orangutans because in the last round of Experiment 1 she significantly reversed her choices (χ 2 = 6, p = 0.014; see table 1 for more details).”
6 of 6

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?

  • Studies using the what-where-when paradigm predominantly focus on the content criterion, and there is little evidence for the structure and flexibility criteria in the literature.

    “these predominantly focus on the content criterion, and as a result, there is little evidence for the structure (but see [68,75]) and flexibility (but see [74]) criteria in the literature.”

    From Is episodic-like memory <i>like</i> episodic memory? (2024) · cites this paper as [75]

  • Older dogs and apes show lower performances in an incidental encoding and what-where-when test, respectively, compared with younger conspecifics.

    “Furthermore, older dogs and apes who were otherwise healthy showed lower performances in an incidental encoding and what–where–when test, respectively, compared with younger conspecifics [75,146].”

    From Is episodic-like memory <i>like</i> episodic memory? (2024) · cites this paper as [75]

  • The same binding of multiple event features, permitting discrimination between two similar events, has also been demonstrated in rats and apes.

    “The same binding of multiple event features, permitting the discrimination between two similar events, has also been demonstrated in rats and apes [68,75].”

    From Is episodic-like memory <i>like</i> episodic memory? (2024) · cites this paper as [75]

  • Some studies use non-natural methodological elements to test for episodic-like memory, such as pecking or approaching shapes or coloured panels, or requiring subjects to recall their own or others' previous actions out of an array of behaviours.

    “Some studies, however, use non-natural methodological elements to test for episodic-like memory [75], such as pecking or approaching certain shapes or coloured panels that are presented in front of the subjects [56,78–81], or requiring subjects to recall their own or others’ previous actions out of an array of behaviours [95,96].”

    From Is episodic-like memory <i>like</i> episodic memory? (2024) · cites this paper as [75]

Statistics recomputed

Every reported test result, recomputed from its test statistic and degrees of freedom. A result shows as not adding up only once an independent check has confirmed it.

  • Consistentz = 3.12reported p = .002 · recomputed p = .002

    “z = 3.12, p = .002”

  • Consistentz = 2.55reported p = .011 · recomputed p = .011

    “z = 2.55, p = .011”

  • Consistentz = 1.79reported p = .037 · recomputed p = .073

    “z = 1.79, p = .037”

    The paper states a one-tailed test

3 of 3

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.

  • The 24-hour pre-test was less accurate than the 2-minute pre-test

    Major

    Table 1 shows 100% accuracy at 2 minutes for every subject, but several subjects scored below 100% at 24 hours. The claim of equal accuracy underpins the paper's argument that there was no noticeable forgetting.

  • Experiment 2 percentages for Fifi do not fit six trials

    Minor

    Each Experiment 2 trial included a choice from both platforms, so six trials would yield six choices for each reported platform percentage. Fifi's reported 80% and 20% are not possible proportions of six choices; they correspond to proportions of five.

2 of 2

Cites

Flagged first, then by citations

Research works printed but not linked: 2

  1. Haccou P, Meelis E (1994) Statistical analyses of behavioural data. Oxford University Press, Oxford
  2. Schwartz BL (2005) Do humans primates have episodic memory? In: Terrace HS, Metcalfe J (eds) The missing link in cognition. Oxford University Press, Oxford, pp 225–241

Cited by

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Related

Authors
Martin-Ordas, G., Haun, D., Colmenares, F., & Call, J.
Affiliations
  • Max Planck Institute for Evolutionary Anthropology (DE)
  • Universidad Complutense de Madrid (ES)
ORCID
Venue
Animal Cognition
Publisher
Springer Science and Business Media LLC
Published
2009-09-27
Volume
13
Issue
2
Pages
331-340
ISSN
  • 1435-9448 (ISSN-L)
  • 1435-9456
DOI
10.1007/s10071-009-0282-4
PMC
PMC2822233
OpenAlex
W2165494708
Semantic Scholar
448390e361ed5bf7a1a2721c8b62068b1f5cf1b0
Cited by
244
References
69
Citations by year
2026: 14 · 2025: 9 · 2024: 11 · 2023: 14 · 2022: 12 · 2021: 22 · 2020: 14 · 2019: 35 · 2018: 8 · 2017: 23 · 2016: 6 · 2015: 14 · 2014: 17 · 2013: 10 · 2012: 12
FWCI
15.04
Type
journal article
Language
en
Open access
Licence
Locations
  • Animal Cognition (publishedVersion, cc-by-nc)
  • PubMed Central (publishedVersion, cc-by-nc)
  • PubMed (publishedVersion)
  • Max Planck Institute for Plasma Physics (submittedVersion)
  • Max Planck Digital Library (submittedVersion, other-oa)
  • MPG.PuRe (Max Planck Society) (submittedVersion, other-oa)
  • MPG.PuRe (Max Planck Society) (submittedVersion)
Topics
  • Social Sciences › Psychology › Social Psychology › Primate Behavior and Ecology
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Memory Processes and Influences
  • Social Sciences › Psychology › Developmental and Educational Psychology › Child and Animal Learning Development
Keywords
episodic-like memory, great apes, chimpanzees, bonobos, orangutans, temporal memory, temporal coding, age differences
MeSH terms
Animals, Pan troglodytes, Feeding Behavior, Female, Food Preferences, Male, Pongo pygmaeus, Mental Recall, Time Factors, Time Perception, Hominidae, Pan paniscus

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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