ANIMAL BEHAVIOUR, 2004, 67, 165e170doi:10.1016/j.anbehav.2003.04.005

White-faced capuchin monkeys show triadic

awareness in their choice of allies

SUSAN PERRY*†‡, H. CLARK BARRETT†‡ & JOSEPH H. MANSON*†‡

*Max Planck Institute for Evolutionary Anthropology, Leipzig

yDepartment of Anthropology, University of California, Los Angeles

zCenter for Behavior, Evolution and Culture, University of California, Los Angeles

(Received 1 November 2002; initial acceptance 6 January 2003;

final acceptance 27 April 2003; MS. number: 7517)

The social intelligence hypothesis, which holds that social challenges have selected for increasedintelligence and social skills, has been supported by evidence that, in catarrhine primates, individualsknow about the characteristics of groupmates’ social relationships. Evidence for such ‘triadic awareness’has not been sought for platyrrhine primates, although two platyrrhine genera, capuchins, Cebus, andsquirrel monkeys, Saimiri, are among the most highly encephalized primates. We examined patterns ofcoalitionary recruitment in wild white-faced capuchins, C. capucinus. Analyses have shown that moredominant individuals are more likely to join aggressive coalitions than low-rankers, and that individualspreferentially support those with whom they have stronger affiliative relationships. Data from 110 fights,analysed using simulation techniques that produced distributions of results expected under nullhypotheses, revealed that contestants preferentially solicited prospective coalition partners that (1) weredominant to their opponents, and (2) had better social relationships (higher ratios of affiliative/cooperative interactions to agonistic interactions) with themselves than with their opponents. Furtheranalyses showed that soliciting dominant partners could be explained by either of two simpler rules,‘Solicit an ally that outranks yourself’ or ‘Solicit the highest-ranking available individual’. However,soliciting partners with better social relationships appears to indicate triadic awareness, because subjectsdid not preferentially solicit the nearby individual with whom they shared the highest-quality socialrelationship. Effects of relative relationship quality on coalition solicitation decisions were independent ofeffects of dominance rank.

� 2004 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

According to the social intelligence hypothesis (Jolly1966; Humphrey 1976; Byrne & Whiten 1988; Cheney &Seyfarth 1990), the challenges of navigating a complexpolitical landscape have been a major selective force in theshaping of the primate mind. Primates living in complexsocial groups need to understand the nature of the socialrelationships between other group members, so that theycan use such information to their advantage whenselecting social partners for particular purposes. Sincethe social intelligence hypothesis was originally proposed,a database has slowly accumulated supporting the ideathat Old World monkeys and apes understand the natureof other individuals’ social relationships (reviewed in

Correspondence: S. Perry, Max Planck Institute for EvolutionaryAnthropology, Deutscher Platz 6, 04103 Leipzig, Germany (email:perry@eva.mpg.de). H. C. Barrett is at the Department of Anthropology,UCLA, 405 Hilgard Avenue, Los Angeles, CA 90095-1553, U.S.A.

1650003e3472/03/$30.00/0 � 2004 The Association

Tomasello & Call 1997). However, New World primateshave been largely overlooked in this endeavour. Becausecapuchin monkeys, Cebus, along with squirrel monkeys,Saimiri, have the largest encephalization quotients of anynonhuman primate (Stephan et al. 1988), they representa particularly valuable source of data in the quest tounderstand the selective factors affecting the evolution ofintelligence.Experimental studies of Old World monkeys provide the

most convincing source of evidence of ‘triadic awareness’(i.e. animal A understands some aspect of the quality ofrelationship between animals B and C) in primates. Forexample, Dasser (1988a, b) showed that juvenile long-tailed macaques, Macaca fascicularis, understand the kin-ship structure of their groups, successfully matchingmothereoffspring and sibling pairs in a picture-sortingtask. Cheney & Seyfarth (1990) performed playbackexperiments on vervet monkeys, Chlorocebus aethiops, in

for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

ANIMAL BEHAVIOUR, 67, 1166

which females indicated knowledge of mothereoffspringrelationships by looking towards the mother of a juvenilewhose scream had just been played to them. Another setof experiments on baboons, Papio cynocephalus ursinus(Cheney et al. 1995), indicated that females understandone another’s rank relationships, because they respondedwith more interest to a playback of a dominant expressingsubmission to a subordinate than vice versa. Pairs ofunrelated female baboons also reacted differently tosimulated conflicts as a function of the apparent contest-ants’ kin relationship to themselves, in a manner suggest-ing triadic awareness of kinship (Cheney & Seyfarth1999). Bachmann & Kummer’s (1980) experiments withhamadryas baboons, Papio cynocephalus hamadryas, in-dicate that adult males assess the quality of the relation-ships of maleefemale pairs and use that informationwhen deciding whether to challenge the male for pos-session of the female.In addition to the experimental evidence, there is much

evidence from observational studies suggesting thatmonkeys and apes show triadic awareness (e.g. Cheney& Seyfarth 1990; Tomasello & Call 1997). For example, thepatterning of reconciliation and redirected aggression invervets (Cheney & Seyfarth 1989), stumptailed macaques,M. arctoides (Call et al. 2002), and pigtailed macaques,M. nemestrina (Judge 1991), suggests that these monkeysunderstand kinship relationships. Observed patterns ofcoalition formation (e.g. Silk 1992; Perry 2003) alsosuggest a sophisticated understanding of rank, kinshipand affiliative relationships. However, observational stud-ies are usually limited in their capacity to rule outalternative cognitive interpretations.Silk (1999) showed that male bonnet macaques,

M. radiata, understand others’ rank relationships, by de-monstrating via simulation techniques that they solicitmales ranking higher than their opponents more oftenthan is expected by chance, ruling out the possibility thatthey use a simpler rule of thumb (e.g. ‘Solicit a male thatoutranks yourself’ or ‘Always solicit the most dominantindividual’). We extended this general approach to wildwhite-faced capuchin monkeys, Cebus capucinus, to testwhether they understand the rank relationships andrelationship quality of other group members and use thisknowledge in their solicitation of allies.Research on the coalitionary aggression of white-faced

capuchins (Perry 1996, 1997, 1998a, b, 2003) has revealedthe following three basic rules regarding their decisionsof which opponent to support in an ongoing fight: (1)support females versus males (85% of 95 fights); (2)support the dominant opponent (57% of 202 fights; thisrule is in conflict with rule 1, because females aresubordinate to males, but in fights between same-sexedopponents, dominant females were supported 98% of thetime (N ¼ 40 fights) and dominant males at least 89% ofthe time; N ¼ 36 fights in which rank was definitelyknown); (3) support the monkey with whom the decision-maker has the better relationship, as measured by theproportion of interactions that were affiliative (85% of 170fights). Given that high-rankers are far more likely thanlow-rankers to choose to become involved in fights (Perry1996, 1997), and are probably more effective allies, we

predicted that individuals involved in ongoing dyadicdisputes would be more likely to solicit support fromothers that are dominant to their opponent. Given thetendency of white-faced capuchins to support the oppo-nent with whom they have the stronger affiliativerelationship, we also predicted that individuals involvedin ongoing fights would preferentially solicit support fromothers that have a stronger affiliative relationship withthemselves than with their opponent.

METHODS

Subjects

Data were collected as part of an observational study ofcapuchin social relationships at Lomas Barbudal BiologicalReserve and surrounding private and public lands inGuanacaste, Costa Rica (Perry 1995, 1996, 1997, 1998a, b).The data used in this study are from a single study group,Abby’s group, obtained from May 1991 to May 1993. Thegroup consisted of 21 individuals: four adult males (one ofwhom immigrated in November 1992 at the time of a rankreversal involving the alpha male; Perry 1998a), six adultfemales and 11 immatures. Adults and large juveniles wererecognizable by natural differences in features such asscars, colouring and facial shape. Small juveniles weremarked with Clairol Born Blonde hair dye, squirted attheir backs from 1e2 m with a 100-cc syringe from whichwe had removed the needle. This procedure neverproduced noticeable distress in the subjects.

The study was approved by the University of MichiganCommittee on Use and Care of Animals. Marking wasapproved by the Servicio de Parques Nacionales de CostaRica and the regional division (Area de ConservacionTempisque).

Procedure

Data were collected in the form of 10-min focalfollows, during which continuous data were recordedon all social behaviours (Perry 1995, 1996, 1997, 1998b).The fights used in this study were drawn from a sampleof 1405 h of focal data. Every 2.5 min, we conducteda scan sample in which we recorded the identities of allindividuals in view of the focal animal as well as theirprecise proximities to the focal animal. These scan datawere used to determine the relevant audience (i.e. pool ofpotential recruitees) for each fight. Any monkey withinview of the focal animal was considered to be a potentialrecruitee. The precise distance depended upon visibility,but the radius of animals considered to be recruitable wasabout 10e20 m. Two observers participated in datacollection; one watched the focal individual, narratingthe action into a microcassette recorder, while the othercalled out the identities of other individuals who wereapproaching or directing vocalizations and gesturestowards the focal animal or its opponents. Wheneverthe two observers disagreed on the identities of partic-ipants or their activities, these fights were dropped fromthe sample.

PERRY ET AL.: TRIADIC AWARENESS IN CAPUCHINS 167

Data Analysis

Two criteria had to be met for the fights to be includedin the sample for analysis. First, the fight had to be seriousenough to warrant an agonistic response from the targetof the initial aggressive act. We used this criterion becausewhite-faced capuchins sometimes form coalitions againstdistant individuals that are not attending to them (andmay even be sleeping), possibly as a form of communi-cation between the coalition partners, and such inter-actions are not triadic because they do not necessarilydepend on the ‘victim’s’ characteristics. Second, therecruitment signals used had to be obviously directed ata particular individual, such as the headflag gesture (headis jerked quickly towards the solicitee and then backtowards the opponent), embrace, cheek-to-cheek posture(two monkeys stand side-by-side with their cheekstouching while jointly threatening a common opponent)and overlord posture (monkeys align themselves on top ofone another, with heads stacked like a totem pole andhands clasping the partner’s chest, and jointly threatenthe common opponent).Ranks were determined by examining submissive

responses (avoidance and cowering) within dyadic inter-actions (i.e. situations in which potential allies were notclose at hand to bias the results; see also Perry 1996,1998b). Females formed a clear linear hierarchy, in whichall females were subordinate to all males. There were sixdyads for which we were unable unequivocally to de-termine rank: one of these was a pair of subordinate adultmales, and the others were pairs of juveniles who had notyet attained their adult ranks. For the purpose of analysis,we assigned tied ranks to the members of these dyads.There was one rank reversal involving a pair of malesduring the study. For these males, we used the rank thatwas current for the time of each fight included in theanalysis.The index of relationship quality was calculated in the

following way. For each of the 210 dyads, we extractedtheir entire history of interactions. For each 10-min focalfollow, any interactions for the dyad were coded as beingneutral, affiliative (e.g. grooming, resting in contact) and/or cooperative (e.g. supporting one another in fights), oragonistic (aggressive or submissive). Then we divided thenumber of samples including affiliative/cooperative be-haviours by the sum of the numbers of samples withaffiliative/cooperative interactions and samples with ago-nistic behaviours. This measure has several advantagesover more traditionally used relationship quality mea-sures, such as grooming rates, aggression rates or timespent in proximity, because it incorporates many aspectsof the relationship into a single measure. Because thestudy group’s adult males’ social relationships changeddramatically following a male rank reversal (Perry 1998a),we calculated separate relationship quality indices beforeand after rank reversal for every dyad in the study group,and used for analyses whichever index was current at thetime of the fight.Statistical results were obtained by conducting Monte

Carlo simulations (H. C. Barrett, unpublished softwareprogram in Visual Basic) that used data on observed

audience composition for each fight to determine thedistribution of decision outcomes under the null modelthat our subjects solicited coalition partners at random. Inthese simulations, the program randomly selected a mon-key from the audience (or from some designated subsetof the audience) for each fight in the database. Eachsimulation was run 20000 times to produce an expecteddistribution of proportions of ‘correct’ decisions accordingto the criterion in question, that is, decisions in which aparticular hypothesized decision rule was followed, if thesubjects were soliciting prospective coalition partners atrandom. To determine statistical significance for eachprediction, we then noted where, within each simulation-generated distribution, the observed proportion of correctdecisions fell.

RESULTS

In describing the results, we use the following codes: D isthe decision-maker (the individual deciding whom torecruit), O is the decision-maker’s opponent, and S is thepotential ally whose support is solicited by the decision-maker.

Characteristics of the Sample

One hundred and ten conflicts met the criteria de-scribed above for inclusion in the sample (XGSD audiencesize ¼ 3:42G1:83; mean proportion of audience membersthat outranked O ¼ 0:52G0:35; mean proportion ofaudience members that had a higher relationship qualityindex with D than with O ¼ 0:59G0:38; mean proportionof audience members that both outranked O and hada higher relationship quality index with D than withO ¼ 0:30G0:33).

Triadic Awareness of Rank Relationships

Decision-makers preferentially solicited support from Ssthat outranked O (71.8% of cases). The observed pro-portion of correct decisions fell above the highest pro-portion generated by the simulation in 20 000 runs(P!0:00005; Fig. 1a). However, Ds showed an evenstronger preference for soliciting Ss that outrankedthemselves (78.2% of cases, P!0:00005). This result raisedthe possibility that subjects were following a cognitivelysimpler rule (‘Solicit a prospective ally that outranksyourself’) rather than a cognitive rule requiring triadicawareness. To resolve this ambiguity, we replicated ananalysis carried out by Silk (1999) that compared observeddecisions to those predicted by a null model in which Dchooses randomly only from a pool of potential allies thatare dominant to D. In other words, we generated a nullmodel of outcomes that would be obtained if D followedthe simple rule, ‘Solicit a prospective ally that outranksyourself’, to see whether this rule alone would havegenerated our observed distribution of fight outcomes bychance. For each fight in which O outranked D (N ¼ 48),the simulation selected an audience member at random. Ifthis audience member did not outrank D, the simulation

ANIMAL BEHAVIOUR, 67, 1168

chose another audience member at random. Uponselecting an audience member that did outrank D, thesimulation scored a correct decision if this audiencemember outranked both D and O; otherwise it scored anincorrect decision. The observed percentage of correctdecisions (58.3% of the cases in which O outranked D)was not significantly greater than expected by chance(P ¼ 0:19), suggesting that the simple rule ‘Solicit a pro-spective ally that outranks yourself’ alone could havegenerated our observed proportion of cases in which Soutranked both D and O.We also considered whether our subjects were simply

soliciting support from the highest-ranking audiencemember, perhaps distinguishing this individual usinga cue such as piloerection or posture rather than triadicawareness of dominance relationships. First, we replicatedSilk’s (1999) analysis in which she examined whether

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Relationship quality index (%)

39 43 46 50 54 57 61 65 68 72

49 51 53 55 56 58 60 62 64 65 67 69

38 42 46 49 53 57 61 65 68

(a)

(b)

(c)

Figure 1. Monte Carlo simulations of decision-makers’ (D) choicesof whom to solicit (S) against an opponent (O). In all simulations, an

ally was chosen at random from the audience members for each of

110 observed fights, and a correct decision was scored when the

chosen ally met the specified criterion. The program repeated thisprocedure 20 000 times to generate a distribution of proportions of

correct decisions expected if D were choosing S at random from the

audience members. Observed percentages of correct decisions are

indicated by arrows. (a) A correct decision was scored when S wasdominant to O. (b) A correct decision was scored when S had

a higher relationship quality index with D than with O. (c) For fights

in which the observed S outranked O (N ¼ 79), a correct decisionwas scored when S had a higher relationship quality index with D

than with O.

there was a correlation between S’s dominance rank andthe rank of the higher-ranked of the two contestants Dand O. Silk reasoned that if D consistently solicited thehighest-ranked audience member, regardless of O’s rank,then no correlation between these variables would beexpected. On the other hand, if Ds solicited prospectiveallies based on whether they outranked Os, then Ds facedwith lower-ranking Os would have a larger number ofpotential Ss to choose from compared with Ds faced withhigher-ranking Os. Thus, on average, the Ss selected by Dsfacing lower-ranking Os would rank lower than the Ssselected byDs facing higher-rankingOs. Using each fight asa separate data point,we obtained a trend towards a positivecorrelation between S’s dominance rank and that of thehigher-ranked of the two contestants D and O (Spearmanrank correlation rS: rS ¼ 0:17, N ¼ 110, P ¼ 0:07), but theresult vanished when we used, as data points, the meandominance rank of S across all cases in which the highestranking of D and O held a particular ordinal rank(Spearman rank correlation: rS ¼ 0:40, N ¼ 14, P ¼ 0:16).Second, we ran a simulation that revealed that our subjectspreferentially chose the highest-ranking audience member(65.5% of cases; P!0:00005).

Triadic Awareness of Quality ofSocial Relationships

Decision-makers preferentially solicited support from Ssthat had higher relationship quality indices with them-selves than with O (67.3% of cases; P ¼ 0:02; Fig. 1b). Thisresult could have been produced by a decision rule thatdoes not involve triadic awareness: ‘Solicit the audiencemember with whom you have the highest relationshipquality index’. However, our simulation revealed that Dsdid not follow this rule at a frequency greater thanexpected by chance (41.8% of cases; P ¼ 0:61).

Effects of Rank and Relationship Quality

Our subjects used both dominance rank and relativerelationship quality as criteria for choosing whom tosolicit. Among those audience members that had higherrelationship quality indices with D than with O, Dspreferentially solicited the highest-ranking audiencemember (26.4% of cases; P ¼ 0:00005).

However, dominance rank and relative relationshipquality had independent effects on solicitation decisions.Considering only the 79 cases in which S outranked O, Dspreferentially solicited Ss that had higher relationshipquality indices with themselves than with O (60.8% of 79cases; P ¼ 0:035; Fig. 1c). Considering only the 74 cases inwhich S had a higher relationship quality index with Dthan with O, Ds preferentially solicited Ss that outrankedO (64.9% of 74 cases; P!0:00005).

Finally, we tested whether our subjects might have usedthe following rule, which does not require triadicawareness: from the audience members who rank higherthan D, solicit the individual having the highest relation-ship quality index with D. The monkeys did not solicit

PERRY ET AL.: TRIADIC AWARENESS IN CAPUCHINS 169

help from such individuals at a rate higher than expectedby chance (27.8% of 79 cases; P ¼ 0:30).

DISCUSSION

These results suggest that white-faced capuchin monkeysconsider both relationship quality and dominance rankwhen deciding whom to recruit as allies in coalitionaryaggression. However, although our subjects appeared toshow triadic awareness by using relative criteria ofrelationship quality, they may use dominance rank onlyas an absolute criterion, preferring the highest-rankingavailable prospective ally regardless of their opponent’srank. Furthermore, these results should be interpretedwith some caution because they are based on observationsof a single social group.

Dominance Rank and Solicitation Decisions

Our analyses indicate that our subjects preferentiallysolicited high-ranking coalition partners. However, it isunclear whether they used a decision rule incorporatingtriadic awareness (‘Solicit an ally that outranks youropponent’), a simpler decision rule using only theirknowledge of their own dominance relationships (‘Solicitan ally that outranks yourself’), or the rule ‘Solicit thehighest-ranking available conspecific’. Solicited individu-als outranked decision-makers’ opponents, but whenopponents outranked decision-makers, solicited individu-als were no more likely than expected by chance to out-rank both decision-makers and their opponents. Theseresults suggest that white-faced capuchins follow thesimpler rule, ‘Solicit an ally that outranks yourself’, whenchoosing coalition partners. The highest-ranking audiencemember was solicited much more frequently thanexpected by chance. When we sought to clarify whetherour subjects used the ‘Solicit the highest-ranking availableconspecific’ rule by calculating the correlation betweenthe solicited individual’s rank and the higher of the twocontestants’ ranks, we obtained equivocal results. In sum-mary, our results do not permit us to conclude whetherwhite-faced capuchins have triadic awareness of domi-nance relationships. They may use a combination of deci-sion rules concerning dominance rank when choosingcoalition partners, and some of these rules may incor-porate triadic awareness. It is also possible that usingabsolute dominance rank as a recruitment criterion issufficient to generate efficacious recruitment decisions;perhaps the highest-ranking ally is almost always the mostwilling and effective ally, regardless of the relative ranks ofdecision-maker and opponent. In this case, testingwhether our subjects followed the rule ‘Solicit an ally thatoutranks your opponent’ would be an inappropriate assayof triadic awareness in this species.

Relationship Quality and Solicitation Decisions

Our results regarding the role of relationship quality inour subjects’ coalitionary solicitation decisions were more

straightforward. Using an index of proportion of allinteractions that were affiliative or cooperative, we foundthat white-faced capuchins preferentially solicited alliesthat had better relationships with themselves than withtheir opponents. This result was not attributable to Dssoliciting Ss that had the highest relationship qualityindex with themselves among audience members. There-fore, we infer that Ds compared their own relationshipwith the prospective ally to their opponent’s relationshipwith that individual, and used this comparison whendeciding whom to solicit. Thus, they showed triadicawareness of other group members’ social relationships.An alternative interpretation is that, rather than

showing triadic awareness, the decision-makers weresoliciting monkeys who had better relationships withthemselves than with their opponents because of cues thatare given by the audience members during or just beforethe fights. Individuals with better relationships with Dmay bemore likely to signal their willingness to aid D thanindividuals with worse relationships with D. Perhapsdecision-makers use these signals, rather than theirknowledge of audience members’ social relationships, todecide whom to solicit. To address this hypothesis, werestricted analysis to cases in which S did not aid D. Inthese cases, it is unlikely that S signalled its intent tointervene in the conflict in support of D. Nevertheless, wefound for this subsample, as in the entire sample of fights,that D was significantly more likely than expected bychance to solicit Ss that had higher relationship qualityindices with D than with O (62.9% of 35 cases; P ¼ 0:034).It is important to distinguish between the effects of

dominance rank and the effects of relationship quality oncoalition solicitation decisions, because they could havebeen confounded. For example, low-ranking white-facedcapuchins might have generally lower-quality socialrelationships with other group members than high-rankers, or rank distance might influence the quality ofsocial relationships. Our subjects followed both decisionrules simultaneously (i.e. ‘Solicit the highest-rankingpotential ally from those that have a higher relationshipquality index with you than with your opponent’) morefrequently than expected by chance. However, by ana-lysing subsamples of the observed fights, we found thatdominance rank and relationship quality had indepen-dent effects on coalition solicitation decisions. Whenconsidering only those cases in which subjects solicitedindividuals that outranked their opponents, we foundthat they preferentially solicited individuals that hadbetter relationships with themselves than with theiropponents (but did not preferentially solicit the individ-ual from that subset having the highest relationshipquality index with themselves). Similarly, in the sub-sample of cases in which subjects preferentially solicitedindividuals that had better relationships with themselvesthan with their opponents, they preferentially solicitedindividuals that outranked their opponents.

Conclusions

These results, like those of Silk (1999), show that purelyobservational data, analysed using simulation techniques,

ANIMAL BEHAVIOUR, 67, 1170

can shed light on triadic awareness in nonhuman animals,and that recruitment of coalition partners is a behaviouraldomain that can reveal the extent of monkeys’ knowledgeabout others’ social relationships. Furthermore, theseresults represent the first within-species test of any portionof the social intelligence hypothesis in a platyrrhineprimate. Although comparative treatments of this hy-pothesis (Barton and Dunbar 1997) have begun to includeNew World monkey taxa as data points, the extent towhich platyrrhines actually show sophisticated socialcognition is still largely unexplored.

Acknowledgments

We thank J. Gros-Louis and L. Sirot for their invaluableassistance in data collection. S.P. thanks the followingfunding agencies: L.S.B. Leakey Foundation (two grants),National Science Foundation (graduate fellowship to S.P.,and grants to B. Smuts and J. Mitani), National Geo-graphic Society, Sigma Xi, Rackham Graduate School(Research Partnership grant with B. Smuts, predoctoralfellowship and dissertation grant), the Evolution andHuman Behavior Program and the University of MichiganAlumnae Society. We thank the Costa Rican Servicio deParques Nacionales and the ACT for permission to work inLomas Barbudal Biological Reserve, and the community ofSan Ramon de Bagaces and Rancho Jojoba for permissionto work on private lands near the reserve. L. Sirot, M.Tomaszycki, M. Landys and S. Newman assisted in datatranscription and data entry into the computer. G. Frankieand J. Frankie, the Rosales family and M. Cedillosprovided logistical assistance in the field. J. Silk, D. Stahl,J. Gros-Louis, R. Seyfarth, R. Kurzban and two anonym-ous referees provided helpful comments regarding dataanalysis or comments on the manuscript. The MaxPlanck Institute for Evolutionary Anthropology fundedS.P. and J.M. during the writing of this paper, and theCulture and Cognition Working Group at MPI-EVANprovided comments.

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