Brandom, following Kant and Wittgenstein, distinguishes between acting according to a rule and acting according to a conception of a rule. In the first case, there are regularities that describe one’s behavior, but one need not be aware of them. In the second case, one’s behavior may be described by a rule precisely because one aspires to adhere to it. In the latter case, an agent’s conception of the rule constrains her behavior, constituting a reason for her to act in one way and not another. This is the idea of a norm. A norm is a rule that agents feel, in some sense, obliged to follow.
Norms are philosophically interesting because they make room for a distinction between how one acts and how one thinks one should act. This distinction is central to many forms of behavior, including ethical behavior, and the formation of group identities. While norms can be both social and non-social, here we discuss only norms whose function is to constrain our interactions with others.
Social norms prohibit or encourage the performance of certain behaviors within a community. They guide both how we present ourselves to others, and how we assess others’ actions. Awareness of social norms emerges early in ontogeny (Schmidt, Rakoczy and Tomasello 2011) and seems to be a universal feature of human societies. The emergence of normatively governed social behavior was likely therefore a crucial stage in the development of distinctively human forms of living, and one that contributed to our development in many ways. For example, Boyd and Richerson (2005) have argued that social norms stabilize within-group homogeneity and drive between-group differentiation (Boyd and Richerson 2005). Such behaviors likely played an important role in reinforcing group bonds, enabling norm-following communities of early humans to outcompete neighboring groups in competitive ecological niches. Zawidzki (2013) has argued that the emergence of social norms played an important role in the development of human social cognition by making human minds more easily interpretable. Finally, Kitcher (2011), Korsgaard (2010), and Tomasello (2016) – among others – have argued that the emergence of norms was necessary for the emergence of morality.
Given the importance of normative behavior to human forms of living, it is natural to ask whether our closest living relatives understand and follow norms. While some have argued that there is evidence of normative behavior in chimpanzees and monkeys (e.g., Andrews 2009), we argue against this conclusion. We start by considering a recent (and representative) example of a group-specific, socially transmitted behavior pattern in chimpanzees and argue that necessary preconditions for attributing normativity are not met here. We then spell out some alternative, non-normative explanations of group-specific behaviors in chimpanzees, and discuss which kinds of evidence would be needed to support claims of normativity. We finish by setting out recent evidence on majority influences in chimpanzees (‘conformity’), and considering potential cases of morally normative behavior in chimpanzees.
One common feature of social norms – particularly where they relate to the establishment of group identities – is that they are arbitrary. This means the members of a group conform to the normative behavior only because their peers do.1 Such behaviors likely vary between communities – and may be consciously varied by the members of rival communities, to differentiate themselves from one another. The following characterization of social norms borrows from Bicchieri (2006):
A behavior R is a norm in a community P if and only if:
Here, clause (1) captures the idea that normative behavior requires acting according to a conception of a rule, and not merely in accordance with it. Clause (2) captures the idea that members of P expect others to conform; and clause (3) specifies the conditions under which they will conform. Where R is arbitrary, commitment to it will likely be contingent upon commitment by others. Nonetheless, the members of P may still see fit to punish non-conformity. Where members desire to preserve group norms, transgressions may give rise to ‘moral’ emotions – from indignation and upset to anger; and to even more robust forms of norm enforcement, like gossip, censure, ostracism, or dishonor.
It is now well established that some behaviors vary arbitrarily between neighboring groups of chimpanzees (e.g., Whiten et al., 1999). The following discussion focuses on the community-specific tool preferences of chimpanzees in the Taï National Park (Luncz, Mundry and Boesch 2012). Since the behavior can be explained neither by genetic variation nor ecological differences between populations, it must be socially learned (see Moore 2013b; van Leeuwen et al. 2015 for discussion). Since variance between neighboring groups might also be interpreted as statements of group identity – “This is how we do things around here!” – this behavior has been interpreted as potentially normative (van Schaik 2012).
Luncz, Munddry and Boesch (2012) studied the coula edulis nut-cracking behavior of three neighboring chimpanzee groups in the Taï forest. Coula nuts dry out and become easier to crack as the nut season progresses. If apes use the most efficient tools, then all communities should use stone hammers (which are harder to find, but better for opening fresh nuts) early in the season, and wooden hammers (which are more common and good enough to open dried nuts) later. Luncz and colleagues found that while this happened in two groups, the third (‘South’) group continued to use mostly stone hammers. Additionally, there were between-group differences in the size of wooden hammers selected. Since the three communities live in the same forest, and sexually mature females migrate between the groups, both ecological and genetic explanations of these differences can be ruled out.
Further research (Luncz and Boesch 2014) showed that despite the migration of adult females, group practices remained constant over 25 years; and analysis of one migrating female’s behavior showed that she adopted the practices of her new group. A study of the archaeological record (Luncz, Wittig and Boesch 2015) confirmed that chimpanzees migrating from a population south of the South group cracked nuts with wooden tools prior to migrating, but adopted the new group’s preference for stone tools when they relocated. Since life for new females in a group can be difficult – it takes a year for them to be accepted by other females in the group – Luncz and colleagues suggest that females may adopt the practices of their new group as a way of smoothing their integration.
These socially learned and group-specific patterns of behavior are good candidates for social norms. We can assess whether they are genuinely normative by asking whether or not they satisfy the criteria for social norms adopted above.
The nut-cracking behavior of the South group at Taï can be described by the rule When possible, always use stone hammers. Furthermore, the finding that migrating females adopt the practice of their new group is evidence that they act in accordance with this rule only because others do too. However, there is no reason to suppose that chimpanzees are aware of the rules that describe their behavior, nor to think that they expect others to conform to them. Thus, there is no reason to think that Taï chimpanzees satisfy clauses (1) and (2) of the criteria identified above. Moreover, while it is possible that failure to conform to the group rule would exacerbate the bullying of migrating females – and so constitute a form of sanction for non-conformity, fulfilling criterion (3)(iii) – there is currently no evidence of the sanctioning behavior that would support this conclusion.
In fact, the social modulation of tool preferences does not entail they are normative. Different preferences between groups can all be explained by low-level phenomena, like the relative salience of alternative tool types. Consequently, individuals in the group need not even be aware of the rules that describe their behavior – let alone aspire to conform to them. So there is currently no evidence that different between-group tool preferences are brought about by social norms.
The behavior of the North and East chimpanzee groups at Taï observed by Luncz and colleagues can be explained on the assumption that chimpanzees adopt the most rational techniques. Some individuals in those groups may have discovered that, as the season progresses, they can use the more readily available wooden tools. In turn, this would make these tools more salient to their peers, who might then start to use them more often. This explanation does not require that the apes are even aware of the changes in their search behavior. Since chimpanzees are known to copy the behavior of influential group members (Biro et al. 2003; Horner et al. 2010; Boesch 2012; Kendal et al. 2015), practices adopted by influential individuals might spread rapidly within groups.
Both the behavior of the South group, and the different sizes of wooden hammer used by all groups, can be similarly explained. In the South group, perhaps no ape ever learned that tools can be changed during the nut-cracking season. Alternatively, it may be that one or two high-ranking individuals preferred to use stone tools regardless of the time of year – perhaps because they had grown up surrounded only by others who used stone tools. If the preferences of these individuals served to advertise the use of stone tools to others in the group, then those searching for hammers may have been disposed to search for stone tools through low-level processes of association. Such a pattern could have spread in the group at one point and then stabilized itself over time. Although using stone tools instead of sticks may sometimes be less efficient than using wooden tools, the differences need not be so great as to radically disadvantage groups who prefer stones.
In the above cases, tool-choice preferences might be similar to regional accents. While individuals can deliberately adopt a local accent to help them fit into a group, and while group accents are sometimes normative, individuals can also acquire accents without being aware of doing so. Subconscious copying causes within-group similarity and between-group differences, but these differences need not indicate the presence of norms.2
Many studies on social influences on human behavior – including the famous Asch conformity experiments (1951) – show that we change our behavior to fit in with the crowd. Although the findings described above do not show that chimpanzees change their behavior for normative or affiliative reasons, experimental paradigms have been used to investigate this possibility.
Some studies (e. g. Whiten, Horner and de Waal 2005; Hopper et al. 2011) have tested for chimpanzee conformity by watching the spread of behaviors within groups. Whiten, Horner and de Waal (2005) trained two high-ranking chimpanzees from different groups with different but equally efficient techniques to extract food from a specially designed apparatus.3 These individuals were then used to demonstrate the same technique to members of their respective groups. Observing apes learned the technique that they had seen demonstrated, so that different behavioral traditions emerged between the groups.
Whiten and colleagues (Whiten, Horner and de Waal 2005) interpret this data as reflecting conformist tendencies in chimpanzees, which they conceptualize as “adoption of the group’s norm despite being able to use both methods” (p. 738). However, their finding is consistent with the possibility that apes just reproduce salient behaviors more often than less-salient alternatives (where salience is determined by prior experience). A stronger test would be needed to establish that the apes were copying for affiliative reasons, or because the performed behavior was a social norm.
To investigate whether chimpanzees copy for affiliative reasons, van Leeuwen and colleagues tested whether they abandon individually learned information in favor of a majority strategy. They found that chimpanzees do not change a first-learned strategy to conform to a majority, although they will do so to gain higher rewards (van Leeuwen et al. 2013; see also Hrubesch, Preuschoft and van Schaik 2009; and van Leeuwen and Haun 2013). This suggests that chimpanzees are not motivated to “do what the others do” merely to fit in (Leeuwen and Haun 2013).
In humans, individuals reduce social stress by imitating those around them – for instance, when they face exclusion or ostracism (Williams, Cheung and Choi 2000; Lakin, Chartrand and Arkin 2008). While such affiliative conformity has also been found in five-year-old children (Over and Carpenter 2009), there is no direct evidence of it in apes.4 Nonetheless, there are documented cases of idiosyncratic and possibly affiliative behaviors appearing in chimpanzee communities. For example, van Leeuwen and colleagues describe a case in which chimpanzees at Chimfunshi copied a high-ranking female’s behavior of sticking a piece of grass in her ear (van Leeuwen, Cronin and Haun 2014); and Hobaiter and Byrne describe chimpanzees at Budongo as copying the unusual movements of a physically disabled peer (Hobaiter and Byrne 2010). However, non-affiliative explanations of these behaviors cannot be ruled out. It may be, for example, that chimpanzees who first saw and then tried the grass-in-ear behavior found it pleasurable, and so repeated it; or simply that they copied a salient behavior.
Three possible behaviors would provide better evidence of affiliative or normative copying. First, instances of costly affiliation, in which adopting a prevalent behavioral variant proved disadvantageous for the conformist, would support the claim that copying behavior is affiliative. Second, if apes copied conspecifics’ behavior significantly more frequently when faced with ostracism and social stress, as children do (Over and Carpenter 2009), the case for affiliative conformity would also be strengthened. Third, one could look at whether chimpanzees copy target behavior more often when candidates for affiliation are present than when observed individuals are alone. For example, if immigrant chimpanzees at Taï reverted to older tool-use patterns when alone, then this would suggest an affiliative function when matching occurred. While this evidence could be collected, there are grounds to doubt that it will be forthcoming: existing evidence seems to suggest that chimpanzees are insensitive to others’ evaluations of them, since they do not attempt to manage their reputation around peers (Engelmann, Herrmann and Tomasello 2012).
Even if affiliative conformist tendencies were found in chimpanzees, these would not constitute evidence of fully normative behaviors. In human communities, not only do individuals prefer to conform, they also uphold the principles of their group – for example, by punishing those who do not conform. In humans, third-party enforcement of arbitrary conventional norms emerges in children as young as three years (Schmidt, Rakoczy and Tomasello 2012). Humans are also willing to suffer costs in order to sanction norm violations, even if they themselves were not harmed by the violation (Fehr and Fischbacher 2004). Currently, there is no evidence that chimpanzees enforce social norms. While they punish those who harm them directly (Jensen, Call and Tomasello 2007), this is consistent with them punishing out of revenge, and not because they think group norms should be upheld. They do not seem to engage in ‘third-party punishment’. For example, Riedl and colleagues (2012) found that chimpanzees would not retaliate against a conspecific when a third-party’s food was stolen.
The Bicchieri-influenced account of normativity adopted here is both cognitively and motivationally demanding. If behavioral evidence suggested that chimpanzees do conform to social norms, issues of the cognition required for normativity may need to be reconsidered. However, in the absence of behavioral evidence of normativity, these questions can be deferred.
Andrews (2009, 2012) has defended a simpler conception of norms, on the basis of which she is happy to grant understanding of such norms to several nonhuman species. On Andrews’s account, norms are taken to be just familiar patterns of behavior. Norm violations occur when individuals act in ways that are an exception to a regularly performed behavior. She argues that such norm violations are philosophically interesting because they lead us to search for deeper explanations of an agent’s behavior. They might therefore play a foundational role in our reason-giving practices.
Andrews may be right about the role of violations in the development of folk psychology. However, the types of norms that she is seeking to characterize are not the same as those described by Brandom and Bicchieri. On one common use of the word, a norm is what is normal – that is, a statistical regularity, deviations from which might be easily detected by many different kinds of species and systems. In a second sense that we have described here, a norm is what an individual or a society deems acceptable or appropriate. These meanings are importantly different, because construing an agent’s actions as unusual does not imply any understanding that they are inappropriate. Andrews sometimes slides between these different uses of ‘norm’, from making a claim about statistical regularities to claims about what one ought to do. For example, she writes that:
[N]onhuman primates … have the ability to develop variations in their behavioral repertoire that involve creating, following, and violating social norms having to do with trust, harm, and cooperation. These primates appear to have societal norms, and individuals appear to have at least an implicit understanding of the relevant normative rules.
(Andrews 2009: 444)
However, there is currently no good evidence that chimpanzees understand norms in the second sense.
Andrews (2009) illustrates her case with different examples from the ape literature: in particular, when groups of chimpanzees patrol their territory borders, which Andrews interprets as reflecting norms of property; and group hunting with designated hunting roles and meat distribution according to these roles, which she interprets as showing norms of cooperation and fairness. However, the evidence to which she appeals is highly controversial. For example, there is no reliable evidence that chimpanzees do follow coordinated hunting strategies (Bullinger et al. 2011); and properly controlled studies suggest that chimpanzees do not act in light of considerations of fairness (Bräuer, Call and Tomasello 2006). Furthermore, border patrols likely reflect not an understanding of property rights, but an adaptive drive to protect scarce resources.
Unlike conventional norms, which emerge arbitrarily and show a great variety among human cultures, moral norms may be grounded in species-general empathic and prosocial tendencies.5 Chimpanzees may possess moral norms or precursors to them, even if they lack conventional norms. Some (e.g., Rudolf von Rohr et al. 2010, 2012, 2015) argue that a protean form of morality may be present in chimpanzees. Candidates for moral behaviors include reconciliation and consolation behavior (de Waal and van Roosmalen 1979), instrumental helping (Warneken and Tomasello 2006), and the especially gentle treatment of infants (Rudolf von Rohr et al. 2010).
Rudolf von Rohr et al. (2010) argue that evolutionary precursors of moral norms may be present in chimpanzees, as they possess certain preconditions for morality (sophisticated socio-cognitive skills, and some degree of empathy) and show behaviors derived from expectations about how others should be treated. The same authors (2012) report observations of ‘policing’ behavior, in which uninvolved chimpanzees intervene in others’ conflicts. These interventions may reflect “community concern” for the need to maintain order, which “can be seen as the very foundation of human morality and indeed social norms” (Rudolf von Rohr et al. 2012: 7). In a comparison of policing interventions across four groups, high-ranking individuals of both sexes were found to police, and to do so more often in times of social instability (but see Riedl et al. 2012). Moreover, self-interested explanations of the policing behavior were ruled out.
Nonetheless, it would be premature to interpret policing behavior as evidence of norm-enforcement – since policing individuals may simply prefer not to live in unstable, conflict-ridden groups. If so, then anyone whose interventions could calm a tense group may be motivated to intervene. No group norms need be assumed.
It has been reported that when chimpanzees witness aggression against even unrelated infants, they react strongly – for example, by screaming, and intervening defensively. Rudolf von Rohr et al. (2015) showed chimpanzees videos of conspecific infanticide to see if this would elicit responses suggestive of an understanding of moral norms. Apes looked longer at videos of unfamiliar individuals committing infanticidal attacks than at control videos (e.g., of chimpanzees behaving aggressively towards adults). However – with the exception of one individual who performed threat displays towards the video screen – watching infanticide did not elicit negative emotional arousal. The authors interpret the findings as showing that while chimpanzees may recognize norm violations, these violations elicit strong emotional responses only when they affect group members.
Again, this conclusion is premature. The looking-time measure employed by the authors is standardly interpreted as showing that subjects were surprised by or interested in what they saw. However, while this suggests that chimpanzees have expectations regarding the treatment of infants, this seems to support a claim only about what chimpanzees take to be predictable. This is a norm sense of the word used by Andrews, but not the sort of norm that is relevant to moral evaluation. Although the authors claim to provide “evidence that chimpanzees … are sensitive to the appropriateness of behaviors that do not affect themselves” (p. 157), it is unclear that a longer looking time is evidence of this. The lack of emotional arousal in most apes also suggests that they did not care strongly about what they saw (consistent with the absence of a norm); and the negative reactions of one individual is consistent with her simply disliking what she saw.
Given the ambiguity of these data, it is clear that future work should focus on eliciting unambiguous criteria for the attribution of normative behavior. The best evidence for this would be third-party interventions in cases where the intervening individual did not stand to gain from entering the dispute. However, unambiguous cases may be difficult to identify. In the meantime, it is premature to conclude that chimpanzees understand and follow norms. They seem not to distinguish between what individuals do, and what they should do.
For empirical studies of chimpanzee normativity, see Rudolf von Rohr, Burkart, and van Schaik (2011) on the possibility of moral norms in chimpanzees; and on the question of whether there are group-specific cultural norms, see Luncz, Mundry, and Boesch (2012) (along with van Schaik’s commentary (2012)), and van Leeuwen et al. (2015). For the most explicit philosophical development of the claim that primate behavior is normative, see Andrews (2009), and the forthcoming Bayertz and Roughley (eds.).
For discussions and valuable feedback on the contents of this chapter, we thank Kristin Andrews, Lydia Luncz, and Edwin van Leeuwen.
1 Not all social norms are arbitrary. For example, incest is a universally adopted social norm with a clear biological justification. Although the content of a given norm may be grounded in principles conferring survival advantages to those who act in accordance with them, what matters for the purposes of this discussion is that followers of norms are intrinsically motivated to conform. For relevant discussion of arbitrary norms, see Moore (2013a).
2 Similarly low-level explanations of behavior transmission could be used to explain other group traditions in apes – including, for example, group-specific grooming handclasp techniques (van Leeuwen et al. 2012).
3 Chimpanzees are known to copy preferentially from high-ranking individuals (Horner et al. 2010). However, this need not reflect any understanding of the normative nature of group behaviors. It could simply be an attentional bias that reflects apes’ knowledge of likely sources of expertise.
4 Although, see also Paukner et al. (2009) for a relevant finding in capuchin monkeys.
5 If moral norms are not arbitrary, the characterizations of social norms offered above would need to be adjusted to ground an account of moral norms. In particular, clause (3) would need to be reformulated to show that conformity to moral norms can be independent of others’ conformity, and instead be driven by a sense of what is morally right.
Andrews, K. (2009) “Understanding norms without a theory of mind,” Inquiry 52(5), 433–448.
Asch, S. (1951) “Effects of group pressure upon the modification and distortion of judgments,” in: Guetzkow, H. (ed.) Groups, Leadership and Men; Research in Human Relations, Oxford: Carnegie Press.
Bayertz, K., and Roughley, N. (eds.) (forthcoming) The Normative Animal? On the Anthropological Significance of Social, Moral and Linguistic Norms, Oxford: Oxford University Press.
Bicchieri, C. (2006) The Grammar of Society: The Nature and Dynamics of Social Norms, New York: Cambridge University Press.
Biro, D., Inoue-Nakamura, N., Tonooka, R., Yamakoshi, G., Sousa, C., and Matsuzawa, T. (2003) “Cultural innovation and transmission of tool use in wild chimpanzees: Evidence from field experiments,” Animal Cognition 6, 213–223.
Boesch, C. (2012) Wild Cultures: A Comparison Between Chimpanzee and Human Cultures, Cambridge: Cambridge University Press.
Boyd, R., and Richerson, P. (2005) The Origin and Evolution of Cultures, New York: Oxford University Press.
Brandom, R. (1994) Making It Explicit: Reasoning, Representing, and Discursive Commitment, Cambridge, MA: Harvard University Press.
Bräuer, J., Call, J., and Tomasello, M. (2006) “Are apes really inequity averse?” Proceedings of the Royal Society B 273, 3123–3128.
Bullinger, A., Wyman, E., Melis, A., and Tomasello, M. (2011) “Coordination of chimpanzees (Pan troglodytes) in a stag hunt game,” International Journal of Primatology 32, 1296–1310.
de Waal, F., and van Roosmalen, A. (1979) “Reconciliation and Consolation among Chimpanzees,” Behavioral Ecology and Sociobiology 5, 55–66.
Engelmann, J., Herrmann, E., and Tomasello, M. (2012) “Five-year olds, but not chimpanzees, attempt to manage their reputations,” PLoS ONE 7(10), e48433.
Fehr, E., and Fischbacher, U. (2004) “Third-party punishment and social norms,” Evolution & Human Behavior 25, 63–87.
Hobaiter, C., and Byrne, R. W. (2010) “Able-bodied wild chimpanzees imitate a motor procedure used by a disabled individual to overcome handicap,” PLoS One 5(8), e11959.
Horner, V., Proctor, D., Bonnie, K. E., Whiten, A., and de Waal, F.B.M. (2010) “Prestige affects cultural learning in chimpanzees,” PLoS ONE 5(5), e10625.
Hrubesch, C., Preuschoft, S., and van Schaik, C. (2009) “Skill mastery inhibits adoption of observed alternative solutions among chimpanzees (Pan troglodytes),” Animal Cognition 12(2), 209–216.
Jensen, K., Call, J., and Tomasello, M. (2007) “Chimpanzees are vengeful but not spiteful,” PNAS 104(32), 13046–13050.
Kelly, D., Stich, S., Haley, K., Eng, S., and Fessler, D. (2007) “Harm, affect, and the moral/conventional distinction,” Mind & Language 22, 117–131.
Kendal, R., Hopper, L., Whiten, A., Brosnan, S., Lambeth, S., Schapiro, S., and Hoppitt, W. (2015) “Chimpanzees copy dominant and knowledgeable individuals: Implications for cultural diversity,” Evolution & Human Behavior 36, 65–72.
Kitcher, P. (2011) The Ethical Project, Cambridge, MA: Harvard University Press.
Korsgaard, C. (2010) “Reflections on the evolution of morality,” The Amherst Lecture in Philosophy 5, 1–29.
Lakin, J. L., Chartrand, T. L., and Arkin, R. M. (2008) “I am too just like you: Nonconscious mimicry as an automatic behavioral response to social exclusion,” Psychological Science 19(8), 816–822.
Luncz, L., and Boesch, C. (2014) “Tradition over trend: Neighboring chimpanzee communities maintain differences in cultural behavior despite frequent immigration of adult females,” American Journal of Primatology 76(7), 649–657.
Luncz, L., Mundry, R., and Boesch, C. (2012) “Evidence for cultural differences between neighboring chimpanzee communities,” Current Biology 22(10), 922–926.
Luncz, L., Wittig, R., and Boesch, C. (2015) “Primate archaeology reveals cultural transmission in wild chimpanzees (Pan troglodytes verus),” Philosophical Transactions of the Royal Society B 370(1682), 20140348.
Moore, R. (2013a) “Imitation and conventional communication,” Biology and Philosophy 28(3): 481–500.
Moore, R. (2013b) “Social learning and teaching in chimpanzees,” Biology and Philosophy 28, 879–901.
Nucci, L., and Turiel, E. (1978) “Social interactions and the development of social concepts in preschool children,” Child Development 49, 400–407.
Over, H., and Carpenter, M. (2009) “Eighteen-month-old infants show increased helping following priming with affiliation,” Psychological Science 20, 1189–1193.
Paukner, A., Suomi, S., Visalberghi, E., and Ferrari, P. (2009) “Capuchin monkeys display affiliation towards humans who imitate them,” Science 325(5942), 880–883.
Riedl, K., Jensen, K., Call, J., and Tomasello, M. (2012) “No third-party punishment in chimpanzees,” PNAS 109(37), 14824–14829.
Rudolf von Rohr, C., Burkart, J., and van Schaik, C. (2011) “Evolutionary precursors of social norms in chimpanzees: A new approach,” Biology & Philosophy 26, 1–30.
Rudolf von Rohr, C., Koski, S., Burkart, J., Caws, C., Fraser, O., Ziltener, A., and van Schaik, C. (2012) “Impartial third-party interventions in captive chimpanzees: A reflection of community concern,” PLoS ONE 7(3), e32494.
Rudolf von Rohr, C., van Schaik, C., Kissling, A., and Burkart, J. (2015) “Chimpanzees’ bystander reactions to infanticide,” Human Nature 26(2), 143–160.
Schmidt, M., Rakoczy, H., and Tomasello, M. (2011) “Young children attribute normativity to novel actions without pedagogy or normative language,” Developmental Science 14(3), 530–539.
Schmidt, M., Rakoczy, H., and Tomasello, M. (2012) “Young children enforce social norms selectively depending on the violator’s group affiliation,” Cognition 124(3), 325–333.
Tomasello, M. (2016) A Natural History of Human Morality, Cambridge, MA: Harvard University Press.
van Leeuwen, E., Cronin, K., and Haun, D. (2014) “A group-specific arbitrary tradition in chimpanzees (Pan troglodytes),” Animal Cognition 17, 1421–1425.
van Leeuwen, E., Cronin, K., Schütte, S., Call, J., and Haun, D. (2013) “Chimpanzees flexibly adjust their behaviour in order to maximize payoffs, not to conform to majorities,” PLoS One 8(11), e80945.
van Leeuwen, E., and Haun, D. (2013) “Conformity in nonhuman primates: Fad or fact?” Evolution and Human Behavior 34, 1–7.
van Leeuwen, E., Kendal, R., Tennie, C., and Haun, D. (2015) “Conformity and its look-a-likes,” Animal Behaviour 110, e1–e4.
van Schaik, C. (2012) “Animal culture: Chimpanzee conformity?” Current Biology 22(10), 402–404.
Warneken, F., and Tomasello, M. (2006) “Altruistic helping in human infants and young chimpanzees,” Science 311(5765), 1301–1303.
Whiten, A., Goodall, J., McGrew, W., Nishida, T., Reynolds, V., Sugiyama, Y., Tutin, C., Wrangham, R., and Boesch, C. (1999) “Cultures in chimpanzees,” Nature 399(6737), 682–685.
Whiten, A., Horner, V., and de Waal, F. (2005) “Conformity to cultural norms of tool use in chimpanzees,” Nature 437(7059), 737–740.
Williams, K., Cheung, C., and Choi, W. (2000) “Cyberostracism: Effects of being ignored over the Internet,” Journal of Personality and Social Psychology 79(5), 748–762.
Zawidzki, T.W. (2013) Mindshaping: A New Framework for Understanding Human Social Cognition. Cambridge, MA: MIT Press.