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Games from experimental economics have provided insights into the evolutionary roots of social decision making in primates and other species. Multiple primate species' abilities to cooperate, coordinate and anti-coordinate have been tested utilizing variants of these simple games. Past research, however, has focused on species known to cooperate an...
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... this game, paired participants choose between two options, Stag and Hare. If both participants choose Stag, they receive the highest payoff, whereas any partner that plays Hare receives a lower payoff irrespective of what their partner plays (playing Hare is risk dominant, because the subject receives a reward regardless of what their partner plays; see Figure 1). Thus, there are two coordinated Nash Equilibria (NE; the NE is the outcome for which neither player can do better by playing a different option given their partner's choice), coordinating on Stag (the payoff dominant NE) or coordinating on Hare. ...
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... this game, individuals can play Dove, yielding to their partner, or Hawk, fighting for the resource. One participant benefits when they play Hawk and the other plays Dove; however, if both play Hawk, the resources are lost (see Figure 1). There are two asymmetric Nash equilibria in this game (i.e., one player plays Hawk and the other Dove), and the payoff dominant strategy is to alternate the NE (i.e., take turns playing Hawk and Dove). ...
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... in situations like the AG coordination may be easy to establish, as there is no incentive to defect, in real life there is often tension between defecting and working with others. In the PDG, individuals do best in the long run by cooperating, but, in the short term, they do best by defecting, no matter what their partner plays (and indeed, mutual defection is the NE; see Figure 1). Most studies have found that animals primarily defect in the PDG (Clements & Stephens, 1995;Green et al., 1995). ...
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... token types, differentiated by color or pattern, represented the two outcomes for each game (Figure 1). Although the tokens differed by color (e.g., black/white) and/or pattern (patterned/plain) within a game, across the different games, differently shaped, colored and patterned tokens were used to make it as clear as possible to the subjects that the game had changed. ...
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... order was chosen because the AG was assumed to be the easiest for the subjects to solve (for the reasons described in the Introduction) and we wished to give them experience with an easier game first to maximize the odds of finding a solution to the more difficult games. All games followed the same procedure, and only the payoffs for each game differed (outlined in Figure 1). An independent researcher coded a randomly selected 20% of the trial outcomes from video tape, and inter-rater reliability between this researcher and the results GV noted as she collected the data was high (Kappa = 0.89, p < .001). ...
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... in which subjects selected tokens in a sequential manner were analyzed to assess whether the first player's choice influenced the second player's choice using generalized linear mixed effect models (GLMM) run in R (R Development Core Team, 2015) using lme4 (Bates et al., 2015). We constructed 'response order' models that included the second player's choice as the dependent variable and the first player's choice as the predictor variable, with who played first and second entered as random effects. ...
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... token types, differentiated by color or pattern, represented the two outcomes for each game (Figure 1). Although the tokens differed by color (e.g., black/white) and/or pattern (patterned/plain) within a game, across the different games, differently shaped, colored and patterned tokens were used to make it as clear as possible to the subjects that the game had changed. ...
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... order was chosen because the AG was assumed to be the easiest for the subjects to solve (for the reasons described in the Introduction) and we wished to give them experience with an easier game first to maximize the odds of finding a solution to the more difficult games. All games followed the same procedure, and only the payoffs for each game differed (outlined in Figure 1). An independent researcher coded a randomly selected 20% of the trial outcomes from video tape, and inter-rater reliability between this researcher and the results GV noted as she collected the data was high (Kappa = 0.89, p < .001). ...
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... in which subjects selected tokens in a sequential manner were analyzed to assess whether the first player's choice influenced the second player's choice using generalized linear mixed effect models (GLMM) run in R (R Development Core Team, 2015) using lme4 (Bates et al., 2015). We constructed 'response order' models that included the second player's choice as the dependent variable and the first player's choice as the predictor variable, with who played first and second entered as random effects. ...
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... The Stag Hunt paradigm is versatile, having been used in a variety of scenarios for adults and children (Siposova et al., 2018) including a human vs. a computer (Craig et al., 2013), computers vs other computers (Antonioni et al., 2013), and non-human primates (Brosnan et al., 2011;Brosnan et al., 2017;Hall et al., 2019;Vale et al., 2019). Cooperation (i.e., playing stag) is associated with pre-game communication of any form between the participants, especially if communication is free or low cost to the participants (Blume et al., 2017;Büyükboyacı & Küçükşenel, 2017;Hernandez-Lagos, 2019). ...
The purpose of this study was to evaluate the validity of a previously published work on cooperation and trust by replicating the original study and adding an additional condition. Participants listened to one of three audio files designed to encourage them to trust others, encourage them to trust themselves, or a control condition designed to encourage relaxation, and then played 40 rounds of the Stag Hunt game post-intervention. The total number of times the participant played stag was recorded. The results revealed that the audio condition did influence cooperation in the Stag Hunt Game. Those participants in the condition designed to influence them to trust others were statistically more likely to cooperate than either other condition. Neither the trust self-condition participants nor the control condition participants played differently from chance.
... Juvenile chimpanzees attend to older and same-aged models when cracking nuts; infants attend to juveniles and adults F I G U R E 1 Synthesis and framework for understanding how, from whom, and in what contexts peer learning occurs, and the macro-level influences that shape its distribution across societies. (Horner et al., 2005;Melis & Tomasello, 2013Vale et al., 2019). For instance, in a series of collaboration tasks, captive chimpanzees preferentially recruited previously successful peers over unsuccessful ones (Melis et al., 2006). ...
In this article, we integrate cultural evolutionary theory with empirical research from developmental psychology, cultural anthropology, and primatology to explore the role of peer learning in the development of complex instrumental skills and behavioral norms. We show that instrumental imitation, contingent teaching, generative collaboration, and selective copying contribute to domain-specific transmission of knowledge between peers. Stages of development and characteristics inherent to the learner and model influence how and when children learn from each other. Peer learning is persistent across societies despite cultural beliefs that favor adult–child transmission in some settings. Comparative research hints at the possibility that children's greater motivation to interact with and learn from each other may set humans apart from other primates. We conclude by outlining avenues for future research, including how individual characteristics and developmental changes in social networks, motivation, and cognition may contribute to cultural evolution.
... We recently tested the hypothesis that species which were reported to cooperate more frequently in the wild would also coordinate more often in the Assurance game by testing squirrel monkeys, a platyrrhine primate that is sympatric and confamilial with capuchins, as well as highly social, but shows far less evidence of cooperation. Nonetheless, they showed relatively similar rates of coordination in the manual Assurance game as compared to the capuchins (at least on the capuchins' first exposure to the task; [75]). One possible explanation is that they were simply treating the task as a reward maximization task. ...
... One possible explanation is that they were simply treating the task as a reward maximization task. The squirrel monkeys did not show any evidence of changing their behaviour contingent upon their partner's previous choice, nor did they show any evidence of playing a Nash equilibrium in either the Hawk-Dove game or the PD game [75]. More intriguingly, however, it was the female pairs who showed the tendency to coordinate. ...
The origins of evolutionary games are rooted in both economics and animal behaviour, but economics has, until recently, focused primarily on humans. Although historically, specific games were used in targeted circumstances with non-human species (i.e. the Prisoner's Dilemma), experimental economics has been increasingly recognized as a valuable method for directly comparing both the outcomes of economic decisions and their underlying mechanisms across species, particularly in comparison with humans, thanks to the structured procedures that allow for them to be instantiated across a variety of animals. So far, results in non-human primates suggest that even when outcomes are shared, underlying proximate mechanisms can vary substantially. Intriguingly, in some contexts non-human primates more easily find a Nash equilibrium than do humans, possibly owing to their greater willingness to explore the parameter space, but humans excel at more complex outcomes, such as alternating between two Nash equilibria, even when deprived of language or instruction, suggesting potential mechanisms that humans have evolved to allow us to solve complex social problems. We consider what these results suggest about the evolution of economic decision-making and suggest future directions, in particular the need to expand taxonomic diversity, to expand this promising approach.
This article is part of the theme issue ‘Half a century of evolutionary games: a synthesis of theory, application and future directions'.
... However, one demographic, the female Bolivian squirrel monkey, shows some evidence of cooperation in both field and laboratory studies. For instance, in the wild, females form alliances or coalitions to defend resources (Boinski & Cropp, 1999;Boinski et al., 2002;Mitchell et al., 1991), and in captive settings, they coordinate to some degree in the assurance game (Vale et al., 2019). In addition, female common squirrel monkeys, Saimiri sciureus, show sensitivity to inequities with outgroup, but not ingroup, female partners in a different methodology than has been used previously (Bucher et al., 2020), also suggesting some tendency towards an inequity response in females. ...
... Individuals of similar ages were subgrouped by their regular care staff. As noted, we chose to test the females rather than males because females show more evidence of longer-term relationships and cooperation in both field (Boinski, 1999;Mitchell et al., 1991) and laboratory (Vale et al., 2019; see detailed discussion, in Introduction) settings, making for a stronger test of the cooperation hypothesis. Participants were housed at the Michale E. Keeling Center for Comparative Medicine and Research, UT MD Anderson Cancer Center, U.S.A. (KCCMR). ...
Primates of several species respond negatively to receiving less preferred rewards than a partner for completing the same task (inequity responses), either rejecting rewards or refusing to participate in the task when disadvantaged. This has been linked to cooperation, with species that cooperate frequently refusing to participate in inequity tasks (the ‘cooperation hypothesis’). However, inequity is a social response, and previous research has involved dyads, precluding studying the effects of additional social partners. While dyads allow for tighter control in experimental settings, dyadic interactions in nature do not take place in a social vacuum, so understanding the role of the social context is needed to verify that the pattern of results supports the cooperation hypothesis. Here we focus on Bolivian squirrel monkeys, Saimiri boliviensis, a highly social species that does not generally cooperate and has not responded to inequity in previous dyadic research, although they do respond to receiving a lower reward than they expected. In the current study, we provide a more nuanced test by studying female Bolivian squirrel monkeys, the demographic most likely to cooperate in both field and laboratory contexts, in a more socially relevant group setting. For some reward values, females responded in both the inequity condition, rejecting less preferred rewards when they were disadvantaged relative to their social group, and a contrast condition, wherein all animals received a lower reward than they expected, making it difficult to disentangle contrast from inequity. As in capuchin monkeys, refusals increased when monkeys were to receive low-value rewards compared to medium-value rewards. These results suggest that the relationship between cooperation and inequity responses may be more nuanced than previously suggested, with demographic, social context and reward value potentially influencing outcomes even within species.
... Juvenile chimpanzees attend to older and same-aged models when cracking nuts; infants attend to juveniles and adults F I G U R E 1 Synthesis and framework for understanding how, from whom, and in what contexts peer learning occurs, and the macro-level influences that shape its distribution across societies. (Horner et al., 2005;Melis & Tomasello, 2013Vale et al., 2019). For instance, in a series of collaboration tasks, captive chimpanzees preferentially recruited previously successful peers over unsuccessful ones (Melis et al., 2006). ...
In this article, we integrate cultural evolutionary theory with empirical research from developmental psychology, cultural anthropology, and primatology to outline the role of peer learning in the development of complex instrumental skills and behavioural norms. We show that instrumental imitation, contingent teaching, generative collaboration, and the application of selective social learning biases contribute to high-fidelity domain-specific transmission of knowledge between peers. Further, peer learning is persistent across cultures despite norms which favour adult-child transmission in some settings. Comparative research further suggests that children’s greater motivation to interact with and learn from each other sets us apart from other primates. We conclude by outlining avenues for future research, including how individual characteristics, social networks, motivation, cognition, and developmental changes in these may contribute to cultural evolution.
... Versions of the Stag Hunt game have also been programmed into Excel as part of role-playing simulations (Bridge, 2016). While most participants in psychological studies are adults, the Stag Hunt game can be modified for young children (Siposova et al., 2018) as well as non-human primates such as chimpanzees (Brosnan et al., 2017;Hall et al., 2019), capuchin monkeys (Brosnan et al., 2013;Brosnan et al., 2011;Brosnan et al., 2017), rhesus monkeys (Brosnan et al., 2013;Brosnan et al., 2017), and squirrel monkeys (Vale et al., 2019). The current study was set up to mimic a player vs. player approach, however one player (the researcher) was playing as an artificial opponent with randomly generated responses. ...
The “Stag Hunt Game” is frequently used to tease out factors which may influence cooperation, a fundamental building block of human society. The present study is an attempt to influence human cooperation by means of positive imagery in the context of the Stag Hunt Game. Participants listened to one of two audio files designed to encourage them to trust others or encourage them to trust themselves, and then played 40 rounds of the Stag Hunt game post-intervention. The total number of times the participant played stag was recorded. The results revealed that the audio condition did influence cooperation in the Stag Hunt Game such that participants chose the more cooperative option when encouraged to trust others than when encouraged to trust themselves.
... Neither squirrel monkeys (Saimiri boliviensis: Freeman et al., 2013;Talbot et al., 2011; although also see Bucher et al., 2020) nor orangutans (Pongo pygmaeus: Bräuer et al., 2009;Brosnan et al., 2011) show extensive evidence of cooperation in the wild. The one exception is Bolivian squirrel monkey females, who do form coalitions in the wild (Cropp et al., 2002) and show some evidence of food sharing (Stevens, 2004) and cooperation (Vale et al., 2019) Laumer et al., 2020). However, one key primate species that has been almost entirely overlooked is the gorilla, the only African great ape that is not known to cooperate as extensively as the two Pan species, although they, too, form coalitions and alliances (Harcourt & Stewart, 1989;Watts, 1997). ...
... It might be that even within gorilla species, there is considerable variation in responses to inequity, although our ability to test this possibility is limited by the lack of captive populations of other sub-species beyond Western lowland gorillas. Indeed, some work suggests that looking at the species level may not be appropriate for particularly widespread or variable species; among squirrel monkeys, Bolivian female squirrel monkeys appear to be somewhat more likely to cooperate than other demographic groups (Cropp et al., 2002;Vale et al., 2019), although whether this will hold up to further testing in other species and populations of squirrel monkey is unknown. ...
Although individuals in some species refuse foods they normally accept if their partner receives a more preferred one, this is not true across all species. The cooperation hypothesis proposes that this species-level variability evolved because inequity aversion is a mechanism to identify situations in which cooperation is not paying off, and that species regularly observed cooperating should be more likely to be averse to inequity. To rule out other potential explanations of inequity aversion, we need to test the converse as well: species rarely observed cooperating, especially those phylogenetically close to more cooperative species, should be less likely to be inequity averse. To this end, we tested eight zoo-housed Western lowland gorillas (Gorilla gorilla gorilla) on a token exchange task in which subjects received either the same food reward or a less-preferred reward for the same or more effort than their partner, recording both refusals to participate in the exchange and refusals to accept the reward. Supporting the cooperation hypothesis, even with procedural differences across sessions, gorillas were significantly more likely to refuse in all conditions in which they received a low-value food reward after completing an exchange, regardless of what their partner received, suggesting that gorillas were not inequity averse, but instead would not work for a low-value reward. Additionally, gorillas were more likely to refuse later in the session; while the pattern of refusals remained unchanged after accounting for this, this suggests that species should be tested on as many trials as is practical.
... Rhesus macaques (Macaca mulatta) also do very well, playing Stag/Stag, but apparently based on a preference for the on-average higher paying token (Parrish et al., 2014). Somewhat surprisingly, female Bolivian squirrel monkeys showed some degree of coordination, albeit less than the other species (Vale et al., 2019). Although squirrel monkeys are not generally cooperative, this is the demographic that is the most so, suggesting a need to be more specific when considering the demographics of cooperation. ...
Unequal outcomes disrupt cooperation in some situations, but this has not been tested in the context of coordination in economic games. To explore this, we tested brown capuchins (Sapajus [Cebus] apella) on a manual version of the Stag Hunt (or Assurance) Game, in which individuals sequentially chose between two options, Stag or Hare, and were rewarded according to their choices and that of their partner. Typically, coordination on Stag results in an equal highest payout, whereas coordinating on Hare results in a guaranteed equal but lower payoff and uncoordinated play results in the lowest payoff when playing Stag. We varied this structure such that one capuchin received double the rewards for the coordinated Stag outcome; thus, it was still both animals' best option, but no longer equally rewarding. Despite the inequality, capuchins coordinated on Stag in 78% of trials, and neither payoff structure nor their partner's choice impacted their decision. Additionally, there was no relationship between self-scratching, a measure of stress in capuchins, and choices. After completing the study, we discovered our reward, cheerios, was sufficiently valuable that in another study, capuchins never refused it, so post hoc we repeated the study using a lower value reward, banana flavored pellets. Capuchins completed only 26% of the pellet trials (compared to 98% with cheerios), constraining our ability to interpret the results, but nonetheless the monkeys showed a decrease in preference for Stag, particularly when they received fewer rewards for the coordinated Stag outcome. These results reinforce capuchins' ability to find coordinated outcomes in the Stag Hunt game, but more work is needed to determine whether the monkeys did not mind the inequality or were unwilling to sacrifice a highly preferred food to rectify it. In either case, researchers should carefully consider the impact of their chosen rewards on subjects' choices.
... www.nature.com/scientificreports/ a very recent study presented squirrel monkeys, a primate species that rarely cooperates in nature, with a set of computerized social dilemmas previously presented to more cooperative species such as the capuchin monkeys (Cebus apella). Vale and colleagues 17 found that squirrel monkeys (Saimiri boliviensis) behaved similar to capuchin monkeys in cooperative scenarios such as the assurance game. Squirrel monkeys were able to coordinate with their partner to obtain the highest rewards. ...
Social primates face conflicts of interest with other partners when their individual and collective interests collide. Despite living in small, primarily bonded, groups compared to other social primates, gibbons are not exempt from these conflicts in their everyday lives. In the current task, we asked whether dyads of gibbons would solve a conflict of interest over food rewards. We presented dyads of gibbons with a situation in which they could decide whether to take an active role and pull a handle to release food rewards at a distance or take a passive role and avoid action. In this situation, the passive partner could take an advantageous position to obtain the rewards over the active partner. Gibbons participated in three conditions: a control condition with no food rewards, a test condition with indirect food rewards and a test condition with direct food rewards. In both test conditions, five rewards were released at a distance from the handle. In addition, the active individual could obtain one extra food reward from the handle in the direct food condition. We found that gibbons acted more often in the two conditions involving food rewards, and waited longer in the indirect compared to the direct food condition, thus suggesting that they understood the task contingencies. Surprisingly, we found that in a majority of dyads, individuals in the active role obtained most of the payoff compared to individuals in the passive role in both food conditions. Furthermore, in some occasions individuals in the active role did not approach the location where the food was released. These results suggest that while gibbons may strategize to maximize benefits in a competitive food task, they often allowed their partners to obtain better rewards. Our results highlight the importance of social tolerance and motivation as drivers promoting cooperation in these species.
... Surprisingly, the squirrel monkey, a close relative of the capuchin monkey and a species upon which there is little research in the cooperation literature, had a much higher rate of cooperation with three of the four pairs playing stag consistently (Vale et al., 2019). ...
... It appears that one consideration is the expected likelihood of working with that person again, with repeated interactions assumed to increase the likelihood of cooperation between two people (Al-Ubaydli et al., 2013). That being said, experiments have examined one-shot scenarios (Belloc et al., 2019;de Souza & Rêgo, 2014;Girtz et al., 2017;Jansson & Eriksson, 2015) as well as repeated interaction scenarios (Al-Ubaydli et al., 2013;Antonioni et al., 2013;Blume et al., 2017;Bosworth, 2013Bosworth, , 2017Brooks et al., 2018;Brosnan et al., 2013;Brosnan et al., 2011;Brosnan et al., 2017;Bullinger et al., 2011;Büyükboyacı & Küçükşenel, 2017;Cartwright & Singh, 2018;Ekins et al., 2013;Feltovich et al., 2012;Hall et al., 2019;Hilbig et al., 2018;Le Coq et al., 2015;Parrish et al., 2014;Vale et al., 2019). As Hernandez-Lagos, 2019), and how quickly the payout will occur (Deck & Jahedi, 2015). ...
Cooperation has been one of the most foundational aspects of human society and is frequently studied via use of “The Stag Hunt” which has been used to tease out factors which may influence cooperation. The present study is the first study to attempt to influence human cooperation by means of positive imagery. Participants included 33 males and 72 females who listened to either a 7-minute audio designed to encourage them to trust others or an audio designed to encourage them to trust themselves. Participants played 40 rounds of the Stag Hunt game. The total number of times the participant played stag was recorded. An independent-samples t-test found a significant difference in the scores for the trust others (M= 21.47, SD=3.28) and the trust self (M=19.82, SD=3.92) conditions. This suggests guided imagery tasks may influence cooperation.
