How Social Context, Token Value, and Time Course Affect Token Exchange in Capuchin Monkeys (Cebus apella)

Abstract

Although numerous studies have examined token-directed behaviors in primates, few have done so in a social context despite the fact that most primate species live in complex groups. Here, we provided capuchin monkeys with a relatively limited budget of tokens, likely to elicit intragroup competition, and, after an overnight delay, we allowed them to exchange tokens while in a group setting. We aimed to 1) evaluate whether social context affects token-directed behaviors of knowledgeable subjects, i.e., subjects already proficient in token exchange before the present study, as well as of naïve subjects, i.e., subjects that never showed exchange behavior before this study; 2) appraise whether capuchins indeed value tokens; and 3) assess whether capuchins can refrain from throwing tokens outside their enclosure when the experimenter is not present. Overall, the social context positively affected high-ranking individuals and negatively affected low-ranking ones. All 6 highranking naïve subjects, but none of the 4 low-ranking ones, quickly acquired token exchange behavior, whereas 9 of 12 low-ranking knowledgeable subjects, but only 1 high-ranking knowledgeable subject, never displayed token exchange in social contexts. Thus, competition constrained token exchange in low-ranking subjects and prompted exchange behavior in high-ranking naïve subjects. Capuchins were unable to inhibit the exchange of valueless items when the experimenter was soliciting them and, at the group level, knowledgeable subjects did not exchange more valuable tokens than less valuable (or valueless) ones. However, the 3 high-ranking knowledgeable subjects that exchanged most of the tokens first preferentially exchanged more valuable tokens over less valuable or valueless ones. Finally, capuchins inhibited exchange behavior in the absence of the experimenter, thus recognizing the appropriate conditions in which a successful exchange could occur. Int J Primatol (2011) 32:83-98

Captive chimpanzee foraging in a social setting: a test of problem solving, flexibility, and spatial discounting

“…Rather than exhibiting behavioral inhibition in the presence of dominants and ending participation altogether, as reported previously for primates (e.g., Macaca mulatta, Drea & Wallen, 1999 ; S. boliviensis, Hopper et al, 2013 ; P. troglodytes, Cronin et al, 2014 ), this female continued to exchange tokens, but at alternative locations. Beyond this specific female, and contrary to our predictions based on the findings of previous research (e.g., Bonnie et al, 2007 ; Addessi et al, 2011 ; Hopper et al, 2011 ), in this group of six chimpanzees there was a negative correlation between rank and total number of exchanges made (i.e., low-ranked individuals made more exchanges than high-ranked individuals).…”

“…Additionally, we provisioned our chimpanzees with a greater number of tokens to exchange compared to previous studies, which also likely reduced within-group competition and therefore scrounging rates (e.g., this study provided = 25 tokens/subject while, for example, ( Bonnie et al, 2007 ) provided 1.7 tokens/subject). Our experimental design, in combination with the small number of chimpanzees that this group is comprised of, may help to explain why, unlike in previous studies (e.g., Bonnie et al, 2007 ; Addessi et al, 2011 ), lower-ranking chimpanzees were able to exchange more tokens than higher-ranking individuals (they could avoid dominants by exchanging at alternative locations) and levels of scrounging were relatively low (tokens were not easily monopolized).…”

“…Chimpanzees can learn how to exchange tokens very quickly when given training (e.g., Hopper et al, 2011 ; Van Leeuwen et al, 2013 ) or from watching group mates ( Bonnie et al, 2007 ). Beyond this, in previous studies that have presented socially-housed primates opportunities to exchange tokens for food rewards, dominant individuals monopolized access to tokens ( P. troglodytes , Bonnie et al, 2007 ) and made more exchanges with them ( C. apella , Addessi et al, 2011 ).Therefore, our first prediction was that all the chimpanzees would learn how to exchange the tokens with researchers for food rewards, either through individual trial-and-error learning or by using social information, and that, once the chimpanzees had learned to exchange tokens for food, higher-ranking chimpanzees would exchange more tokens than low-ranking individuals. Accordingly, the chimpanzees received no training prior to the start of this study either in how to exchange tokens or where the exchange locations were.…”

“…Previous research has demonstrated that primates can associate different types of tokens with different associated food rewards ( C. apella , Brosnan & de Waal, 2004 ; Addessi, Crescimbene & Visalberghi, 2007 ; Addessi et al, 2011 ; P. troglodytes , Hopper et al, 2011 ; Van Leeuwen et al, 2013 ) and that chimpanzees will selectively exchange tokens at specific locations in order to obtain more desirable rewards when the two options are equally accessible ( Van Leeuwen et al, 2013 ). Extending this, we were interested in the likelihood of the chimpanzees traveling farther for the more-preferred rewards and if they would continue to do so when the locations where they could exchange tokens for food rewards changed.…”

Socially transmitted diffusion of a novel behavior from subordinate chimpanzees

“…One might suppose that this would occur for strategic reasons (dominant individuals are successful, so copying them might be an adaptive option), due to normative effects (copying the dominant individual facilitates social cohesion), or simply as a result of an attentional bias towards these individuals (e.g., dominant individuals are central in the social network). In capuchin monkeys, it has been found that subordinate individuals tend not to demonstrate acquired token‐exchange behaviors in a group context (Addessi, Mancini, Crescimbene, & Visalberghi, ) or in the presence of a dominant individual (Lonsdorf et al, ), which means there is an inherent rank‐bias in the source of social information available to observers. Although it has also been found that capuchins preferentially observe older, more dominant, and more proficient nut‐crackers in the wild, suggesting a more active learning bias (Coelho et al, ).…”