Task design influences prosociality in captive chimpanzees (Pan troglodytes).

Bailey R House,Susan P Lambeth,Joan B Silk,Steven J Schapiro

doi:10.1371/journal.pone.0103422

Abstract

Chimpanzees confer benefits on group members, both in the wild and in captive populations. Experimental studies of how animals allocate resources can provide useful insights about the motivations underlying prosocial behavior, and understanding the relationship between task design and prosocial behavior provides an important foundation for future research exploring these animals' social preferences. A number of studies have been designed to assess chimpanzees' preferences for outcomes that benefit others (prosocial preferences), but these studies vary greatly in both the results obtained and the methods used, and in most cases employ procedures that reduce critical features of naturalistic social interactions, such as partner choice. The focus of the current study is on understanding the link between experimental methodology and prosocial behavior in captive chimpanzees, rather than on describing these animals' social motivations themselves. We introduce a task design that avoids isolating subjects and allows them to freely decide whether to participate in the experiment. We explore key elements of the methods utilized in previous experiments in an effort to evaluate two possibilities that have been offered to explain why different experimental designs produce different results: (a) chimpanzees are less likely to deliver food to others when they obtain food for themselves, and (b) evidence of prosociality may be obscured by more “complex” experimental apparatuses (e.g., those including more components or alternative choices). Our results suggest that the complexity of laboratory tasks may generate observed variation in prosocial behavior in laboratory experiments, and highlights the need for more naturalistic research designs while also providing one example of such a paradigm.

Highlights

The literature on social behavior in chimpanzees (Pan troglodytes) shows clearly that cooperation is common in these animals
On those trials in which no food was placed in the Actor bin, Actors were relatively more likely to pull the handle on trials in which food was placed in the Recipient bin
Given that only Recipients could directly access food in the Recipient bin, the pattern of results suggests that Actors comprehended how their choices impacted group members, and that they learned to ignore trials that didn’t deliver benefits to conspecifics or to themselves

Summary

Introduction

The literature on social behavior in chimpanzees (Pan troglodytes) shows clearly that cooperation is common in these animals They cooperate when patrolling territorial boundaries and attacking neighboring groups [1]; collaboratively hunting small prey [2]; sharing meat and other foods [3,4,5]; exchanging grooming for other valuable resources [6,7,8]; and jointly guarding mates [9]. This rich record of cooperation drawn from observational studies does not fully answer the question of how this behavior is motivated. Experiments with captive animals offer opportunities to control these variables, and to describe animals’ social motives

Methods

Results

Conclusion