Abstract # 15:

Scheduled for Thursday, June 21, 2012 02:30 PM-02:45 PM: Session 4 (Camellia ) Oral Presentation


A. Kibler-Campbell1, C. Thompson2 and L. K. Sheeran1,3
1Central Washington University, Primate Behavior Department, 400 E. University Way , Ellensburg, Washington 98926 , USA, 2The College of Wooster, Psychology Department, 3Central Washington University, Anthropology Department
     The ability to make instantaneous causal inferences among nonhuman animals continues to be a subject of much debate among researchers. This study tested for causal inference abilities in captive capuchin (Cebus apella) monkeys by “naturalizing” the task to be in accordance with the wild capuchin tool-use behavior of rock-hammering. Six out of seven monkeys studied were able to use the rocks to crack open the nuts provided. Among those six, all were able to make inferences about the properties of the tools presented in order to choose the most functional tool. All six did so significantly above a random chance level (9/10 correct choices; z = 2.52, p < .01) at some point during the initial presentation of the tools. Ability to choose the correct tool differed among the six monkeys, and only one passed criterion on all of the first three conditions upon their presentation. Use of the incorrect tool during the first condition is also possible evidence of causal inference in terms of using a familiar tool in a novel way. Monkeys did not show a strong preference between differently weighted, visually identical tools when faced with opening different species of nut (differing vastly in shell hardness). These results are some of the most convincing evidence of causal inference in capuchins to date because no training or previous exposure to rocks was involved.