Abstract # 34:

Scheduled for Thursday, August 18, 2005 03:45 PM-04:00 PM: Session 5 (Mayfair Room) Oral Presentation

Self-control and tool-use in captive tufted capuchin monkeys (Cebus apella)

T. A. Evans, S. Howell and G. C. Westergaard
Alpha Genesis, Inc., 95 Castle Hall Road, PO Box 557, Yemassee, SC 29945, USA
     Self-control is defined as foregoing immediate gratification to obtain a greater reward. Tool-use may relate to self-control, as some tool behaviors require foresight and deliberate control over one’s actions. We assessed twenty capuchin monkeys for the ability to delay gratification in a tool task. Subjects were given rod shaped food items that could either be consumed immediately, or could be carried to an apparatus and used to extract a more preferred food. Monkeys were tested in three conditions. In one condition, the apparatus was positioned, unbaited, nearby the subject. In the other two conditions, the apparatus was positioned, baited, either nearby or distant from the subject. Monkeys’ responses were converted to a bivariate dummy code (0 = consumption of the item; 1 = use of the item as a tool) and were tested in a Repeated Measures ANOVA. We found that the most self-control responses occurred in the baited-near condition, the second most in the baited-far condition, and zero in the unbaited condition (F2, 78 = 146.42, P < 0.001). Also, highly-experienced tool-users exhibited the most self-control responses, moderately experienced tool-users the second most, and inexperienced tool-users the least (F2, 78 = 165.67, P < 0.001). These results indicate that capuchins are capable of delaying gratification when a higher quality reinforcer is present, and that delay period and tool experience can influence levels of self-control.