Abstract # 91:

Scheduled for Thursday, August 17, 2006 07:00 PM-09:00 PM: Session 8 (Regency West 1/3 ) Poster Presentation

Self-control in a delay maintenance task by rhesus macaques (Macaca mulatta)

T. A. Evans and M. J. Beran
Language Research Center, Georgia State University, 3401 Panthersville Road, Decatur, GA 30034, USA
     Self-control is studied for its importance to goal-oriented behavior. In a delay maintenance task, self-control is the tendency to deny oneself a mediocre, constantly available reward so as to receive a more valuable, delayed reward. Here, nine monkeys were tested for the ability to refrain from reaching into a container in order to maximize the accumulation of sequentially delivered food items. Three different task versions varied the quantity and quality of available food items. First, ten preferred food items were delivered over 30 s time, or until a monkey consumed the items. Second, one preferred food item and nine less-preferred food items were presented, with the preferred food item delivered first, fifth, or tenth in sequence. Monkeys’ delays were not significantly different between these tasks of differing reward quality (Paired t(8) = 2.023, p = 0.078); however, a significant positive relationship was found between preferred item position and self-control (linear contrast: F(2, 16) = 5.728, p = 0.044). In the final task, one less-preferred food item was followed by one preferred food item with variable delay between items. Some monkeys delayed gratification for this small reward quantity even with relatively long delays (120 s). However, the same few monkeys exhibited high performance in all three different task versions indicating that self-control by macaques is not as prevalent in these tasks as in chimpanzees and humans.