Abstract # 3047 Poster # 188:

Scheduled for Sunday, September 18, 2011 07:00 PM-09:00 PM: Session 23 (Salon G (Sixth Floor)) Poster Presentation


J. C. Songrady1,2, S. J. Suomi1,2, L. C. Egan3 and A. Paukner1,2
1National Institute of Health: Animal Center, 16701 Elmer School Rd., Dickerson, Maryland 20842, USA, 2National Institute of Child Health and Human Development , 3Kellogg School of Management, Northwestern University
     All over the world external rewards and pressures are used to motivate people (e.g. giving students gold stars for a job well done). While this method is highly accepted, some psychologists support the over-justification hypothesis, which states the use of external (extrinsic) pressures will decrease future internal (intrinsic) motivation. Interestingly, this hypothesis has been supported primarily in humans, but not in other animals. The majority of animal studies investigating reward effects support learning theory, which suggests the occurrence of behaviors will increase when rewarded. To test whether over-justification exists in other primates we first introduced infant rhesus macaques [n=22] to 2 novel toys for 5-minute baseline measurements. In the following session, we gave the subjects food rewards for every 10 seconds they interacted with one toy and not the other. We tested for reward effects two days (phase 1) and 1 week (phase 2) after the reward session by again observing the subject interacting with the toys. Baseline, phase 1, and phase 2 were coded for time spent with each toy. Results showed a significant increase of reward-toy interactions [ANOVA, alpha=0.05], suggesting rewards have no detrimental effect on subsequent intrinsic motivation in monkeys. The analysis contradicts the over-justification hypothesis and supports learning theory. However, whether this study design transfers to humans is still open for debate.