Abstract # 61:

Scheduled for Saturday, September 19, 2009 06:30 PM-09:00 PM: Session 5 (Mission Bay Ballroom CDE) Poster Presentation


SYMBOLIC QUANTITY DISCRIMINATION AND SUMMATION IN CAPTIVE WESTERN LOWLAND GORILLAS (GORILLA GORILLA GORILLA)

T. L. Vratanina and D. I. Sharpe
University of Georgia, Department of Psychology, Athens, GA 30602, USA
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Some non-human primate species have demonstrated the capacity for quantity discrimination and summation with secondary reinforcement in the form of tokens. We examined this capacity in seven western lowland gorillas. In Phase I of the experiment, the gorillas were asked to make a choice, by pointing, between two unequal values (e.g., 1 cylinder token = 5 blueberries vs. 1 cube token = 1 blueberry). Choices were recorded for two blocks of 12 trials each with the highest-value token recorded as the correct choice. Criterion was successfully met when the subject made at least 10 of 12 correct choices in two consecutive blocks. Three of the seven gorillas successfully completed Phase I. In Phase II of the experiment, subjects were presented with homogeneous choice combinations (e.g., 2 pyramid tokens = 6 blueberries vs. 4 cube tokens = 4 blueberries). Choices were recorded for blocks of 12 trials over nine or ten days, one block of trials per day. A chi-squared analysis revealed that one subject performed successfully on the summation task, utilizing the strategy of choosing the largest sum [Χ2(1)=14.43, p<0.001] over the alternative strategies of choosing the largest number of tokens [Χ2(1)=1.94, ns] or choosing the highest-value token [Χ2(1)=0, ns]. We conclude that western lowland gorillas have the capacity to perform summation using symbolic representation.