Reasoning by exclusion in food-caching Eurasian jays (Garrulus glandarius)

Abstract

Two related methods have been widely used to test animals capacity to reason by exclusion: Calls (2004) 2-cups task, where subjects choose between two cups in which one reward was hidden and the empty cup is revealed; and Premack & Premacks task (1994) where one reward goes in each of the two cups and one reward is removed. In both cases, success is identifying the cup with the reward. It has been suggested that among corvids, the demands associated with caching may foster exclusion abilities by reinforcing the experience of relevant contraries (e.g., empty vs. full), or by supporting domain general capacities that support caching and exclusion inferences. However, Shaw et al. (2013) found that Eurasian jays, proficient cachers, failed a version of Calls 2-cups task. To further test the caching hypothesis, we amended the procedure using invisible displacement to hide rewards, removing aspects of Shaw et al.s procedure that may have masked competence of Eurasian jays. We tested seven Eurasian jays, who showed spontaneous success on both Calls 1-reward/show-empty (80% correct) and Premack and Premacks 2-reward/remove-1 (85% correct). These results align with the hypothesis that corvids exclusion reasoning is related to caching behaviour.