Discrimination Learning: Squirrels vs Raccoons

Abstract

Squirrels and raccoons were compared in terms of their discrimination performance with respect to such form parameters as sidedness, axial rotation, and areal asymmetry. Sixteen two-choice discrimination problems were used; two problems from each of the eight classes representing the possible combinations of the presence and absence of differences in each of these three stimulus characteristics. When all three characteristics were equated between the two figures comprising a problem, the number of correct responses did not exceed chance. Differences between the members of a problem in terms of these three dimensions resulted in discrimination performance significantly above chance. Rotation was the most significant single cue, and rotation with sidedness the most effective combination for both animals. For the squirrels, performance was comparable for all problems containing differences in asymmetry, though the more efficient cues of rotation and rotation and sidedness in combination were also present. The performance of the raccoons was also reduced in the presence of asymmetry cues, though these animals, unlike the squirrels, did appear capable of using the cue of rotation when asymmetry cues were also available. These data are seen as confirming the value of a quantitative approach to the comparative study of the discrimination behavior of the sub-primates, particularly since the squirrels and raccoons appear to utilize information differently.