Category difference facilitates oddity learning in honeybees (Apis mellifera).

Performance of honeybees resembles that of vertebrates in a variety of associative learning experiments. Recent work has focused on relational learning phenomena not easily explained by associative principles, including same/different problems, the simplest of which is the oddity problem. Free-flying bees were trained to visit a laboratory window and were rewarded for choice of the odd stimulus among a set of stimuli. There were two stimulus categories, single-color solids and two-color patterns. The training was trial-unique, with new sets of stimuli on each trial. In Experiment 1, 4 groups were trained in a 3-stimulus oddity problem, 2 with solid odd and patterns nonodd and 2 with pattern odd and solids nonodd. For 1 group in each condition, the odd and nonodd stimuli shared a color. The performance of all groups was better than chance. The bees could solve the problem on the basis of oddity (same vs. different) or category (solid vs. pattern). These possibilities were unconfounded in Experiment 2 with 2 groups trained in a 4-stimulus oddity problem. Group 1 was trained with a category difference on each trial; the solid color was odd on half the trials and the pattern odd on the others. Group 2 was trained with no category difference; all stimuli were patterns. Both groups showed better-than-chance performance, and the irrelevant category difference facilitated oddity discrimination for Group 1. The results support previous findings of oddity learning in honeybees, the only invertebrate species for which any relational learning phenomena have been demonstrated. (PsycInfo Database Record (c) 2020 APA, all rights reserved).