Facilitation of learning of a simultaneous discrimination between rotated patterns by bumblebees

The failure to discriminate between a pattern consisting of four orthogonal bars and the same pattern rotated by 45° has been interpreted in the literature as evidence against pictorial representations in honeybees. This study determines whether prior training can facilitate the discrimination. In Experiment 1, one group of bumblebees was trained with a rewarding spiral pattern (S+) vs. its unrewarding 45° rotation (S−). A second group was trained with two different patterns, the spiral (S+) and the chevron (S−). Both groups were then tested with the spiral and its rotation, both of which were unrewarding. The first group failed in the discrimination while the second succeeded. The same was true when the training period was defined by choice frequency instead of time (Experiment 2). The facilitation due to prior experience was pattern specific (Experiments 3 and 4). These results show perceptual learning in bumblebees and weaken the case against pictorial representations.