SENSORIMOTOR LEARNING AND ITS RELEVANCE FOR TASK SPECIALIZATION IN BUMBLE BEES

Individual bees often restrict their visits to only a few species out of the multitude of available plants. This flower constancy is likely caused by limitations of memory for motor patterns, sensory stimuli, o r reward levels. Here we test the implications of sensorimotor learnin g and memory for flower constancy. Artificial ''flowers'' with two dis tinct ''morphologies'' were used, so that in each flower type, a diffe rent motor pattern was needed to reach the nectar. As in natural flowe rs, these morphological types were associated with sensory signals (bl ue and yellow color stimuli). Bees which learned only a single task we re more efficient in several ways than those which had learned two: th ey made fewer errors, had shorter flower handling times, took shorter times to correct errors, and transitions between flowers were initiall y more rapid. For bees which had learned two tasks, performance depend ed strongly on the training schedule: if each task was learned with bl ocked trials, the memory for the second appeared to interfere with tha t for the first. Interference affected only the association between fl ower signal and motor pattern, not the motor pattern itself. This was not the case if bees were trained for both tasks with alternating tria ls. In that case, bees rapidly learned both tasks, albeit with worse s aturation levels than bees which had learned only one. Bees transferre d the experience gained on one task to a second task: their initial pe rformance on the second task was better than their initial performance on the first. On the other hand, performance on the second task in th e saturation level (in which bees no longer improve their efficiency) was worse than on the first task (negative transfer). In the saturatio n phase, performance did not directly depend on switch frequency, but on whether the bee had one or two options in memory. Thus, while bees would become proficient at two tasks more quickly if their acquisition phase included switches, such switches had no measurable effect in th e saturation phase. The implications of these findings for foraging ar e discussed using modern learning theory.