K. Grandy’s research while affiliated with Technische Universität Berlin and other places

Free-flying bees were conditioned on a vertical wall to a vertical tactile pattern consisting of parallel lines of grooves and elevations. The asymptote of the learning curve is reached after approximately 25 rewards. Bees can discriminate the conditioned vertical pattern from a horizontal or diagonal alternative. Angle discrimination is apparent only for relatively coarse tactile cues. The proboscis extension response of fixed bees was used to condition bees to a vertical tactile pattern which was presented to the antennae. The learning curve reaches an asymptote after 4 rewards. After 7 unrewarded extinction trials the conditioned responses are reduced to 50%. Bees show best discrimination for patterns whose edges they can scan with their antennae. The animals show a high degree of generalization by responding to an object irrespective of the trained pattern. Under laboratory conditions fixed bees can discriminate the angles and spatial wavelengths of fine tactile patterns consisting of parallel grooves. Bees can also discriminate forms and sizes of tactile patterns. They do not discriminate between different types of edges and between positive and negative forms.

Honeybees fixed in small tubes scan an object within the range of the antennae by touching it briefly and frequently. In our experiments the animals were able to scan an object for several minutes with the antennae. After moving the object out of the range of the antennae, the animals showed antennal movements for several minutes that were correlated with the position of the removed object. These changes of antennal movements are called “behavioural plasticity” and are interpreted as a form of motor learning. Bees showed behavioural plasticity only for objects with relatively large surfaces. Plasticity was more pronounced in bees whose compound eyes were occluded. Behavioural plasticity was related to the duration of object presentation. Repeated presentations of the object increased the degree of plasticity. After presentation durations of 30 min the animals showed a significant increase of antennal positions related to the surface of the object and avoidance of areas corresponding to the edges. Behavioural plasticity was compared with reward-dependent learning by conditioning bees to objects. The results of motor learning and reward-dependent conditioning suggest that bees have tactile spatial memory.