Serial reversal learning in bumblebees (Bombus impatiens).

Bumblebees are capable of rapidly learning discriminations, but flexibility in bumblebee learning is less well understood. We tested bumblebees (Bombus impatiens) on a serial reversal learning task. A serial reversal task requires learning of an initial discrimination between two differentially rewarded stimuli, followed by multiple reversals of the reward contingency between stimuli. A reduction in errors with repeated reversals in a serial reversal task is an indicator of behavioural flexibility. Bees were housed in a large indoor environment and tested during foraging flights. Testing free-flying bees allowed for large numbers of trials and reversals. All bees were trained to perform a simultaneous discrimination between two colours for a nectar reward, followed by nine reversals of this discrimination. Results showed that bumblebees reduced errors and improved their performance across successive reversals. A reduction in perseverative errors was the major cause of the improvement in performance. Bees showed a slight increase in error rate in their final trials, perhaps as a consequence of increasing proactive interference, but proactive interference may also have contributed to the overall improvement in performance across reversals. Bumblebees are thus capable of behavioural flexibility comparable to that of other animals and may use proactive interference as a mechanism of behavioural flexibility in varying environments.