Learning speed and contextual isolation in bumblebees.

Bumblebees will learn to approach one of a pair of patterns (a 45 degrees grating) and to avoid the other (a 135 degrees grating) to reach a feeder, and to do the opposite to reach their nest (approach a 135 degrees grating and avoid a 45 degrees grating). These two potentially competing visuo-motor associations are insulated from each other because they are set in different contexts. We investigated what training conditions allow the two sets of associations to be acquired without mutual interference. If the discrimination at the feeder has already been learnt, then the discrimination at the nest can be readily acquired without disrupting the bees' performance at the feeder. But, if the two are learnt simultaneously, there is mutual interference. Prior experience of the two contexts before the discriminations are learnt does not prevent interference. We conclude that visual patterns and contextual cues must already be associated with each other for a visuo-motor association to be isolated from the interfering effects of a competing association that is acquired in a separate context. This pattern of results was mimicked in a simple neural network with Hebbian synapses, in which local and contextual cues were bound together into a configural unit.