Route switching in imitation: should I stay or should I go?

The dual-route models of action imitation predict that, normally, known actions are imitated by using a semantic route - i.e. by activating a representation of the action from memory - whereas unknown, new actions are reproduced by using a direct route - i.e. by performing a visuo-motor transformation of the input into an output. Here we aimed at establishing the nature of the dominant process used by healthy adult individuals in imitation. Participants performed an imitation task with both predictable switches and pseudorandom, unpredictable switches The predictable switches are less cognitively demanding, and allow the voluntary selection of the most suitable process for performing the task; whereas the unpredictable switches are more demanding and lead to a more intense use of strategies. We observed significant switch costs only in the predictable switch condition, when subjects had to rely on working memory to keep track of the underlying sequence, but not in the pseudorandom sequences, where participants could select the direct route to decrease the cognitive effort. These findings suggest that the semantic route is the dominant, more automatic and less-demanding process for action imitation. The strategic selection of route in action imitation and in monitoring behaviour seems to be an adaptive acquisition.