Praxic and executive components in tool use learning: the role of imitation.

Recent research in comparative psychology suggests that similarities between the behaviour of two individuals may not be the consequence of imitation only, but also of nonimitative social-learning processes. In the present study we aimed to investigate whether these alternative learning processes can take place in human adults, specifically in patients whose ability to imitate has been reduced by brain damage. Left (LBD) and right (RBD) brain-damaged patients were asked to perform four tool use tasks in three experimental conditions: exposure to the apparatus (N); demonstration of the correct solution (C); and demonstration of a failed attempt followed by the correct solution to the problem (I + C). Results suggest that the left hemisphere is indeed critical for action and that selective neuropsychological deficits can affect action imitation and selection of goal-directed movements, independently from each other. Findings also indicate that when the ability to imitate actions is lowered emulation may become available.