Automatic imitation and spatial compatibility in a key-pressing task

Automatic imitation has been often confounded with spatial compatibility effects. Heyes (2011) called attention to this confound, and proposed some criteria which must be satisfied before these effects could be unequivocally taken to be an index of the functioning of the human mirror system. Evidence satisfying such criteria has been reported by Catmur and Heyes (2011), using a relatively unfamiliar finger abduction movement. However, because many previous studies relied on more familiar actions, we aimed at testing whether analogous effects could be obtained with a more practiced key-pressing task. In Experiment 1, we used anatomical controls (i.e., views of right vs. left hands) under conditions affording mirror imitation, and showed that spatial compatibility masked the effects of automatic imitation. Experiment 2 used rotated conditions to control for this spatial-anatomical confound, and it showed unequivocal effects of automatic imitation, which were obtained regardless of its relation to the spatial stimulus-response mapping. These results cast some doubts on the interpretation of previous reports relying exclusively on scenes presented from a mirror perspective, and suggest the convenience of using both rotated scenes and anatomical controls in order to assess automatic imitation.