Are visual stimuli sufficient to evoke motor information? Studies with hand primes.

In two experiments we assessed whether seeing objects automatically activates information regarding how to manipulate them. In Experiment 1 participants categorized photographs of objects that could be manipulated either with a power or a precision grip into artefacts or natural kinds. Target-objects were preceded by primes consisting of photographs of hands in grasping postures (precision or power grip). Experiment 2 involved a preliminary motor training phase in which each visual prime was associated with the actual motor action. In both experiments, natural kinds graspable with a power grip produced the fastest responses. In Experiment 2 we also found a congruency effect between the prime and the kind of grip required by the object (precision, power). Results suggest that visual stimuli automatically activate motor information. Specific motor programs are, however, activated only if motor training is performed before the categorization task. Implications of the results for the understanding of the organization of conceptual and motor information in the brain are discussed.