Contingency is Crucial for Creating Imitative Responses

A commentary on Acquisition of automatic imitation is sensitive to sensorimotor contingency In order to imitate, we must translate the visual representation of an action into the motor commands which will produce the same action. A growing body of evidence suggests that the mirror system – comprising brain areas active during both the observation and the performance of actions – is involved in this process (Heiser et al., 2003; Catmur et al., 2009). It has also been suggested that, by representing another person's action in one's own motor system , the mirror system underlies not only imitation but also action understanding (Rizzolatti and Craighero, 2004). A similar self-other matching system may produce empathic responses to others' emotions. Now, a new study (Cook et al., 2010) has provided the first evidence to distinguish between the predictions of two competing theories of how mirror responses are acquired, and has demonstrated the key role of sensorimotor contingency. How do mirror responses arise? Over the last 5 years it has become clear that mirror system responses to others' actions depend on experience, and in particular on sensorimotor experience, where the same action is observed and performed at the same time (Calvo-Merino et al., 2006; Catmur et al., 2007). Two contrasting theories have been proposed to explain how such experience can produce mirror responses. Heyes' Associative Sequence Learning (ASL) model (Heyes and Ray, 2000; Heyes, 2001) suggests that general processes of associative learning, such as those which support instrumental and Pavlovian conditioning, are sufficient to produce mirror responses. Alternatively, the Hebbian perspective (Keysers and Perrett, 2004) considers mirror responses to result from Hebbian learning. These two accounts are similar in many ways, but differ in particular on one important point. Hebbian learning, as illustrated in the axiom " cells that fire together, wire together, " relies on the temporal contiguity between stimuli and responses (observed and performed actions): any two representations which are active at the same time can become associated. Thus, under the Hebbian account, as long as they occur together, any observed action could become associated with any performed action. This has led to suggestions that the Hebbian account cannot fully explain why most mirror neurons respond to the observation and performance of the same action. Keysers and colleagues have therefore suggested that sensorimotor experience during development must be " canalized " to provide the right kind of matching input to the mirror …