Imitating, copying what someone else does, is only one of the many things humans can do. Yet while most vertebrates are sensitive to the timing of conspecifics' behavior, only a few nonhuman species learn by imitating. Songbirds, parrots (Pepperberg, 2000), and cetaceans (Janik & Slater, 1997) exhibit vocal imitation and to some extent nonhuman primates imitate nonvocally (Whiten, this volume). The species that imitate do tend to be comparatively advanced cognitively (e.g., Pepperberg, 2000). These facts make imitation a prime suspect for being a precursor of much that is uniquely human in human cognition, including its enrichment by sociocultural influences (see also Donald, 1991). In the neurodevelopmental context, I shall present imitation as a foundational building block of cognitive development, and specifically as a source of body awareness and of interpersonal affiliation.

I propose the following: attention is preparatory for action. Percepts are encoded enactively, that is, in terms of the response possibilities that they afford. Mature individuals hold the actual, overt, response in abeyance until the situation calls for it. They accomplish this not by mere inaction but by active restraint, exerted through prefrontal inhibition. Prefrontally injured patients exhibit excessive, unwanted imitation. Infants are also prefrontally inadequate, because the requisite relatively late-occurring neural maturation has not yet taken place. Infants' imitation may be uninhibited enactive perception.