Searching for Roots of Entrainment and Joint Action in Early Musical Interactions

When we observe someone performing an action, do our brains simulate making that action? Acquired motor skills offer a unique way to test this question, since people differ widely in the actions they have learned to perform. We used functional magnetic resonance imaging to study differences in brain activity between watching an action that one has learned to do and an action that one has not, in order to assess whether the brain processes of action observation are modulated by the expertise and motor repertoire of the observer. Experts in classical ballet, experts in capoeira and inexpert control subjects viewed videos of ballet or capoeira actions. Comparing the brain activity when dancers watched their own dance style versus the other style therefore reveals the influence of motor expertise on action observation. We found greater bilateral activations in premotor cortex and intraparietal sulcus, right superior parietal lobe and left posterior superior temporal sulcus when expert dancers viewed movements that they had been trained to perform compared to movements they had not. Our results show that this 'mirror system' integrates observed actions of others with an individual's personal motor repertoire, and suggest that the human brain understands actions by motor simulation.

We argue for the importance of processes of shared intentionality in children's early cognitive development. We look briefly at four important social-cognitive skills and how they are transformed by shared intentionality. In each case, we look first at a kind of individualistic version of the skill -- as exemplified most clearly in the behavior of chimpanzees -- and then at a version based on shared intentionality -- as exemplified most clearly in the behavior of human 1- and 2-year-olds. We thus see the following transformations: gaze following into joint attention, social manipulation into cooperative communication, group activity into collaboration, and social learning into instructed learning. We conclude by highlighting the role that shared intentionality may play in integrating more biologically based and more culturally based theories of human development.

Perceiving other people's behaviors activates imitative motor plans in the perceiver, but there is disagreement as to the function of this activation. In contrast to other recent proposals (e.g., that it subserves overt imitation, identification and understanding of actions, or working memory), here it is argued that imitative motor activation feeds back into the perceptual processing of conspecifics' behaviors, generating top-down expectations and predictions of the unfolding action. Furthermore, this account incorporates recent ideas about emulators in the brain-mental simulations that run in parallel to the external events they simulate-to provide a mechanism by which motoric involvement could contribute to perception. Evidence from a variety of literatures is brought to bear to support this account of perceiving human body movement.