Humans, being highly social creatures, rely heavily on the ability to perceive what others are doing and to infer from gestures and expressions what others may be intending to do. These perceptual skills are easily mastered by most, but not all, people, in large part because human action readily communicates intentions and feelings. In recent years, remarkable advances have been made in our understanding of the visual, motoric, and affective influences on perception of human action, as well as in the (...) elucidation of the neural concomitants of perception of human action. This article reviews those advances and, where possible, draws links among those findings.Acronyms and DefinitionsApparent motion: perception of smooth motion from brief, successive exposures of static imagesChameleon effect: tendency for people to mimic the actions of others without even knowing itCommon coding principle: theory that perceiving and acting share common mental representationsDynamic noise: an array of randomly positioned dots that can camouflage perception of PL animations when the noise dots are sufficiently denseEvent-related potential : electrical brain activity registered from the scalpExtrastriate body area : brain region activated when a person views a human body or body partsFunctional magnetic resonance imaging : widely used technique that reveals brain activation patterns based on hemodynamic responses to neural activityInversion effect: difficulty of perceiving PL animations when they are shown upside downKinematics: analysis of the motions of objects without regard to the forces producing themMirror neurons: brain cells responsive when an animal engages in an activity or when it watches another animal engaged in that activityPoint-light animations: biological activity portrayed by small light tokens placed on the major body parts of an actorPositron emission tomography : brain imaging technique that uses radioactively labeled tracers to allow visualization of active brain areasSpatiotemporal jitter: means of degrading perception of PL animations, where the relative timing and positions of the moving dots are perturbedSuperior temporal sulcus : region of the cortex the posterior portion of which contains neurons selectively responsive to human activityTemplate-matching model: theory that perception of biological motion results from concatenation of static views of the bodyTranscranial magnetic stimulation : technique producing a brief disruption of neural processing. (shrink)

This article argues that mirror neurons originate in sensorimotor associative learning and therefore a new approach is needed to investigate their functions. Mirror neurons were discovered about 20 years ago in the monkey brain, and there is now evidence that they are also present in the human brain. The intriguing feature of many mirror neurons is that they fire not only when the animal is performing an action, such as grasping an object using a power grip, but also when the (...) animal passively observes a similar action performed by another agent. It is widely believed that mirror neurons are a genetic adaptation for action understanding; that they were designed by evolution to fulfill a specific socio-cognitive function. In contrast, we argue that mirror neurons are forged by domain-general processes of associative learning in the course of individual development, and, although they may have psychological functions, they do not necessarily have a specific evolutionary purpose or adaptive function. The evidence supporting this view shows that mirror neurons do not consistently encode action “goals”; the contingency- and context-sensitive nature of associative learning explains the full range of mirror neuron properties; human infants receive enough sensorimotor experience to support associative learning of mirror neurons ; and mirror neurons can be changed in radical ways by sensorimotor training. The associative account implies that reliable information about the function of mirror neurons can be obtained only by research based on developmental history, system-level theory, and careful experimentation. (shrink)

The mechanism by which humans perceive others differs greatly from how humans perceive inanimate objects. Unlike inanimate objects, humans have the distinct property of being “like me” in the eyes of the observer. This allows us to use the same systems that process knowledge about self-performed actions, self-conceived thoughts, and self-experienced emotions to understand actions, thoughts, and emotions in others. The authors propose that internal simulation mechanisms, such as the mirror neuron system, are necessary for normal development of recognition, imitation, (...) theory of mind, empathy, and language. Additionally, the authors suggest that dysfunctional simulation mechanisms may underlie the social and communicative deficits seen in individuals with autism spectrum disorders. (shrink)