The Lure of the Mirror
We begin this section with a brief background sketch of sensorimotor theories to understand why over time they have appeared so attractive. As we already mentioned, scientists and philosophers have long been attracted by the idea that we grasp the semantics of the actions we observe directly from the observed motor patterns. The fundamental claim of such theories is that there is no need to assume intermediate processing steps during which the meaning of an observed motor pattern is elaborated in the brain/mind. This appears to suppose that there is indeed something like a 1:1 relation between each motor pattern and the meaning of the action it implements. But this is the heart of the problem. Would this approach really work for bodily expressions, even before the extensions of the framework to include social and emotional aspects?
A HISTORICAL NOTE ON SENSORIMOTOR THEORIES OF PERCEPTION
Motor theories of perception have a long history. When we see how they promise to solve the really difficult and age-old epistemological problem of mental representation, the mind-world correspondence and the causes of actions, it is understandable that motor theories again and again have seduced the philosopher as well as, more recently, the scientist. Motor theories of perception have a substantial pedigree with roots in the early days of physiology, and later with scientists like Washburn (1914, 1916). In philosophy, the motor theories of cognition go back in back at least to Berkeley (1709). A radical behaviorist like Watson understood the attraction of motor theories to explain mental processes. One of the recent books to connect current neuroscientific research with the long and interesting history of these ideas is that of Jeannerod (e.g., 1997).
The basic notion is that highly developed animals have adapted to living in social groups with very complex patterns of social interactions and that they depend on these stable interaction patterns for survival. Understanding the meaning of other people’s behavior is an essential aspect of group communication. The largest subset of our daily observations is about the actions of other people and concerns the objects at the core of social actions and interactions (Barresi & Moore, 1996). Indeed, a surprisingly large portion of our daily life is spent watching, interpreting, and reacting to the actions of others. This is even more evident for whoever observes a large vervet monkey family. It is truly amazing to see how little time is spent eating compared with the time spent endlessly observing the behavior of others in the multigenerational family. Therefore, from a functional perspective, we would expect that the brain has evolved procedures for optimizing the processing of these highly important and frequent stimuli that are the people around us. And historically motor theories of perception have been prime candidates for explaining these social perception skills, even before currently popular notions like social perception or social brain were en vogue.
Since the nineties, the human neural mechanism underlying our ability to represent others’ goals by the observation of their motor actions has been the target of considerable psychological research performed independently of physiological theories of mirror neuron mechanisms. Behavioral experiments had already suggested that the subjective system for generating and representing actions is also used in the perception of the actions of others (see Blake & Shiffrar, 2007, for a review; e.g., Knoblich & Prinz, 2001). Motor resonance seems to respect the biomechanical constraints of our body, imposed by our skeleton and articulations. Shiffrar and Freyd (1993) showed that it was possible to influence the subject’s perception by varying the time of presentation of pictures of body positions (see Blake & Shiffrar, 2007 for a review).