Brain Mirrors, Brain Motors
June 13, 2009 1 Comment
Brains, brains, glorious brains. I wrote about Sapolsky’s lecture on how an interest in religion might be neurologically motivated because I feel R.S. galumphs rather irresponsibly into dangerous ideological territory. As neuroscience creeps closer to the murkily catholic discipline known as cognitive science, critics often point to what they see as the sinister goal of the field—to someday “see” thought, demystify experience and offer a biologically plausible but totally inadequate account of what it means to think and be alive.
Sandra Aamodt, former editor of Nature Neuroscience, writes the following in a book review about the tendency in “pop” neuroscience to speculate about the disorders of various historical figures:
wherever the historical Mt. Sinai actually was and whatever occurred either at its base or at its summit, Mosaic hypoxia is not likely to explain much about his subsequent teachings. Although seizures may have produced the visions of St. Theresa of Avila, they do not explain her capacity for vivid communication or, for that matter, her organizational abilities as a religious leader. Trying to explain too much with reductive biomedical arguments is an occupational hazard of popular science; despite the examples adduced here, the authors largely avoid this pitfall (for example, there is no mention of El Greco’s putative astigmatism).
To wit: there are things that neuroscience should not do. Trying to retroactively construct Shakespeare’s brain based on his writings is one of those things (it has been tried). But there are things it can help with: understanding the neural bases of empathy, for instance. Or tracing the neuroanatomical links between action, intention and spectatorship. It can help us, in other words, think a little more critically (and yes, biologically) about what it means to be an audience and how we participate in the stories we hear or read.
The skeleton key to this sort of enterprise is the now-famous phenomenon of mirror neurons, a cortical system which, when you watch someone grasp a baseball, increases the excitability of your own motor cortex and baseball-grasping muscles. Basically, this is a class of neurons that discharges both when you grasp a baseball and when you watch someone else grasp one. In their 1998 paper describing this discovery, Gallese and Goldman write that “every time we are looking at someone performing an action, the same motor circuits that are recruited when we ourselves perform that action are concurrently activated.”
Although the phenomenon was first observed in monkeys, it’s also been found to operate in humans, and on a much broader scale. Gallese and Goldman suggest that the mirror neuron system enables a kind of “mind-reading,” which they define as “the activity of representing specific mental states of others, for example, their perceptions, goals, beliefs, expectations, and the like.”
G and G take it as read that humans are pretty good at developing some internal representation of a conspecific’s mental state, and offer two mechanisms through which we might do so. The first, amusingly named “theory theory” (TT), speculates that we operate according to strict logical principles and create a “commonsense theory of mind” which acknowledges that only one’s mind is knowable through introspection, and that we have no direct access to the minds of others. All we can do is posit causal relationships and explanations. It’s an “if A, then B” sort of model that will give us the subject’s emotional state as output. For example, if we see John get hit in the face by Sam, we’ll assume that since people don’t usually like to get punched, especially not in the face, it is probably safe to conclude that John is angry at Sam.
The second, “simulation theory” (ST), suggests that we actually guess at someone’s emotional state by “putting ourselves in their shoes,” creating an entire system of pretend desires and beliefs through which we filter the available information and come up with an output. Gallese and Goldman offer the following example: Mr. A and Mr. B are sharing a cab to the airport and get caught in a traffic jam. They get the airport 30 minutes after their scheduled departure times. Mr. A is told his flight left on time, Mr. B is told his left just five minutes ago. Who was more upset? 96% of people say Mr. B was more upset. According to TT, we would need to come up with some sort of psychological law for why this should be so. According to ST, the “law,” even if we could find it, would be a product of our own internal decision-making mechanism with all its preferences and beliefs.
Now here’s where it gets tricky. Yesterday Slate published an article on whether or not Judge Sotomayor really would be a better judge because of her Latinaness and womanity. Dahlia Lithwick mentions a phenomenon called “imaginative identification” which she explains as follows:
The gist of it is that in order to get ahead in the world, you learn to see life through the eyes of those who have already succeeded. According to at least some anthropologists, women have had to get awfully good at understanding what it would be like to be a man. Men, on the other hand, are rarely forced to think about life in a woman’s Manolos.
A commenter on Lithwick’s article raises the important question: granted that perhaps we do pretend to step into each other’s shoes, how good are we at doing it? Or, as Gallese and Goldman put it, “if simulation is going to make accurate predictions of targets’ decisions, pretend desires or beliefs must be sufficiently similar to genuine desires and beliefs that the decision-making system operates on them the same way as it operates on genuine desires and beliefs. Are pretend states really similar enough to the genuine articles that this will happen?”
This is their answer, which stays in the realm of motor activity and doesn’t pretend to go into the more nuanced problems of reading emotion:
Homologies between pretend and natural (i.e. non-pretend) mental states are well documented in the domains of visual and motor imagery. (We assume here that visual and motor imaging consist, respectively, in pretending to see and pretending to do; see Currie and Ravenscroft.) These visual and motor homologies do not show, of course, that other pretend mental states, for example, desires and beliefs, also functionally resemble their natural counterparts, but informal evidence suggests this.
Curiously, the mirror system can go too far when impaired. One of the curious things about the mirror system is that although it increases the excitability of the muscles involved in a particular movement, it very rarely results in the movements themselves. An important exception: imitation behavior—people with prefrontal lesions who compulsively mimic behaviors performed in front of them.
G and G interpret this as a failure of the inhibitory system. They theorize that when one sees an action done, one forms a “plan” to perform the action oneself, which gets inhibited by the prefrontal lobe. When the relevant part of that lobe is damaged, the inhibition is lifted and the plan goes into effect.
Chilling, isn’t it?