Sensorimotor Excesses

Historically, we owe some of the most exciting scientific discoveries to the rigorous interaction between reductionism and its opposite.

In the ancient world, the atomists made great strides by attempting to demonstrate how various ordinary phenomena—colour perception, moral values—could be reduced to the shape and movement of atoms. But atomism fell to an extraordinary theoretical insight of Aristotle’s. For as the great geneticist Max Delbrück once wrote in a sparkling little essay entitled “Aristotle totle totle,” this great philosopher and student of nature pointed out that it is a “fundamental aspect of Nature that human beings beget human beings, and do not beget rabbits or an ear of corn.” The atomists cannot explain this.

Delbrück particularly appreciated that this “wonderful man” had posited form as the cause of reproduction (“and not a mini-man”), and impishly attributed to him the discovery of DNA. He was wrong, of course: because Aristotle had abandoned the atomists’ bottom-up compositional principle, and had thus actually blocked the road to the double helix.

In the last century, the study of the mind underwent a similar sequence.

The story is, of course, well known. Shunning unobservable immaterial entities, the behaviourists tried to reduce mind to behaviour. Chomsky refuted them Aristotle-style by pointing to a very familiar phenomenon, in this case infant language learning, that cannot be explained by their principles. The linguistic stimulation infants receive is too impoverished to drive language acquisition, which is, in any case, precisely timed by age and not dependent on quality or quantity (above some threshold) of exposure. In subsequent decades, new phenomena that Elizabeth Spelke has called “core cognition” emerged: other precisely timed sequences of cognitive development under impoverished stimuli. It seemed that we are born with internal representations of syntax, number, causation, etc. Behaviouristic reduction was a goner. Requiescat.

Some wonder, though, if something valuable was not inadvertently thrown on the bonfire of the Skinner boxes. In the new dawn of mental representation, the mind has once again assumed the role of the detached ratiocinator that makes an avocation of controlling the body. Philosophers and cognitive scientists in the post-behaviourist era did not functionally integrate mind with the body it serves. And yet perception and thought must surely be dedicated to action. How else could they have evolved? Humans did not become fit by silently contemplating Plato’s heaven. Thus: “The human mind is embodied in our entire organism and the world,” writes (my respected colleague) Evan Thompson.

It is this theoretical gap that “enactive mind” and sensorimotor theorists seek to fill. Perception and thought cannot be dissociated from action, says Alva Noë, the apostle of sensorimotor theory. “All perception . . . is intrinsically active. Perceptual experience acquires content thanks to the perceiver’s skillful activity.”  This is not just a slogan for Noë. His insistence on the action-embeddedness of perception has led him to be critical, for instance, of the idea that there are two visual streams in the brain, one of which provides us with representations of the world that bear no relation to action. Noë's philosophical orientation carries empirical clout.

In the coming weeks, I intend to say more about this line of thought. Despite the virtue noted above, I believe it is deeply flawed. For now, let me simply note that it exceeds its brief. Of course, perception and thought must serve action. But this does not mean that this is all that it must do. Perception is for action, but perception is also for knowledge—even for abstract knowledge that has no consequences for bodily action. Some theorists are committed to the complete detachment of mental representation. One can deplore their tendency without becoming embroiled in the idea that colours and shapes must be defined in terms of bodily movement.