Neuroscience’s Inference Problem And The Perils Of Scientific Reduction

In Science’s Inference Problem: When Data Doesn’t Mean What We Think It Does, while reviewing Jerome Kagan‘s Five Constraints on Predicting Behavior, James Ryerson writes:

Perhaps the most difficult challenge Kagan describes is the mismatching of the respective concepts and terminologies of brain science and psychology. Because neuroscientists lack a “rich biological vocabulary” for the variety of brain states, they can be tempted to borrow correlates from psychology before they have shown there is in fact a correlation. On the psychology side, many concepts can be faddish or otherwise short-lived, which should make you skeptical that today’s psychological terms will “map neatly” onto information about the brain. If fMRI machines had been available a century ago, Kagan points out, we would have been searching for the neurological basis of Pavlov’s “freedom reflex” or Freud’s “oral stage” of development, no doubt in vain. Why should we be any more confident that today’s psychological concepts will prove any better at cutting nature at the joints?

In a review of Theory and Method in the Neurosciences (Peter K. Machamer, Rick Grush, Peter McLaughlin (eds), University of Pittsburgh Press, 2001), I made note¹ of related epistemological concerns:

When experiments are carried out, neuroscientists continue to run into problems. The level of experimental control available to practitioners in other sciences is simply not available to them, and the theorising that results often seems to be on shaky ground….The localisation techniques that are amongst the most common in neuroscience rely on experimental methods such as positron emission tomography (PET), functional magnetic resonance imaging (fMRI), electroencephalography (EEG), and magnetoencephelography (MEG). [In PET] a radioactive tracer consisting of labelled water or glucose analogue molecules is injected into a subject, who is then asked to perform a cognitive task under controlled conditions. The tracer decays and emits positrons and gamma rays that increase the blood flow or glucose metabolism in an area of the brain. It is now assumed that this area is responsible for the cognitive function performed by the subject. The problem with this assumption, of course, is that the increased blood flow might occur in one area, and the relevant neural activity might occur in another, or in no particular area at all….this form of investigation, rather than pointing to the modularity and functional decomposability of the brain, merely assumes it.

The fundamental problem–implicit and explicit in Kagan’s book and my little note above–is the urge to ‘reduce’ psychology to neuroscience, to reduce mind to brain, to eliminate psychological explanations and language in favor of neuroscientific ones, which will introduce precise scientific language in place of imprecise psychological descriptions.  This urge to eliminate one level of explanation in favor of a ‘better, lower, more basic, more fundamental’ one is to put it bluntly, scientistic hubris, and the various challenges Kagan outlines in his book bear out the foolishness of this enterprise. It results in explanations and theories that rest on unstable foundations: optimistic correlations and glib assumptions are the least of it. Worst of all, it contributes to a blindness: what is visible at the level of psychology is not visible at the level of neuroscience. Knowledge should enlighten, not render us myopic.

Note: In Metascience, 11(1): March 2002.