Intelligence: Nature vs. Nurture

July 15, 2009

    There appear to be two diametrically opposed camps regarding the age-old nature vs. nurture intelligence debate. The outcome of this tug-of-war is crucial to the question of whether or not brain training is possible. (And conversely, if brain-training is possible, then it would seem to me to point toward the malleability of the brain.)

(1) The "Nature" School: Intelligence Is a Physiologically-Determined Inherited Trait
    Intelligence is genetically determined, and equates to the quality of the myelin sheathing that insulates the nerves. The better the myelin "insulation", the better the signal-to-noise ratio in the brain. This is strictly an inherited trait, and manifests itself in terms of "inspection times" and similar chronometric measures of brain processing speeds. Arthur Jensen and Chris Brand are two psychologists whose names are associated with this position.

(2) The Nurture School: Intelligence is Malleable, and Can Change Over Time in Response to Cultural Imperatives
   This is the interpretation of intelligence espoused by James R. Flynn and  William T. Dickens. The average IQ in most industrialized countries has risen nearly 30 points in the 93 years since the 1916 edition of the Stanford-Binet IQ test was first published (the Flynn Effect). Even more striking, these gains have occurred not in the more-trainable areas of vocabulary, arithmetic, and general information ("crystallized" intelligence), but almost entirely in the realm of pattern recognition and inductive problem-solving ("fluid" intelligence). ("Fluid" intelligence refers to the ability to solve problems on the spot without drawing upon accumulated knowledge.) In other words, the gains on tests of "fluid" intelligence such as the Raven Progressive Matrices have been nearly twice the 30 points of overall IQ gain. ("Fluid" intelligence declines with age in a manner consistent with declines in physiological parameters relating to the brain.) Flynn and Dickens believe that cultural demands in the area of fluid reasoning coupled with an enormous increase in visual presentations (TV, computers) have elicited brain changes that boost scores on tests of "fluid" intelligence such as the Raven.
The Flynn Effect
    It's worth noting that the Flynn Effect seems to be focused on bringing up low and average IQ scores without appreciably altering the IQ scores of individuals in the upper registers of the IQ spectrum. One of the paradoxes that originally plagued James Flynn was the realization that the Flynn Effect would seem to imply that the average citizen of 1900 would be borderline retarded, with an average IQ of about 70. He/she wouldn't have been able to understand the intricacies of baseball or to run the complex world they inhabited. And obviously, that doesn't make sense. (My grandfathers and Dr. Flynn's are as smart as their equivalents today.)
    The realization that the great minds of the past... the Shakespeares, the Newtons, the Leibnitzes...  are as capable as the great minds of today could be explained by the fact that, for whatever reasons, the Flynn Effect doesn't apply to those at the highest reaches of the intelligence continuum.
    More recently, Dr. Flynn has proposed that the gains in scores on tests of "fluid" intelligence are real enough, and are demanded by, and of benefit to modern society.
    The proponents of intelligence-as-an-inherited-capacity that can no longer be significantly altered in adults argue that the momentous gains on tests such as the Raven are "hollow with respect to g". They reflect an enhanced ability to deal with visual constructs but don't represent an actual increase in intelligence.
Throwing Out the Baby with the Bath Water?
    One huge problem that I see in claims that the nearly 30-point gains in IQ scores over the past 93 years are "hollow with respect to g"...i. e., don't really represent increases in IQ... is that they would seem to me to imply that IQ tests are, and have always been  worthless as measuring instruments for IQ... which raises the question: what's IQ if IQ tests fail to measure it?
    One problem with adopting the idea that IQ can't be altered by environmental programs is that it tends to be a self-fulfilling prophecy. If you think it can be done, you won't try.
    I've gotten the impression that the proponents of intelligence-as-an-inherited-trait have shifted to equating intelligence to brain processing speed, and are turning to tests of inspection times and decision times to try to assess intelligence.

My Notions About Nature Versus Nurture
    Flynn and Dickens have proposed that children amplify small differences in initial intellect by selecting (or creating) their own micro-environments that tend to reinforce their slight initial edges. They see that they're a bit better at something than the children around them so they gravitate toward activities that will feed their area of natural capability. I don't believe that for a moment. In the first place, children don't generally socialize a lot before they're around three, and when they do, the comparisons aren't apt to be about who's smarter than whom. Also, there are too many cases in which children like Michael Kearney start to talk and to read long before they could have any conception of comparisons with other babies. Then, too, I know a few super-smart individuals whose parents discouraged their precocity. I think the bulk of intelligence is innate. But the Flynn Effect seems to me to offer the hope that intelligence can be nurtured, and perhaps, to a remarkable degree if we can find out how to do it.