Why IQ Tests Don't Measure Intelligence

Consider a surgeon, a composer, an artist, and a physicist. Each is the world's best. Each therefore is highly intelligent as the Oxford English Dictionary defines intelligence:

the ability to acquire and apply knowledge and skills,

And as they are all highly intelligent, then, according to the psychologist's understanding of the term intelligence, they must all have really high IQ's. But do they? And even were it so, what would that mean?

The surgeon for all his astonishing deftness with a scalpel, and his knowledge of human anatomy, may be dumb as a brick at math, and not especially articulate either. The composer probably can't draw, and the artist may be unable to carry a tune. And the physicist,  may, like the great Paul Dirac,  be linguistically monosyllabic. So to say that these highly intelligent people are equally intelligent, even in the unlikely case that they scored equally on an IQ test, would be meaningless. They are not equally intelligent at all. They are each vastly more intelligent, than all the rest in their own particular way.

What's hard to understand about that? Everyone knows that that is how it is. Intelligence is not one thing, one faculty, one gift: it is an array of abilities, each person having intellectual strengths and weaknesses. How then did psychologists come to adopt the seemingly nonsensical idea that one number, the so-called Intelligence Quotient, could measure a persons intellectual worth?

The answer to that question is two-fold. First, IQ testing is like the busted science of phrenology — the reading of cranial bumps: it allows the practitioner to claim to know a person's intellectual standing in the world, and hence their future potential. It is this claimed ability to judge the worth of a man that places the psychologist in a position of authority.

The second reason that psychologists proclaim the power of IQ tests to measure mental horse-power is a piece of mathematical data manipulation invented by a Victorian eugenicist and statistician, Karl Pearson. The math in question is called factor analysis, and what factor analysis does is to examine the relationships among various characteristics of some class of things, for example, towns, countries, planets, acorns, or apples, thereby to discover whether there is a common factor or factors underlying these relationships.

An underlying factor, is exactly what the psychometricians — as the quantifiers of mental capacity call themselves — found when they examined variation from individual to individual in mental abilities. Those who score high on mathematical logic, tend to do relatively well on other tests such as verbal reasoning, or the interpretation of geometric puzzles. This factor, quantified by Pearson's factor analysis, they named "G" for "General Intelligence."

Having gone thus far, it was a small step to the conclusion that a person's mean score on the various components of a test of cognitive abilities was a valid way to estimate General Intelligence, hence the results of tests of multiple cognitive tasks was called an "Intelligence Quotient" or IQ, and the test itself, an IQ test.

This view led to a general belief that intelligence is just one thing, underlain by some as yet unidentified common factor, which determines a person's overall intellectual capacity.

But the correlations among cognitive capacities are low. In fact, mostly very low. See here, for example, where correlation coefficients (r values) among a large number of tests averaged less than 0.3. That means that, on average, less than 10% (r squared values) of the variation in any one ability is explained by variation in any other ability.

So yes, mental capacities share at least one common underlying factor, but its effect is weak, meaning that an individual's relative ability at one kind of mental activity will rarely be an accurate guide to their ability at another type of mental task.

It is the weakness of G, and the dependence upon it of their conception of IQ as a measure of intelligence, that psychologists have been loathe to admit. Thus has emerged a widely held idea that G as estimated from an IQ test score measures the essence of intelligence, just as chip speed measures the power of a computer central processing unit. What this is widely understood to imply is that intelligent mental activity depends on either a common mechanism, or a common feature of nerve cells that dictates the scope and power mental activity. However, the slightest awareness of brain anatomy and physiology would disabuse one of the notion that the brain has anything equivalent to a CPU, or even a uniform functional cellular capacity. On the contrary, different mental activities depend on different neural lobes, networks and ganglia, or on hierarchies of lobes, networks and ganglia.

Moreover, these components of the brain are far from identical in physiology and structure. There are many types of nerve cells or neurons and their supporting glial cells, as there are many different signalling methods within the brain, these involving at least eighty neurotransmitters. Despite the subjective unity of mind, the brain is thus a collection of many neurological machines, each with its own genetic determinants and its own history of past experience.

Thus, G or general intelligence, far from representing a fundamental component of intelligence, reflects only the dependence of the functioning of the entire brain on either other organs or some weakly influential characteristic of all brain tissue.

For example, brains without oxygen die within seconds, which means that brain function depends on lungs, heart and the vascular system. Moreover, without a continuous supply of glucose brains cannot function, which means a dependence on the liver and on the endocrine system that controls blood sugar. And without means to dispose of waste products, the brain is rapidly poisoned, meaning dependence on the kidneys. As to general properties of brain tissue, effective function depends on  many general features such as mitochondria, ribosomes, microtubules, and much else, all of which must function properly or the brain will function poorly or not at all.

Thus the mystery of G is revealed. It is a reflection, simply, of the brain's dependence on the rest of the body and on the cellular machinery common to all nerve cells. If all supporting systems and sub-cellular components are in the highest working condition, then the multiple components of the brain can all function at the peak capacity. But all defects or limitations in the performance of supporting systems and cellular organelles limit mental performance. Thus, beside variation in relative power of the various components of the brain there will be variation from brain to brain due the functionality of the brains support systems and components.

Thus just as a large town will tend to have more crime, traffic congestion and air pollution than a small town, so those with the best overall health and the best cellular machinery, will tend to have higher IQ's than those whose mental function dependent on defective support systems or cellular machinery. But still, among individuals, the big differences in intellect, are on specific tasks not on overall performance, or G, as assessed by a so-called IQ test.

So, yes, IQ-ism is largely bunk and the sooner we're rid of it the sooner will psychologists be able to study intelligence more intelligently.

What Is Intelligence?

Over at the Unz Review, an innocent named Sam complains that in writing about IQ, resident psychologist, James Thomson:

… does not address that/those portion(s) of the human brain that deal with intelligence.

But like the psychologists, Sam has the wrong model. The brain isn’t like a computer. There is no central processing unit that determines computing power, FLOPS or IQ.

The brain is the product of evolution. It is built on the Rube Goldberg principle. A bunch of junk put together and then endlessly tested in the struggle for existence, endlessly modified by mutation, and endlessly retested.

The end product of this evolutionary process does all kinds of amazing things in amazing ways, but not in the neat tidy ways a good engineer would design things to work, but maybe completely crazy ways, but ways that work nevertheless — somehow, just…

The result is that intelligence is not one thing. It is not the product of one bit of brain or one brain module. It is the product of numerous neurological modules and networks, each doing its own thing, each dependent on its own particular structure and biochemistry, each subject in its development to its own set of controlling genes. Did you know that, in the male brain, there’s even a specialized knot of neurons that seems to have no function except to light up at a girl’s smile? Cool.

That’s why IQ testing is nonsense. It’s possible to be both a genius and an idiot — in different areas of mental activity: an obvious fact, but one that seems rarely to have crossed the mind of a psychologist.

But the IQ-ist's notion of intelligence is much wronger than would result merely from the mistaken notion that intelligence is a single thing embodied in a single bit of the brain, equally involved in the composition of a symphony, the formulation of a mathematical theorem, or the deftness of the artist's or surgeon's hand, and hence to be viewed as a single variable defined by one number, or intelligence quotient.

The IQ-ist compounds the error of assuming that the brain has a central processing unit that determines the intelligence of every thought or action, by making the further error of assuming that intelligence is strongly genetically determined. This idea leads IQ-ists naturally to a toxic belief in the existence of immutable racial and class hierarchies in intelligence, an idea bolstered by test results that blatantly confuse cultural and environmental differences in cognitive development with racial and class differences in genetic endowment for intelligence.

It is true that intelligence has a genetic basis, as does every other organismal trait. But the influence of genetics is always modified by environment. Raise a child in an iron cage without human contact, as was the fate of the Russian Tsar, Ivan VI (1740-1764), crowned at the age of two months but deposed a year later and then held in solitary confinement until his murder 23 years later, and it will severely stunt the mind, as was the case with poor Ivan. From that we can deduce that  intelligence is not fixed, but is something that grows or withers in response to experience and use.

That, in turn, means that intelligence is not fixed genetically or socially. It develops over time, increasing or decreasing according to circumstances. Hence, the idle Harvard undergraduate with a perfect SAT score may be outpaced intellectually by the committed student of lesser SAT-endorsed intelligence who strives for mastery whether in academia, socially or in some other sphere of endeavor.  

Accompanying growth or atrophy of intellectual skills occur radical changes in brain structure. During infancy,  hundreds of thousands of the brain's synaptic connections are eliminated every second over a period of many months. Later, during adolescence, much of the tissue of the cerebral cortex, the supposed seat of intelligence, is eliminated. Such developmental processes undermine the idea, common among IQ-ists, that intelligence is a function of brain mass. The implication, rather, is that, depending on mental effort and experience, intelligence grows or fails to grow whatever the individuals genetic endowment. 

And that is obvious when you come to think of it. Give a plumber a plumbing problem and he'll likely figure it out faster than you could, even if you've got a high IQ and understand hydraulics. Same in any field: hard work and experience increases performance, including problem-solving skill, and that equals increased intelligence. 

IQ-ism: the Third Phase in the Development of Psychology as a Pathological Discipline

One of the things I have to tell you about IQ research is this: if you don't buy IQ research, you might as well throw away all the rest of psychology. And the reason for that is that the psychologists who developed "intelligence testing" were among the early psychologists that instantiated the statistical techniques that all psychologists use to verify and test all of their hypotheses. So you end up throwing the baby out with the bath water.

And the IQ people have defined intelligence in a more stringent and accurate way that we have been abnle to define almost any other psychological construct. So if you toss out the one that is most well defined, then you're kind of stuck with the problem [of] what are you going to do with all the other ones that you have left over.... whose predictive validity is much less.
Jordan B. Peterson

In a comment thread at the Unz Review, among the most thoughtful and well-informed participants remarked on  what they held to be the importance of IQ research. The claim prompted me to the following remarks dismissing the entire business of what may be called IQ-ism as, at best, a scholastic blunder of epic proportions, and at worst, a grotesque fraud:

Speaking of "reasons to support IQ research," I would say that there are none. IQ-ism is just a phase in the development of psychology as a pathological intellectual discipline. IQ-ism is the latest in a series of attempts to comprehend the vast complexity of the operation of the brain by alchemically simplistic means.

First, in the history of this crackpot discipline was psychoanalysis, aptly described by Peter Medowar as:

... like a dinosaur or a zeppelin; no better theory can ever be erected on its ruins, which will remain for ever one of the saddest and strangest of all landmarks in the history of twentieth century thought.

Then there was Behaviorism, which sought to explain human behavior and personality in their entirety solely in terms of the acquisition of operant conditioned reflexes. That theory crashed and burned as cybernetics confirmed what Behaviorists had denied, namely, that humans are conscious beings and that what consciousness tells of our feelings and intentions is a valid source of information.

And now we have IQism, which claims to be able to quantify a person's intelligence on a unidimensional scale by means of a simple paper and pencil test involving a few logical puzzles plus, depending on the test of choice, miscellaneous other items.

How do the IQ-ists sell this idea? Primarily by the artful use of language. Their little test, they call an "intelligence test," thereby establishing in the minds of the masses the unquestioned assumption that intelligence is what the IQ-ist's test measures. In fact, however, as a Google search will confirm, intelligence is the ability to acquire and to use information, whereas an IQ test measures neither except in an incredibly limited domain and with a test the results of which are subject to massive circumstantial bias.

But the IQ-ist scam has worked so well for so long that psychology has yet to even broach the real scientific questions that must underlie the measurement of  intelligence: namely, how to measure the capacity for information acquisition; and how to measure skill, effectiveness, Darwinian fitness, or whatever, in the use of information.

When one considers the measurement of intelligence in those terms, one is immediately confronted with the complexity of reality, and in particular, the fact that information is acquired via multiple channels, auditory, olfactory, visual, proprioceptive, etc. with data from each channel processed by a specialized brain module, or probably in most if not all cases, by multiple specialized brain modules.

So now if we take account of the fact that there are hundreds if not thousands of structural genes that impact the development and characteristics of those sensory channels and processing modules, we see that the capacity for the acquisition of information is not dependent on a single characteristic of the brain but on a large collection of independent variables. This fact is well known to common sense. People vary hugely in powers of memory and, moreover, that variation is type specific. Mozart transcribed the entire Allegri miserere after a single hearing, Stephen Wiltshire sketched the whole of Red Square from memory after a brief visit. But, so far as we know, Mozart had no special gift of visual memory, and Stephen Wiltshire is no musical genius. Others do more or less brilliantly remembering faces, voices, poetry, the numbers of pi, conversational tittle tattle, etc., but as far as is known, no one able to remember the first ten thousand places of pi, has composed  a decent symphony or a popular opera.

So in only the matter of data acquisition, we see that intelligence is multiple not unitary. But much more complex to analyse than the capacity for information acquisition is the capacity for the use if information. In fact, perhaps, that is an impossibly difficult challenge. But it is a challenge that must be faced by anyone who claims to measure intelligence in a scientific and quantitative way.

As for the innateness of intelligence, something about which IQ-ists are most emphatic, it is axiomatic that the potentiality is entirely innate. Moreover, we know that there are hundreds, perhaps thousands of genes that direct brain development, plus probably many thousands of hereditary controlling elements, most yet to be identified, that shape the development of the brain and hence intelligence.

But the function of the brain is to record both sensory inputs, i.e., experience, and the internal workings of the brain, i.e., the development of our ideas, both of which shape the way we use information. So it is beyond question that environmental factors, through their effect on the contents of mind, have a huge impact on the degree to which the innate intellectual potential is expressed. Thus focusing on the genetic basis of intelligence to the exclusion of environmental factors, such as education and culture, cannot result in a comprehensive understanding of the phenomenon.