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Quantifying Intelligence

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Biology 202
2004 First Web Paper
On Serendip

Quantifying Intelligence

Maria Scott-Wittenborn

Quantifying intelligence is something that makes people anxious. Most people, when asked, cannot pinpoint what exactly it is about assigning a number or value to a person's intelligence that makes them so uncomfortable. What most people do know is that there is something about intelligence that causes it to take precedence over other culturally valued traits such as athletic prowess or physical attractiveness. That out of all the characteristics that humans value, intelligence is the one that matters the most. It is not a incorrect assessment: while athleticism might give one an edge in a sports game or appearance might help one in social situations, intelligence helps one navigate life and the broader and more complex challenges of living every day. Much of the anxiety over trying to quantify intelligence stems from the conflict between the deeply held cultural belief that all people are born with equal opportunity and the realities demonstrated by the IQ Test that some people are born with greater intellectual potential than others . While our society might aspire to be egalitarian, the fact remains that intellectual ability varies from individual to individual (1). It is an important difference too, research done over a period of years confirms that intellectual ability of the type measured by the IQ test has a profound and widespread impact on the way in which a given individual lives his or her life (1).

In an individual person's professional life, there appears to be a strong (and not terribly surprising) correlation between an individual's IQ and the type of employment he or she is able to sustain. Those in the top five percent of the adult IQ distribution (above 125) are able to enter whatever profession they choose (1). Individuals with average IQ are not competitive for most high level jobs, but are able to perform the majority of the jobs in the America (1). Individuals in the bottom five percent of the IQ distribution (below 75) are not competitive within in the workforce (1). The government recognizes the correlation between ability and IQ: during World War II Congress banned the enlistment of those with an IQ below 80 because they were too difficult to train (1).

The effect of IQ is not limited to the professional arena. There is an undeniable correlation between low IQ scores and negative social experiences, probably due at least in part to the strong correlation between an individual's IQ and their socio-economic status. Individuals with IQs somewhat below average are seven times more likely to be jailed than those with somewhat higher than average IQs (1). They are eighty-eight times more likely to drop out of high school and are 50 percent more likely to be divorced (1). Obviously one cannot make assumptions about any individual based on these numbers—after all there are many people with high IQs who are divorced. It would also be erroneous to assume that from this information one could attribute the poverty, single motherhood or divorced state of any given individual to a lack of intelligence. Rather these statistics suggest that the lives of those who are not as well equipped to deal with intellectual complexities tend to be more difficult in today's society in economic, social and personal matters.

In order to understand why an individual's ability to do well on the seemingly odd tasks that are involved in an IQ test is so closely linked to the individual's success in life, one has to understand what trait causes the correlation in the first place. At the turn of the last century by the British Psychologist Charles Spearman noticed a pattern of correlation when analyzing the results of IQ tests. The IQ test is made up of subtests on a variety of unrelated topics, yet an individual who did well on one subtest was likely to do well on all of them, no matter how disparate the contents of the various subtests were. This observation lead Spearman to conclude that there was another force at work, a "general intelligence" or g that accounted for this consistency in performance. It is important to note that g is not simply the cumulative result of someone being good at literature and math and spatial exercises. Rather, it is it's own separate function, which has recently been shown to take place in the lateral frontal cortex of one or both hemispheres (2). This is the area that high-g tasks call on, not a wide variety of cognitive functions (2).

The existence of g is not simply an abstract concept created by scientists. The notion that some people are more able at some things than others is familiar to all of us and used by all of us from the time we are small children. People intuitively sense the existence of g, they just have different names for it. Someone might be considered 'bright' or 'smart' which could just be another way of saying that they are able to handle cognitive complexity. That someone is 'quick' is particularly interesting word choice in light of the fact that recent testing has shown that it does indeed take less time and less energy for the brains of those with high IQs to solve problems (2). Which makes it also rather appropriate that people with less high IQs were often called 'slow'. How precisely to define g is exactly is difficult. Simply stated, g can be defined as "the ability to deal with cognitive complexity" (1). Being able to interpret information, recognize similarities and differences and to understand ideas and concepts are all the hallmarks of the intelligent person, and are also the abilities that constitute g (1).

The discomfort that most people feel at the idea of having a value assigned to their intelligence is a natural reaction given that in many ways it would seem that the results of an IQ test are not predictive so much as prophetic. Given that intellectual ability effects so much, it is easy to understand how the individual could feel that there is little room left for autonomy or self-determination. It would indeed be disconcerting if one felt that the results of a single test determined one's fate. I think that viewing g and the continued study of what effects and is effected by g in such a way would not only be incorrect, but also be a serious mistake. The concept of g is a useful one, but only if it seen for what it is: one way of quantifying an individual's ability to function with relative ease in the world. The test itself exists in a cultural context, a culture that values highly the results of tests. As with any test the claims to make broad judgements about an individual's future, could be self-fulfilling (5). As is the case with most differences between people, it is not the differences themselves that pose a potential problem; rather, it is the value judgements that other make based on those differences that are problematic.

The notion of g is not egalitarian one; few things about human makeup are egalitarian. While we may not think of it in those terms, we all accept and make our peace with this inequality every day (4). That I am not skilled at tennis like Venus Williams, musically gifted like Billie Holiday or beautiful like Julie Christie is not news to me or to the other 99.9% of the world for whom the same can be said. And while I admire the ability in other to do what I cannot, I don't feel that it detracts in any way from the capabilities that I do have. The same principle applies to intelligence, even though the effect of intelligence on one's life is more far-reaching than musical skills or athleticism. Every day we all tacitly acknowledge the existence of g in whose advice we seek, who we do or do not consider competent to perform a given task and the assumptions we make about people based on their profession, socio-economic status or lifestyle. As is true with any valued trait, the ability to quantify it carries with it the concern that we will begin to allow the value society places on the trait to determine the value society places on the individual who happens to possess (or not possess) it. There are a lot of ways that people can be extraordinary and there are a lot of ways that people can lead productive, useful lives regardless of how they score on a test. If correctly approached, the study of g can help us understand why people have the experiences that they do in life and can ultimately help us as a society to accept the mixed bag of skills and weaknesses that are each person.


1)Godfredson, Linda. The General Intelligence Factor, A very thorough article detailing the implications and importance of g in daily life.

2) Duncan, John. A Neural Basis for General Intelligence. Science Magazine. Vol.289; 21 July 2000.

3) Article by Ari Berkowtiz on Serendip, Quite a good discussion of the role genetics plays in IQ among other things.

4) An Article from Science on the International Society For Intelligence Research, General thoughts on uses of intelligence and such.

5) Letter to the Editor of NY Times Book Review by Professor Grobstein Pretty much what the title says what it is: a letter to the editor of the NYT Book Review by PG



Continuing conversation
(to contribute your own observations/thoughts, post a comment below)

06/15/2005, from a Reader on the Web

The article on IQs is informative, but I want to draw your attention to what I believe is a word-choice error. "Given that intellectual ability effects so much, it is easy to understand how the individual could feel that there is little room left for autonomy or self-determination." The sentence should read, "Given that intellectual ability AFFECTS so much . . ." There are several other possible misuses of the word "effect" throughout the article; you may want to review it. Great article though. Thanks. Sadie Blanchard

08/09/2005, from a Reader on the Web

Upon reading "Quantifying Intelligence" by Maria Scott-Wittenborn, on your website, I felt quite validated in my thinking that all people are not created equal. I have had many discussions with many people who speak judgementally of our less than brilliant brothers and sisters. Just the other day, a colleague of mine was berating another coworker because of her inability to understand some basic things about the job she was doing. As I watched my friend's face, it showed disdain for the young girl, who was obviously trying her best, but it has just not been good enough, in spite of three years on the job. I made the comment that some people are just not born with as much ability as others. This got me a rash of statements about how we are "all created equal, mentally, and it's all about what we do with it." I told the attacker that I truly believe everyone is born differently in intellectual ability, and that I was certain that much scientific study would bear me out. We agreed to disagree. It seems that many people want to believe that others who are not as successful as they are are simply lazy, or are just not trying. If we believe that our own successes are entirely from our own doing, and everyone else could do as well if they wanted to, it makes us look like we are better than others through our own efforts and decisions. In order to sustain that belief, we would have to convince ourselves that if someone is not doing as well as we are, then it's their own fault, and conversely, it is our own doing that we are as successful as we are. I know that much of what I have accomplished and will accomplish in life is through the "accident" of the intelligence I was born with, and that many of the failures I have are largely a result of the "accidents" of genetics and life's experiences that I had no control over. The conclusion, for me, is to take the cards I have been dealt, which are better than some, and poorer than others, and do what I can with them. I do not feel cheated. I treat all people the same...with respect and dignity. Whatever level a person is on, mentally, physically, or psychologically, that person deserves at least that much.



Leon Edward's picture

Good Solid Post but results have margin of error unstateable

If there is someone adept at test taking versus an anxious person taking exams, then intelligence testing will have an unknown variable with results confounded. This is an extreme example for comparison, but there are all sorts of people with varying degrees of test taking skills which means according to testing results probable that because they have these skills, they are more intelligent...

I don't know how to quantify this kind of error but one would need to be attached as a possibility though

Beauty articles's picture

that's really a fantastic

that's really a fantastic post ! ! added to my favourite blogs list..