The Psychometric Approach to Intelligence: How Smart am I?

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Biology 202
2004 Second Web Paper
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The Psychometric Approach to Intelligence: How Smart am I?

Bradley Corr

Aristotle and Cicero were some of the first great minds to contemplate, and even allocate a word to, the phenomenon now referred to as intelligence (1). History has been filled with people trying to pin down the precise existence of the term because of the general belief that it is an exact term. In this century the psychometric approach has been the primary method of studying intelligence (2). This method is based on the presumption that intelligence is a measurable factor, and thus the IQ test was born.

Over the past several decades children across the globe have been given IQ tests at some point in their elementary education. A letter comes home and parents are given a number which compares their child to all other children their age. This number is meant to be a measure of the child's intelligence and is believed to play a role in determining his or her track in life. However, the downfall of these results is that they have created the modern day common belief that intelligence is a finite characteristic. It is universally understood that different people contain varying degrees of intelligence, however it is highly misunderstood what intelligence is.

IQ, or "Intelligence Quotient," was originally obtained by dividing a person's mental age by their actual age (2). More recently IQ tests have been defined to measure specific abilities. These abilities include but are not limited to such things as verbal ability, problem-solving ability, social competence, knowledge, motivation, dealing with abstract concepts, ability to classify patterns, ability to modify behavior, ability to reason deductively, ability to reason inductively, and ability to understand (3) (4). There are literally hundreds of different skills or abilities that can be measured. These measurements are scaled in comparison with many other people of the same age. The scale is set to have a mean of 100 and standard deviation of 15 (5). The belief behind the psychometric principle of measuring intelligence is that, like many modern psychiatrists and psychologists today believe, intelligence is essentially what the tests measure (3). However, these measurements are merely data. This data is used to draw conclusions, and hopefully a definition of intelligence.

The purpose of collecting intelligence data is to better understand the meaning of intelligence itself. Although the notion of intelligence is widely accepted and referred to, the definition is vague. At one specific symposium, twelve psychologists were separately asked to define intelligence, and twelve distinct responses were returned (1). This vagueness is evident in the fact that there are hundreds of separate IQ tests that measure many different abilities. Granted that an actual IQ test will cover several of these abilities, it is inevitable that many will be left out. To render this problem Charles Spearman, in the 1920's, created a statistical extraction using factor analysis called the general factor (g) (6). The g factor is a correlation among the varying IQ tests and mental abilities. The significance of the g factor is that it claims to explain the differences among ability tests and will hold up regardless of the test type or manner in which the test is administered (6). Many professionals do not doubt that the g factor does enter, to varying degrees, the countless mental activities that guide human behavior (1). The g factor is an extractable statistical factor of intelligence.

The implications of obtaining a correlation among all mental abilities, and therefore intelligence, are immense. It gives us the capability to set levels of intelligence, as well as make predictions about such things as way of life, success in life, and even happiness. Although it has been found that a persons given intellectual performance can vary from day to day, as well as among abilities (2), it has also been found that a person's intellectual ability is generally stable and unchanged after adolescence (6). This infers that intelligence is a set factor and therefore so is their intelligence based fate. Studies have been shown that a person's g factor and IQ positively correlate with success both in school and out of school (2) (6). Thus, the smart people will be successful and the stupid people will not. Not only will they not be successful but they cannot be helped. The U.S. army banned people with IQ scores below the tenth percentile from enlisting during WWII because they felt they could not be taught to be good soldiers (6). These correlations can even imply that due to an inability to succeed in life, a person's happiness will be determined by intelligence. The intelligent will be rich and happy while the unintelligent will be poor and sad. These implications are extremities, but not far fetched. The holes and misconceptions of the g factor and psychometric principle become clear in the extremities of their implications.

The major fault of the psychometric principle, that intelligence is measurable, is in its central understanding. An essential aspect of the theory is that even though there are innumerable mental abilities of intelligence there is a general g factor that correlates to them all and can be extracted. However, in admitting to the multitude of mental abilities that comprise intelligence, any removable characteristic is negated as being a sole representation of intelligence. In searching for a finite characteristic of intelligence, this theory provides evidence that in fact there is no fixed attribute. In the 1980's these problems sparked new theories of intelligence.

The evolution of intelligence theory began to acknowledge the vastness of what the term intelligence represents. People such as Howard Gardner and Robert Sternberg approached the concept arguing that the psychometric attempt leaves out much of what intelligence is. While analytical mental capabilities were measured, practical and creative aspects were ignored (1) (3) (5). This new train of thought was based on a perception that there are many types of intelligence in which only some can be measured. There are many aspects to intelligence which make it too complex to distinguish. This makes the phenomenon of intelligence indefinable, but rather better described, in order to portray a more detailed image than any definition could provide (4). It is this idea that has fueled the search and study of intelligence in the past few decades. The idea of "painting a clearer picture" is the motivating force behind the research.

Unfortunately, the aspiration of finding a certain aspect of intelligence that can be recognized as the primary factor has still fogged modern research. There have been studies both proving and disproving positive and negative affects on intelligence by such factors as knowledge, education, exercise, stress, and even listening to Beethoven (2) (5) (6). Correlations between such things as brain size, gender, and ethnicity have gone through cycles of being published, then disputed, then revoked, and republished (7) (8). The disputes over causes and affects are often about specific characteristics but also often deal with the issue of environment verses genetics. Which is the dominant factor in intelligence, or is it both? Research on issues such as stress and upbringing clearly emphasize environmental factors of intelligence. However genetics are often referred to as essentially important. Until recently, the beneficial aspect of these research elements is that both sides understood and further exclaimed that it is most likely both aspects which affect intelligence.

In most recent times technological advances, such as the completion of the human genome project and advanced brain scanning techniques like MRI, have driven the research and beliefs about intelligence to go full circle. We are now in a time when once again the search for a specific factor of intelligence is underway with new technology. Twin studies have tried to determine the factors of environment and genetics and even more specifically tried to find specific genes related to intelligence (9). Although it is understood that the relationship between genes and behavior is rarely a one to one correlation (9), this has not halted the search for the linked genes. New measurable factors such as the degree of branching in cortical neurons, the rate of brain metabolism, and the number of neural connections are being studied with regards to intelligence as well (2). These studies are simply using new tools for the psychometric approach of measuring intelligence. It is not impractical to predict that the near future will entail new IQ tests which simply take a sample of DNA and a brain scan to report a new number of intelligence.

The psychometric approach has provided very good correlations to many varying aspects of intelligence. It has set standards and scales that future researchers can compare with and expand upon. However, it ignores the major factor of its theory; the enormity of what intelligence really is, a conglomeration of the many mental abilities both measurable and immeasurable. The realization of this factor has been set aside because it creates great difficulty in providing validation to intellect studies. Yet, every study and researcher makes note of it. In essence future research would be wise to deal with the primary issue of the extensive nature of intelligence rather than the futile search of a straightforward quantifiable conclusion.


1)The Evidence for the Concept of Intelligence, A rich source of both history and intelligence theories

2)IQ and Intelligence, A article on the relations between IQ and Intelligence

3)Genetics of Childhood Disorders, A good article demonstrating disagreements about intelligence

4)The Concept of Intelligence in Cognitive Science, A review of modern theories of intelligence

5)Intelligence: Knowns and Unknowns, An in depth look at intelligence theories and research

6)The general Intelligence factor, An explanation of the g factor and intelligence

7) Does Brain Size Matter? , Research relating brain size to intelligence

8)Cranial Capacity and IQ , Research relating cranial capacity to intelligence

9)Our genes, ourselves?, An in depth look into the role of genetics and environment in intelligence

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