The Measurement of Differences- IQ
Psychologists have been measuring intelligence with standard tests for a number of decades and the IQ score has been imbedded into educational evaluations and methods, even though IQ tests are a limited sample of human abilities. While this sample is interesting, IQ tests are not real life tests of intelligence and IQ scores receive more attention than they deserve. Group IQ tests are usually multiple choice, pen and paper tests, used in education, business and the military to screen large numbers of people. Individual tests are more time consuming and are used to evaluate individuals who may be gifted or retarded.
The two most popular individual tests are the Stanford-Binet and the Wechsler scales. Binet's test emphasized verbal skills and was arranged by age level so that 80-90% of any given age could pass at their own age level. The test score is expressed as a mental age, which corresponds to the average age of normal children who perform as well as the individual being scored. Binet's original assumption was that people who performed below their age level were retarded, those who performed at it were normal, and those who performed above it were gifted. In 1916, Lewis Terman revised Binet's test for use in the United States and it became known as the Stanford-Binet Intelligence Scale. This was the first test to generate an intelligence quotient, or IQ, calculated as a ratio between a person's mental age and chronological age. Psychologists now use the test to compute a score known as the standard age score. The Stanford Binet Intelligence Scale is standardized and can be administered sequentially at a variety of ages. The Wechsler Scales differ from the Stanford Binet Test and include three separate tests, each designed for a different age group; the age ranges are 4 to 6.5 years, 6 to 16 years, and late adolescence to adulthood. Scores on the Wechsler Scales are based on the raw test score in relation to the normal distribution curve of intelligence.
Aptitude tests are tests that are designed to test how much someone would benefit from being admitted into an educational program or course of study. They are generally concerned with the subject's ability rather than the subject's prior knowledge.
Achievement tests evaluate how well someone has learned the material from a given course. The Scholastic Aptitude Test (SAT) is a multiple-choice test, widely used in the USA. The purpose of the SAT is to evaluate aptitude for college level work. The original test had two sections, verbal and mathematics, each of which had a mean score of 500 and a standard deviation of 100.
The reference sample for this standardization was a group of 10,000 American students in 1941. Average scores dropped in the early 1990's (verbal mean 422 and mathematics mean 474 in 1991). In 1994, the test was revised into SAT 1: reasoning tests and SAT 2: subject tests. SAT 1 added questions that require short written answers in addition to multiple choice, and the SAT 2 focuses on different areas of aptitude with more comprehensive testing.
Neurological and neuropsychological examinations are focused on sampling the function of different parts of the brain at an elementary level to detect gross damage to brain function in individuals, but are not good at revealing the a range of learning abilities that IQ tests sample.
An IQ score is calculated to place an individual within a normal group distribution so that an IQ of 100 is the mean and one standard deviation is 15 IQ points. IQ tests are age dependent and different tests are used in different applications. IQ tests do not necessarily correlate with aptitudes, skills and achievements that are highly valuable and rewarded in contemporary society. Among our highest paid citizens are business men, athletes, singers, actors, authors and musicians. Each of these groups has a distinctly different intelligence specialization that may not be predicted by IQ measurement.
Humans live increasingly complex lives and require a surprising range of mental abilities even to live a rather simple life with little or no academic accomplishment. Both IQ and educational measures cut a narrow but important path through the human experience. If, for example, you evaluated Wayne Gretzky’s hockey-playing ability with a standard IQ test you would come to the wrong conclusion. Gretzky became the highest scoring payer in the NHL and earned his title “The Great One” with calm precision over a twenty-year career in the National Hockey League. Gretzky’s genius in sensing, deciding and acting at the fast speed of a hockey game was manifest in sports and would have allowed him to excel as hunter-warrior on the African Savannahs thousands of years ago.
IQ scores of different populations
When IQ scores of different populations are compared and are found to differ, a competitive battle of ideologies ensues. The quarrelling over differences is largely futile. The differences are probably real, biological differences and the task is to understand their origins and implications. We can be thankful that male and female mean IQ scores are the same in matched groups, although there are differences in subscores. Jensen stated: “Whatever their cause, IQ differences are related to variables of immense practical consequence in the modern world. The substantial correlation of IQ with many educational, social and economic criteria has been well established. In the USA there are statistical differences in IQ measures of groups differing by racial and ethnic origins. The most dramatic difference lies between black and white populations, consistent over the past eighty years. The average difference is 1.2 standard deviations or 18 IQ points. While these measurements are abundant and study after study has explored the differences, the bare conclusion is that populations can and do differ by average IQ and that this difference in due in part by genes is resisted by many."
The recognition and understanding of population differences is essential to compassionate and effective science. Jensen is careful to point out that group differences and individual differences are not the same. Clearly, there are smart black people and dumb white people so that pre-judging the ability of individuals by skin color is foolish. In Jensen's words: "Consider the fact that the mean difference in IQ between members of the two racial groups is little different from the average difference of full siblings raised in the same family. But because "brighter" and "duller" siblings are not immediately recognizable and therefore categorized as such, there has been neither widespread nor institutionalized discrimination against the latter in favor of the former, not policies enacted in the hope of redressing the statistical inequity that does in fact exist between these two groups."
When Gretsky was asked if he thought his children would inherit his extraordinary hockey talent, he suggested humorously that they could be unlucky and get his IQ and his wife’s skating ability. He was right about genetics. The mixture of his genes and his wife’s genes shuffles the genetic deck; it is unlikely that another great one would emerge from his family. Gretsky was probably a rare combination that occurred when his parents’ genes decks were shuffled and combined on the night of conception. Like all great ones, Gretsky worked hard at perfecting his game. He also benefited from the teaching and support of a father who wanted him to succeed.
One of his attributes was the determination to be the best he could be and the determination was expressed as daily, disciplined practice since five years of age. The best IQ test for hockey paying ability is the game itself and scouts for professional teams will scan the players in the farm teams for outstanding abilities. Performance scores in professional hockey are logged at each game in detail and provide real-time assessments of the hockey intelligence of each player. You could argue that IQ tests are limiting samples and are designed to be convenient for psychologists and institutions to use. Real-life tests tend to be more complex and richer in materials and contexts.
We know that all human performance is context -dependent and we know that humans are unstable, pulsing creatures whose performance varies from minute to minute and day to day. Performance may be different before and after lunch. We can accept the IQ measurement as an artificial, somewhat arbitrary and limited sample of mental ability, but a sample that is useful nevertheless, because of well-known correlations of IQ data with other measures of social importance. Studies of inborn talent often produce confusing results because of the interaction of innate ability, practice and opportunity. Children who live in enriched environments with supportive parents and practice skills at an early age will tend to do better than children who lack opportunity.
Enriched early learning opportunities will show transient benefit in terms of improved IQ scores, but the disappointing discovery is that the benefits of early enrichment tend to disappear in late adolescence. Everyone knows that some children excel and others, even with the most supportive environments and diligent practice will only achieve passable or mediocre levels of performance. Gretzky was surrounded by the best hockey payers that the world could produce and many worked as hard as he did, but only one or two others could match his extraordinary level of performance. Mario Lemieux was another great one considered to be “one of the most naturally gifted players in NHL history.” In 1987, Lemieux joined Gretzky to lead Team Canada in victory over Team USSR in world hockey competition.