Differences in Intelligence
In this module, we will consider the extremes of intelligence -- from the very bright to the very dull. We will also look at a few of the many studies that have been done with IQ scores, correlating many things from sense of humor (Brumbaugh, 1939) to racial background. A few of these correlation studies and their results will be described in this module.
As you read the text, try to answer the following questions.
EXTREMES OF INTELLIGENCE
Measured human intelligence follows a normal distribution in the total population. Scores on intelligence tests range from near 0 to around 200, but the mean is 100. Figure 13 shows an adult IQ distribution developed by Wechsler.
|IQ||DESCRIPTION||PERCENT OF ADULTS|
Figure 13. Distribution of intelligence scores on the Intelligence Scale
People who score above 130 on intelligence tests are usually considered gifted. An important study of gifted children was undertaken by who devised the Stanford-Binet test. In the course of developing that test, Terman and his associates tested many thousands of children, and then did further research on those who had lO's of 140 or more. This group of more than 1500 children was in the top 1% of the population. Terman followed most of these children from 1921 until his death in 1956. Some of his associates are still continuing this detailed longitudinal study.
The study revealed an important fact related to the home environments of the children. Approximately one-third were children of professional people and about half were children of persons in business occupations. Only seven percent came from "working classes." These percentages do not agree at ail with the distribution of social class membership in the general population. They indicate that relatively more gifted children come from the higher socioeconomic classes, although they do not tell us why.
Another discovery in Terman's study was that gifted children are more successful in later life. Twenty-five years after the study began, about 700 of the original group were still in contact with Terman. Of these, 150 were considered very successful. This distinction was based on such criteria as being listed in Who's Who or having received recognition for outstanding intellectual or professional achievement. Most of the others were much more successful than people of average intelligence. On the other hand, some persons in the gifted group had committed crimes, dropped out of school early, or been unsuccessful at a number of jobs. Those least successful were more poorly adjusted emotionally and less motivated than the others. On the whole, though, the most striking fact revealed in the study was that gifted children made generally outstanding contributions to society in the form of intellectual achievements.
In their early years, Terman's gifted children were above average in height, weight, and physical development, and they were also better adjusted. It had ben generally believed that very gifted children were likely to be maladjusted and socially backward. Terman's study definitely disproved this notion.
The gifted child is liable to encounter serious difficulties in school. He may be bored by children of his own age and his knowledge may even exceed that of his teacher. Teachers may consider him rude or a show-off. He may become a real problem simply because he is bored and loses interest in a class designed for "average" children. Some schools today are facing this problem by planning appropriate programs for gifted children.
At the other extreme of the intelligence scale is another problem area -- the mentally retarded who have IQ's below 70. These persons have traditionally been classified as morons (IQ 50-70), imbeciles (IQ 20-50), and idiots (IQ below 20). A new classification by degree of retardation was recently drawn up by the President's Panel on Mental Retardation. This classification divides retardation into mild, moderate, severe, and profound. These categories, along with specific characteristics for each category, are shown below.
MILD RETARDATION (IQ 50-