Yerkes Brigham and group intelligence tests

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Terman and Goddard had introduced intelligence testing to America. Soon, world events would turn it into a national priority. In 1917, the year after Terman first published the Stanford-Binet, the United States entered World War I. Like many other Americans, psychologist Robert Yerkes was eager to serve his country. As president of the American Psychological Association, he also wanted show the value of the young science he represented. Yerkes set up committees to explore the military uses of psychology. He made himself chairman of a committee that was charged with developing an intelligence test for matching military recruits to the right jobs. Terman and Goddard were included among the other psychologists named to the committee.

The task Yerkes had taken on was extremely difficult, however. First, given the sheer number of recruits, the individual testing method developed by Binet and refined by Terman would not have been practical. A whole new kind of group intelligence test, which could be given to several people at once, would need to be developed. Second, the test would have to not only screen out those with low ability, but also identify those with high ability who might be officer material. Third, the test would have to be designed specifically for adults, rather than for children. Fourth, the test development would have to be accomplished very quickly, since results were needed right away.

Yerkes' committee promptly put together two prototype tests: one for recruits who could read English, and another for those who could not. A trial on 80,000 men impressed the Army enough that it authorized the testing of all new recruits by the beginning of 1918. The tests were revised and renamed Army Alpha (for literate recruits) and Beta (for illiterate recruits). Soon, the tests were being given to some 200,000 men per month. By the time war ended in November 1918, about 1,750,000 men had taken one of the tests. This prodigious feat brought intelligence testing to the attention of the public. It introduced the idea of nearly universal testing, and it opened up a huge market for group tests after the war. In addition, the massive amount of data collected on the Army tests became the subject of intense study and led to much public debate about the state of intelligence in American society.

In 1921, Yerkes published Psychological Examining in the United States Army, an 800-page book analyzing the Army test data. Two years later, one of his junior colleagues named Carl Brigham published A Study of American Intelligence, which explored the same topic. The books made several questionable claims. For one thing, they claimed that the average mental age for all Army recruits was about 13 years. At the time, the mental age for an average adult was thought to be 16, and a mental age of 12 in an adult was considered the upper borderline for mild retardation. Therefore, the supposed mental age of the recruits was shockingly low. It might have been logical to conclude that the hastily thrown-together tests had been less than accurate. Yerkes, however, concluded that the results indicated a distressingly low level of intelligence in society at large.

Some of Yerkes' and Brigham's other conclusions were even more controversial. For example, the psychologists noted that, compared to native-born whites, immigrants and blacks tended to score lower on the tests. Once again, it might have been sensible to conclude that the tests had been biased toward members of the majority American culture. On the Alpha test, for example, individuals were expected to know that Overland cars were made in Toledo and that Crisco was a food product. On the Beta test, individuals were expected to be familiar with pictures of middle-class objects, such as a tennis court or a phonograph. Yet Yerkes and Brigham instead took the position that the lower scores obtained by immigrants and blacks indicated lower levels of natural mental ability in those groups.

At the time, racial segregation and discrimination were the norms in much of American society. Public sentiment had also turned sharply against immigration. In fact, in 1924, Congress passed a bill that set strict immigration quotas for each national group. This social climate helped to support Yerkes' and Brigham's conclusions. Yet, even at the time, there were opposing voices. One belonged to Franz Boas, a German immigrant himself and a leading American anthropologist of the early 1900s. Boas argued that many racial and ethnic characteristics were passed from generation to generation not by heredity, but by culture, through such mechanisms as shared values, language, and child-rearing customs.

American Otto Klineberg, a graduate student in psychology, was one of the first researchers to apply Boas' ideas to group differences in intelligence test scores. While studying Yakima Indian children in the state of Washington, he noticed that they seemed indifferent to time limits. They took their time, no matter how much they were urged to hurry, but they also made relatively few mistakes. Klineberg noted that, in Yakima culture, speed was not considered a sign of intelligence. On the contrary, it was thought to reflect carelessness. This was clearly a cultural rather than a genetic difference. Yet it put the Yakima children at a disadvantage on timed intelligence tests. Similar observations in other cultures soon added up to a convincing case. By the 1930s, all but the most diehard eugenicists had conceded that culture played an important role in causing group differences in IQ scores.

In 1926, Brigham made his mark on group intelligence testing in another way. He introduced a brand-new kind of standardized test of mental ability. IQ tests looked at general thinking ability. This new type of test, however, looked more specifically at the kinds of word and number skills that were used in school. Brigham's test became the forerunner of the SAT, a test that is still very familiar to high-school students.

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