Psychology 101: Intro to Psychology

Throughout the years, there have been many methods used that attempted to accurately quantify and measure human intelligence. You've probably heard of or taken an IQ test, but what does an IQ test actually measure? Find out in this lesson.

What does it mean to be intelligent? Can intelligence be measured? If so, what's the best way to do it?

Psychologists have tried lots of different ways to measure intelligence. The earliest well-known intelligence test was developed by French psychologist Alfred Binet. The French government wanted a way to identify students with learning disabilities, so Binet conducted studies to determine the average performance levels for different school-age groups.

You may have heard of an IQ test. You may have even taken one. Binet's research provides the groundwork for this type of test by outlining the concept of IQ, or Intelligence Quotient. It's called a quotient because it's calculated by dividing a person's mental age by their chronological age. The mental age is determined by a test, and the chronological age is the test taker's actual age in years.

A person who's intelligent according to these kinds of tests performs at a higher level compared to others who are at the same chronological age. The average score on an IQ test is 100. In order to avoid dealing with fractions, the test's designers decided to multiply all scores by 100, which makes that the average score. Other similar intelligence tests have been standardized around an average score of 100 as well. (IQ = mental age/chronological age, *100)

Many developments in intelligence testing occurred in the U.S., where they were messily intertwined with the American eugenics movement. The term eugenics was coined by an Englishman, Sir Francis Galton, who was the grandson of Charles Darwin, the famous evolutionary natural biologist.

Eugenics quite literally means 'good genes,' and it refers to the goal of improving the genetic makeup of a population by reducing or eliminating allegedly inferior genes. You can probably already see where intelligence testing fits into this; the tests were used to determine who had the 'inferior genes.' Galton and others mistakenly believed that the principles of Darwinian evolution - which effects change over the course of many generations - could be applied to rid the population of what they felt were 'undesirable' human social characteristics. Social Darwinism, as the principle behind eugenics is frequently called, resulted in artificial rather than natural selection for traits deemed most acceptable by high-status Americans. It resulted in unfair treatment of racial minorities, who by the standards of the day, were assumed to represent 'less evolved' forms of humans.

Intelligence testing was used to support discriminatory policies made in the pursuit of 'good genes.' As an example, American psychologist Henry Goddard sought to limit the immigration of supposedly 'inferior people' into the U.S. He began testing immigrants at Ellis Island, and in 1917, he reported that 'as many as 40-50% of immigrants were feebleminded.' These results could be explained by the tests favoring Goddard's own culture and language, but eugenicists took it as further evidence of race and intelligence being intertwined. This is still a problem with modern tests like the SAT, where low scores among certain minority groups are taken as evidence of inferior intelligence rather than as an indication of unequal social and economic opportunity.

There have been some attempts to move intelligence testing away from these problematic, single-factor measurements. Psychologist David Wechsler was dissatisfied with the Binet-based intelligence tests. Wechsler did not wholly endorse the notion of general intelligence. Instead of trying to measure a single quantity, he created tests that were divided into two main areas: verbal-based questions and non-verbal tasks like pattern recognition, each of which are further subdivided. Wechsler's tests are scored differently than Binet's, though the average score is still 100.

To summarize, the history of intelligence testing, at least in the United States, has both provided a way to measure capabilities and led to troubling assumptions about differences in intelligence between ethnic groups. Psychologist David Wechsler developed new types of intelligence tests that measured not only mental abilities, but also a variety of abilities necessary to succeed in life, including personality and emotional traits. Wechsler also argued that a person's circumstances, such as educational and socioeconomic factors, should be kept in mind when evaluating intelligence.