Intelligence has been discussed throughout much of human history. Socrates gave one definition of intelligence: “I know that I am intelligent, because I know that I know nothing.” Intelligence over the years has been defined as such diverse things as understanding others, knowledge gained, who you surround yourself by, what you accomplish, and the ability to reason. Before the 19th century, intelligence was solely in the realm of philosophy. Franz Joseph Gall, who started the phrenology movement, sought to localize intelligence (among other things) in the brain, which was in turn measured on the skull. While many of the ideas of phrenology were inaccurate, the idea of quantifying individual differences and localizing those differences onto the brain was an important one. Over the years, researchers started using better methods of research and understanding individual differences.

Then in the early 20th century, a French researcher was asked by the French government to come up with a way to identify children who would and would not benefit from schooling. He developed the first modern intelligence test. This first intelligence test quantified attention, verbal skills, and memory. About 10 years later, Lewis Terman, a psychologist at Stanford, adapted it for use in the United States. These tests provided an Intelligence Quotient as the quantification of intelligence. It was quickly applied by the military to identify who would make good officers an who should be rejected from service. Charles Spearman, an English psychologist, developed the idea that many disparate components of intelligence all represented an underlying general factor of intelligence (g). This had a large impact on the idea of intelligence and on the development of future measures of intelligence.

David Wechsler developed an intelligence test, largely based on Spearman’s idea of g; this test is the most widely used intelligence test in the United States. The most recent version measures verbal comprehension, perceptual reasoning, working memory, and processing speed. There is considerable controversy whether processing speed — which roughly is how quickly someone can perceive and process new information or perform an action — should be considered a measure of intelligence. Other people balk at assigning a single number to intelligence, especially when there is not a universally agreed upon definition of intelligence. Still others feel that traditional intelligence tests provide a too narrow view of intelligence. One such researcher, Howard Gardner, initially proposed that there are seven intelligences (this has since been modified to include at least two more), including bodily-kinesthetic, linguistic, interpersonal, visual-spatial, and so forth. A problem with his theory is that his intelligences are not easily measured (however, some people would not see this as a fault).

What do the readers think about intelligence? Do IQ tests provide a good measure of intelligence? In other words, is it a meaningful concept? Does Gardner’s theory fit better? Is intelligence even a useful concept to measure? Was Oscar Wilde correct when he said, “The intellect is not a serious thing, and never has been. It is an instrument on which one plays, that is all”?