Who invented IQ tests and How does an IQ test measure intelligence?

Because most people refer to an IQ, or “intelligence quotient,” as a fixed score, with the power to determine one’s education, career choices, and even self respect, you’d think it must be derived from a single, standardized test.

Quite the opposite is true. There are numerous tests, with varying fundamental principles and of course different gradations of complexity depending on the age of the test taker, that can be used to determine an IQ score.

This kind of testing began in France in 1905 when the French government commissioned Alfred Binet and Theodore Simon to develop a test that could be used to separate the children who should attend regular school from those who should go to special schools for slow learners.

In other words, Binet’s test indicated whether or not a child would succeed academically by comparing his rate of learning with that of others his own age. This test, composed of 54 questions, was revised and expanded in 1916 and became the widely used Stanford Binet test, which underwent further revisions in 1937 and 1960. It involves tests of analogs and opposites, comprehension, vocabulary, verbal and pictorial completion, and memory.

The other widely used measure of intelligence is the Wechsler Scale, first used in 1939 to evaluate patients at Bellevue Hospital, New York. The Wechsler Intelligence Scale for Children (WISC) was standardized in 1949 on a sample of 2,200 English speaking white children whose fathers fit into nine occupational categories.

Today the scales have been revised to measure people of all ages, with a test for preschool ages four to six and one half, children six to sixteen, and adults sixteen to seventy four.

Unlike the Stanford Binet, WISC divides a child’s intelligence into categories. An IQ score is derived from measuring each subtest and formulating an average. The subtests are designed to call upon a wide scope of the child’s abilities, from concentration and alertness to practical knowledge and moral sensibility. Critics of the tests, however, say they fail to measure a child’s creativity.

An “Information” section, composed of 30 questions on a broad range of general facts, measures how much information a child has gotten from his environment. Such questions as “How many pennies are there in a dime?” which draw on everyday experience are mixed with others requiring information learned in school, such as “What is the capital of Greece?” or “Who wrote Romeo and Juliet?”

A “Comprehension” section of 14 problem questions has been devised to evaluate social and moral behavior patterns acquired in everyday learning, as well as to measure emotional stability. Practical judgment is required to answer such questions as “What is the thing to do when you cut your finger?” or “Why are criminals locked up?”

An “Arithmetic” subtest of timed problems calls upon the ability to manipulate number concepts, requiring alertness to carry out the four basic operations of addition, subtraction, multiplication, and division. These problems are used to indicate a child’s cognitive development.

“Similarities” involves identification of likenesses, for Wechsler believed the ability to develop classificatory relationships to be an excellent test of human intelligence. These questions require associative thinking, “Lemons are sour and sugar is …”, and reasoning, “In what way are a pound and a yard alike?”

A “Vocabulary” subtest contains a list of words to be defined, with special attention paid to the semantic character of the definition. In this category, educational and environmental influences are obviously significant factors in the child’s chances of success.

“Picture Arrangement” consists of cut up pictures or picture sequences to be assembled. This test, which is timed, is designed to measure perception, visual comprehension, and understanding of causal connections. Other subtests include “Block Design,” “Picture Completion,” “Object Assembly,” and “Coding.”

Proponents of IQ tests believe that 80 percent of intelligence is inherited and only 20 percent stems from conditioning, and that the tests adequately measure pure intelligence.

Critics, whose numbers are increasing, hold that no one has ever actually proved that an IQ test and intelligence are precisely related. They point to culturally biased items that result in higher scores for average income whites than for poor urban blacks. All too many questions draw on how much a child has learned in school, an inadequate indication of potential or basic mental ability.

Another criticism is that an individual’s IQ score often fluctuates, depending on emotional state, age, and the desire of the child or adult to succeed.