Intelligence tests typically include an array of different types of mental tasks, testing various aspects of verbal, numerical, and spatial ability, involving multiple different cognitive processes, including short-term memory, knowledge, perception, and reasoning. British psychologists Charles Spearman found that abilities in these various different areas were positively correlated, and suggested that they could be explained by one single general factor, a ‘g factor’, which would account for about 50% of the total variance across such tests.
General intelligence, he said, can be measured by tests that measure specific skills, which he called s to differentiate with g. People who display skill in one area may also score high on tests in other specific areas. Spearman believed that people possess an innate general intelligence that determines how they perform in a wide range of tests involving a variety of learning mental activities. His “general factor” was a single number representing the average level of intelligence across all these tests. In his view, certain kinds of brain damage could impair the operation of the general factor without affecting the individual’s overall intelligence; thus, the ability to learn new things would not necessarily decline in those with damaged brains. Although these definitions were rejected later, Wundt’s concept of IQ and Spearman’s general intelligence factor continue to be popular models to define intelligence.
