The subtests of IQ measure and quantify factual knowledge, short-term memory, abstract reasoning, visual-spatial abilities and common sense. A score is computed for each of the subtests, which are generally divided into verbal categories and visual categories, and a total score is determined.
The Wechsler Intelligence Scale for Children (WISC) is the most commonly-used IQ test. Designed for children ages 6 to 16, six of the subtests of the WISC measure verbal intelligence through information, comprehension, digit span, similarities, vocabulary and arithmetic. The six performance subtests measure visual and spatial intelligence though object assembly, block design, digit symbol, picture arrangement, picture concepts and picture completion.
The Stanford-Binet Intelligence Test was the first standardized test to measure intelligence. Its subtests measure verbal reasoning, abstract and visual abilities, quantitative reasoning and short-term memory.