Intelligence: Definitions and Measurement

Intelligence

• Wechsler defined intelligence as the ability to think rationally, act purposefully, and effectively interact with the environment.
• Alfred Binet, with Theodore Simon, developed procedures to identify students needing special help. They created tests focusing on basic mental abilities like memory, attention, and recognizing similarities/differences.
• Binet's work led to the concept of "mental age," a measure of intelligence based on average abilities for a given age group, separate from chronological age.
• Lewis Terman adapted Binet's tests, calling it the Stanford-Binet intelligence scale.
• Scores on the Stanford-Binet scale are expressed as an Intelligence Quotient (IQ). IQ is a measure comparing an individual's score to others in a similar group.
• Terman's longitudinal study of high IQ children showed they often had good social adjustment and were physically healthier than average children. However, high IQ wasn't a guarantee of success outside of school.

Development of Intelligence Tests

• IQ tests are designed to measure different mental abilities and provide a global measure of intelligence.
• The Wechsler Intelligence Scale is designed for adults, offering scores on subtests measuring various skills, combining to produce overall verbal and performance scores.
• Wechsler’s scale measures verbal aspects like vocabulary comprehension, knowledge, and other verbal tasks.
• Performance subtests evaluate non-verbal abilities including identifying missing parts, arranging images to tell stories, and arranging blocks to fit patterns.
• The WISC-III scale, revised and updated, measures intelligence in children aged 6 to 16, and revised again as WISC-IV in 2003.

Principles of Intelligence Test Construction

• A good intelligence test requires standardization.
• Standardization involves administering tests to a large, representative sample under controlled conditions to create norms for comparison.
• IQ tests typically follow a normal distribution curve with most scores centered around the average.
• Test reliability measures the consistency of results.
• Test validity measures the accuracy of the test in measuring what it intends to measure.

Theories of Intelligence

• Charles Spearman proposed "g-factor," or general intelligence, suggesting a single, general intellectual ability driving overall performance in mental aptitude tests.
• Louis Thurstone argued intelligence consists of several distinct, "primary mental abilities" that are relatively independent.
• Howard Gardner proposed "multiple intelligences," arguing intellectual abilities are diverse and include several areas like linguistic, logical-mathematical, spatial, bodily-kinesthetic, musical, interpersonal, and intrapersonal, adaptable to different cultural contexts.
• Robert Sternberg suggested three types of intelligence: analytical (mental processes in problem solving), creative (dealing with novel situations), and practical (adapting to the environment).

Roles of Genetics and Environment in Intelligence

• Intelligence is influenced by both genetics and environment, though the exact relationship remains complex.
• Twin studies demonstrate a correlation between identical twins raised together, compared to identical twins raised separately; though IQ scores show less similarity for those raised in different environments.