Psychologists have defined intelligence in various ways. Some psychologists have suggested that intelligence involves a single general factor, or a broad mental capacity. Others suggest intelligence is made up of many different skills and abilities. Strategies for measuring intelligence have changed significantly over time, improving in their standardization, validity, and reliability. Intelligence is influenced by both biological and environmental factors. Environmental factors, such as poverty and limited educational opportunities, can lead to lower scores on intelligence tests.

At A Glance

  • Intelligence includes intellectual ability, possession of specific skills, and the ability to reason abstractly.
  • Modern models of intelligence support the idea that there as many as nine types of intelligence and suggest that analytical, creative, and practical abilities work in concert to create intelligent behavior.
  • Research links biological factors such as brain structure and function with intelligence.
  • Twin, adoption, and family studies have found that genetic factors have a significantly greater impact on intelligence levels than do environmental factors.
  • Environmental factors also play a role in intelligence, and children are more affected than adults by their environmental experiences.
  • Binet and Simon wrote the first IQ test to measure a student's ability to think and reason rather than to acquire knowledge.
  • The Wechsler Adult Intelligence Scale (WAIS) was the first intelligence test written specifically for adults, designed to measure intelligence across various mental abilities.
  • Psychologists use psychometric test-design techniques to make intelligence tests as culture-fair, valid, and reliable as possible.