Levels of Intelligence - Constancy of I.Q.

Intelligence Quotient (IQ) measures how an individual's cognitive ability compares to others of the same age. Researchers have found that IQ typically remains stable throughout childhood and adolescence unless major changes occur in a person’s environment, health, or education.

• IQ scores are mostly stable (±5 points) after age 6.
• Larger fluctuations can occur in preschool years due to rapid development.
• Exceptions may be seen if there are major changes in health, nutrition, or education.
• A few rare cases show significant changes (e.g., changes of 50 points or more).
• Research (e.g., Hirt, 1945; Goodenough, 1940) supports the view that, barring unusual situations, constancy is the rule.

If a child receives better nutrition and education, their IQ may improve slightly. Most children who receive stable, adequate care have IQ scores that stay about the same across years.

• IQ is mostly stable after early childhood.
• Big changes in environment, health, or education can influence IQ, but this is uncommon.
• Early childhood IQ scores can fluctuate more due to rapid development.