Aug 31 / Iakovos Koukas

Intelligence and IQ Scores

Intelligence is not the same as Intelligence Quotient (IQ). IQ is an estimation and a measurement of an individual’s intelligence. Human intelligence is assessed by IQ scores determined by standardized IQ tests. IQ is therefore defined as a score on a standardized test designed to assess human intelligence.

An Intelligence Quotient (IQ) is a standard measure of a person’s intelligence and a score derived from standardized psychological tests designed to assess human intelligence. The abbreviation "IQ" was coined in 1912 by William Stern.

In the early years of IQ testing, IQ was a score calculated by dividing a person's mental age score (which was obtained by administering an intelligence test) by the person's chronological age and multiplying by the number 100 to produce a ratio IQ. The modern concept is called deviation IQ, which is calculated as a function of the discrepancy of an individual score from the mean score. An individual's raw score on a given test is transformed to a normal (or Gaussian) distribution, also known as the Bell Curve, which is symmetric around its mean. The mean (or average) is 100, and the standard deviation is 15 (used in most professional IQ tests).

68% of the population scores between 85 and 115, 95% scores between 70 and 130, 99% scores between 55 and 145, and only 2% scores below 70 or above 130.

Some tests produce more specific IQ scores, such as verbal IQ, which estimates an individual’s verbal-linguistic ability; numerical IQ, which assesses a person’s numerical-mathematical abilities; logical IQ, which evaluates one’s problem-solving abilities and critical thinking; and spatial IQ, which estimates someone’s visual-spatial abilities.

An IQ score is an estimate of an individual’s intelligence as there is not a concrete measure of human intelligence. IQ scores are associated with nutrition, health, mortality, heritability, education, and socioeconomic status.

IQ scores are widely used today for educational placement, choice of profession, assessment of one’s intellectual disability, learning or neurocognitive disorder, and evaluation of job candidates. IQ scores are good predictors of an individual’s school and academic performance, professional career, and they are directly related to income and wealth. They are also used in psychometric research to study the distribution of intelligence in certain samples of the population and the correlations between IQ and other variables. IQ scores for several populations have been rising at an average rate of three IQ points per decade since the early 20th century. This phenomenon is called the Flynn effect. However, there have been newer studies that the Flynn Effect has ended, and in recent years there is a slight decrease in IQ scores.