Intelligence is a general mental ability, often seen as a measure of how successfully an individual adapts to the environment. Psychologists disagree as to what intelligence is, whether it exists at all and whether it can be effectively measured. Binet developed the first IQ tests to weed out the children with cognitive deficits, using a selection of school tasks. Modern IQ tests still follow this tradition and are better thought of as measuring the ability to learn at school rather than general intelligence. Whatever it is that the IQ tests measure, it is fairly stable by the age of 7 and correlates with academic performance and social status achieved in life. However, the effect of IQ is limited and there are numerous other factors that influence academic performance, social status, professional and personal achievements and, ultimately, happiness and fulfillment of the individual.
IQ tests vary in what particular factors they take into account while calculating the overall score, but generally the tasks involved include verbal and non-verbal reasoning, ability to discern patterns in a sequence of images or numbers, and spatial abilities. Many of the most popular IQ tests, including the most commonly used in the US Wechsler and Stanford-Binet scales, include measures of general knowledge, vocabulary and memory.
IQ tests don't measure interpersonal skills and ability to pick up and react to social cues. These social skills and practical abilities are important to the success in a workplace and influence school achievements. The ability to perceive, understand and function in a complex social environment is not related to the test-determined IQ. There are some people who have high cognitive abilities -- for example, they can solve math problems or design spatial arrangements -- but are not great at perceiving emotions, understanding relationships between people or empathizing.
IQ tests don't address any specific talents or abilities, particularly those related to sensory dimensions. These include, for example, bodily-kinesthetic aptitude: a sure hand, sense of timing and an above-average ability to control movement. Dancers, athletes, craftspeople, beauty artists and surgeons all need those skills. Other specific abilities are visual sensitivity and musical talent, expressed as a sensitivity to sound, melody, pitch and rhythm. These are essential to musicians, composers, conductors and singers.
IQ tests don't measure creativity, understood as the ability to come up with original, novel and unusual solutions, called divergent thinking. In fact, many tasks in popular intelligence tests penalize unusual responses and favor conventional, socially acceptable answers. Statistically, IQ and creativity are related but only to a certain level. Up to about the IQ of 120, there is a relationship between IQ and creativity: those with higher IQ score higher on tests of divergent thinking. However, above that level, the connection disappears. A person with an IQ of 110 is statistically more likely to score higher on a creativity test than somebody with an IQ of 90. However, somebody with an IQ of 150 is not likely to achieve higher creativity scores than somebody with an IQ of 130.
IQ tests don't measure personality. However, researchers have shown that several personality traits are good predictors of academic performance. Conscientiousness has a positive association with achievement even though it actually negatively correlates with IQ measures: clearly, effort can compensate for lower ability. Learning styles also influence achievement, above and beyond the IQ scores. Students with high levels of "openness to experience" personality trait and a "deep" learning style (learning for the sake of understanding and internal satisfaction, rather than passing exams) achieve better academic results.
IQ tests don't measure motivation and effort that individuals put into completing tasks. The results of the tests, like results of all ability-related tests, are heavily influenced by how motivated the test-taker is to do well. For teachers or clinicians administering the test to often unwilling subjects, this should be a major concern. Testers should not assume that every person is motivated and tries to do their best during the test. This is particularly important in a clinical context, as people who are depressed or highly neurotic have lower IQ scores, possibly because they are less motivated or less confident.