Precursors to IQ testing
Historically, even before IQ tests were devised, there were attempts to classify people into intelligence categories by observing their … See more

Reliability
Psychometricians generally regard IQ tests as having high statistical reliability. Reliability represents … See more

In general, educational interventions, as those described below, have shown short-term effects on IQ, but long-term follow-up is often missing. For example, in the US, very large … See more

Several neurophysiological factors have been correlated with intelligence in humans, including the ratio of brain weight to body weight and … See more

There are a variety of individually administered IQ tests in use in the English-speaking world. The most commonly used … See more

Environmental and genetic factors play a role in determining IQ. Their relative importance has been the subject of much research and debate.
Heritability See more

Musical training in childhood correlates with higher than average IQ. However, a study of 10,500 twins found no effects on IQ, suggesting that the correlation was caused by genetic confounders. A meta-analysis concluded that "Music training does not reliably … See more