Psychometric G

Psychometric g is the general factor that underlies individual differences on cognitive ability tests. All cognitive tests measure g to some extent, but intelligence quotient (IQ) tests tend to measure it particularly well. Psychometric g is not a cognitive ability per se, but a property of the brain that causes cognitive tests and performances to correlate with one another. Psychometric g is related to the complexity of cognitive processing, not to the surface characteristics of tests (i.e., content). Individual differences in g also appear to be related to both genes and the environment. Psychometric g explains 80% to 90% of the differences in scholastic and occupational outcomes that can be predicted from tests. Personality traits such as conscientiousness and ambition are thought to interact with g to produce individual differences in many real-world outcomes. Intervention studies suggest that g is susceptible to environmental intervention, but that there are limits to its malleability.