Psychometric theories are based on a model that portrays intelligence as a composite of abilities measured by mental tests. This model can be quantified. For example, performance on a number-series test might represent a weighted composite of number, reasoning, and memory abilities for a complex series.
Test–retest data are rarely available, and validation studies are usually not conducted. This means that it is often impossible to test whether respondents understood the questions as they were intended. Psychometric theories focus on measurement, and as such they inform all other creativity theories.
Most important, however, the psychometric theories failed to say anything substantive about the processes underlying intelligence. It is one thing to discuss “general ability” or “fluid ability” but quite another to describe just what is happening in people’s minds when they are exercising the ability in question.
The American psychologist John B. Carroll, in Human Cognitive Abilities (1993), proposed a “three-stratum” psychometric model of intelligence that expanded upon existing theories of intelligence. Many psychologists regard Carroll’s model as definitive, because it is based upon reanalyses of hundreds of data sets.