G factor (psychometrics)
The General factor of intelligence is also referred to as a general factor of intelligence, or g - factor of intelligence. The term implies that many intelligence services more or less participates a general intelligence factor. This justifies to speak of simplification " of " intelligence. The g- factor, however, can be only a rough guide value on the intelligence level of a person or group of persons. In more differentiated consideration, as, for example, require professional advice or neuropsychology, it is often useful to distinguish the characteristics of specific intelligence factors.
The idea of a general mental capability that can be expressed in a single intelligence value was, from the outset ( Spearman ) very controversial and remains so to this day.
General factor of intelligence Spearman
The British psychologist Charles Spearman founded in 1923, the first factor theory of intelligence in psychology at all. He found by comparing different intelligence tests, carried out on a group of subjects that nearly all test modules within such tests correlate positively. The correlations were not high, but left to the conclusion that there must be a universal factor that says something about the intelligence of people and their occurrence heredity plays a controversial role. There continues to Spearman's theory thus a relationship between the various skill areas of a man, and there must be a general "intelligence factor " accordingly: the General Factor of Intelligence "g". In addition to the General Factor of Intelligence of any intelligence test involves, according to Spearman's two-factor theory of intelligence also specific factors.
Thurstone's study
Further investigations were by Louis Leon Thurstone (1938 ): He extracted and compared with the general factor of intelligence from 6 independent test batteries. The correlation of the g factor in each of two test batteries ranged between .52 and .94. The relationship was not perfect, but he was positive. General factors from the tests are therefore similar, but not identical. This finding formed the basis for further factor theories.
Carroll's study
Compared to the two-factor theory of intelligence developed various hierarchical factor models. In them several levels or layers of increasing degree of generality were distinguished, such as " specific factors ", and thus about general " group factors " and at the top of the g - factor.
The most extensive analysis was carried out by John B. Carroll ( 1993). It was based on data from well over 100,000 people. They also confirmed a hierarchical factor structure with a g- factor at the top. He received one level including other factors of fluid and crystallized intelligence ( Raymond Bernard Cattell ). This Cattellsche distinction becomes important when references to information psychological or neurobiological variables are made . Thus, the brain functions humiliated at degraded by glucose or oxygen deprivation immediately fluid intelligence, while crystallized intelligence is less trouble- dependent.
Brief storage
A more recent approach for the determination of a general factor of intelligence is the short memory of the Erlanger School of Information Psychology. After that, the intelligence depends on the speed of information processing and memory span.