Testing the indifferentiation hypothesis during childhood, adolescence, and adulthood.

The general (g) factor is the most general and relevant cognitive ability. This factor is considered to be one of the most important predictors of academic achievement and of many other socially relevant behavioral outcomes. In the last decades, many researchers have investigated the possible changes in the relevance of the g factor from childhood to adulthood. The indifferentiation hypothesis states that the variance attributed to the g factor and the main cognitive abilities will not change over the life span. In the present study, the authors tested that hypothesis in childhood, adolescence, and adulthood by using 2 different cognitive batteries (Test of Educational Ability [TEA; S. A. TEA, 1999], Wechsler Adult Intelligence Scales [WAIS; D. Wechsler, 1955]), which they administered in 2 different countries--Spain (TEA) and the United States (WAIS). The ages of the participants (N = 2,384) ranged from 8 to 54 years. Results showed that the number of factors extracted and the relevance were the same for every age group in both batteries, as predicted by the indifferentiation hypothesis. The authors discuss implications of intelligence assessment.