The role of decision speed in the construct of intelligence

A theory of general intelligence in Spearman's sense has been frequently verified via two complementary approaches, the one using psychometric and the other using experimental methodology. The results led to the conclusion that both, psychometric tests and elementary cognitive tasks in different experimental paradigms measure the same thing in substantial extent. The rapid, error free information processing, reflecting the efficiency of a nervous system with limited capacity, was supposed to be the essential component of the intellect. This view is often criticised by the authors who claim that high correlation between speed of information processing and psychometric intelligence is simply the consequence of the fact that some intelligence tests themselves are "speeded" and that mental speed is merely a marginal variable in both psychometric tests and elementary cognitive tasks. In our study we tested 88 subjects with three psychometric tests, measuring general intelligence in Spearman's sense. Parallel versions of those tests were created by splitting each of them into two equivalent halves by "odd-even" principle. One version was applied under strict time constraints and the other one without time pressure. In addition five speed-of-information-processing paradigms were applied. The relationship between the mental speed and general intelligence measured in timed and untimed conditions was examined. Results suggest that the role of speed of information processing is significant in determining general intelligence. Mental speed also seems to be relatively independent with regarding to time limitations in testing intelligence. The results are discussed in terms of the neural efficiency presumptions