Sensory discrimination and its place in the structure of human cognitive abilities

Bibliogr. s. 38-42; the datasets related to this work are available at: https://osf.io/xp6g8/

The well-known hypothesis of Sir F. Galton posed that individual differences in performance on diverse sensorimotor tasks are rooted in single general sensory discrimination ability. Relatedly, Ch. Spearman hypothesised that this discrimination ability and intelligence share the same neural basis and thus should be statistically equivalent. Despite a century of research, existing evidence for these two hypotheses is still inconclusive. Study 1 modelled the factor structure for, to date, the most comprehensive battery of tasks tapping into visual discrimination, and investigated its relationships with iconic and working memory, as well as intelligence. The CFA and SEM models indicated that performance could be grouped into two considerably correlated, yet statistically separate factors reflecting temporal vs. non-temporal (i.e. featural) sensory discrimination ability. These two abilities correlated considerably with working memory and intelligence but, at the same time, were clearly separable. However, the discrimination-intelligence link disappeared when mediated by working memory, suggesting that sensory discrimination plays no explanatory role in intelligence. In Study 2, the above findings were supported and extended by introducing auditory discrimination tasks. The results indicated three independent factors reflecting: amodal temporal discrimination, visual featural discrimination, and auditory featural discrimination. WM fully accounted for the shared variance among the three abilities and their relationships with intelligence. Overall, both Galton and Spearman validly guessed that various low-level sensorimotor processes can be mutually linked but, contrary to their ideas, sensory discrimination neither constitutes unitary ability nor is equivalent to intelligence.