Fittsʹ law, movement time and intelligence

Recently, several published studies have reported an empirical relationship between Movement Time (MT, i.e. the speed associated with sensori-motor control of movement) and intelligence. However, this finding is very much at odds with early research that suggested that there was no relationship between measures of these two constructs. One explanation for this anomaly is that intelligence has generally been imprecisely defined across disparate research programs, often with reference to a single test. Another explanation is that studies currently conducted involve poor operationalization of psychomotor processes, essentially confounding this aspect with other psychological mechanisms (e.g. Decision Time). In short, analyses of MT and intelligence have not been truly representative of these constructs, at least as conceptualized within more widely accepted models of these psychological processes. The present study examined the relationship between MT and intelligence by first selecting tasks in each domain that are representative of established psychological theories. A total of 179 participants performed a psychomotor task conforming to Fittsʹ law (an information theory principle relating MT to task difficulty) and a battery of 25 psychometric tests. The latter measures were selected in order to define six broad cognitive ability factors under the framework of Gf/Gc theory. Microstructural properties of the psychomotor task were examined in as rigorous a fashion as possible. Evidence indicated adherence to simplex structure, group and intraindividual conformity to Fittsʹ law, and a hitherto unreported linear relationship between variabilily and the pre-scaled function of target distance and width. However, with the notable exception of a well-defined broad speediness function (Gs), correlations between psychomotor parameters and psychometric measures were close to zero. These results are discussed in relation to cognitive and biological models of human cognitive abilities.