THE SUPPRESSED RELATIONSHIP BETWEEN IQ AND THE REACTION-TIME SLOPE PARAMETER OF THE HICK FUNCTION

The two parameters of the Hick paradigm, the intercept (a) and the slo pe (b), of reaction time (RT) as a function of the information load sc aled in bits (i.e., the binary logarithm of the number of stimulus-res ponse alternatives) differ in their (negative)correlation with IQ, a g enerally having a larger correlation than b. The typically low and oft en nonsignificant correlation between b and IQ appears to contradict t he theory that rate of information processing is a component of genera l mental ability (g) as approximated by IQ or other highly g-loaded te sts. The a of the Hick function largely reflects individual difference s in the sensory-motor lags in task performance, while the b supposedl y reflects individual differences solely in the rate of information pr ocessing. Hence b theoretically should be more highly correlated with g or its proxy, IQ, than is a. But in fact, the opposite is commonly f ound. The weakness of the b x IQ correlation, as compared with the cor relation between IQ and a (and with other variables derived from the H ick paradigm) is mainly attributable to statistical artifacts that sup press the b parameter's correlation with any other variables, e.g., a and IQ. When the b x IQ correlation is estimated under conditions that reduce the statistical suppression of this relationship, the correlat ion is appreciably increased and is consistent with prediction from in formation processing theory.