Age and Sex Parameters in Psychomotor Learning

Quantitative relationships were sought among psychomotor response speed (R), number of practice trials (T), chronological age (A), and biological sex (S) for 600 S s in 30 groups between the ages of 8 and 87 yr. All S s received 320 trials on a Discrimination Reaction Time apparatus. Hull's equation R = m (1 – e - iT ) + c was found capable of describing all 30 acquisition curves with an average predictability of 97.98% when the asymptote ( m ), rate ( i ), and R -intercept ( c ) parameters were varied jointly. When m and c were held constant for each sex and only i varied, the average predictability dropped to 64.76%, indicating that rate alone was inadequate to account for variance due to age and sex. Confirming and extending the classical age-performance data, acquisition speeds followed differential trends for both age and sex variation while over-all proficiency was a non-monotonic function of age. There was a rapid growth to a maximum level for females at the age of 16 and for males at 20, then a gradual, non-parallel decline into the seventh decade. Males performed significantly faster than females, and all two-factor interactions were significant. There was no tendency for inter-individual variability to increase with age. We conclude that age and sex are critical parameters in human psychomotor learning and performance. Acquisition curves may be predicted with high accuracy by an exponential equation whose asymptote, rate, and intercept constants jointly reflect inter-individual differences and whose form remains invariant over an extended range. The multiplicative law R = f ( T × A × S ) is proposed for the discrimination-reaction task.