Effects of practice on inspection time for mildly mentally retarded and nonretarded adults

Successive estimates of inspection time (lambda) interspersed with practice were made for 10 mildly retarded adults (mean IQ = 60) and 10 nonretarded adults. Each subject completed approximately 800 trials overall. A significant practice effect was found for both groups, but with average measures of lambda from the retarded group remaining more than twice as long as those from the nonretarded group. Intercorrelations within both groups between measures confirmed that lambda provides a reliable index of discriminative performance. A response requirement involving a keypress was compared with a simplified pointing response, but results indicated that these alternatives did not influence estimates of lambda on the effects of practice.