Decision time and movement time as a function of response complexity in retarded persons.

The decision time (reaction time [RT]) and movement time of retarded persons as a function of the amplitude and precision of a discrete movement in both simple and choice RT paradigms was examined. The results showed that RT for retarded persons was considerably longer and more variable than for nonretarded persons. Movement difficulty only elevated RT with both populations in the choice RT paradigm, and the RT regression coefficient for the retarded subjects was considerably greater than that for the the nonretarded group. Retarded subjects' movement time was significantly slower than that of the nonretarded subjects. Movement difficulty elevated movement time for both populations, as defined by Fitts's (1954) law. The slope of the movement-time regression coefficients was significantly higher for retarded persons and did not change across 5 days of practice. These findings suggest that information-processing differences in motor skills between populations can be attributed to response parameters.