Premotor and motor reaction time as a function of movement extent

The effects of variations in extent of movement on fractionated reaction times (RTs) were studied in 18 male Ss. The means of total RT, premotor RT and motor RT (Weiss, 1965) did not change significantly under the two treatment conditions involving variations in extent of elbow flexion in response to a visual stimulus. These results supported earlier work of Brown and Slater-Hammel (1949), but apparently conflicted with recent data reported by Williams (1971). A differential effect of practice on the two tasks was identified and postulated as a possible factor contributing to the conflict among previous research findings.