Effects on Reaction-Time of Knowledge of Results of Performance

not employed under the no-knowledge condition. For both treatments reacciontime increased systematically with time on task, the greatest amount of change occurring under the no-knowledge condition. In addition, reaccion-rime was a decreasing function of length of interstimulus interval. The findings of the no knowledge portion of the forementioned study are atypical in two respects. Whereas the slope of the linear function relating reaction-time (msec.) to task duration (5-min. blocks) was 11.93, those of one earlier (McCormack, 1958) and rwo later srudies (McCormack, 1960; McCormack & Prysiazniuk, 1961) were 5.46, 4.75, and 3.79, respectively. Also atypical was the finding that reaction-time was a decreasing funccion of length of interstimulus interval since, in each of the three other investigations, an invariant relation was reported. Thus the major conclusions of the scudy employing the 10 females as Ss, especially the no-knowledge but probably the knowledge porcion as well, are highly questionable. The presenc experiments were therefore designed with the purpose of re-exploring the effects on reactiontime of knowledge of results of performance. METHOD S's task was to depress a microswitch as fast as possible each time light from a 15-w bulb was seen through an aperture 1/2 in. in diamecer. The duration of the light was 100 msec. and the apermre was placed at a distance of 7 fr. from S. Reaction-time was recorded by a Hunter Klockounter while the duration of the light was conuolled by a silent timer. A second timer enabled E, who was located in an adjacenc room, to determine whether or not S had responded within a 2-sec. period. In the event of a failure to respond the light was presented 'The research reported in this paper was supported by 3 grant-in-aid from the Associate Committee on Experimental Psychology of the National Research Council, Canada (Grant APBT-40).