Locus of reaction time change in schizophrenics and normal subjects.

Simple reaction time (RT) obtained from trials presented in isotemporal series (preparatory intervals of the same duration) were partitioned into premyographic and myographic time components for 20 schizophrenic and 20 normal subjects according to a previously developed procedure. This procedure allowed for an examination of the relative contributions made by these RT components to: a) overall mean reaction time; and b) the crossover pattern of responding as first observed by David Shakow. In addition, a within-subject comparison of the traditional press-release motor task and an alternative press-only motor task was made. Differential predictions were made as to the effect of the task manipulation from: a) the loss of major set; and b) the reactive inhibition interpretational positions. It was found that the schizophrenics' crossover pattern of responding was specific to the press-release task. Furthermore, it was apparent that both premyographic and myographic components of the RT interval contributed to: a) their overall longer mean RTs, as well as b) their increased magnitude of crossover. The results were seen as supporting the view that inhibitory processes triggered by the increased levels of arousal during the isotemporal series are responsible for the schizophrenics' crossover pattern of responding on the press-release task. It was noted that the loss of major set explanation need not be seen as incompatible with a reactive inhibition explanation of the crossover effect.