An additive factor analysis of the effect of depression on the reaction time of old patients.

Depressed participants display longer reaction times (RTs) than control participants. The present study was aimed at deciphering which stages of processing are affected by depression in old adults. Sixteen old depressed patients and 16 old healthy volunteers performed a two-choice visual RT task. Signal intensity, stimulus-response mapping and foreperiod duration were manipulated so as to affect the stages of stimulus preprocessing, response selection and motor adjustment, respectively. Reaction time data suggest that depression spares the stage of stimulus preprocessing but affects the stage of motor adjustment. An analysis of the error rate leaves open the possibility that depression alters the stage of response selection.