Age-related differences in the timing of stimulus and response processes during visual selective attention: Performance and psychophysiological analyses.

Two groups of 12 each of younger Ss (mean age 22.5 yrs) and older Ss (mean age 72.4 yrs) performed focused (FA)- and divided-attention (DA) tasks. In the FA task, centrally presented target letters could be flanked by compatible or incompatible noise letters. In the DA task, targets could be cued or uncued, and target locations could be spatially compatible or incompatible with the responding hand. In the FA task, performance of older Ss showed greater interference by incompatible flankers than did that of younger Ss because of stronger response competition caused by partial activation of the incorrect response channel by the incompatible flankers. In both tasks, younger Ss showed an earlier start of response execution relative to the onset of response preparation and a higher percentage of incorrect EMG activity than did older Ss