Some Comments on the Methodological Significance of the Definition of a Response

Evidence in the present study, in conjunction with evidence in previous studies, indicates that sensory or perceptual factors do not account for the slowing that occurs in later life. Elderly Ss are slower than young adult Ss, but, up to the point of fairly weak stimulation (55 db), they are as slow in relation to auditory stimuli that are loud and easy to perceive as they are to stimuli more difficult to perceive. An unanticipated interaction involving stimulus intensity was observed which warrants further attention. When, in the course of the study, the intensity of stimulation was systematically decreased, reaction times (RTs) of older Ss with a .5 second preparatory interval (PI) were much slower than when the intensity of stimulation was systematically increased.

An exploratory study was also carried out. In this study, the pacing of stimulus events was predictable, and Ss were instructed to take advantage of this. RTs were quicker with this procedure than with traditional RT procedures, but not significantly more for old adult Ss than for younger ones. However, the level of significance was such as to suggest that timing may be an important clue to the slowing in later life.