The Interaction Effects of Perceptual Difficulty and Stimulus Exposure Time on Age Differences in Speed and Accuracy of Response

Abstract

The purpose of this study was to determine the effect of a reduced stimulus exposure duration on the functional relation between the difficulty of a discrimination task and age differences in accuracy and latency of response. Subjects in two age groups were male volunteers. The older group comprised 34 subjects aged 65 to 79 years, median = 71.0 years. The younger group comprised 26 males aged 18 to 35 years, median = 22.5 years. Each subject was required to judge which of two simultaneously presented lines was the shorter. The lines were tachistoscopically presented for 2.00 sec. This task was done eight times for each of six levels of difficulty, i.e., six percent differences in line lengths. The experiment was then repeated using a 0.15 sec stimulus exposure duration instead of the 2.00 sec exposure. Response latency and errors increased with stimulus difficulty. Latencies and accuracies were decreased with the reduced stimulus exposure duration. The largest reductions in latency were for the older group with the most difficult discriminations, although the younger group was more accurate and faster than the older group. The data are discussed in terms of two related questions that are important in aging research. One question has to do with functions of the nervous system that are slowed down with age, and the other question has to do with functions that can be speeded up by external means. The latter question relates to a methodology for ascertaining the role of compensated behavior.