On the relationship between reaction time to light and latency of blocking of the alpha rhythm

Abstract

1. 1. EEG recordings were taken from the occipital areas of twenty adult human subjects under passive and four reaction conditions, when the subjects responded to visual stimuli. These ranged from discrimination reaction (to light and sound) to a speed∼b reaction when only light stimuli were presented at regular intervals of 2 1 2 sec. Reaction times and latent times of blocking of the alpha waves were computed for each experimental condition. 2. 2. Mean reaction times for the group of subjects decreased systematically from 0.408 sec. under discrimination to 0.319 sec. under the speed∼b condition. Latencies, however, did not decrease effectively and varied only between 0.346 sec. under passive to 0.327 sec. under speed∼b condition. The mean correlation coefficients between the two measures were approximately 0.3. 3. 3. Under every reaction condition there were subjects who responded with longer latencies than reaction times, and under the speed∼b condition an average of 43 per cent of the responses was in this manner. 4. 4. Statistical evaluations of the data showed that the differences between the mean reaction times under any two conditions were significant, whereas the differences of latent times between the passive and any reaction condition were not significant. 5. 5. It was concluded that reaction and latent times were measures of essentially independent systems.