Age Differences in Choice Reaction Time and Cardio-vascular Status among Pilots

Abstract

ATTENTION has recently been directed to the conflict of evidence existing in those data on sensory-motor performance in relation to age to which the mathematics of information theory could be reasonably expected to apply in a straightforward manner¹. Specifically, in the formula for choice reactions²: RT = a + b log₂n (where n is the number of equivalent choices), the well-known slowing of response with age is sometimes reported as an increase in the constant a, and at other times as a rise in b. In an attempt to resolve these contradictory data on choice, discrimination and movement times, it has been suggested that the effective duration of signals may determine the outcome, producing an increase with age in the intercept when signals are brief, but an increase of the slope when they are relatively long. Whereas the latter result leads logically to interpretations in terms of reduced ‘channel capacity’ with age, the former has prompted speculations about the possibility of a change in the level of ‘neural noise’^3,4. These ideas derive from the statistical theory of signal detection⁵, and as compared with classical psychophysics, their novelty consists in postulating that the brain is a rather ‘noisy’ communication channel, so that a decision about sensory input is based on information in some way distorted by random neural activity within the central nervous system itself. Hence, the decision mechanism must ‘test hypotheses’, so to speak, to distinguish between the states of ‘noise alone’ and ‘noise plus signal’. Yet, apart from emphasizing that the latency of a response must be mainly due to the time necessary to collect a statistically reliable sample for a correct decision, it is not clear what properties of the channel are being specified by either type of theory.