Effort of preparation and age

In an experiment on 24 men and women who were selected for short simple RT (reaction time) and who ranged from 22 to 86 yr. of age, choice RT increased monotonically over 3.5 sec. of waiting time during which there was high momentary probability of stimulus occurrence. As use of a choice reaction minimized the possibility of a response set, the occurrence of a waiting decrement was regarded as support for Näätänen's 1971 proposal of short-term mental exhaustion, which was derived from a similar study but for simple RT. The effect of age on endurance was not clear. There appeared to be no greater waiting decrement with age up to about 65 yr., but the possibility of greater decrements beyond that age cannot be discounted. The existence of short-term exhaustion is consonant with Kahneman's (1973) view that effort is required for the generation of processing capacity. Kahneman and other investigators of mental effort have unanimously rejected the existence of any appreciable effort during preparation. However, Näätänen's evidence for short-term exhaustion apparently had not been considered. It is here suggested that short-term exhaustion usually is not incurred in information processing tasks as they are characterized by alternations of high and low demands for capacity, unlike the present high constant momentary probability of signal occurrence. It is further conjectured that such intermittent operation evolved as the optimum way of utilizing underlying resources that are subject to depletion.