The effect of monetary incentive on amount and rate of free recall in older and younger adults.

In a single-trial, free-recall experiment, older and younger adults received either 0, 5, or 50 cents for each word recalled from a 24-word list. Each subject served in each of the incentive conditions. It was hypothesized that monetary incentive would increase the degree of task involvement for older subjects and result in a noticeable reduction in the magnitude of age-related performance differences. In accord with previous investigations, incentive was expected to have no effect on the performance of younger subjects. The results showed that overall recall was not facilitated by incentive, but there was an increase in the rate of recall when incentive was available. This effect of incentive was the same for older and younger subjects, and performance deficits observed for the older subjects were not reduced by incentive. Age differences in recall were largely confined to the first 30 seconds of the recall period, suggesting that age-related differences in willingness or ability to engage in extended memory search were not the source of age-related performance differences. In addition, performance declined steadily across each successive list learned for the older learners, a result we interpreted in terms of susceptibility to interference from prior-list learning.