Effects of memory demand and motivation on sustained attention in young and older adults.

In two experiments, young and older adults performed 60-min cognitive vigilance tests in which memory demands were equated for individual differences in digit span. In the first experiment, the effects of monetary reward on subjects' performance were assessed. The sustained attention of young and older adults who were both paid for their participation did not differ, and it did not decline during the vigil, but young adults who were not paid for their participation evidenced a significant vigilance decrement. In the second experiment, memory demands were increased and there was no mention of monetary reward for participation. The attention of young adults declined rapidly, but that of older adults did not evidence a vigilance decrement. Subjects' sustained attention is explained in terms of task characteristics and intrinsic and extrinsic motivational factors.