Aging and cognitive vigilance: effects of spatial uncertainty and event rate.

Age-related differences in cognitive vigilance were examined in a task requiring identification of a target (a lowercase letter) presented at three levels of spatial uncertainty (low, moderate, and high) and in the context of a low or high event rate. Thirty-six young (18-24 years) and 36 older (60-74 years) adults participated in 30-min vigilance sessions. Increased spatial uncertainty decreased target detection rate and d' to a greater extent in older adults than in young adults. No age differences were obtained for the low-spatial-uncertainty condition. The vigilance decrement--the decline in detection rate over time--was magnified when event rate was high and when spatial uncertainty was high. The results suggest that cognitive vigilance is age sensitive when demands on visual attention capacity are increased by high event rate or spatial uncertainty.