Overall vigilance and sustained attention decrements in healthy aging

Age differences in sustained attention were investigated using a high-event rate digit-discrimination task at 6 levels of stimulus degradation (lastin g 8.1 min each). Twenty-one young, 21 middle-aged, and 20 old healthy subje cts were studied. Overall sensitivity (d') was equivalent in all groups. Al though all subjects showed a sensitivity decrement over blocks, there were no age-related differences in sustained attention capacity. All subjects ha d larger decrements in d' over blocks at higher degradation levels. However , the performance decrement at higher degradation levels was equivalent in all groups, indicating similar decrement rates in sensitivity with increasi ng demands on effortful processing. These results indicate that overall lev els of vigilance and the ability to sustain attention over time are equival ent in all groups under conditions requiring both automatic (low-degradatio n) and effortful (high-degradation) stimulus processing.