Aging and selective attention: an issue of complexity or multiple mechanisms?

Previous studies have shown age-associated deficits in selective attention that vary as a function of task demands. The present study was conducted to dissociate the effect of task complexity on age-related performance differences from qualitative differences in cognitive demands. Twenty-four young and 24 older adults were administered two versions of the Stroop Test (Hartley, 1993). The Color-Block version required identifying the color of a box while ignoring the name of a color printed either above or below the box. The Color-Word version required naming the color of a word while ignoring the semantic meaning of the word (a color name). Each version of the task included a two- and four-color choice condition as a manipulation of task complexity. Old and young adults performed comparably on the Color-Block Task, but older adults were significantly impaired on both conditions of the Color-Word Task, particularly in the four-choice condition. Results suggest age-related differences in the distinct attentional processes demanded by each task are not attributable to general slowing.