Young and old observers performed a feature search task in which a single target was embedded in five distractors. Target-distractor similarity was varied quantitatively (along the feature dimension of orientation) and display duration ranged from approximately 50–400 ms. Identification accuracy was worse on target-absent trials, particularly when distractor similarity was high and display duration brief. An age X duration interaction on accuracy was found to reflect generalized age deficits in sensitivity and duration-dependent age differences in bias. Results suggest that an age deficit in the rate of information extraction produces in the elderly a greater dependence on partial information gained from distractors. Additionally, the additive effects of age and similarity have implications for visual search tasks where display size is varied.
