Investigation of visual and verbal inhibition in aging within a similarity-judgement task

Inhibition is a central component of executive control that allows us to focus on target stimuli and to ignore non-target stimuli. Aging has been associated with reduced inhibitory abilities, but data are contradictory as regards the domain-specificity versus generality of this impairment. The aim of this study was to conduct a comprehensive assessment of inhibitory abilities in aging by focusing on visual and verbal domains (phonological and semantic modalities). A similarity judgement task was administered in all three modalities to thirty young (20-40) and thirty elderly (60-80) adults. Participants had to judge which item out of two was the most similar to two target items. In the facilitation condition, the correct test item was preactivated via a prime appearing briefly before the trial; in the inhibition condition, the prime preactivated the wrong test item which then had to be inhibited for selection of the correct test item. An inhibition score was calculated by subtracting the performance in the inhibition condition from the facilitation condition (for correct responses and reaction times) For correct responses, we observed that the inhibition score was larger in the elderly vs. young group in each of the three modalities. For response times, the inhibition score was larger in the elderly group for the visual and semantic modalities but not phonological modality, meaning that they had more difficulties to inhibit the wrongly primed item. These results confirm inhibitory impairment in healthy aging, in a manner that appears to be rather domain-general (in verbal and visual domains).