Level of uncertainty and brain damage: a reaction time test of attention for clinical use

The goal of this study was to search for effects of aging on visual reaction-time task designed to evidence subtle attentional disturbances in brain-injured subjects. Experiment I showed that the speed of response was affected by the level of task complexity (simple versus two-choice versus four-choice reaction times, with a forced response), irrespective of age. A main effect of age and effects of the responding finger and/or of the spatial location of the stimulus also emerged. Experiment II showed that the complexity effect was not an artifact resulting from the order of the conditions, and Exp. III, by means of a go/no-go procedure, showed that the effect of the location of the stimulus in Exp. I was due to central cognitive operations dealing with the choice of the response finger rather than with visuospatial operations about the stimulus.