Mechanisms of Perceptual Attention

Abstract

Abstract : Attending to some visual inputs rather than others has significant consequences for performance in everyday and industrial tasks that require the monitoring of complex displays. Attention may affect the perceived clarity of visual displays and improve performance. In this project, a powerful external noise method was developed to identify and characterize the effect of attention on perceptual performance in visual tasks. The effect on task performance of adding external noise-- random visual noise (similar to random TV noise) -- associates each mechanism of attention with a signature pattern of performance as external noise exclusion, stimulus enhancement, or internal noise reduction. We evaluated the mechanisms of attention in a variety of perceptual tasks (simple orientation identification, motion direction discrimination, and letter recognition) when attention is focused on a location in the visual array. Evidence was found for external noise exclusion as a primary mechanism of attention in noisy or masked stimulus situations, with stimulus enhancement as a secondary mechanism of attention associated with peripheral cueing. The methods were elaborated to measure the spatial frequency sensitivity of the observer's matching templates and modification of the templates by attention.