Waters, Christopher (2010) Investigating selective attention after mild to moderate traumatic brain injury using perceptual load theory. Other Degree thesis, Victoria University.

Abstract

This study used Lavie's (1995, 2010) perceptual load theory to investigate selective attention deficits after mild to moderate Traumatic Brain Injury (TBI). This theory predicts that when the load involved in a task does not exceed perceptual resources (low load), there is spare capacity for irrelevant distractors to be processed. This leads to distractor interference, with incompatible distractors causing maximal interference compared to neutral and compatible distractors. When perceptual resources are exceeded (high load) differential distractor interference effects are reduced or eliminated. Twelve mild to moderate TBI patients and 12 neurologically intact controls completed two computer-based tasks which manipulated perceptual load, as well as neuropsychological tests of attention. In computer task A target letters flanked by coloured shapes were presented with distractors that were incompatible, neutral or compatible with the target. Computer task B was similar but involved more ecologically relevant targets in the form of line drawings of cups and glasses. Participants were instructed to respond to targets when they appeared with coloured shapes (single feature; low load) or specific shapes of specific colours (conjunction of features; high load) thus manipulating perceptual load by verbal instruction alone. Patterns of responses were consistent with hypotheses; however, no statistically significant differences were found between distractor types under low load in either computer task. Whereas there were no significant differences between groups on RT measures, TBI patients made significantly more errors on the computer tasks and showed poorer performances on neuropsychological tests of selective attention than did controls. Small sample sizes and possible confounding effects of cognitive load may have contributed to the lack of statistically significant results. Future research with mild/moderate TBI patients may benefit from varying display set size to manipulate load instead of the verbal instructions used in the current study.

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