Date of Award

5-1998

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Psychology

Supervisor

Daphne Maurer

Abstract

I examined the influence of binocular deprivation on the development of visual spatial attention in humans. I began by testing normals, in order to work out procedures appropriate for monocular tests of patients (aged 8 to 20 years) who had been treated for bilateral congenital cataracts during infancy. There were two reaction time tasks (Eriksen 1995; Posner, Nissen, & Ogden, 1978): 1. Detection-Participants pushed a button as soon as they detected a target that was presented in a cued, miscued, or noncued peripheral location and that appeared 100, 400, or 800 msec (SOAs) after a central cuel; 2. Discrimination with Distractors-Participants indicated which of two shapes appeared in the periphery 400 msec after a central cue, with those shapes surrounded by compatible or incompatible distractors. On task 1, I compared 32 eyes of 16 patients (mean duration of deprivation = 5.1 mosl range = 1.8 - 19.5 mos) to three groups of normals (8, 10 years, adult, N= 24 per grp). Covert orienting was adult-like by 8 years of age. Patients performed normally when the cue appeared 100 or 400 msec before the target. Patients with more than 4 months of deprivation, unlike normals and patients with shorter deprivation, responded no more quickly on trials with valud cues than on those with valid cues 800 mec before the target. On task 2, I compared 30 eyes of 15 patients (mean duration of deprivation = 4.5 mos; range = 1.8 - 7.6 mos) to 15 age-matched controls, and 24 normal 10-year-olds to 24 adults. On invalid trials, patients were slowed more than age-matched controls by incompatible distractors. As on Task 1 at a 400 msec SOA, patients showed a normal validity effect in the lower visual field. In the upper visual field, there was a larger-than-normal validity effect. As in Task 1, normal 10-year-olds were adult-like in the ability to shift attention covertly; however, they were slowed more than adults by incompatible distractors. Together these findings indicate that the normal development of attention is sensitive to experience early in life: Deprivation disrupts aspects of the attentional system that are involved in shifting and maintaining attention. The results also add to the evidence that deprivation especially disrupts abilities that are immature at birth and that develop slowly during childhood (Maurer et al., 1989). These studies on the normal development of attention showed that while cover orienting is developed by 8 years of age, at least under some conditions, the ability to ignore distracting information is not yet fully developed even by 10 years of age. This result suggests that the parietal system, involved in the ability to shift attention covertly in adults, and the frontal system, involved in the ability to ignore distractors, develop at different rates.

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