Humphreys, Glyn W. and Riddoch, M. Jane and Quinlan, Phillip T and Price, Cathy J. and Donnelly, Nick (1992) Parallel Pattern Processing and Visual Agnosia. Canadian Journal of Psychology, 46 (3). pp. 377-416. ISSN 0008-4255. (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)
A series of visual search experiments are reported examining pattern processing in a visual agnosic patient. We examined search for targets defined by: (1) the combination of their features relative to homogeneous distractors; (2) the combination of their features relative to heterogeneous distractors; and (3) a single feature difference relative to the distractors (their orientation). Normal subjects demonstrate evidence of spatially parallel search when combined-feature targets are detected against homogeneous distractors, and when targets are defined by a salient feature difference. There are non-linear effects of the number of distractors present, and absent responses can be as fast as present. In contrast, search times for combined-feature targets amongst heterogeneous distractors increase linearly with display size, with the slope for absent responses about twice that for present. The contrast between search for combined-feature targets amongst homogeneous and heterogeneous distractors can be attributed to the effects of grouping between distractors and between distractors and targets (Duncan & Humphreys, 1989, 1992; Humphreys & Muller, in press). Grouping between homogeneous distractors facilitates search. An agnosic patient, HJA, showed normal search functions for single-feature targets and for combined-feature targets amongst heterogeneous distractors. However, he was impaired at search for combined-feature targets amongst homogeneous distractors. This suggests that HJA is selectively impaired at grouping conjunctions of form features. The relations between HJA's agnosia and his problem in the parallel grouping of form conjunctions are discussed, as are the implications of the work for understanding normal vision.
|Subjects:||B Philosophy. Psychology. Religion > BF Psychology|
|Divisions:||Faculties > Social Sciences > School of Psychology|
|Depositing User:||P. Ogbuji|
|Date Deposited:||31 Aug 2009 08:41|
|Last Modified:||16 Jul 2014 14:04|
|Resource URI:||https://kar.kent.ac.uk/id/eprint/22521 (The current URI for this page, for reference purposes)|