Neglect and pseudoneglect are asymmetries of spatial attention which are oftenassumed to possess a fundamental theoretical and neurological relationship to each other,although this assumption has never been directly tested and there is as yet no unifyingquantitative theory. A total of 217 subjects participated in five experiments demonstrating thatboth the magnitude and direction of bisection errors in normal subjects (pseudoneglect) aremodulated by stimulus factors that similarly influence the magnitude and direction of neglect.Stimulus positional uncertainty did not abolish pseudoneglect, indicating that bisectionjudgements are made within an object-centered frame of reference. Backward masking linestimuli had no influence on the magnitude of pseudoneglect, signifying that pseudoneglect is nota byproduct of covert directional scanning of the line stimulus in iconic or short-term visualmemory. Finally, bisection errors are influenced by the direction of contrast gradients imposedon line stimuli, such that perceived line midpoint is drawn toward the lower-contrast lineend. The magnitude and direction of pseudoneglect are modulated by stimulus factors that alsoinfluence the magnitude and direction of neglect. Both phenomena are succinctly described asbiases in attention (i.e., neglect is a right-bias, whereas pseudoneglect is a left-bias). The twophenomena are modulated by stimulus factors as follows. Line length: there is anincreased bias with increasing line length for both phenomena, and a cross-over to an reversedbias for short lines. Azimuthal line position: an increasing bias accompanies increasingleftward placement for both phenomena. Line aspect ratio: there is a decreasing bias withincreasing line height for both phenomena. Line elevation: there is a decreasing bias withincreasing elevation for neglect, and an increasing bias with increasing elevation forpseudoneglect. The only case in which a factors influence on the two phenomena is discrepant isfor elevation, and this difference is explicable. Taken together these congruencies stronglysupport the notion that neglect and pseudoneglect are phenomena that are twin manifestations ofparameter changes in a unitary set of underlying hemispheric attentional asymmetries. Copyright (C) 1999 Elsevier Science B.V.
ASJC Scopus subject areas
- Experimental and Cognitive Psychology
- Cognitive Neuroscience
- Behavioral Neuroscience