title: The nature and contribution of space- and object-based attentional biases to free-viewing perceptual asymmetries.
abstract: Two experiments investigated the contribution of space- and object-based coordinates to previously reported leftward perceptual biases (pseudoneglect) at various locations across visual space. Neurologically intact participants (n = 34 and 27) made luminance discriminations between two left/right mirror-reversed luminance gradients (greyscales task), which were variously displaced around the midline in the participants' left and right hemispaces. The orientations of the stimuli were manipulated so that object- and space-based coordinates were congruent or incongruent. Experiment 1 confirmed the presence of a leftward object-based perceptual bias. The bias was moderated, however, by overattention to the more central stimulus. This central spatial effect could have resulted from the use of task-specific strategies, which were controlled by presenting the stimuli sequentially in Experiment 2. The findings of Experiment 1, a leftward object-based bias and a central spatial bias, were replicated. Overall, the results indicate a leftward object-based bias and a central spatial bias, both of which are relevant for the allocation of attention. The results are discussed with reference to a variety of models of the distribution of attention across space.
authors.affiliation: Department of Psychology, University of Melbourne, 3010, Parkville, Victoria, Australia. corr@unimelb.edu.au
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Orr
authors.forename: Michael E R
authors.initials: ME
authors.lastname: Nicholls
mesh_terms: D000293:Adolescent; D000328:Adult; D001288:Attention / Q000502:physiology*; D015982:Bias; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007088:Illusions / Q000502:physiology; D008297:Male; D009483:Neuropsychological Tests; D009949:Orientation / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010468:Perceptual Disorders / Q000503:physiopathology; D010775:Photic Stimulation; D013028:Space Perception / Q000502:physiology*