Asymmetry in spatial judgments : testing bin theory and spatial frequency theory in a double double dissociation design

Abstract

The purpose of this thesis was to determine whether asymmetry in metric and topological spatial judgments could be attributed to the spatial frequency of the stimulus or the size of the attended receptive field. A left hemisphere advantage has been found for topological judgments and a right hemisphere advantage for metric judgments. This asymmetry has been attributed to asymmetrical processing of input conditions, namely size of attended receptive field (called the attentional bin) and spatial frequency of the stimulus. The larger a stimulus, the higher the proportion of low spatial frequencies, so large stimuli are thought to facilitate the extraction of lower spatial frequencies while small stimuli are thought to facilitate the extraction of higher spatial frequencies. A left hemisphere advantage has been reported for high spatial frequencies and small attentional bins and a right hemisphere advantage has been reported for low spatial frequencies and large attentional bins. A method for pitting asymmetrically distributed input conditions against each other using asymmetrically distributed tasks was developed. Three studies were conducted. In the first study, a lack of hemisphere effects suggested bilateral processing of the stimuli. Using an eye tracker, participants were easily able to saccade to the stimulus as was shown in Experiment 2. In Experiment 3, effective exposure duration was reduced so that unilateral viewing was ensured. Under these conditions, bin size and spatial frequency were not dissociable due to a lack of hemisphere effects for spatial frequency and because of task dependency for bin size and spatial frequency processing. Although the assumptions of the double double dissociation were not met, asymmetry in spatial judgments under conditions comparable to those used by Kosslyn et al.(1989) was attributable to a right hemisphere advantage for processing through small attentional bins.