Abstract
Introduction: In line bisection (LB) tasks healthy observers perceive the midpoint (pse) of visual stimuli, such as lines, leftward of veridical - a phenomenon known as pseudoneglect (PN) (Jewell & McCourt, 2000). A rightward bias has been reported for spatial intervals defined by auditory stimuli. Lateral visual cues further bias pse (McCourt et al., 2005). We ask whether auditory cues can similarly bias pse in a visual LB task, and characterize the interaction of visual and auditory spatial cues. Bayesian rules characterize cue combination for many tasks; however, multisensory interactions are frequently superadditive (non-Bayesian). We test various cue combination rules concerning their ability to predict visual line bisection behavior. Methods: Forty-six observers completed a tachistoscopic LB task (McCourt & Jewell, 1999). Pse was determined in an uncued condition, as well as when unilateral visual and auditory cues were delivered, alone or in synergistic or antagonistic combination. Results: A 3 × 3 repeated measures ANOVA demonstrated a significant leftward bias (PN) in line-bisection judgments. Pse was influenced by cues such that left cues induced greater leftward bias than those elicited by right cues. This bias was strongest when the visual cue was presented to the line's left and weakest when visual cue was presented to the line's right. Similarly, leftward bias was significantly smaller when an auditory cue was presented to the line's right than when there was no auditory cue present. Discussion: A Bayesian cue combination model and a Quick-summation model (capable of accommodating both super- and sub-additive summation) were compared in their ability to predict the subject data. Model results and Akaike Information Criteria values for each model are presented.
Supported by: NIH/NCRR P20 RR020151.