Karen L. Gunther¹, Brandon E. Hammer¹; ¹Wabash College

We have conducted a titrated percent congruent speeded classification task with visual and auditory stimuli to test the percent congruency at which the congruency effect flips to faster response times on incongruent stimuli [Chiou & Rich (2012) found this flip with 20% of the trials in a block being congruent, 80% incongruent], and if the strength of the congruency effect is higher when subjects respond to auditory stimuli, consistent with visual dominance (the effect of vision having a particularly strong influence on other senses; e.g., Posner, Nissen & Klein, 1976). We presented subjects with white visual dots on a black background, appearing either above or below fixation, simultaneously with either high or low auditory pitches (1500 and 300 Hz, respectively). High visual dots and pitches, or low of both, are congruent trials; high of one paired with low of the other are incongruent. We presented blocks of trials with 96% congruency, down to 4% congruency, and asked subjects to respond to either the visual stimuli or the auditory stimuli in different blocks of trials. The initial six subjects (of 20 planned) mostly support our hypotheses. At the lower percentages of congruent trials, the congruence score [(incongruent reaction time) – (congruent reaction time)] is lower, reflecting relatively slower reaction times on the congruent trials and thus a weaker congruency effect, although we are not currently observing a strong flip where reaction times to incongruent stimuli pairings are faster in majority-incongruent blocks. Subjects do have higher congruence scores (longer reaction times on incongruent stimuli) when responding to the auditory stimuli, supporting the presence of visual dominance. These results suggest that the proportion of congruent trials can mediate the magnitude and direction of crossmodal congruency effects.

Acknowledgements: The Eldon Parks Memorial Fund supported the second author's summer internship.