Effects of the Simultaneous Presentation of Corresponding Auditory and Visual Stimuli on Size Variance Perception

To overcome limitations in perceptual bandwidth, humans condense various features of the environment into summary statistics. Variance constitutes indices that represent diversity within categories and also the reliability of the information regarding that diversity. Studies have shown that humans can efficiently perceive variance for visual stimuli; however, to enhance perception of environments, information about the external world can be obtained from multisensory modalities and integrated. Consequently, this study investigates, through two experiments, whether the precision of variance perception improves when visual information (size) and corresponding auditory information (pitch) are integrated. In Experiment 1, we measured the correspondence between visual size and auditory pitch for each participant by using adjustment measurements. The results showed a linear relationship between size and pitch-that is, the higher the pitch, the smaller the corresponding circle. In Experiment 2, sequences of visual stimuli were presented both with and without linked auditory tones, and the precision of perceived variance in size was measured. We consequently found that synchronized presentation of audio and visual stimuli that have the same variance improves the precision of perceived variance in size when compared with visual-only presentation. This suggests that audiovisual information may be automatically integrated in variance perception.