Audiovisual integration capacity modulates as a function of illusory visual contours, visual display circumference, and sound type.

Research into the capacity of audiovisual integration has previously assessed whether capacity is strictly limited to a single item, or whether it can exceed one item under certain environmental conditions. More recently, investigations have turned to examining the effects of various stimulus factors on capacity. Across two experiments, we looked at a number of factors that were expected to play a modulatory role on capacity. Experiment 1 deployed a manipulation of illusory polygons, revealing an increase in audiovisual capacity, even in an absence of visual connections. This demonstrates that exceeding the capacity of 1 does not only represent a functional increase in the binding of a singular, complex visual object, but that it can also represent binding of multiple simpler objects. Findings also support the hypothesis that capacity modulates quantitatively, but not qualitatively, with respect to speed of presentation. Experiment 2 examined the effects of different sound types (sine tones or white noise) and of different spatial visual field sizes on the capacity of audiovisual integration. The results indicate that capacity is maximized when stimuli are presented in a smaller circle (7.5°) if alongside a sine tone, and when presented in a larger circle (18.5°) alongside white noise. These results suggest that audiovisual integration capacity is dependent on the combination of sound type and visual spatial field size. The combination of these results reveal additional phenomenological features of the capacity of audiovisual integration, and provides impetus for further research into applications of the findings.