Bimodal audiovisual signals can be detected more quickly and accurately than unimodal visual signals or auditory signals. This beneficial effect is called audiovisual integration. Audiovisual integration has often been described according to the spatial principle, the temporal principle and the inverse effectiveness principle. Inverse effectiveness indicates that the largest audiovisual enhancements are inversely correlated with the strength of the response to unisensory component stimuli; thus, weaker stimuli generate greater enhancement when presented together. In addition, some studies have suggested that the visual contrast feature can modulate audiovisual integration and obtained an inverse relationship between visual contrast and audiovisual integration. This review aims to summarize previous studies and describe the relationship between visual contrast and inverse effectiveness by behavior, ERP and fMRI experimental methods. By summarizing previous studies, we have determined the direction of future work.
