Effects of Visual Contrast on Inverse Effectiveness in Audiovisual Integration

Effects of Visual Contrast on Inverse Effectiveness in Audiovisual Integration

Fengxia Wu (Okayama University, Japan), Xiaoyu Tang (Liaoning Normal University, China & Okayama University, Japan), Yanna Ren (Okayama University, Japan), Weiping Yang (Hubei University, China & Okayama University, Japan), Satoshi Takahashi (Graduate School of Natural Science and Technology, Okayama University, Japan) and Jinglong Wu (Okayama University, Japan)
DOI: 10.4018/978-1-5225-0925-7.ch009
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Abstract

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.
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Introduction

Audiovisual Integration

We recognize an event by many different information channels (such as vision, hearing, tactile, smell), and this information helps us understand the world more naturally. Visual and auditory inputs are the main channels that help us recognize the world. Audiovisual integration plays an important role in everyday life. For example, when we see a movie in a theatre, the combined appearance of a scary sound and a scary picture can make the event scarier than the sound or picture alone. Thus, when we receive auditory information and visual information together, we can rapidly detect and correctly identify the event. How does this phenomenon occur? Why does auditory information increase this scary atmosphere? Some previous studies have explained this phenomenon by suggesting that a combined signal in the environment is often processed faster and more accurately than a unimodal signal presented alone (Calvert, 2001; Molholm et al., 2002). Bimodal audiovisual signals can be detected more quickly and accurately than unimodal visual or auditory stimuli (Miller, 1982) (see Figure 1). This visual and auditory beneficial effect is called audiovisual integration.

Figure 1.

Reaction times and hit rates for visual (V), auditory (A) and audiovisual (AV) modalities. For reaction times, audiovisual modality is faster than visual or auditory modality. For the hit rate, the audiovisual modality is more accurate than visual or auditory modalities. The benefit of audiovisual modality is called audiovisual integration.

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