A Laboratory Study of the McGurk Effect in 324 Monozygotic and Dizygotic Twins.

Guo Feng,John F Magnotti,Wen Zhou,Bin Zhou,Michael S Beauchamp

doi:10.3389/fnins.2019.01029

Abstract

Multisensory integration of information from the talker’s voice and the talker’s mouth facilitates human speech perception. A popular assay of audiovisual integration is the McGurk effect, an illusion in which incongruent visual speech information categorically changes the percept of auditory speech. There is substantial interindividual variability in susceptibility to the McGurk effect. To better understand possible sources of this variability, we examined the McGurk effect in 324 native Mandarin speakers, consisting of 73 monozygotic (MZ) and 89 dizygotic (DZ) twin pairs. When tested with 9 different McGurk stimuli, some participants never perceived the illusion and others always perceived it. Within participants, perception was similar across time (r = 0.55 at a 2-year retest in 150 participants) suggesting that McGurk susceptibility reflects a stable trait rather than short-term perceptual fluctuations. To examine the effects of shared genetics and prenatal environment, we compared McGurk susceptibility between MZ and DZ twins. Both twin types had significantly greater correlation than unrelated pairs (r = 0.28 for MZ twins and r = 0.21 for DZ twins) suggesting that the genes and environmental factors shared by twins contribute to individual differences in multisensory speech perception. Conversely, the existence of substantial differences within twin pairs (even MZ co-twins) and the overall low percentage of explained variance (5.5%) argues against a deterministic view of individual differences in multisensory integration.

Highlights

Humans have the remarkable ability to combine information from the mouth of a conversation partner with information from their voice in order to facilitate communication (Campbell, 2008)
One obvious question is whether inherited differences in perceptual abilities influence McGurk perception, a question that can be explored with twin studies
If MZ twins are more similar than DZ twins for a particular trait, it suggests that genetics and prenatal environment contribute to the development of the trait

Summary

Introduction

Humans have the remarkable ability to combine information from the mouth of a conversation partner with information from their voice in order to facilitate communication (Campbell, 2008). One surprising fact about the McGurk effect is that even though humans are experts in audiovisual speech perception, the illusion is not universal: even among healthy young adults, some participants never perceive the illusion, while others always do (Gentilucci and Cattaneo, 2005; Nath and Beauchamp, 2012; Stevenson et al, 2012; Strand et al, 2014; Basu Mallick et al, 2015; Magnotti and Beauchamp, 2015; Shahin, 2019). The origin of this individual variability is unknown. High heritability has been reported for some basic perceptual phenomena including binocular rivalry rate (Miller et al, 2010) and musical pitch recognition (Drayna et al, 2001); weaker heritability has been reported for olfactory sensitivity (Hubert et al, 1980), face perception (Zhu et al, 2010), and language skills such as vocabulary, syntax, and semantics (Hayiou-Thomas et al, 2012)

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