ABSTRACT
In around 95 percent of people the left hemisphere is in charge of skilled sequentially organised tasks, like the articulation of speech sounds – and decoding them too. An insight into the functional significance of asymmetrical mouth movements during speech has been provided by Graves and Potter. Asymmetries in mouth movements may also affect the visual communication of speech. This type of communication, known as lipreading, plays an important role in speech perception in individuals with hearing impairments, as well as those with normal hearing. The visual expression of speech was indexed using the McGurk effect. To investigate asymmetries in the expression of speech, we covered either the left or right side of the mouth in our stimuli. The interaction between orientation and the side of the mouth covered provides an insight into the mechanisms that underlie the asymmetry. Our results demonstrate the importance of the right side of the mouth to the visual expression and comprehension of speech.
