Multisensory and sensorimotor interactions in speech perception
Jean Luc Schwartz
Speech is multisensory since it is perceived through several senses. Audition is the most important one as speech is mostly heard. The role of vision has long been acknowledged since many articulatory gestures can be seen on the talker's face. Sometimes speech can even be felt by touching the face. The best-known multisensory illusion is the McGurk effect, where incongruent visual articulation changes the auditory percept. The interest in the McGurk effect arises from a major general question in multisensory research: How is information from different senses combined? Despite decades of research, a conclusive explanation for the illusion remains elusive. This is a good demonstration of the challenges in the study of multisensory integration. Speech is special in many ways. It is the main means of human communication, and a manifestation of a unique language system. It is a signal with which all humans have a lot of experience. We are exposed to it from birth, and learn it through development in face-to-face contact with others. It is a signal that we can both perceive and produce. The role of the motor system in speech perception has been debated for a long time. Despite very active current research, it is still unclear to which extent, and in which role, the motor system is involved in speech perception. Recent evidence shows that brain areas involved in speech production are activated during listening to speech and watching a talker's articulatory gestures. Speaking involves coordination of articulatory movements and monitoring their auditory and somatosensory consequences. How do auditory, visual, somatosensory, and motor brain areas interact during speech perception? How do these sensorimotor interactions contribute to speech perception? It is surprising that despite a vast amount of research, the secrets of speech perception have not yet been solved. The multisensory and sensorimotor approaches provide new opportunities in solving them. Contributions to the research topic are encouraged for a wide spectrum of research on speech perception in multisensory and sensorimotor contexts, including novel experimental findings ranging from psychophysics to brain imaging, theories and models, reviews and opinions.