Perception of speech and music is known to rely to some extent on shared brain resources, but the extent to which those resources are shared, and how they are orchestrated is not known. With funding from the National Science Foundation, Dr. Patrick C. M. Wong and colleagues of Northwestern University, and Dr. Alice H. D. Chan of Nanyang Technological University of Singapore are investigating relationships between speech and music for perception and production. In the past, research in this area has focused on individuals with typical abilities and on individuals with extensive musical training. The current project examines the speech-music relationship from a different point of view. Namely, it considers what perceptual disorders in processing pitch reveal about speech and music. Pitch is ubiquitous in our environment. We rely on pitch to classify different types of environmental sounds, differentiate vocal sounds such as various patterns of crying, distinguish who is talking, identify the emotion of talkers, track the speech signal in adverse listening conditions, perceive musical melodies, and distinguish musical instruments. However, pitch perception can be difficult for an estimated 5% of the population in the Western world. This deficit, known as 'amusia' or 'musical tone deafness' (mTD), occurs in the absence of other known neurological or psychiatric disorders. Whether this deficit also affects other auditory domains is important to understand for its implications concerning the neural architecture of auditory perception. This project involves participants in the U.S. and in Singapore whose native language uses tone (pitch) contrasts to signal differences between words. If the brain resources required to process pitch are shared between speech and music, tone language speakers who suffer from mTD should show deficits in perceiving and producing linguistic pitch and musical pitch. The project is intended to expand our understanding about the organization of music and speech processing by our nervous system.
In addition to basic scientific information regarding speech and music, the research could lead to clinical applications. Tone deafness is not classified as a disorder by any medical or professional groups. The real-world impact of tone deafness has yet to be documented, and treatment research has not begun. This research could allow for a better understanding of the communicative consequences of tone deficits, which could ultimately lead to formal clinical recognition and treatment. Tone languages are estimated to be spoken by at least 1.66 billion people in the world, most of whom live in lower-middle income countries as classified by the World Bank. In the U.S., over 26% of non-native English or Spanish speakers (over 3.4 million total) speak a tone language, and this number is growing. Research into pitch perception and its communicative consequences has the potential to benefit large groups of individuals. The findings from this research are relevant to public and global health concerns and will be of interest to many individuals outside the English-speaking world, potentially increasing interest in international collaboration.