Pitch and tone: Primacy of production criteria in auditory perception

The brain performs diverse and complex operations effortlessly. Its sensitivity to minute stimulus changes, and precision in scaling sensory magnitudes, are yet to be understood by humans. Nevertheless, its limitless vault is accessible only if scientists can discipline themselves to abide by the laws of their science. There exist well-established psychophysical principles for dealing with sensory, mental, and all intangible phenomena. However, in hearing research, the generation of law-abiding scientists are long gone; the current generation of computer-oriented scientists hope to resolve all problems through random and effortless computations of endless varieties of meaningless variables without the concept of invariance. The case in point is hearing research; we are still searching for pitch (or tone) after 2,500 years of intensive inquiry. The failure augurs the existence of fundamental errors in the science. This paper describes a search for the origin of pitch which plays lexical and intonational roles in Yoruba, a tone language. The approach is based on the ecological conception of sound, with experimental evidence from speech surrogates (drums) and strings, guided by the concept of invariance. The investigations attain the conclusion that the brain does not perform any computations at all in pitch and tone perception, neither in music nor in speech. Rather, the data show that the brain measures a unique mechanical parameter of the sound source to which all physical and mechanical transformations lead. In every pitch/tone perception context, therefore, the brain discards all other factors which convey other attributes of sound outside pitch and tone. This finding accounts for constancy in auditory code perception despite overwhelming variability at the production and acoustic levels. Implications for all aspects of auditory perception research and neurophysiological investigations into brain mechanisms are discussed.