Voice Modulation: A Window into the Origins of Human Vocal Control?
Trends in Cognitive Sciences
An unresolved issue in comparative approaches to speech evolution is the apparent absence of an intermediate vocal communication system between human speech and the less flexible vocal repertoires of other primates. We argue that humans' ability to modulate nonverbal vocal features evolutionarily linked to expression of body size and sex (fundamental and formant frequencies) provides a largely overlooked window into the nature of this intermediate system. Recent behavioral and neural evidence
... dicates that humans' vocal control abilities, commonly assumed to subserve speech, extend to these nonverbal dimensions. This capacity appears in continuity with context-dependent frequency modulations recently identified in other mammals, including primates, and may represent a living relic of early vocal control abilities that led to articulated human speech. The Dynamic Human Voice Recent research examining the communicative function of the human voice has effectively established the roles of two key acoustic componentsthe fundamental frequency (F0) (see Glossary) and formants (Box 1)in the expression of many biological and psychological dimensions, including sex and age, body size and shape, hormonal condition, dominance, masculinity or femininity, and attractiveness (for reviews see      ). For example, men and women whose voices are characterized by low frequencies are typically judged by listeners as more dominant, physically larger and stronger, and more masculine than are speakers with higher-frequency voices  , and these stereotypes appear partly driven by the physical, anatomical, and physiological mechanisms that influence and constrain F0 and formant production. In addition to typically having larger bodies than women, men also tend to have relatively larger larynges, longer vocal tracts, and lower-frequency voices (Box 1). As a consequence, listeners often associate lower frequencies with stereotypically male traits [6, 7] .