We can easily and reliably identify the gender of an unfamiliar interlocutor over
the telephone. This is because our voice is “sexually dimorphic”: men typically speak
with a lower fundamental frequency (F0 - lower pitch) and lower vocal tract resonances
(ΔF – “deeper” timbre) than women. While the biological bases of these differences are
well understood, and mostly down to size differences between men and women, very
little is known about the extent to which we can play with these differences to
accentuate or de-emphasise our perceived gender, masculinity and femininity in a range
of social roles and contexts.
The general aim of this thesis is to investigate the behavioural basis of gender
expression in the human voice in both children and adults. More specifically, I
hypothesise that, on top of the biologically determined sexual dimorphism, humans use
a “gender code” consisting of vocal gestures (global F0 and ΔF adjustments) aimed at
altering the gender attributes conveyed by their voice. In order to test this hypothesis, I
first explore how acoustic variation of sexually dimorphic acoustic cues (F0 and ΔF)
relates to physiological differences in pre-pubertal speakers (vocal tract length) and
adult speakers (body height and salivary testosterone levels), and show that voice
gender variation cannot be solely explained by static, biologically determined
differences in vocal apparatus and body size of speakers. Subsequently, I show that both
children and adult speakers can spontaneously modify their voice gender by lowering
(raising) F0 and ΔF to masculinise (feminise) their voice, a key ability for the
hypothesised control of voice gender. Finally, I investigate the interplay between voice
gender expression and social context in relation to cultural stereotypes. I report that
listeners spontaneously integrate stereotypical information in the auditory and visual
domain to make stereotypical judgments about children’s gender and that adult actors
manipulate their gender expression in line with stereotypical gendered notions of
homosexuality. Overall, this corpus of data supports the existence of a “gender code” in
human nonverbal vocal communication. This “gender code” provides not only a
methodological framework with which to empirically investigate variation in voice
gender and its role in expressing gender identity, but also a unifying theoretical
structure to understand the origins of such variation from both evolutionary and social
perspectives