A new study has found that the way people pronounce the letter "s" can reveal one's gender.
The study found that the style of speech can impact perceptions of a person's gender as well, not simply the pitch of his or her voice.
The way people pronounce their "s" sounds and the amount of resonance they use when speaking contributes to the perception of gender, according to University of Colorado Boulder researcher Lal Zimman.
"In the past, gender differences in the voice have been understood, primarily, as a biological difference," Zimman, who studied transgender people transitioning from female to male, said.
"I really wanted to look at the potential for other factors, other than how testosterone lowers the voice, to affect how a person's voice is perceived."
As part of the process of transitioning from female to male, participants in Zimman's study were treated with the hormone testosterone, which causes a number of physical changes including the lowering of a person's voice. Zimman was interested in whether the style of a person's speech had any impact on how low a voice needed to drop before it was perceived as male.
What he found was that a voice could have a higher pitch and still be perceived as male if the speaker pronounced "s" sounds in a lower frequency, which is achieved by moving the tongue farther away from the teeth.
"A high-frequency 's' has long been stereotypically associated with women's speech, as well as gay men's speech, yet there is no biological correlate to this association," said CU-Boulder linguistics and anthropology Associate Professor Kira Hall, who served as Zimman's doctoral adviser.
"The project illustrates the socio-biological complexity of pitch: the designation of a voice as more masculine or more feminine is importantly influenced by other ideologically charged speech traits that are socially, not biologically, driven."
Vocal resonance also affected the perception of gender in Zimman's study.
A deeper resonance - which can be thought of as a voice that seems to be emanating from the chest instead of from the head - is the result of both biology and practice. Resonance is lower for people whose larynx is deeper in their throats, but people learn to manipulate the position of their larynx when they're young, with male children pulling their larynxes down a little bit and female children pushing them up, Zimman said.
The study was recently presented at the annual meeting of the Linguistic Society of America in Boston.