People can accurately identify a child's gender just by the sound of their voice from the age of five, a new study reveals.
Researchers in the US played volunteers audio clips of children's voices and asked them to guess their gender.
They found the talker's gender could be identified from age five – almost a decade before differences in the vocal tracts of males and females start developing during puberty.
Humans tend to assess another speaker's gender primarily on their voice pitch and resonance, but also based on age, height, and other physical characteristics, the experts say.
We tend to assess speaker's gender primarily on a speaker's voice pitch and resonance, researchers at the University of California, Davis and the University of Texas at Dallas report
Pitch is the high or low frequency of a sound, while resonance refers to a sound quality of being deep, full and reverberating.
'Resonance is related to speaker height – think violin versus cello – and is a reliable indicator of overall body size,' said study author Santiago Barreda at the University of California, Davis.
'Apart from these basic cues, there are other more subtle cues related to behaviour and the way a person "chooses" to speak, rather than strictly depending on the speaker's anatomy.'
The perception of gender in children's voices is of special interest to researchers, because voices of young boys and girls are very similar before they hit puberty.
Adult male and female voices, on the other hand, are usually quite different acoustically, making gender identification fairly easy.
Researchers therefore wanted to investigate what types of changes occur in children's voices as they gradually get older.
Talkers can be identified almost a decade before differences in the vocal tracts of males and females start developing during puberty, such as growth of the larynx (or voice box, shaded in this artistic rendering)
For the study, the team developed a database of speech audio samples of children speaking, aged from
