UNITED KINGDOM - Humans instinctively perceive a phone caller's body size and attractiveness from the frequency and voice quality, despite the growing influence for thousands of years of complex language.
Research by scientists and colleagues at the University College of London reveals that humans are similar to animals and birds in that they find deep male voices and high-pitched female voices more attractive because listeners gauge the speaker's body size from the sound.
In one experiment, 10 young male native English speakers heard a recorded female voice saying the sentence "Good luck with your exams," and were asked to rate its attractiveness.
The sentences were pre-recorded by a female speaker in three voice qualities and then digitally modified to signal a small body size and happiness, or large body size and anger.
Female listeners heard a male voice that had been similarly altered to indicate a larger body size.
Researchers found that male listeners preferred female voices that correlated with a smaller body size, while females preferred to hear low-pitched male voices that suggested larger body size.
The scientists were surprised to find that female listeners also preferred male voices that are breathy, which the analysts believe might soften the aggressiveness associated with a large body size.
The findings back up previous research carried out in the animal kingdom which, for example, shows that low frequency growls such as a lion's roar are more likely to indicate larger body size, dominance or a potential attack, while higher frequency and pure-tone-like sounds suggest smaller size, submissiveness and fear.
Male voices with lower fundamental frequency are in general preferred by female listeners. This seems to be associated with an evolutionary mechanism for protection from danger.
Females meanwhile raise their voice pitch when speaking to men they find attractive.
The difference between male and female voices could be explained by the theory that many birds and mammal species use vocal characteristics that indicate body size to signal their intentions.
Accordingly, human males may have evolved to have longer vocal folds to suggest a larger body size so that they can compete with other males for dominance in attracting female mates.
Females, on the other hand, may have developed shorter vocal folds to project a small body size in order to attract male mates.