People with voices deemed sexy and attractive tend to have greater body symmetry upon close inspection, suggesting that what we hear in a person can greatly affect what we see in them.
"The sound of a person's voice reveals a considerable amount of biological information," said Susan Hughes, an evolutionary psychologist from Albright College in Reading, Pa. "It can reflect the mate value of a person."
Hughes, whose new study is detailed in the June 2008 edition of the Journal of Nonverbal Behavior, cautions that an attractive voice does not necessarily indicate that this person has an attractive face.
A symmetric body is genetically sound, scientists say, and in evolutionary terms, in the wild, it can be an important factor when selecting a mate. But sometimes changes during prenatal development can slightly skew this balance. For instance, the length ratio between index and ring fingers, known as the digit ratio, is fixed by the first trimester, a time that corresponds with vocal cord and larynx development. If the hormone surge that affects vocal development also affects finger growth, there should be a connection between an individual's voice and digit ratio.
Hughes could not demonstrate a connection between voice attractiveness and digit ratio in her previous work, possibly due to vocal changes that occur during puberty. So in the new study, about 100 individuals listened to previously recorded voices and independently rated them on nine traits important during mate selection: approachability, dominance, healthiness, honesty, intelligence, likelihood to get dates, maturity, sexiness and warmth.
Study participants generally agreed on what made a voice attractive. But when Hughes used a spectrogram to analyze these voice ratings according to different acoustic properties such as pitch, intensity, jitter and shimmer, she could not find a common feature that made these voices seem attractive.
This indicates our perceptual system may be more advanced than expected.
"We can agree on what's an attractive voice yet I can't capture it with a computer," Hughes told LiveScience.
Investigating if a combination of these properties can define an attractive voice may shed light on a connection, she said.