Northwestern University graduate student Eric Smith, along with Professors Marcia Grabowecky and Saturo Suzuki, asked study participants to examine images of human faces that were not easily categorized as male or female. While looking at the faces, researchers played beeping tones having frequencies typical of either male or female voices.

When the androgynous face was paired with a tone within the frequency range of a typical female voice, study participants were more likely to report the face was that of a female. But when the same face was paired with a tone more characteristic of a male voice, participants were more likely to report the face was that of a male.

"We think that the effect demonstrates a direct input from early auditory processing to visual perception," said Grabowecky. "If sound can implicitly bias visual gender perception, then we need to consider whether other senses, such as smell, might yield similar effects," said Smith.

The study appears in the journal Current Biology.