If you really want to know if someone is into you – as in, wants to have your babies – never mind what they say. It’s all in how they say it. A team of researchers led by Juan David Leongómez, a psychologist at the University of Stirling, has discovered that certain “paralingual” features of the human voice, particularly changes to pitch and modulation, can betray the speaker’s hidden sexual attraction to his or her listener. What’s more, these instinctive, unconscious vocal adjustments actually seem to work in terms of increasing the speaker’s odds of getting laid: listeners prefer and respond more favorably to opposite-sex voices that contain these special subtle acoustics than to those that don’t.