We’ve heard of the physical effects on our body when we are talking to someone we are attracted to, like pupils getting larger or butterflies in our stomach.

Numerous self-help websites offer tips on how to read body language to tell if the object of our affection is interested in us.

Apparently, if their feet are facing towards us, that’s a good sign. If their arms are folded, not so much. But you can also gauge the level of someone’s attraction by their voice.

Male and female pitch

The biological gender differences in the human voice are very clear. Female voices have higher pitch and male voices have lower pitch.

These differences are thought to be because of evolutionary pressures such as mating choices. In the animal world, pitch is associated with larger animals that can cause a bigger threat.

So by lowering their pitch, males can show their physical dominance in front of their competitors and appear more sexually fit to females. As a result, women find men with lower-pitched voices more attractive. It’s the opposite for men, who are more attracted to women with higher-pitched voices, which is perceived as a marker for femininity.

Attractiveness in the voice is important for the impressions we give our potential partners. In research settings, this is studied by asking listeners to rate voices of people they have never seen as either attractive or unattractive.

Using this method, one study showed that people who reported being more sexually experienced and sexually active were rated to have more attractive voices by strangers. That is, the specific qualities that the raters were perceiving in the voices were indicative of these people’s mating behaviours and sexual desirability.

We actually have the ability to change the attractiveness of our voice depending on our interlocutor, and we do this without knowing. Women sometimes modify their voices to sound most attractive during the most fertile part of their menstrual cycle. Men also modify the pitch in their voice, specifically when confronted with potential competitors in dating scenarios.

This means that just like we fix our hairstyle or clothes to look more attractive for a date, we also give our voices an unconscious makeover to sound more attractive and sexually fit.

Sounding the same

Another phenomenon that may also cause changes in the way we speak when talking to a love interest is something called “phonetic convergence”. People who talk to each other tend to start sounding more similar, completely unaware they are doing so.

This similarity can be speech rate (how fast we’re talking), the pitch or intonation patterns we use, or even the way we produce individual words or sounds. This adaption can happen over long (months or years) and even very short (one-hour lab study) periods of time.

One study compared the speech of five pairs of new roommates who had just moved in together. At the beginning and end of semester, researchers took recordings of each person and asked them to rate how they felt about their new roommate. They found that the roommates sounded more similar at the end compared to the beginning of semester and that this convergence was related to the ratings of closeness.

So how could this relate to physical attraction? One proposed explanation of phonetic convergence, the similarity attraction hypothesis, is that people try to be more similar to those they are attracted to. So, in an effort to be more similar to someone we are interested in, we may start to talk more similarly and maximise the chances they will also find us attractive.

The opposite can also happen: this is called “phonetic divergence”. Divergence may occur when we want to be more distinct, or less similar to our speaking partner, perhaps when we aren’t attracted to them.

It also doesn’t necessarily take months for this to happen. Phonetic convergence can occur in a much shorter time.

In another experiment, researchers brought previously unacquainted pairs of participants into the lab to complete a task. Both partners have a map, but only one has the route drawn on their map. Their job is to describe the route to their partner so they can draw it, without using pointing or other gestures, only words.

The researchers found convergence occurred in the session and even persisted after participants had completed the experimental task.

The great news is these changes happen automatically and unconsciously. When we face an attractive partner, our voices and speech are modified to sound more attractive and alike. So during a conversation with that special someone, your voice may be doing the hard work to let them know you are interested, which may increase your chances of getting a second date.

By Heather Kember, Research fellow in speech processing, Western Sydney University and Marina Kalashnikova, Researcher in Infancy Studies, Western Sydney University

This article was originally published on The Conversation. Read the original article.