Mind & Body

What Makes a Voice Trustworthy?

Think about the last person you met who gave you the impression that they weren't trustworthy. Assuming they weren't cackling maniacally, glancing around nervously, or straight-up telling you "You can't trust me," there was probably something in their voice that gave it away. According to research, even just a simple "hello" is enough for you to judge whether you should trust someone or not. And now, researchers have figured out just what makes that so.

I Had You at Hello

For a study published in 2014, researchers from the University of Glasgow and Princeton University recruited 320 people to listen to the word "hello" uttered by 64 different people. After hearing each recording, the volunteers rated it on one of 10 personality traits — some volunteers rated them all for how dominant they were, others rated them for likability, others for trustworthiness, and so on.

Even though the voices played for less than a second, most of the participants recorded the same ratings for each one. "It is amazing that from such short bursts of speech you can get such a definite impression of a person," co-author Phil McAleer told Science at the time. "And that, irrespective of whether it is accurate, your impression is the same as what the other listeners get."

The team wanted to find out why. So for a study published in 2017, they created a computer voice model that averaged the acoustical traits of the voices that the 2014 participants had rated as most and least trustworthy. Then, they created a slew of audio clips of that voice saying "hello" with various levels of trustworthiness. To see how they judged these utterances, the team had 500 people listen to them online and judge how trustworthy they were on a scale of 1 to 7. The test is still online, so you can try it for yourself.

What did they find? Put simply, people trust a "hello" that has personality. The most trustworthy audio clips offered varied tones: beginning high, dropping in the middle, then rising at the end. The least trustworthy ones were mostly flat, with a slight rise. According to the researchers, if you want people to trust you, put some life in your words.

Intonation of the various sound clips, color-coded from low trustworthiness (blue) to high trustworthiness (red). While low trustworthiness clips have a flat or slightly rising contour, high-trustworthiness ones have a drop at the end of the first syllable to finish the second syllable on a rising tone.

Just Trust Me

It should be said that both of these studies only demonstrate what people perceive as trustworthy, not that they can actually tell who is and who isn't. That is to say, you can use this information to help shape how people think of you, but you can't use it to read someone's mind. More importantly, the findings go beyond personal interactions and into the realm of computer speech and AI. That means that in the future, the electronic voices that you deal with every day could make you trust them — as long as they use the right tone.

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Written by Ashley Hamer November 29, 2017