People are judging your intelligence on this one personal attribute.

Image: Legally Blonde.

Whether people deem you to be intelligent or not has nothing to do with how you look or how many certificates you have on your wall, apparently.

The one way people are judging how smart you are is something much more simple. It’s all about your voice. And it could be the secret to nailing that job interview, or making people think you’re a genius.

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New research by the University of Chicago Booth School of Business found that when giving a pitch, a person’s voice, rather than what they wrote down, was the most convincing factor helping them judge intellect. (Post continues after gallery.)

So basically you can have an IQ worthy of Mensa, but if people don’t hear your voice they’re not as likely to deem you intelligent.

For the study published in Psychological Science, researchers got prospective employers to watch, listen or read transcripts of MBA students doing pitches.

They found the evaluators rated the job candidates as more “intelligent, thoughtful and competent” when they heard their pitch rather than when they read it.

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Even seeing the video pitch didn’t impact the evalulator’s assessments any more than simply hearing the candidate’s voice.

However, study author Nicholas Epley argues this doesn’t mean appearance is free from influence.

“Our data does not show that appearances don’t matter. What they show is that your intelligence is not necessarily something I can see on your body, but I think it’s a cue that we can pick up or hear in your voice,” he said.

Professor Epley warned while we might be concerned about saying the wrong thing, we could be doing more damage by not saying anything at all.

"People seem to be afraid of sounding stupid or something, but in fact, they seem to be in danger of seeming stupid when they type," he said.

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In the context of a job interview, the study suggests that if there's an opportunity to speak to someone directly, take it. Stand out from the crowded internet applicants and pick up the phone, Skype them or even pay them a visit. And leave the fake glasses at home.

What's your best tip for nailing a job interview?