Pupil dilation patterns may reveal if someone is listening to you or not, according to a new Dartmouth study.

The research, published in the Journal of Experimental Psychology: General, found listeners were the most tuned in when speakers discussed the emotional peak of their story. This was revealed by synchronized pupil dilation patterns collected through videotape and eye tracking.

Read: Lying Eyes, Or Something Else? How Blink Rate, Pupil Dilation Give Insight To Honesty And Attraction​

“‘The eyes are the window to the soul’ is an ancient saying supported by many scientific studies linking pupil dilation and eye gaze to mental states such as attention and intention,” said Thalia Wheatley, according to Medical Xpress. “Here we show that the eyes not only reveal the inner workings of one mind, but reveal when two minds connect.”

The findings also suggest empathy plays a role in how often a person tunes in. Overall, those with higher empathy tuned in more frequently than listeners with low empathy.

All of the study participants were Dartmouth students, aged 18 or older with normal to corrected vision and hearing. Some of the subjects were selected to be speakers, who were videotaped while telling their stories, and the others were assigned to be listeners, who watched the pre-recorded narratives. The study authors looked for shared attention by comparing the speakers and listeners' pupils and looking for moments of synchronized dilation.

In the future, the researchers hope to track the pupil dilations of the speaker and listener at the same time.

Your pupil, or the black center of the eye, is vital to your vision. It works similar to the opening of a camera, and determines how much light enters your eye depending upon the condition. When it's bright out, your pupils are much smaller, and as light dims, they become visibly larger.

See also: Your Pupils Reveal More Than You Might Think: How Subtle Eye Movements Give You Away

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