Overhearing someone else’s cellphone conversation literally drives our brains nuts because we can’t help but try to imagine what the rest of the conversation is about. 

University of San Diego researchers had volunteers listen to a conversation between two people or listen to the exact same conversation being conducted on a cellphone – so they only heard one side of it. 

The result? People who overheard the cellphone conversation were much more distracted, and irritated, and they also had much more difficulty completing tasks they were given than those who eavesdropped on the two people talking face-to-face.

So, why does a one-sided conversation mess with our mind so much? Lead researcher Dr. Veronica Galvan says that your brain is attracted to novelty and the unexpected. And when you listen to half of a conversation – which experts have nicknamed a “half-a-logue” - your brain is instantly hooked, and automatically goes into detective mode, trying to predict what’s going to happen next in the conversation.

And all of that wondering draws your attention away from whatever else you’re doing, making it impossible for you to focus.

So, next time you overhear someone gabbing on their phone at the mall, or on the train, you may want to throw on noise-canceling headphones and give your brain a break from detective duty.