I’m sure this has happened to you. You approach someone who says “Hello” and you smile and return the greeting. Only to have them ignore you because they weren’t addressing you, but instead talking on a Bluetooth device or on speaker via the cell phone clipped to their belt.

For some reason, I feel really stupid. Why did I think that that handsome guy jogging past had suddenly noticed me? Or that woman who never acknowledged Liz or me in before–on a whim decided to be friendly?

Now I check the hands and ears of the speaker to ensure they’re not communicating with someone else. Seeing a person walk past without acknowledging my presence makes me feel unsettled, as if I’ve become invisible.

But concentration on a device blocks out everything and everyone around you, including the sounds and sights of nature, friendly smiles or imminent danger. I’ve seen a woman nearly bump into a tree and a man almost collide with a pick-up truck in the parking lot while gazing at their phone screens.

Tunnel vision may cost you possible friendships, opportunities for relaxation–or even your life…