Soon you'll be able to prove it as researchers have unveiled a groundbreaking way to track when your brain is working too hard—with a face tattoo. In a study published today in the Cell Press journal Device,

The novel, low-profile system accurately measured mental workload and predicted mental strain in a small study.

Researchers gave participants face tattoos that can track when their brain is working too hard. Published in the journal Device, the study introduces a non-permanent wireless forehead e-tattoo that decodes brainwaves to measure mental strain without bulky headgear.