Grab some pocket change and put your depth perception to the test with this simple experiment you can play at home. #BrainGames | National Geographic TV

How accurate is your brain’s internal clock? Here’s a quick cognitive test that neurologists and researchers use to assess executive function, attention, and internal timing: 👉 Close your eyes 👉 Start a 30-second timer (but don’t look) 👉 Raise your hand or say “stop” when you think 30 seconds have passed Now open your eyes and check. What this test shows: If you stopped way too early (10–20 sec) → Your brain may be in fast mode - often linked to stress, anxiety, high cortisol, caffeine overst