475,000 adults squeezed a handle in a lab: the weakest hands scored worst on tests that had nothing to do with muscle
A landmark study of nearly half a million adults found that grip strength is a surprisingly accurate predictor of cognitive performance—memory, reasoning, and reaction time all correlate strongly with how hard you can squeeze. Researchers discovered this connection isn’t about causation but shared biology: the brain regions controlling fine motor movement overlap with those managing memory and processing speed.