Margen
'Sleep on it' turned out to be advice with scientific backing. In 2004, a German team led by Jan Born put it to the test. They taught volunteers to solve a number task that hid a shortcut, a secret rule that made the problem trivial… if you spotted it.
They split people into groups: some slept eight hours between training and testing, others stayed awake. Those who had slept uncovered the hidden trick more than twice as often as the rest.
During sleep, the brain doesn't switch off: it reorganises what you've learned, connects loose pieces and sometimes lays the answer out ready for when you open your eyes.
So faced with a tough decision or a stuck problem, the smartest move is often not to force it late at night, but to sleep and let your brain work without you.