Spindle events begin with a surge of electrical energy generated by the rapid firing of structures deep in the brain. The main culprit is the thalamus, an oval shaped region which acts as the brain’s main ‘switching centre’, sending incoming sensory signals in the right direction. While we’re sleeping, it acts like an internal earplug, scrambling external information to help you stay asleep. During a spindle event, the surge travels up to the brain’s surface and then back down again to complete a loop.

Intriguingly, those who have more spindle events tend to have greater ‘fluid intelligence’ – the ability to solve new problems, use logic in new situations, and identify patterns – the kind Einstein had in spades. "They don’t seem related to other types of intelligence, such as the ability to memorise facts and figures, so it’s really specific to these reasoning skills," says Fogel. This ties in nicely with Einstein’s disdain for formal education and advice to "never memorise anything which you can look up".

And though the more you sleep, the more spindle events you’ll have, this doesn’t necessarily prove that more sleep is beneficial. It’s a chicken and egg scenario: do some people have more spindle events because they are smart, or are they smart because they have more spindle events? The jury is still out, but a recent study showed that night-time sleep in women – and napping in men – can improve reasoning and problem solving skills. Crucially, the boost to intelligence was linked to the presence of spindle events, which only occurred during night-time sleep in women and daytime slumbers in men.

It’s not yet known why spindle events would be helpful, but Fogel thinks it may have something to do with the regions which are activated. “We’ve found that the same regions that generate spindles – the thalamus and the cortex [the brain’s surface] – well, these are the areas which support the ability to solve problems and apply logic in new situations,” he says.

Luckily for Einstein, he also took regular naps. According to apocryphal legend, to make sure he didn’t overdo it he’d recline in his armchair with a spoon in his hand and a metal plate directly beneath. He’d allow himself to drift off for a second, then – bam! – the spoon would fall from his hand and the sound of it hitting the plate would wake him up.

DAILY WALKS

Einstein’s daily walk was sacred to him. While he was working at Princeton University, New Jersey, he’d walk the mile and a half journey there and back. He followed in the footsteps of other diligent walkers, including Darwin who went for three 45 minute walks every day.

These constitutionals weren’t just for fitness – there’s mountains of evidence that walking can boost memory, creativity and problem-solving. For creativity at least, walking outside is even better. But why?