Chidi had a big exam at 8 a.m.

At 9 p.m,  he opened his notes.

 At 2 a.m, he was still reading, phone in one hand, tea in the other.

"Sleep is for the weak," he told himself. 

"I'll sleep after the exam."

At 8 a.m, he sat in the hall. 

The first question looked familiar. 

He knew he had read it. 

But the answer would not come.

"I studied all night," he whispered. "Where did it go?"

His roommate Bayo, who had slept 7 hours, finished the paper early. 

That evening, Chidi asked him how the exam was. 

"Simple," said Bayo. "Your brain doesn't store what you read while you're awake. 

It saves it while you sleep."

What really happens

While you study, your brain takes in information, like pictures dropped into a messy inbox.

During deep sleep, the brain sorts that inbox.

 It moves important facts into long-term memory and clears the clutter.

Without sleep, the sorting never happens.

 The facts are still sitting in the inbox, hard to find.

The phone problem

Chidi's phone made things worse. 

Screens give off blue light, which tells your brain it's still daytime. 

Your body then delays melatonin, the hormone that makes you sleepy.

What Chidi did next time

He studied until 11 p.m., put the phone away, and slept.

 On exam morning, the answers came easily.