Memrise is built to discourage cramming. It’s easy to spend five minutes learning vocabulary with the app, but hard to spend 50. That is by design. One of the best-demonstrated principles of memory – proven both in the controlled setting of the laboratory and in studies conducted in the wilds of the classroom – is the value of what’s known as “spaced repetition”. Cognitive scientists have known for more than a century that the best way to secure memories for the long term is to impart them in repeated sessions, distributed across time, with other material interleaved in between. If you want to make information stick, it’s best to learn it, go away from it for a while, come back to it later, leave it behind again, and once again return to it – to engage with it deeply across time. Our memories naturally degrade, but each time you return to a memory, you reactivate its neural network and help to lock it in. The effect on retention of learning in this manner is staggering. One study found that students studying foreign language vocabulary can get just as good long-term retention from having learning sessions spaced out every two months as from having twice as many learning sessions spaced every two weeks. To put that another way: you can learn the same material in half the total time if you don’t try to cram.