We’ve all had to face a tough exam at least once in our lives. Whether it’s a school paper, university final or even a test at work, there’s one piece of advice we’re almost always given: make a study plan. With a plan, we can space out our preparation for the test rather than relying on one or two intense study sessions the night before to see us through.

It’s good advice. Summed up in three words: cramming doesn’t work. Unfortunately, many of us ignore this rule. At least one survey has found that 99% of students admit to cramming.

You might think that’s down to nothing more than simple disorganisation: I’ll admit it is far easier to leave things to the last minute than start preparing for a test weeks or months ahead. But studies of memory suggest there’s something else going on. In 2009, for example, Nate Kornell at the University of California, Los Angeles, found that spacing out learning was more effective than cramming for 90% of the participants who took part in one of his experiments – and yet 72% of the participants thought that cramming had been more beneficial. What is happening in the brain that we trick ourselves this way?

 

It’s better to spread out revision before the big exam (comedy_nose/Flickr/CC BY 2.0)

 

Studies of memory suggest that we have a worrying tendency to rely on our familiarity with study items to guide our judgements of whether we know them. The problem is that familiarity is bad at predicting whether we can recall something.

Familiar, not remembered

After six hours of looking at study material (and three cups of coffee and five chocolate bars) it’s easy to think we have it committed to memory. Every page, every important fact, evokes a comforting feeling of familiarity. The cramming has left a lingering glow of activity in our sensory and memory systems, a glow that allows our brain to swiftly tag our study notes as “something that I’ve seen before”. But being able to recognise something isn’t the same as being able to recall it.

Different parts of the brain support different kinds of memory. Recognition is strongly affected by the ease with which information passes through the sensory areas of our brain, such as the visual cortex if you are looking at notes. Recall is supported by a network of different areas of the brain, including the frontal cortex and the temporal lobe, which coordinate to recreate a memory from the clues you give it. Just because your visual cortex is fluently processing your notes after five consecutive hours of you looking at them, doesn’t mean the rest of your brain is going to be able to reconstruct the memory of them when you really need it to.

 

Merely thinking hard about what’s on the blackboard isn’t enough to make learning actually happen (Thinkstock)

 

This ability to make judgements about our own minds is calledmetacognition. Studying it has identified other misconceptions too. For instance, many of us think that actively thinking about trying to learn something will help us remember it. Studies suggest this is not the case. Far more important is reorganising the information so that it has a structure more likely to be retained in your memory. In other words, rewrite the content of what you want to learn in a way that makes most sense to you.

Knowing about common metacognitive errors means you can help yourself by assuming that you will make them. You can then try and counteract them. So, the advice to space out our study only makes sense if we assume that people aren’t already spacing out their study sessions enough (a safe assumption, given the research findings). We need to be reminded of the benefits of spaced learning because it runs counter to our instinct to relying on a comforting feeling of familiarity when deciding how to study

Put simply, we can sometimes have a surprising amount to gain from going against our normally reliable metacognitive instinct. How much should you space out your practice? Answer: a little bit more than you really want to.

Tom Stafford / BBC Future