You may remember a scenario like this: you painstakingly learn your GCSE French vocab and get it 100 per cent right in the mini test you set yourself. Then, when you go back to it two days later, most of it has vanished from your memory. You want to unleash a volley of French expletives - but you can’t remember any. Instead, you fling the book at the wall, sulk for a bit and then return to the task of pushing the boulder up the hill once again by relearning it all, weeping bitter tears of inadequacy all over your revision timetable.

At the time, this kind of thing feels like failure. However, some researchers say it’s actually a crucial element of the learning process: a “desirable difficulty”.

Desirable difficulties have been a common feature of research discussions in schools and at conferences over the past few years, but does everyone using the term understand the concept fully, and is everyone using it correctly? Education is full of lethal mutations when it comes to research, so let’s find out.

The term “desirable difficulties” was coined in 1994 by cognitive psychologist Robert Bjork, who, alongside his wife Elizabeth Ligon Bjork, heads up the Bjork Learning and Forgetting Lab at the University of California, Los Angeles.

Nate Kornell, an associate professor of cognitive psychology at Williams College in Massachusetts, is a former graduate student of Bjork’s. He has tested out and refined the concept of desirable difficulties in subsequent experiments, becoming one of the world’s leading authorities on the topic.

“The basic idea is that our minds are like muscles in that, if they work hard, that’s how they grow,” says Kornell. “When you have to process information, when you have to think hard about it, it gets encoded better.”

According to Kornell, a desirable difficulty is “any kind of educational intervention that causes students to do worse in the short term but better in the long term”.

The concept of desirable difficulties encompasses spacing (leaving gaps between multiple study sessions - the opposite of “massing”, where all learning on a subject is done in one session), interleaving (spacing study by chopping it into blocks on related but distinct topics, which are interspersed), testing oneself, and generating one’s own answers (rather than having them provided).

In one of the Kornell/Bjork experiments, participants were asked to learn the styles of 12 different artists by viewing six different paintings by each artist. Half of the artists’ works were presented in spaced form and half were in massed form. After this learning phase, participants were shown new paintings by the same 12 artists and asked to select, from a list of all the artists’ names, the artist who had painted each one.

In the paintings experiment, 78 per cent of the participants performed better when viewing the spaced presentations than they did with the massed presentations.

Unfortunately, desirable difficulties are a tough sell in some respects. These difficulties “are not always desirable from the perspective of making the children happy or making the children feel successful or even making the teacher feel successful”, says Kornell. “When you make things difficult, students struggle more while they learn.

“One of the big messages for teachers is: focus on improvement even though it’s going to hurt [immediate] performance. But that’s really hard to do.”

So, why are things like spacing and testing oneself so effective?

Spacing between study sessions “allows your brain to consolidate the information that you’ve been learning, but also to forget some stuff. So, when you return to it after a delay, your brain has to actually re-encode the information, [and] you get value from that”, Kornell explains.

In testing oneself, the benefit is all about “the value of trying to make a retrieval attempt, to probe your own memory to see if there’s something there”, he adds. “When you do that it creates a fertile ground for the information that you’re being tested on to be encoded.”

And mistakes are a key part of desirable difficulties. “Making a lot of mistakes feels like failure. It can actually be really good,” says Kornell. “Testing yourself, even if you get the answers wrong, you oftentimes learn more than if you just read the answers.”

In their work, Kornell and Bjork have talked about the need for individuals to become “sophisticated learners” who understand key aspects of how humans learn and how memory works, and use techniques “that enhance the storage and subsequent retrieval of to-be-learned information”.

The thing that teachers can do to show children the value of desirable difficulties is “pulling out the triumphs”, says Kornell.

“When a kid is struggling with something and they finally get it right, take a second to remind them: ‘Hey, remember how much you struggled with this? Now you get this and notice that your struggle paid off.’”

And teachers can also “stop giving help that…does the hard part of the problem for the kid”, he adds.

You may be tempted to take this research and turn your classroom into a space of finely optimised desirable difficulties. But if you did that, you would not be following the research, says Kornell.

He stresses that he isn’t offering up the concept of desirable difficulties as some kind of miracle solution for learning. Instead, he describes what he studies as a “drop in the bucket” of the ingredients for a good classroom.

Kornell adds it is likely that good teachers will already be bringing desirable difficulties into their teaching.

“The best teachers intuitively take advantage of desirable difficulties: that’s part of the reason why their students learn so much - because they are challenging them and letting them struggle,” he observes.

Does Kornell fear his work will become a fad, though? It is certainly a popular technique in certain groups of teachers. He thinks not, mainly because what he’s talking about is not a quick fix and thus is not the sort of thing that becomes fadish.

“What I’m telling the teachers is, ‘There’s no easy answer - struggle and make it hard,” he says. “I don’t think what I’m saying is really good fad material.”

He also points to the fact that the message does not seem to be getting through in some quarters. Most textbooks are “still completely blocked, not interleaved”, he notes.

Bjork and Kornell are pushing on, though, and they are targeting perceptions of difficulty and individual potential at a societal level and how that might be changed. They have argued, for example, that there is an “over-appreciation in our society of the role played by innate differences among individuals in determining what can be learned and how much can be learned”.

Though Kornell is critical of the way that growth mindset has gone from a valid concept in psychology to a “faddish” application in schools, he does “totally agree with the idea that kids should try to have a growth mindset”.

“I think a lot of times kids don’t recognise how much value there would be in just working harder,” he continues.

At Williams College, Kornell sees that new students who went to “fancy private schools” have already thoroughly grasped that, but others have not.

“In terms of creating more equality [in education and society], part of the issue - it is a small part of the big issue - is getting everybody to realise they have more potential than they think,” he says.

That’s likely to be a difficult task, but it’s certainly a desirable one.

John Morgan is a freelance journalist

This article originally appeared in the 4 December 2020 issue under the headline “Tes focus on…desirable difficulties”