How to improve your memory: what actually works

Test yourself: retrieval practice

The single most reliable way to make something stick is to pull it back out of your head. Psychologists call this retrieval practice, or the testing effect. Reading notes again feels productive, because the material looks familiar. But familiarity is not the same as being able to recall it.

In a well-known experiment, Henry Roediger and Jeffrey Karpicke (2006) had students read short passages and then either reread them or take recall tests with no feedback. Five minutes later, rereading had done slightly better. Two days and a week later, the pattern flipped: the students who had tested themselves remembered substantially more, even though the rereaders felt more confident.

A large review by John Dunlosky and colleagues (2013) rated ten common study techniques. Only two earned "high utility": practice testing and spreading practice out over time. Highlighting, rereading and summarising were rated low.

• Close the book and write down everything you remember, then check.
• Use flashcards, and say the answer before you flip.
• Explain the idea out loud to someone, or to an empty room.
• Do practice questions before you feel ready. Struggling to recall is part of what makes it work.

Space it out

Cramming works for tomorrow and fails for next month. The spacing effect is one of the oldest findings in memory research. Nicholas Cepeda and colleagues (2006) pulled together 317 experiments from 184 articles and found that spreading study sessions apart beat massing them together for long-term recall.

They also found that the best gap depends on how long you need to remember. If the test is next week, a gap of a day or so between sessions is sensible. If you want to remember for months, the gaps should grow too.

Sleep on it

Sleep is when the brain does much of its filing. A review in Nature by Robert Stickgold (2005) concluded that the evidence leaves little doubt that memories are reprocessed and strengthened during sleep. Sleep before learning matters too: a tired brain takes in new information less well, and attention slips.

The US Centers for Disease Control and Prevention (CDC) recommends seven or more hours a night for adults aged 18 to 60, and seven to nine hours from 61 to 64. Pulling an all-nighter before an exam trades the sleep that would have locked in what you learned for a few extra hours of tired rereading.

Move more

Regular aerobic exercise is one of the better-supported things you can do for your brain over the long run. In a year-long trial with 120 older adults, Kirk Erickson and colleagues (2011) found that walking 40 minutes, three days a week, increased the size of the hippocampus (a brain area central to memory) by about 2%, while it shrank slightly in a group who did stretching and toning.

Be careful with the headlines, though. Other researchers pointed out in reply that the memory test scores themselves did not clearly differ between the groups after a year. The fair summary is that exercise is good for the brain's structure and for health generally, and a reasonable bet for memory, but it is not a quick fix. The 2014 consensus statement from the Stanford Center on Longevity and the Max Planck Institute called regular aerobic exercise a moderately effective way to support brain function.

Chunking: fewer, bigger pieces

Short-term memory holds only a few things at once. George Miller's famous "seven, plus or minus two" from 1956 is often quoted, but Nelson Cowan (2001) argued that when you stop people from grouping things, the real limit is closer to about four chunks.

The trick is in the word "chunk". A chunk can be a single digit or a whole familiar pattern. The phone number 07700 900 461 is eleven digits, but three groups. "FBIBBCNASA" is ten letters, or three acronyms you already know.

• Group numbers in threes or fours.
• Link new items to patterns you already know: dates, names, shapes.
• Learn the structure first (the five main headings), then the detail under each.

You can feel this limit in Brainbay's number memory test and chimp test: the scores climb when you start grouping, not when you stare harder.

Mnemonics and the method of loci

The method of loci, or memory palace, is the technique memory champions use. You picture a route you know well, such as your home, and place each item you want to remember at a spot along it, ideally as a vivid, odd image. To recall, you walk the route in your mind.

It is not just for champions. In a study in Neuron, Martin Dresler and colleagues (2017) trained ordinary volunteers in the method for 30 minutes a day over 40 days. They improved on a 72-word recall task far more than a group that did working-memory training or a group that did no training, and most of the gain was still there four months later. Their brain connectivity also shifted towards the pattern seen in memory athletes.

The catch is that mnemonics suit lists and ordered facts better than understanding. Dunlosky's review rated the keyword mnemonic, a related trick for vocabulary, as low utility for general study. Use a memory palace for a speech, a shopping list or the order of the planets, and retrieval practice for the rest.

1. Pick a route you know by heart, with ten clear stops.
2. Make each item an image that is big, silly or moving.
3. Place one image per stop, and pause to "see" it there.
4. Walk the route in your head straight away, then again tomorrow.

Elaboration: ask why

Facts with no connections slip away. Facts tied to things you already know stay. Elaboration means asking "why is this true?" and "how does it connect to what I know?" as you learn. Dunlosky's review rated two forms of it, elaborative interrogation and self-explanation, as moderate utility: helpful, with less evidence behind them than testing and spacing.

In practice, it looks like this: rather than memorising that the heart has four chambers, ask why a mammal needs two separate pumps. Rather than learning a word alone, use it in a sentence about your own life.

What brain games can and can't do

Memory games are fun, and you will get better at them with practice. What the research does not support is the idea that getting better at a memory game makes your everyday memory better.

A meta-analysis of working-memory training by Monica Melby-Lervåg, Thomas Redick and Charles Hulme (2016), covering 87 publications, found reliable short-term gains on similar memory tasks, but no convincing improvement on things further away, such as reasoning, reading or arithmetic. Notably, in the Dresler study above, the working-memory training group did no better on word recall than the group with no training at all. A strategy you can use (the memory palace) transferred; drilling a task did not.

Where games can genuinely help is as a short, pleasant warm-up that gets you focused, and as a place to try strategies such as chunking and see the difference straight away. The visual memory, sequence memory and word memory tests are good for that.

A simple weekly plan

Sources

• Roediger, H. L. & Karpicke, J. D. (2006). Test-enhanced learning. Psychological Science, 17(3).
• Dunlosky, J. et al. (2013). Improving students' learning with effective learning techniques. Psychological Science in the Public Interest, 14(1).
• Cepeda, N. J. et al. (2006). Distributed practice in verbal recall tasks. Psychological Bulletin, 132(3).
• Stickgold, R. (2005). Sleep-dependent memory consolidation. Nature, 437.
• CDC. About sleep: how much sleep do I need?
• Erickson, K. I. et al. (2011). Exercise training increases size of hippocampus and improves memory. PNAS, 108(7).
• Cowan, N. (2001). The magical number 4 in short-term memory. Behavioral and Brain Sciences, 24(1).
• Dresler, M. et al. (2017). Mnemonic training reshapes brain networks to support superior memory. Neuron, 93(5).
• Melby-Lervåg, M., Redick, T. S. & Hulme, C. (2016). Working memory training does not improve performance on measures of intelligence or other measures of far transfer. Perspectives on Psychological Science, 11(4).
• Stanford Center on Longevity and Max Planck Institute for Human Development (2014). A consensus on the brain training industry from the scientific community.
• NHS. Memory loss (amnesia).