01
7294156
7294156
Group
Chunk
Group digits into pairs or triples as they arrive. Three chunks fit far more easily than seven singles, it’s why phone numbers are split up.
7±2
The magic number
In 1956 psychologist George Miller noticed that people hold about seven items at once, give or take two. Digit span is the simplest way to measure it. The trick to beating it isn't a bigger memory; it's chunking.
Same 10 digits
4
1
5
5
5
5
0
1
3
2
10separate items, beyond most people's span
Two directions, two skills
482
Forwards = storage
Hold the list as it came. Mostly a test of how much your short-term store can carry.
Typical adult span6–7
482
Backwards = manipulation
Hold the list and flip it. That extra mental work is why backward span runs one or two shorter.
Typical adult span4–5
Both directions appear in the Wechsler intelligence scales, where digit span is part of the Working Memory Index.
Eight ways to hold more digits
Strong players rarely have a bigger memory, they use a better method. Try one per round, then keep the ones that work for you.
02
638
66·36·3·8
Voice
Rehearse
Say the string silently, over and over, adding each new digit as it appears. Your inner voice keeps the whole run alive.
03
415550
415 da-da-DA550 da-da-DA
Voice
Add rhythm
Give each chunk a beat, the way a phone number is read aloud. Rhythm glues digits into a single unit.
04
159
↘ diagonal line
Image
See the keypad
Picture each digit as a key on a phone keypad and trace the shape it makes. Shapes are easier to hold than lists.
05
1969
1969 = moon landing
Image
Find a meaning
Spot years, ages, times or familiar numbers hiding in the string. One meaningful chunk can replace four digits.
06
7294
seventy-twoninety-four
Voice
Say pairs as numbers
Hear “seven, two” as “seventy-two”. Two-digit numbers halve the words you need to rehearse.
07
284
swansnowmansailboat
Image
Give digits a picture
Turn each digit into an image (2 a swan, 8 a snowman, 4 a sailboat) and link them into a quick scene.
08
38149
94183
Reverse
Reverse chunk by chunk
For backwards, don’t flip the whole string at once. Chunk it forwards, then recall the last chunk first and reverse each one.
Where your span shows up
Any time you hold something in mind for a few seconds and act on it, you’re using the same system this game trains.
Codes and numbers
Keeping a verification code or phone number in mind long enough to type it.
Directions
“Second left, past the station, third door”, a sequence you hold and replay.
Mental arithmetic
Carrying digits while you work on the rest of a sum.
Conversation
Holding someone’s point in mind while you form your reply.
INSIDE YOUR BRAIN
Which parts of your brain Digit Span uses
Brain-imaging studies show that holding digits mostly runs on the left side of the brain, the side that handles language. Forwards leans on speech areas; backwards calls in the frontal lobe to do the reordering.
1
Based on Gray's Anatomy, fig. 728 (public domain)
1Visual cortex2Broca’s area3Supramarginal gyrus4Dorsolateral prefrontal cortex
Visual cortex
Occipital lobeBoth sidesIts job
Turns light hitting your eyes into shapes you recognise.
In this game
Reads each digit in the fraction of a second it’s on screen.
Broca’s area
Frontal lobeLeft sideIts job
Plans speech, including the silent inner voice you hear when you read.
In this game
Rehearses the digits “under your breath” so they don’t fade.
Supramarginal gyrus
Parietal lobeLeft sideIts job
A short-term store for speech sounds, lasting a couple of seconds.
In this game
Holds the string itself while your inner voice keeps refreshing it.
Dorsolateral prefrontal cortex
Frontal lobeBoth sidesIts job
Works on what you’re holding: reorders, updates and protects it from distraction.
In this game
Flips the order in backwards mode, the main reason backwards is harder.
CONTROL
Frontal areas steer
Broca’s area and the prefrontal cortex keep the digits refreshed and, in backwards mode, rearrange them.
STORAGE
Parietal areas hold
The left parietal lobe keeps the sound of the digits available for a few seconds.
WITH PRACTICE
The network gets more efficient
After weeks of working memory training, imaging studies have found increased activity in prefrontal and parietal regions.
Brain science sources
- Smith, E. E. & Jonides, J. (1999). Storage and executive processes in the frontal lobes. Science, 283, 1657–1661.
- Paulesu, E., Frith, C. D. & Frackowiak, R. S. J. (1993). The neural correlates of the verbal component of working memory. Nature, 362, 342–345.
- Olesen, P. J., Westerberg, H. & Klingberg, T. (2004). Increased prefrontal and parietal activity after training of working memory. Nature Neuroscience, 7, 75–79.
One of psychology’s oldest tests
The game you just played has been measuring memory for well over a century.
1887A London teacher starts it
Joseph Jacobs reads digits to pupils and records the longest string each can repeat.
1905Into the first IQ test
Binet and Simon include repeating digits in their intelligence scale for children.
1939Wechsler adds backwards
The Wechsler–Bellevue scale uses both directions, as its successors still do.
1956Seven, plus or minus two
George Miller links span limits across many kinds of memory experiments.
2001Closer to four
Nelson Cowan argues that without chunking or rehearsal the true limit is about four items.
SourcesJacobs, J. (1887). Experiments on “prehension”. Mind, 12, 75–79.Miller, G. A. (1956). The magical number seven, plus or minus two. Psychological Review, 63, 81–97.Cowan, N. (2001). The magical number 4 in short-term memory. Behavioral and Brain Sciences, 24, 87–114.Wechsler, D. (2008). Wechsler Adult Intelligence Scale, Fourth Edition. Pearson.
WHAT THIS GAME TRAINS
How many digits you can hold
Hear or see a string of digits, then repeat it. Part of nearly every IQ test since the 1900s, it measures the size of your short-term verbal store.
corestrongsomelight
coreVerbal short-term memoryHolding a list of digits in order.
strongWorking memoryReversing the order in backward span.
someAttentionTaking in every digit as it appears.
someChunkingGrouping digits into pairs or triples.