Digit span test: what it measures and what your score means

How many numbers can you hold in your head at once? Here's how the classic test works, what typical scores look like, and how to do better.

The digit span test is one of the oldest and simplest tests in psychology. Someone reads out a string of digits, and you repeat them back. The strings get longer until you start making mistakes. The longest string you can reliably repeat is your digit span. Versions of it still appear in widely used intelligence and memory assessments today, because it's a quick, reliable window into working memory.

What the digit span test measures

Digit span measures working memory, the small mental workspace that holds information for a few seconds while you use it. It's what you rely on to keep a phone number in mind before you dial it, or to follow a list of directions.

There are two main versions:

• Forward span: repeat the digits in the same order. This mostly measures how much you can hold at once.
• Backward span: repeat them in reverse. This adds mental manipulation on top of storage, so it leans more on attention and control.

Our game Sequence uses the forward version, with digits shown one at a time.

What's a normal digit span?

In 1956 the psychologist George Miller published one of the most cited papers in psychology, describing the span of immediate memory as "the magical number seven, plus or minus two." That still holds up as a rule of thumb: most healthy adults have a forward span of around 5 to 9 digits, with 6 or 7 very common.

Backward span is usually shorter, typically by about one and a half digits, because reversing the order takes extra mental work. Studies of older adults, for example, have found average forward spans of around 5.5 digits and backward spans of around 4.

Later research by Nelson Cowan suggests that the true limit of working memory is closer to four meaningful chunks. We reach seven digits by grouping them, which is why "482 917" is much easier than "4 8 2 9 1 7".

Does digit span change with age?

Digit span develops through childhood and is fairly stable across most of adulthood. Normative studies have found it holds steady from the 50s into the late 60s, with lower average scores from about age 70. Backward span tends to decline more than forward span, since it depends more on attention and mental control.

Age isn't the biggest factor, though. In several studies, years of education predicted digit span more strongly than age. Familiarity with numbers and practice with strategies both help.

How to improve your digit span

1. Group digits into chunks. Three at a time works well. "482, 917" is two items instead of six.
2. Rehearse the whole string. Keep silently repeating all the digits as new ones arrive, not just the latest one.
3. Look for patterns. Runs like 3-4-5, repeated digits, or a familiar year are free chunks.
4. Say it and see it. Hear the numbers in your head and picture them written down. Two copies are sturdier than one.
5. Sleep well. Working memory is noticeably weaker when you're tired.

These strategies can raise your score on the test itself. Whether that improves memory in everyday life is a separate question; see do brain games work? for what the research says.

Digit span world records

Memory competitors can recall hundreds of digits after studying them, but they use elaborate techniques like the memory palace and take their time. That's a different skill from the quick, one-at-a-time recall in a digit span test, where even experts rely on chunking.

Frequently asked questions