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Classic experiments explained

Digit Span

In short

Digit span was investigated by J. Jacobs (1887), as an investigation into how much information short-term memory could retain, thus its capacity. Later, G. A. Miller (1956) built on this experiment, suggesting that 'chunking' could enhance our short-term memory capacity. Miller also asserted that we could hold 7, plus or minus 2, items in our short-term memory at one time.

Digit Span task

In Jacobs' classic 'Experiments on "prehension"', the researcher read a short sequence of digits, letters, or nonsense syllables as stimuli. Participants were then asked to verbally recall this sequence in the correct order. This process repeats and the length of the sequence increases with each trial, until the participant can no longer recall the sequence correctly. From this, the researcher notes the participant's digit span. Jacobs found the mean span was highest for digits and lowest for nonsense syllables.

A gif of an example digit span task from the participant's view. Once the instructions have been read, a sequence of numbers are presented one at a time, separated by a fixation cross. Once the sequence has been presented, the participant recalls the numbers and submits the answer.

How does digit span relate to short-term memory?

Digit span is understandably higher than letter span, considering there were only 8 digits compared to 24 letters in the available stimuli pool. The number 7 and letter W were not used as they consist of two syllables. In general, we are more accustomed to digits being presented in a haphazard order, such as telephone numbers. Whereas, letters are less likely to be presented in such a way. Short-term memory capacity for syllables is low, since they are generally much less familiar to the participant, so they absorb more of their attention. This may explain why our digit span is the highest out of these stimuli types.

Digit span theory

Miller observed that many commonalities in everyday life appear in sevens. For example, 7 days of the week and 7 notes on the musical scale. So, it was hypothesised that short-term memory held 7 (plus or minus 2) items, with specific 'slots' to store them in. This can be explored further in his paper, 'The Magical Number Seven'.

Chunking theory explores how our short-term memory can hold more information. Jacobs found that 6 words can be recalled as successfully as 6 letters, showing that the amount of information we can retrieve is increased if we group letters into units via chunking.

Moreover, the working memory model demonstrates how our digit span is associated with the phonological loop, a system that preserves the order in which information arrives. Within the phonological loop, the phonological store stores the digits we hear and the articulatory process enables maintenance rehearsal of these digits. It's likely that participants with a better phonological memory will have a higher digit span.

Can I use a digit span task in online research?

Yes, absolutely! In fact, other researchers have already used a digit span memory task to study reaction times and working memory in middle-aged gamers and non-gamers (Ziv et al., 2022).

How does it work in Gorilla?

You can try out and clone our sample of a digit span task. Of course, you can also tweak this sample to use your own stimuli.

Have a look: Try a Digit Span task in Gorilla

Are there any papers Gorilla users have written about the misinformation effect?

Yes, there are! Have a look at the following article:

Reaction time and working memory in middle-aged gamers and non-gamers.


Jacobs, J. (1887). Experiments on “prehension”. Mind, os-12(45), 75-79.

Miller, G. A. (1956). The magical number seven, plus or minus two: Some limits on our capacity for processing information. Psychological Review, 63(2), 81-97.

Ziv, G., Lidor, R., & Levin, O. (2022). Reaction time and working memory in middle-aged gamers and non-gamers. Acta Psychologica, 228, 103666.

This page was written in collaboration with Lizzie Drury