No. 05
What Affects Working Memory — Sleep, Anxiety, Noise and Age
The same person may remember 7 digits one day and 5 the next. Here are the factors research has shown to lower working memory performance, plus the testing conditions that matter.
Digit span is not a fixed stat. The same person's span drops by a digit or two after a bad night's sleep, when nervous or in a noisy place. Below are factors that research has confirmed repeatedly.
Lack of sleep
Lim and Dinges (2010) meta-analyzed studies on how short-term sleep deprivation affects cognition. Simple attention and vigilance declined the most, but complex tasks including working memory also showed clear impairment. If you test your digit span after pulling an all-nighter, it's natural to score below your usual level.
Anxiety and stress
Attentional control theory (Eysenck et al., 2007) explains that anxiety pulls attention toward worries and makes working memory's central executive less efficient. A meta-analysis by Moran (2016) likewise found that higher anxiety tends to go with lower performance on working memory tasks. Getting tense about your score can itself lower it.
Background sound, especially speech
Speech you can hear, even while trying to ignore it, disrupts tasks where you remember digits or letters in order. Salamé and Baddeley (1982) showed that background speech impaired serial recall even when participants tried not to listen (the irrelevant speech effect). This is thought to happen because speech flows automatically into the phonological loop. Test in a quiet place, and use earphones for listening mode.
Age
In childhood, digit span grows steadily with age. Gathercole et al. (2004) reported that in children aged 4 to 15, the structure of working memory stayed much the same while performance on each component improved with age. In later adulthood, many studies report declines in processing speed and working memory performance. This site doesn't provide age norms, so don't compare your score with other age groups.
Language and the length of number words
How fast you can silently rehearse digits depends on how short the number words are in your language. Languages with shorter number words tend to produce longer spans. See the language and digit span guide for details.
Testing conditions
| Condition | Effect on results |
|---|---|
| --- | --- |
| Presentation speed | Too fast and digits vanish before you can rehearse; too slow and the early digits fade. One second per digit is close to the standard. |
| Presentation mode | Seeing everything at once makes visual grouping easy and tends to raise scores; one by one puts more load on order. |
| Screen and sound | A small screen, low brightness, small speakers or an indistinct synthetic voice make it hard even to perceive the digits. |
| Practice effects | Repeating tests back to back makes you familiar with the task and raises scores; going on too long lowers them through fatigue. |
When comparing your results
- Test with the same settings (direction, sense, presentation, time).
- Testing at a similar time of day and in a similar environment reduces variation.
- Look at the trend over several weeks rather than one low score. If you feel your memory has become much worse than usual and stays that way, talk to a professional rather than relying on this site.
Sources: Lim & Dinges (2010) Psychological Bulletin 136(3):375–389 · Eysenck, Derakshan, Santos & Calvo (2007) Emotion 7(2):336–353 · Moran (2016) Psychological Bulletin 142(8):831–864 · Salamé & Baddeley (1982) Journal of Verbal Learning and Verbal Behavior 21(2):150–164 · Gathercole, Pickering, Ambridge & Wearing (2004) Developmental Psychology 40(2):177–190