They used to think that the size of working memory was 7 items, on average.

Now, according to fMRI, it's believed to be only 4.

Source: In his TED talk, around 5:20, Peter Doolittle says the estimate had to be revised:

We tend to remember about 4 things. It used to be 7. But with functional MRI, apparently, it's 4.

  • $\begingroup$ "7 items" is not wrong, it's an observation, specifically about 7 +/- 2 is the number of random digits that someone can hold in working memory, called "digit span". $\endgroup$
    – Bryan Krause
    Mar 16, 2021 at 21:22
  • $\begingroup$ @BryanKrause Bless your heart. Aren't you the same guy who claimed Covid survivors should still get vaccinated, despite scientific evidence that reinfection is a myth? I even deleted my account on medicalsciences, because that place was so hopeless. $\endgroup$
    – user16005
    Mar 16, 2021 at 21:42
  • $\begingroup$ Don't really want to get into the same argument about shortsightedness here. Did not realize you were that same person... $\endgroup$
    – Bryan Krause
    Mar 16, 2021 at 21:59
  • $\begingroup$ @BryanKrause I remember you, because I've literally never seen you be right. Even here, you claim that 7 is just an observation, which was limited to digits, but in fact "The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information" is one of the most highly cited papers in psychology. $\endgroup$
    – user16005
    Mar 16, 2021 at 22:23
  • $\begingroup$ @bobcat It's cited because it's a useful result and an important paper that started an area of research. Not because the people citing it believe "7 is the magic size of working memory storage". It does happen to be a fairly simple paradigm, though, that is still used in IQ tests and measures of working memory in aging adults. $\endgroup$
    – Bryan Krause
    Mar 16, 2021 at 22:29

1 Answer 1


In the TED talk he's making a joke ("memory used to be X, now it's Y!"). Likely referencing the "good ol' days" trope where one talks about how things used to be different when the comedian/speaker/audience was younger, or more specifically the tendency of memory to decrease with age.

The "span" of working memory depends on the type of "object" being remembered, how exactly it is remembered, and what other distractions or tasks are interfering. The original "7 +/- 2" paper is quite old, and although it did propose a limited working memory capacity with a particular span, I do not think it supports your claim that psychologists "used to think that the size of working memory was 7 items". Rather, in one experiment with one type of object the average was 7 items. People had to do further experiments with other types of items to find out if the span was constant over all objects; once doing those experiments, they found that it was not, but consistently found that there was some capacity beyond which it was difficult to remember more objects without more elaborate strategies or training (such as the "memory palace"/method of loci).

Wikipedia has a pretty extensive article on memory span that is probably a good place to start if you're interested in the topic. Some of the characteristics listed on that page that influence the span include relatedness of the items, distractors, rhythm and rate of how objects are presented, modality (auditory, visual, etc), motor cost (longer words take more "space"), how exactly responses are scored (total recalled? number before error? how are adjacent/similar objects scored?), and other distractions.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy