How much can humans process?

9 Mar 2005 - 8:25am
9 years ago
1 reply
584 reads
Dan Saffer

Of some interest to interaction designers:

In a new study, cognitive scientists show that humans can usually track
just four mental variables when trying to solve a problem. In the
journal Psychological Science, cognitive scientists from the University
of Queensland and Griffith University report on a study where they
tested these limits of processing capacity. It's tough to measure
because people commonly break down complex problems into manageable

For example, a baker doesn't have to think: "break egg one into bowl,
break egg two into bowl, etc." Instead, he'll track it as one chunk:
"add all the eggs." To measure their test subjects, the researchers
devised problems involving statistical interactions between fictitious
variables. The details of the test are vague, but apparently the
problems couldn't immediately be broken into "bite-size chunks." From
the press release:

The researchers found that, as the problems got more complex,
participants performed less well and were less confident. They were
significantly less able to accurately solve the problems involving
four-way interactions than the ones involving three-way interactions,
and they were (not surprisingly) less confident of their solutions. And
five-way interactions? Forget it. Their performance was no better than

After the four- and five-way interactions, participants said things
like, "I kept losing information," and "I just lost track."

(Found via Boing Boing)



10 Mar 2005 - 4:10am
Mike Baxter

Dan>> In the
journal Psychological Science, cognitive scientists from the University
of Queensland and Griffith University report on a study where they
tested the limits of information-processing capacity.
The full article is available on-line at
I think this sort of stuff is important for interaction designers but holds
potential dangers. This type of research finding is all too easy to
translate into a simple and misleading rule of thumb (remember the 3-click
rule?). Perhaps a better example is George Miller's magical number 7 plus or
minus two. Under well-controlled experimental conditions, Miller discovered
a limit on our short-term memory storage - we could remember 7+/- 2 chunks
of information. This seemingly simple discovery has popped up in interaction
design several times to my knowledge. One suggestion was that navigation
panels should have no more than 7 +/- 2 links in them. A rule like this can
be beguiling - it is founded on scientific fact, it is reasonable and it
offers a simple way of making what could otherwise be an difficult decision.
The only slight hiccup is that it is wrong! (see ) The reason is likely
to be that the magical number 7 +/- 2 relates only to short term memory
whereas our use of links in a navigation panel does not depend solely on
memory - we can repeatedly glance at the page to see what's there.
What we need is guidance on key findings in cognitive science (and other
research disciplines) and how they can safely and meaningfully be applied to
interaction design.
Any resources like this that anyone uses?

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