100 Things You Should Know about People: #3 — You Can Only Remember 3 to 4 Things At A Time (The Magic Number 3 or 4) 0 comments
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2009-11-18 21:49:00
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7 + - 2???3 or 4???Those of you who have been in the field of usability or user experience for a few years have probably heard the phrase “The Magic Number 7 Plus Or Minus 2″. This refers act ...
7 + - 2???
3 or 4???
Those of you who have been in the field of usability or user experience for a few years have probably heard the phrase “The Magic Number 7 Plus Or Minus 2″. This refers actually to what I would call an urban legend. Here’s the legend part:
Legend: “A guy named Miller did research and wrote a research paper showing that people can remember from 5 to 9 (7 plus or minus 2) things and that people can process 7 plus or minus 2 pieces of information at a time. So you should only put 5 to 9 items on a menu or have 5 to 9 tabs on a screen”.
Have you heard this? If you’ve been reading about usability for a while I’m sure you have. Well it’s not quite accurate. Another guy named Baddeley questioned all this urban legend. Baddeley dug up Miller’s paper and discovered that it wasn’t a research paper it was a talk that Miller gave at a professional meeting. And it was basically Miller thinking out loud about whether there is some kind of inherent limit to the amount of information that people can process at a time.
Baddeley conducted a long series of studies on human memory and information processing. And what he concluded is that the number is 3 to 4 not 5 to 9.
You can remember about 3-4 things (for about 20 seconds) and then they will disappear from memory unless you repeat them over and over. For example let’s say you are driving in your car and talking on your cell phone (ok you shouldn’t be doing that) and someone gives you a number to call. But you don’t have a den handy and anyway you are driving. So you try to memorize the number long enough to hang up from one call and dial the new number. What do you do? You repeat the number over and over (putting it back into short term memory each time which buys you another 20 seconds). The interesting thing about phone numbers is that they are more than 3 or 4 numbers long. So they are hard to remember for more than 20 seconds.
712-569-4532
We also tend to chunk information into groups that have 3-4 items in them. So a phone number in the US is: 712-569-4532. Three chunks with 3-4 items in each chunk. If you know the area code “by heart” (i.e. it’s stored in long term memory) then you don’t have to remember that so one whole chunk went away. Phone numbers used to be easier to remember because you mainly called people in your area code so you had the area code memorized (plus you didn’t even have to “dial” the area code at all). And then if you were calling people in your town each town had the same “exchange” — that is the 569 part of the phone number above. So all you had to remember was the last four numbers. No problem! I know I’m “dating” myself here by telling you how it used to be back in the old days. (I live in a small town in Wisconsin and people here still give their number out as the last four digits only).
But that’s not all! Researchers working in the field of decision-making tell us that people can’t effectively choose between more than 3 to 4 items at a time.
So what does all this mean? Can you really only have 4 items on a navigation bar? or 4 tabs on a screen or 4 items on a product detail page at an e-commerce web site? No not really. You can have more as long as you group and chunk.
Here’s an example: At the Upton Tea site they have lots of tabs but the tabs are not chunked into groups of 3 or 4.
I’ve covered more than 4 items in this blog post so I’ll stop now! For those of you who like to read research here are some references:
* Baddeley A. D. (1986). Working memory. New York: Oxford University Press.
* Baddeley A. D. (1994). The magical number seven: Still magic after all these years? Psychological Review 101 353-356.
* Miller G. A. (1956). The magical number seven plus or minus two: Some limits on our capacity for processing information. Psychological Review 63 81-97
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