- Let's play a little game.
I will show you a bunch of letters on a screen.
You'll see them for a few seconds then I will remove them.
Now, write them down.
How many did you remember?
If you're like most people, it's probably about seven,
plus or minus two.
This is what the magical number seven refers to.
It's the capacity of human short-term memory,
the amount of information that people can remember
without study and rehearsal.
Now, let's play this game again
with a different set of letters.
Now, write down as many as you can remember.
Feel free to pause the video in order to do so.
How many letters did you recall this time?
Most people remember
around seven words in experiments like this.
That means about three times seven equals 21 letters.
A lot more letters than in our first experiment.
Why is that?
How come the size of your short-term memory
suddenly got bigger?
Back in the late 1950s, the Psychologist George Miller,
reviewed several studies of human memory and noticed
that in all of them people could remember
seven plus or minus two items,
hence "The Magical Number Seven, Plus or Minus Two",
the title of his paper.
But for Miller, this wasn't the interesting part.
This being the era of information theory,
he was fascinated by the fact that the unit,
the type of items that could be remembered
was different in different studies.
In some studies, people remember seven letters,
in other seven numbers or words.
Thus, he figured that the capacity of short-term memory
shouldn't be measured in bits,
the traditional unit for information,
but rather in mini units called chunks.
And these units could be as big as one would want.
So that means you can increase the size
of your short-term memory
as long as you group items into meaningful chunks.
Characters into words, words in sentences,
digits in numbers and so on.
A process known as chunking.
It's a principle that you may have encountered before
when you try to memorize information.
Now, keep in mind,
the major implication of the magical number seven is that,
you can expect people to keep roughly
seven items of information in their short-term memory.
So they won't remember things like random coupon codes,
links that they may have visited before,
password requirements or lots of instructions.
Now, the magical number seven is often involved
as an argument in UX wrongly.
I've heard people using it to argue
for seven items in a menu bar or in a pull-down menu,
seven bullet points on a slide, seven point rating scales.
The truth is, the human short-term memory capacity
is not relevant for these tasks.
You're not supposed to remember all options in the menu
or all the bullets on a slide
or all the points on a rating scale.
They are normally visible or accessible
and there could be other good reasons
for which you might not want to have too many,
but the magical number seven is not one of them.