- Suppose someone asked you to add the numbers,
259 and 374 in your head.
How would you do it?
You may try to mentally line up the numbers
and then add the corresponding digits for units,
tens and hundred.
Whatever the method,
chances are that this task will be challenging.
That's because you have to keep a lot of information around.
Not only the exact numbers to be added
but also the intermediate products of the addition.
This task is difficult
because it overloads your working memory.
Human working memory is a buffer or scratch pad
in which the mind stores information
relevant to the current task.
The working memory buffer has a limited capacity.
Think of it as an egg carton
with a small number of slots, say six.
The actual capacity will vary from person to person.
If a task requires more than six items
of information to be kept into working memory
some of them won't fit in our six slot carton
and we may not be able to remember them when we need them.
As a result, we may end up working harder
to recover that data
and we may take longer to do the task
or we might make mistakes.
In our addition example we may end up dumping out a carry
or a digit from one of the original numbers
and produce the wrong answer
or have to start all over again.
A UX concept that is related to that of working memory
is cognitive load.
If a task incurs a high cognitive load
it usually means
that it puts a high burden on the working memory.
To make the experience pleasant and usable,
designers must make sure that a user's working memory
won't be overloaded.
It's easy to say limit the working memory burden.
But certain tasks are naturally more complex than others.
How can we help users
get around their working memory limitations?
In our original addition example we cannot change the task.
The addition is what it is
but we can make it easier by providing pen and paper
so people can write down the numbers
and the intermediate products in a task
without having to store them in their working memory.
The paper acts as a physical scratch pad,
a fake working memory.
An extension of it
it's what we call a type of external memory.
External memory refers to any tool or UI feature
that allows users to explicitly save
and access information needed during a task.
A typical example of a web task
involving a high working memory burden is item comparison.
The user has to weigh in the pros and cons
of several alternatives and choose the best.
Whether comparing hotels, shoes or insurance plans,
comparison involves remembering the available options
and deciding which option combination is optimal.
Tools such as comparison tables
are a form external memory.
They allow users to select a set of items of interest
and explicitly compare their pros and cons
lined up with each other in an easy to see table.
Different tasks have different working memory requirements.
Designers must understand what kinds of information
users will need to keep in their working memory
as they attempt to reach their goals on a website.
And they will need to provide UI features
that act as external memory
to help people offload that burden
and perform the task faster.