Balancing visual and structural complexity in interaction design
How visual simplicity can harm usability
Usability is based on principles such as "Less
is more" and "Keep it simple, stupid". But there is more
to simplicity than meets the eye. By reducing visual complexity at the
cost of structural simplicity, you will give your users a hard time
understanding and navigating the content of a web site.
In their effort to make things simple and user
friendly, designers often try to reduce the visual complexity of web
pages. They cut down the number of menu items, hide them away in dropdown
menus, move related content and details to other pages, and split articles
into multiple pages. The reason is often an aesthetic one, but designers
find support in widely held beliefs about users, such as:
- Users can only manage a certain amount of information
at a time
- Users don't want to wait for things to
- Users don't want to scroll
While such statements hold a grain of truth, they are oversimplified,
undifferentiated, and at worst misleading. Taking them too literally
will most likely do harm to usability. It's true that the more
simple a page looks, the easier users can find information on it. But
reducing visual complexity to make things pleasing to the eye by hiding
critical information from users will inevitably increase structural
complexity, and make it difficult for users to grasp and navigate the
In the following I will show some common pitfalls,
where studies have proven that what appears to be simple isn't
always what is easy to use.
7 +/- 2 items
One of the most misleading arguments used in favour of reducing visual
complexity is the rule of 7 +/- 2. The rule states that the human brain
can't handle more than 7 +/- 2 items at a time. If you apply the rule
to visual design, it would mean that things such as lists of menu items
or items in a bulleted list can be no more than nine.
The trouble with this rule is that the psychologist George Miller
who formulated it was studying the limitations of short-term memory
- not limitations of what people can perceive visually at a time.
Humans can only retain 7 +/- 2 items in the immediate memory, but have
no problem in dealing with great amounts of information in the field
of vision. As long as you have information present for continuous reference,
immediate memory plays no significant role in your perception.
The rule of 7 +/- 2 can be quite harmful when
applied to navigation. On the surface it might seem reasonable that
reducing the number of menu items of each web page will make it easier
for people to navigate. But this is not true. Reducing the number of
menu items will make the site hierarchy deeper and thereby increase
structural complexity. Research
has shown that users generally find information faster in broad and
shallow menu architectures than narrow and deep ones. Roughly 16 top
level links leading into 2-3 subsequent menus seems to be the most efficient
and least error prone.
Another argument for reducing visual complexity is download time.
The more content on a page, the longer it will take to download it.
It's true that people don't want to waste their time, but fact is that
perception of download time and the actual time it takes aren't strictly
by the usability consultancy UIE on how people perceived download
time at 10 different sites showed that there was no correlation between
the actual download time and the perceived speed reported by users.
Instead, UIE found a strong correlation between perceived download time
and whether the test participants successfully completed their task.
Thus focusing on supporting users in finding what they are looking for
is a better strategy than reducing visual complexity in order to make
pages look clean and load fast.
Users and clients tell us that they don't like to scroll, and many
designers will go far to make their pages fit nicely into the browser
window. Their view has been supported by Jakob Nielsen's "Top
Ten Mistakes in Web Design" since 1996, where he reported that
only 10% will scroll beyond the information that is visible on the screen.
But according to Jakob himself this is no longer true. Studies of
his from 1997 have shown that most users are perfectly willing to scroll
even long pages, and Jakob has declared that scrolling is now allowed
and "no longer a usability disaster."
More recent studies
from UIE and the
usability research laboratory SURL support his findings. According
to UIE users are willing to scroll if the pages give them strong clues
that it might help them find what they are looking for. And research
from SURL has shown that scrolling through articles is significant faster
than reading articles split into multiple pages. The test participants
stated that they found such articles to be "too broken up",
and where frustrated by having to go back and forth to search for information.
The prejudice against scrolling is that information
is hidden from users. But as UIE rightly states, "Short pages
may avoid this potential problem by showing more (or all) of an individual
page, but the information is still hidden — on other pages."
By hiding information on other pages, you will inevitable increase structural
Hiding critical information isn't just annoying for users. It may
also have an impact on the bottom-line of e-commerce sites. Another
study by UIE has shown that when product lists provide insufficient
product details, people will buy less.
In their study, UIE observed that when product lists provided enough
information for the test participants to make selections they where
five times more likely to add items to their shopping carts, than when
they had to click back and forth between product lists and product description
pages to make up their mind. They also found that the participants who
didn't find enough information in the product lists where one-third
more likely to quit shopping and had lower opinions of the sites tested.
Striking the right balance
Usability has become an important aspect of many web projects. For
people with little experience in interaction design it's tempting to
rely on what you see and what people tell you. Clients, co-worker, managers,
and prospective users will want simplicity and will complain about information
overload if your screens look crowded. But as we have seen, there is
more between heaven and earth than meets the eye.
For the interaction designer it's a question of striking the right
balance between visual and structural complexity. People will complain
about a visually complex page at the sight of it. But they will also
complain if the information they need isn't immediately available to
them when they start using the site. It's the good old story about the
difference between what people say and what they do. If a site isn't
solely for visual pleasure, you should rely on user behaviour and not
on what people tell you. Use findings such as those mentioned in this
article as guidelines and test your designs with prospective users.