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Fw: Balancing visual and structural complexity in interaction design

From: david poehlman <david.poehlman@handsontechnologeyes.com>
Date: Sat, 21 Aug 2004 08:32:10 -0400
Message-ID: <000f01c4877a$e21826d0$6401a8c0@DAVIDPC>
To: "wai-ig list" <w3c-wai-ig@w3.org>


Balancing visual and structural complexity in interaction design
How visual simplicity can harm usability

GUUUI, ISSUE 08 - OCTOBER 2003

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 download
* 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 site.

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.

Download time

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 related.

A study 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.

Scrolling

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 complexity.

Product lists

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.
Received on Saturday, 21 August 2004 12:31:36 UTC

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