|
Ockham’s razor |
A main source of mental workload is the multitude of
options and features that marketing love it add to the system specification.
With many screen displays, users spend more time learning where to find the information
they need. With many controls, users spend more time learning which control
is relevant to which task. The basic means to reduce mental workload is to
shave away all unnecessary features and
options. This guideline,
originally targeting scientific argumentation, is applicable also to
engineering. Simple is better, because it is easier
for the users to find the
information and the controls they need for their task. |
|
Simplicity |
Complexity may be defined by the number of links between objects.
In contrast with Ockham’s razor, which applies here
to refer to objects, simplicity is about the relationships between objects.
The second basic means to reduce mental workload is to remove unnecessary constrains, such as conditions and
sequencing, to enable direct transition
from intention to action. Combined with ockham’s
razor, we have the well known KISS (Keep It Simple, Stupid) principle. |
|
Information tunneling |
Software programs implementing Service Oriented
Architectures (SOA) enable the user to reach all privileged properties and
methods (use cases) of all objects. However, users are often overwhelmed by
such design. The example of production waste above demonstrates the problem
of irrelevant information. Typically, at a given point of a given procedure,
they need to view only few properties, and to access a single method. To
reduce the mental workload of finding the properties and methods relevant to
the particular procedure stage, we arrange the operational procedures
according to scenarios. In a scenario based design, we present to the user
only the information required for the task they chose to perform. |
|
Apparent power |
Many customers do not appreciate the
benefits of simplicity or stupidity (http://www.joelonsoftware.com/items/2006/12/09.html
). They prefer systems that look complex over those that look simple, because
they seem to be powerful (http://www.jnd.org/dn.mss/simplicity_is_highly.html
). We can see this trend in huge selections of complex watches in watch and
jewelry shops. |
|
Progressive disclosure |
Interaction designers face a dilemma: ·
Users want power, features, and enough options to handle all of their
special needs ·
Users want simplicity; they don't have time learn a profusion of features
in enough depth to select the few that are optimal for their needs. Progressive disclosure enables satisfying both of these
conflicting requirements. The idea is that redundant or unimportant features should be visible, but should be
clearly separated from the features which are most significant for the main
user tasks. Progressive disclosure defers advanced or rarely
used features to a secondary screen, making applications easier to learn and
less error-prone. (http://www.useit.com/alertbox/progressive-disclosure.html).
Initially, we show users only a few of the most important options. Then, we
offer a larger set of specialized options upon request. Disclose these
secondary features only if a user asks for them, meaning that most users can
proceed with their tasks without worrying about this added complexity. |
|
The legend of adaptive systems |
Computer scientist who seek to reduce complexity, are
often tempted to adapt the system behavior to the user’s activity. For
example, the menus of certain MS-Office programs, which are overloaded with
items, first show the items used most frequently, and then, after few
seconds, the remaining menus. All experiments intended to show the benefits
of this method failed. The explanation for these results is that after the
users have learned a particular setup, they expect it to remain the same;
otherwise they need to learn it over and over again. It is easier to learn
the setup once, so that in subsequent operation the mental workload is
dedicated to real tasks. |
|
Types of usability mismatch |
This article defines two types of operational faults
involving usability mismatch:
|