The mental model
• Mental models are structures in long term
• They consist of elements and relations between
They represent relevant knowledge structures • They represent relevant knowledge structures
analogous to physical, organizational, and
procedural structures in the world.
• These mental models become instantiated when
activated by an actual need arising to make a
decision related to an element of this knowledge.
The mental model
• People tend to form their own mental model of a
system. For example:
• a video card game player visualizes cards on a
• a video golf game player can image actually • a video golf game player can image actually
• a flight simulator gives the user a realistic sense
of flying an airplane.
• The mental model helps the user understand how
the system works.
The mental model
• A good mental model allows the user to
predict the system’s response to a given
stimulus, and the more accurate those
predictions, the more intuitive the system
• When the user understands the system at an
intuitive level, the need for training declines,
the error rate improves, and the user becomes
The mental model
• When designing a user interface, the designer
should try to select a mental model that makes
sense to the user. For example,
• If the user filled out a paper form in the old
system, that form might be simulated on the
• If the mental model cannot be based on the
user’s experience, the user must be trained to
understand the new mental model and the
designer must be prepared to adjust the model if
the user has trouble understanding it.
The mental model
• A good approach is to adopt a known
metaphor such as the Microsoft Windows
• There is no point reinventing the wheel, and • There is no point reinventing the wheel, and
time spent on Windows training might
simplify training for future applications.
How can Mental Models be applied in Software
• Software interfaces should be designed to help users
build productive mental models of a system.
• (Preece, 1994) Common design methods employed to
support and influence users’ mental models include:
• Since mental models simplify reality, interface design
should simplify actual computer functions.
• A function should only be included if a task analysis
shows it is needed.
• Basic, most frequently used functions should be
immediately apparent, while advanced functions
should be less obvious to users.
• Cluttering an interface with many advanced functions
only distracts users from accomplishing their goals.
• A well-organized interface that supports users’ tasks
fades into the background and allows the user to work
• An interface should allow users to build on prior
knowledge, especially knowledge gained from
experience interacting in the world.
• The use of concepts and techniques that users
already understand from their real world
experiences allows them to get started quickly
and make progress immediately.
• The Windows operating system (and originally
the Apple system) uses an office metaphor to
leverage existing knowledge in this way.
• Its folder and document icons combined with drag and
drop functionality, allow users to grasp basic concepts
more quickly than traditional command-based systems.
• A small amount of knowledge used consistently
throughout an interface can empower the user to
accomplish a large number of tasks.
• Concepts and techniques can be learned once and then
applied in a variety of situations.
• By choosing to be consistent with something the user
already understands, an interface can be made easier
to learn, more productive, and even fun to use.
• An interface should provide visual cues,
reminders, lists of choices, and other aids,
either automatically or on request.
• Humans are much better at recognition than • Humans are much better at recognition than
• Users should never have to rely on their own
memory for something the system already
knows, such as previous settings, file names,
and other interface details.
• An interface should support alternate
interaction techniques, allowing users to
choose the method of interaction that is most
appropriate to their situation.
• Users should be able to use any object in any
sequence at any time.
• Flexible interfaces are able to accommodate a
wide range of user skills, physical abilities,
interactions, and usage environments.
• A system should provide complete and
continuous feedback about the results of actions.
• (Norman, 1988) Any feedback a user gets that
supports their current mental model strengthens
• Feedback that contradicts the current mental
model causes it to adapt.
• (Sears, 1997) Immediate feedback allows users to
assess whether the results were what they
expected and take alternative action immediately
• A user’s actions should cause the results the user
• Users should feel confident in exploring, knowing
they can try an action, view the result, and undo
the action if the result is unacceptable.
• Users feel more comfortable with interfaces in
which their actions do not cause irreversible
• An affordance refers to the properties of an object (
the kinds of operations and manipulations that can be
done to the particular object).
• For example, a chair affords support and sitting; glass
affords seeing through and breaking; folders afford
opening and storing files; a trash can affords throwing
• Affordances provide clues to how an object can be • Affordances provide clues to how an object can be
• Perceived affordance is what a person thinks can be
done with an object.
• An interface can take advantage of affordances by
using real-world representations of objects in the
interface. Users will intuitively know what to do with
the object just by looking. (Norman, 1988)
How do we Capture and Validate Users’ Mental
1. Task Analysis
• Task analysis is the process of identifying and
understanding users’ goals and tasks, the strategies they
use to perform the tasks, the tools they currently use, any
problems they experience, and the changes they would like
to see in their tasks and tools.
• Tasks may include those that involve the computer and
those that are manually performed.
• For example, a task analysis of a word processing system
would include tasks such as identifying the purpose and
subject matter of a document, as well as automated tasks
such as typing, saving files, spell checking, etc.
2. Surveys and Questionnaires
• Surveys and questionnaires are useful for
collecting demographic and opinion data.
• They can help determine users’ background and
levels of subjective satisfaction.
• Questions may be open-ended, fill-in-the-blank,
multiple choice, or rating scales.
• Questions should be carefully written so as not to
lead users to the desired answer.
• Data from questionnaires is relatively easy to
tabulate and analyze, but questionnaires usually
cannot provide in-depth information.
3. Focus Groups and Interviews
• Focus groups and interviews are widely-used
informal techniques that can be useful for
planning or evaluating a system design.
• A focus group involves a moderator questioning
a group of users.
• An interview is conducted one-on-one with an
• These methods are valuable for questioning users
about their work or their opinion about a system.
• Interviewers may ask users to describe a typical
day or task, why they do certain things, what they
would do when certain events occur, etc.
• Interviews or focus groups may also include
asking users to evaluate simple sketches of a
• When analyzing data from focus groups and
interviews, it is important to identify patterns of
responses and not to overemphasize any single
• Like questionnaires, focus groups and interviews
collect self-reported data.
• This may be problematic because users often do
not remember or accurately describe what they