ERIC Identifier: ED337203
Publication Date: 1991-10-00
Author: Marchionini, Gary
Source: ERIC Clearinghouse on
Information Resources Syracuse NY.
Psychological Dimensions of User-Computer Interfaces. ERIC
The human-computer interface is a communications channel between the user and
the computer. The interface includes both physical and conceptual components.
PHYSICAL COMPONENTS include input devices such as keyboards, mice, touch panels,
joy sticks, speech recognizers, eye trackers, and data gloves; and output
devices such as visual displays and sound or speech synthesizers. CONCEPTUAL
COMPONENTS include selection methods such as command languages, menus, or direct
manipulation; and representation schemes such as screen layout and graphic/text
The field of human-computer interaction (HCI) is concerned with interface
design and is highly interdisciplinary in nature. It involves researchers from
psychology, computer science, information science, engineering, education, and
communications. A central concern of HCI research is to determine the effects of
human physical, cognitive, and affective characteristics on the interactions
between users and computers for specific tasks. Thus, HCI researchers develop
models of human activity and use these models in designing new interfaces.
The INFORMATION PROCESSING MODEL OF COGNITION prevalent in cognitive
psychology provides a foundation for interface design. This model establishes
that: (1) humans have a working memory limited to five to seven "chunks" of
information; (2) humans must have their attention refreshed frequently; and (3)
RECALLING information requires more cognitive effort than RECOGNIZING
information. Computer interface styles consistent with this model include menus,
query-by-example, and direct manipulation. Novices and casual users prefer menus
to command languages because recognizing an appropriate option is easier than
remembering a command. Direct manipulation interfaces (such as touch panels in
information kiosks or input devices and graphic displays in most video games)
overcome many psychological limitations because they share the "load" between
physical and cognitive activity. In addition, their immediate feedback and
easily reversibility invite user exploration.
The psychological theory of mental models has also been applied to interface
design. Humans develop internal representations (mental models) for objects,
events, and ideas. These mental models are active, called into play to explain
the world and to predict which actions to take. Mental models are incomplete and
often inaccurate, but they help people deal with the world on a daily basis.
Users develop mental models for computer systems, and HCI researchers believe
that the interface is the basis for the mental models that users develop.
Designers are thus concerned with ways to assist users in quickly developing
accurate and useful mental models for their systems.
A common approach is to define a metaphor that links existing user knowledge
to system function. The desktop metaphor is perhaps the best known example,
although more fundamental metaphors such as the screen as a scroll of paper or
online interaction as human-to-human dialogue have had earlier and wider impact.
Metaphors are useful, but they can also constrain the user's view of the unique
aspects of a system. In effect, concern with ease of learning can eventually
interfere with skilled use. HCI researchers have proposed a variety of solutions
to the learning-using tension, including: minimal manuals, incremental learning
through online help, and progressive disclosure of system features and
capability. The most general solution is to develop interfaces that adapt to the
users' abilities and needs. In addition to the many technical challenges such
interfaces offer, there is a philosophical debate over whether the interface
should adapt to the user automatically or only through specific user control.
PRINCIPLES FOR INTERFACE DESIGN
Psychological research has
led to a number of design principles:
The interface should compensate for human physical and cognitive limitations
whenever possible. However, the interface should be "transparent," not getting
in the way of the user's actions or impeding his or her progress. The interface
itself should not overload the user with complexity or unnecessary "bells and
whistles" that interfere with or distract from the task at hand.
The physical components of the interface should be ergonomically designed,
taking into account the comfort and health of the user as well as his or her
special needs and characteristics. For example, a touch panel design for a word
processing program demands far too much arm movement for lengthy sessions, but
serves quite nicely in an information kiosk of a shopping mall when positioned
to be touchable by users of various heights.
The interface should be consistent. For example, selection methods, positioning
of important text and buttons, text fonts and styles, and window layout and
management should be consistent in all parts of an interface.
Non-command interaction styles such as direct manipulation and menus are
preferable to command languages, although the expert user should be given "type
ahead" capability to quickly move through layers of menus.
The interface should handle errors by providing simple and concise error
messages that assist the user in recovery and future avoidance.
The interface should support reversible actions (e.g., the UNDO capability in
The interface should be subjected to usability testing early in the design
process and as each iteration of the product evolves.
Perhaps the most basic principle is that the interface should be designed
around the needs of the user rather than added on after a system has been
completed, thus serving the constraints imposed by the system. This principle is
sometimes expressed by the admonition to "know your user!"
TRENDS IN INTERFACE DESIGN
Computer systems are becoming
increasingly interactive, and this trend will continue as new interfaces are
developed. Interactivity will be supported by new input and output (I/O) devices
that take fuller advantage of the many communication channels humans employ. For
example, some of the devices that are under active investigation in HCI
input devices (handwriting, drawing)
sensing devices that focus on personal transmitters (e.g., on finger rings) or
that monitor physiological activity
display monitors a few centimeters square
Perhaps more significant than the many different types of I/O devices is the
development of interfaces that support multiple I/O devices in parallel.
Interface that accept voice and gesture concurrently will give richer control to
users who must move about while controlling systems and make possible a variety
of virtual reality applications. Likewise, video and sound output together
provide a more powerful communication channel for information flow.
In addition to advances in physical interface components, there is active
research in conceptual components such as interaction styles. Direct
manipulation interfaces will continue to emerge and more robust adaptive systems
will be developed that change according to the type of task and user experience
level. Intelligent agents are also under development. Agents can be assigned
specific tasks by the user and then sent out to execute those tasks. The next
metaphor of the computer world may be the theatre or command center, where
directors assign roles to software agents and examine the results of their
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