4 Introduction to HCI
In the previous lecture:
In this lecture:
Q:Why are so many human-made devices so difficult to learn, understand and use?
A: Poor or inappropriate design.
Q: Should users accept poor design?
Q: How do we judge quality of design? How do we improve design?
A: ...well we've mentioned it already and we'll continue to talk about it here and in future lectures...
Human-Computer Interaction (HCI)
Spherical compass Pocket compass (antique) Gimbled Ship's Compass (antique) Silva orienteering compass
Balls - throwing
Knobs - turning
Handles - grasping
Glass - looking through (or breaking)
Paper (and toilet doors) - writing on
Finger holes in scissors
Push-plates on a door
Non-square shape of 3.5" floppy diskettes
Functions on a digital watch
Operations entered on a command-line UNIX interface
The more possible interpretations a thing has, the more difficult it will
be to use.
Mappings (in general) are relationships between things.
In terms of design, mapping might be between controls, their movements, and the result of the operation on/in the world.
Natural mapping leads to immediate understanding because it takes advantage of physical analogies (folk physics) and cultural standards: a close and natural relationship between control and function.
A car steering wheel - the direction the driver turns the wheel top matches the direction the car steers.
A formula-1 car steering wheel. Is this intuitive? (http://www.f1technical.net/article30.html) How does this device make affordances visible to the driver?
An aeroplane joystick - pushing it forward (away from the pilot) drops the nose of the aeroplane (away from the pilot).
The joystick (front/bottom and left of center) is just one of many visible controls. A pilot does not have time to cycle through a series of menus to locate various functions of his control. (http://staff.tay.ac.uk/bstmjc/mjc_research1.htm)
Rising level - indicates 'more' of something and vice versa, as does an increase in numeric value and, in Western (English speaking) culture, left to right.
Light switch position - up indicates 'off', down indicates 'on' (in Australia)
What might an increase in pitch (of an audio tone) indicate?
- People will always make mistakes (too err is human )
- Bad design blames the user for incorrect operation (self blame)
- Complex systems still need to be learned
- People's understanding of the world is not, in general, the same as that of experts
- Refusing to believe the evidence instruments indicate that something is wrong is something really wrong or are the instruments wrong?
The action cycle: execution and evaluation
Some design questions
How easily can a user...
...determine the function of the device?
...tell what actions are possible?
...tell if the system is in the desired state?
...determine mapping from intention to physical movement?
...determine mapping from system state to interpretation?
...perform the action?
...tell what state the system is in?
Much knowledge is "in the world" not "in the head". Most of our "in the head" knowledge is vague and imprecise. (e.g. try to remember the layout of the QWERTY keyboard).
Information a person needs to perform a task: put as much in the world as possible. Use physical and cultural constraints.
Types of knowledge:
Knowledge in the world:
Knowledge in the head:
Applications to Multimedia and User-Interface Design
Visibility: make the functions clear. Differentiate opposing functionality. Use visual function to confirm the user's mental model of operation. Sometimes sound can be used to make things visible (e.g. vacuum cleaner clogging up).
Feedback: give actions immediate feedback, to reinforce the user's mental model.
Design for error: people make mistakes for many reasons. Good design accepts mistakes as a normal part of operation and accommodates them.
Try to minimize the causes of errors by understanding them.
Make actions reversible (undo).
Make it easy to discover when errors do occur and make them easy to correct.
Think of "actions as approximations of what is desired", as opposed to "user errors".
Forcing functions: provide constraints of operation in certain situations.
"In theory, an interface designer adopts a metaphor as a means of making the application easier to learn. This theory is based on the premise that the user will be able to transfer his or her knowledge of a familiar object structure to the new application. In practice however, an interface designer often adopts a metaphor as a means of expressing his or her model of how the system is organized. That the metaphor might make the application easier to use is often an after-the-fact and unsubstantiated rationalization of the design." (Interface Hall of Shame)
Some web sites of interest:
An understanding of cognitive design can assist in creating high-quality, user-centered objects, interfaces and multimedia.
CSE3325 courseware | CSE3325 lecture notes
©Copyright Alan Dorin 2005