Model Human Processor
Human cognition is often understood in terms of a model of
information processing. See figure 2-14 (p. 26) for a simple diagram.
Most of this information is presented in The Psychology of
Human-Computer Interaction by Card, Moran and Newell.
Components
- Perception
- Motor processor
- approximately 70 msec cycles
- Fitts' law: Pointing time (seconds) = 1 + .1 * log2 (distance / size + .5)
- Working Memory (also called short-term memory)
- Limited approximately 3 chunks
- Includes perceptual and motor stores
- Long-term memory
- Essentially unlimited
- Acquired through active usage of working memory
- Organizes information in chunks (see p. 27)
- Cognitive processor
- Applies long-term memory to modify working memory
- Operates at approximately 70 msec cycles
- Conscious versus unconscious cognition
Important cognitive principles
- Recognition is easier than recall
- Short-term memory limits multi-tasking
- Practice creates procedural knowledge for automatic behavior
Constants for keystroke-level model
- K = 0.2 sec Keying: the time it takes to tap a key on the
keyboard or a button on the mouse.
- P = 1.1 sec Pointing: the time it takes to move the mouse
to a position on the display.
- H = 0.4 sec Homing: the time it takes to move the hand from
the keyboard to the mouse or from the mouse to the keyboard.
- M = 1.35 sec Mental preparing: the time it takes to
mentally prepare for the next step.
- R Responding: the time needed for the computer to respond.
High-level psychological constructs
Issues for discussion
- What are examples of automatic procedural behavior?
- What are some of the mental models or metaphors people use when they have these difficulties presented to tech service staff?
- What do the keystroke constants suggest for developing an
efficient user interface?
Last modified: Tue Sep 12 13:26:25 Central Daylight Time 2006