The Nature of Users

Overview

To frame our discussion, consider:

What does a software developer need to know about humans and how might that influence system development?

How does the nature of the task influence design choices?

How can we best think about HCI as a discipline?

Information Processing Model of Humans

SENSE	DETECTION THRESHOLD	SMALLEST DETECTABLE THRESHOLD	LARGEST PRACTICAL (TOLERABLE)
Sight	Candle Flame seen at 30 miles on a dark clear night	10-6 mL	104 mL
Hearing	Tick of a watch under quiet conditions at 20 feet	2x10-4 dynes/cm2	103 dynes/cm2
Taste	Teaspoon of sugar in 2 gallons of water
Smell	Drop of perfume diffused into the entire volume of a three-room apartment	Very sensitive to some substances (4x10-7 molar quinine sulfate)	Unknown
Touch	Wing of a bee falling on your cheek from a distance of 1 centimeter	Pressure .05 to 1.1 erg	Unknown

Sensory store - modality specific, holds information for a very brief period of time (tenths of seconds)
Short-term/working - holds limited information for short period of time (seconds)
Long-term memory - holds information indefinitely

syntactic - device dependent details, ill-structured
refers to low level mechanics required to use the system. This would include a keystroke level model of using the device.
semantic - structured, hierarchical, includes low-level actions and mid-level strategies, source is the task or problem domain
the underlying understanding of the functions that are provided, the meaning of input and output, and the goals and objectives of the system.
How it works
How to do it knowledge

Novices	No syntactic knowledge of the system and little semantic knowledge of the application or computer use in general
Intermittent Users	Reasonable semantic knowledge of the application, but relative low recall of syntactic information necessary to use system
Frequent Users	Good semantic and syntactic knowledge

Communication	Activities that enable information to be transferred from client to server (producer/consumer).
Dialogue	Activities that enable the user to direct and control interaction with the computer-based system.
Cognitive	Activities that are performed once information has been obtained. User oriented activities related to the functions of the system.
Control	Activities that allow the user to control information and cognition and order the process through which other tasks occur.

Go To Lecture [Outline] [Overview]

Go To [311 Course Outline] [CIS Department Page]

Bailey (1989) Human Performance Engineering (2nd Ed.). Prentice Hall, p. 53-54

Preece, J., Y. Rogers, H. Sharp, & D. Benyon (1994) Human-Computer Interaction. Reading, MA: Addison-Wesley.