TITLE: INFORMATION PROCESSING P.871 AUTHOR: QUENCY DATE: 10/16/2013 11:10:05 PM CATEGORY: 人因工程設計 STATUS: publish ---- BODY:
Information Display / Decision Making
P871
HUMAN INFORMATION-PROCESSING
CAPABILITIES
Humans can transmit only about 5 to 10 bits of information per second (b/s). They can transmit about 2 b/s when the stimuli they receive are fairly well structured, although this can often be doubled by adding appropriate coding or anchoring of the input. The relationship between bits per item and the bits-per- second limitation depends on what is referred to as “attention switch time" (e.g., 0.1 to 0.2s). Thus an operator can accept no more than two or three items of data per second.
As the speed of information-processing demand increases， the number of errors typically increases. Thus the overall information transfer rate tends to remain constant at about 10^-2 b/s. Through careful input display design, however, this rate can be increased to10^-3 or even 10^-6 under good conditions. The following error classification scheme, which was suggested by Kidd, [56] helps characterize types of information-processing errors and why they occur:
1.Failure to detect a signal: input overload or underload and/or actual interference
2.Misidentification: insufficient cues
3.Improper weighting of informational factors and/or selection of input factors: poor or inadequate conceptualizations or evaluation of action choices
4.Action failure: A wrong action at the right time or a right action at the wrong time
INFORMATION STORAGE CAPACITY
Information storage is of two distinct types: long-term and short-term. Short-term memory storage capacity is generally limited to about 30lb or eight individual items. The human generally organizes stored information in terms of sensory modality (visual, auditory, etc.). The most significant storage problem occurs because of the potential interference between (“held") information and new items that present themselves during the holding period. This accounts for the frequent “reversal errors" in information processing. As a general principle, human memory is more effectively utilized as a means of orienting and sequencing information than as a depository for isolated data or symbolic items.
INPUT CAPACITY
The total sensory input capacity of the human systern is about 10^9 b/s (as compared with output capacity of 10 b/s). The five basic input categories for the visual channel are:
Relative position
Shapes
Brightness
Color
Movement
For the auditory channel they are:
Pitch
Loudness
Rhythm
Timbre (the quality that allows one to distinguish different voices, instruments, or special auditory displays)
DECISION MAKING
Three basic kinds of information must be available for an operator to make good decisions:
Information regarding policies and objectives
Information regarding possible alternatives and consequences
Information about the current state of the system
It is impotant to recognize that, in making decisions, people pursue two different courses of action:
1.Evaluating likely outcomes
2.Keeping options open as long as possible
STRESS SUSCEPTIBILITY
Human information processing is subject to a variety of stresses that may affect the efficiency with which information is received, processed, and acted upon. Two basic factors are important to consider:
1.The state of arousal of the human system (alertness)
2.Potential skill deterioration due to disorganization, cumulative disruption, and/or fatigue
The effects of, and reactions to, skill breakdown have been categorized as shown in the table.
Skill Breakdown
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Effect Reaction
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Failure of selective attention fails Narrowing of attention
Perceptual disorganization Reduction in the size of the data
sample and actions upon it and
reduction in filtering efficiency
Cumulative disruption Temporary halts (complete stop-pages)
with start-overs
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INFORMATION DISPLAY IN RELATION TO DECISION MAKING[57]
Although research has shown that, on the basis of information acquisition only, added display complexity generally degrades operator performance, decision-making performance is not always similarly affected:
The relationship between "fact density" and decision adequacy may be curvilinear; i.e., where there is a decreasing slope under low-density conditions and/or an increasing slope under high-density conditions, actual decision-making performance may improve. For example, although complexity of information acquisition degrades overall performance when fact density is low, decision-making performance may actually increase with increases in fact density.
When information is compressed, an inverted “U-shaped" relationship occurs, with moderate levels of compression prOducing the best decision-making performance; i.e., the critical variable is not merely symbol count, etc., but also the subjective weighting of the particular facts being compressed.
At levels of low fact density, high compression, and high display clutter, simple coding (e.g., color) may be superior to more elaborate encoding combinations. However, at other levels of fact compression and clutter, a double coding is usually more effective (e.g., color plus size).
Subject motivation (incentive) works only at low informational levels. At high levels of motivation, degraded performance is often mediated by scattered attention.
Increases in perceptual clutter sometimes increase performance rather than degrading it, as one might expect, because we are used to working in a particularly cluttered type of information-transfer environment. The more random an irrelevancy, the more performance is facilitated because of our
need to have irrelevancies for a "figure- ground" decision-making background.
It is important, however, to recognize the importance of input validity to decision making, since humans quickly recognize and react to the futility of trying to decide on information that destroys or degrades the quality of their decisions.
[56]原書並未說明
[57]After W. T. Singleton, “The Ergonomics of Information Presentation, " Applied Ergonomics, vol. 2, no. 4, pp. 213-220, 1971.
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