TITLE: INFORMATION PROCESSING P.873 AUTHOR: QUENCY DATE: 10/20/2013 06:38:44 PM CATEGORY: 人因工程設計 STATUS: publish ---- BODY:
INFORMATION PROCESSING P.873
Summary Guidelines
VISUAL AND AUDITORY CODING METHODS[59]
KEEPING TRACK OF SEQUENTIAL EVENTS[60]
At slow event-presentation rates (one per second or less), individual events falling into two categories can be discriminated one at a time and mentally tallied with considerable accuracy.
As either the number of categories or the trial length increases， the number of errors per trial increases, generally very rapidly. For a given trial length, one should present the operator with fewer categories with multiple occurrences rather than large numbers of categories with fewer occurrences.
At fast presentation rates, the ON/OFF ratio has little effect on performance as long as the ON time is sufficient for accurate stimulus perception. Intermediate-rate-short-stimulus ON time tends to optimize performance. Slow-rate-short-stimulus ON time degrades performance.
It is generally desirable to "pace" operator performance by means of cues as to the expected occurrence of a next event.
In general, the slower the rate of presentation, the better the performance, a truism that nevertheless is important to remember.
Irrelevant information along with relevant information does not necessarily degrade performance, provided that it is introduced in a manner that allows operators to pace themselves.
Irregular rates, on the other hand, disrupt performance because the operator cannot anticipate the occurrence of the next stimulus.
Stimuli with a "natural" or built-in order result in better performance. Whenever possible, sort out information categories prior to displaying information to the operator and align visual information elements spatially so that each category appears in its own unique location each time it is presented.
Subtractions are more difficult than additions in setting up informational content, and they should be kept to a minimum in any given sequence.
Information of greater value generally is "remembered" best, although typically at the expense of the remaining information. The number of multiple categories displayed simultaneously can be increased to three with no significant degradation when the information rate is held constant.
SUMMARY GUIDELINES RELATIVE TO INFORMATION-PROCESSING OPTIMIZATION
Multidimensional coding typically results in more information transmission than single-dimension coding.
Information-processing capacity is adversely affected by both load and speed; ie., the number of sources should be limited.
When time sharing of sensory inputs occurs, signals should be separated temporally (preferably by 0.5 s or more).
When operators can control the input rate (are self-pacing) and have some method of identifying the more important input (if they have a choice), auditory signals are generally more durable than visual signals.
Simultaneous presentation of the same information via two sensory modalities usually increases the probability of reception.
Signals presented on one channel (such as audition) can serve as cues to facilitate the use of another channel.
Time sharing of visual tasks adversely affects primarily those tasks with greater uncertainty and those which depend on short term memory; thus speed stress does not affect all tasks equally.
Summary of Certain Visual and Auditory Coding Methods
(Numbers refer to number of levels which can be discriminated o.n an absolute basis under optimum conditions.)
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Alphanumeric Single numerals, 10; single letters,26; combinations,
unlimited. Good; especially useful for identification;
uses little space if there is good contrast. Certain
items easily confused with each other.
Color Hues, 9; hue, saturation, and brightness combinations,
15-24. Particularly good for searching and counting
tasks; poorer for identification tasks; trained observers
can use many codes (up to 24). Affected by some
lights; problem with color-defective individuals.
Geometric shapes 15 or more. Generally useful coding system, particularly
in symbolic representation; good for CRTs. Shapes used
together need to be discriminable; some sets of shapes
more difficult to discriminate than others.
Visual angle 24. Generally satisfactory for special purposes such as
indicating direction, angle, or position on round instru-
ments like clocks, CRTs, etc.
Size of forms
(such as squares) 5. Takes considerable space. Use only when specifically
appropriate; preferably use less than.
Visual number 6. Use only when specifically appropriate， such as to
represent numbers of items. Takes considerable space;
may be confused with other symbols.
Brightness of lights 3-4. Use only when specifically appropriate. Preferably
limit to two levels; weaket signals may be masked.
Flash rate of lights 4. Limited applicability. Preferably limit to two levels;
combination of individual flashes and controlled time
intervals may have special application, such as light-
house signals and naval communications.
Sound frequency 5. For untrained listeners, use less than 5 levels; space
widely apart, but avoid multiples and low and high
frequencies; intensity should be 30 dB above threshold.
Frequency changes easier to detect than single
frequencies; combinations usually require trainihg
except for clearly distinguishable sounds such as bells,
buzzers, and sirens.
Sound intensity 4. Preferably use less than 4. Intensity changes easier
to detect than single intensities; for pure tones restrict
to 10000-4000 Hz, but preferably use wide band.
Sound duration Use clear-cut differences, preferably 2 or 3.
Sound direction Difference in intensity to two ears should be distinct;
particularly useful for directional information (i.e., right
versus left).
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[59]E. J. McCormick, Human Factors engineering, 3d ed., McGraw-Hili Book Company, New York, 1970, p. 113.
[60]After R. A. Monty, "Keeping Track of Sequential Events: implications for theDesign of Displays, " Ergonomics, vol. 16, no. 4, 1973.
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