Displays
Human Factors Psychology
Dr. Steve
Perceptual Principles of
Display Design
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Absolute Judgment Limits – avoid making the operator
judge the represented variable level on the basis of a
single sensory dimension (color, size, pitch, etc.)
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Top-Down Processing – signals are perceived and
interpreted based on operator’s past experience
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Perceptual Principles of
Display Design
Gain –
presenting a signal in more
than one way increases the
likelihood it will be interpreted
correctly
Redundancy
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ex: NO TURN ON RED
Discriminability – similar
appearing signals are likely
to be confused
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ex: Speed or RPM?
Mental Model Principles of
Display Design
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Principle of Pictorial Realism – Display looks like the
variable it represents
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Principle of Configural Displays – elements are configured in
same manner as environment it represents
Some “Door Ajar” indicators not only tell you that
the door is open, but show you which one
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Principle of the Moving Part – Moving elements should
move consistently with the user’s mental model
The tape indicator moves in the
same direction the tape is playing to
make it easier to know whether to FF
or REW
Mental Model Principles of
Display Design
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Ecological Interface Design – Displays that closely
correspond to the environment (direct perception)
Ecological invariants:
• compression – horizontal lines appear to
get closer in distance
• splay – angle of convergence of parallel
lines (shape of runway on descent)
• optical flow – when moving objects
appear to flow from vanishing point
• time to contact – rate of optical flow
OZ display developed at IHMC
• global optical flow – rate of optical flow
“Oz transforms the instrument flying process
in relation to ground (motion parallax)
from one of complex mental modeling and
• edge rate – flow of parts w/in a texture
slow sequential information gathering to one
(rumble strips as approach stop sign)
of instantaneous direct perception.”
Attention Principles of
Display Design
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Minimize Information Access Cost – frequently accessed
sources of info should be readily available
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Proximity Compatible Principle – info that needs
to be integrated or compared should be presented
close together (allows for patterns to emerge)
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Ex: right mouse button (PC) brings up menu of common commands
Close spatial proximity increases the likelihood of parallel
processing
Principle of Multiple Resources – facilitate processing of info
by presenting via more than one medium
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Memory Principles of
Display Design
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Principle of Predictive Aiding – Displays that
project into the future allow operator to
be proactive, not reactive
Predictive display showing
where aircraft are projected
to be in a given time
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Knowledge in the World – Make info visible when needed
to minimize reliance on memory

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Ex: Benefit of menus (Windows) over command language (DOS)
Principle of Consistency – Displays should present info in
a consistent manner
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Ex: All MicroSoft programs have same main menu (File Edit View)
Alerting Displays
Warnings – most critical – signaled by salient
auditory (omnidirectional) alerts
Cautions – moderately critical – may be signaled
by less salient auditory alerts
Advisories – Least critical – may be signaled
with peripheral cue (visually)
Human Factors implication: Could tactile cueing be used instead of
auditory, and if so, how would you indicate varying criticality levels?
Color-Coded Warning Scales
Asteroid Threat Scale
Terror Alert Scale
Severe
Critical
Serious
Guarded
Normal
Labels
Labels – static displays of knowledge in the world
 Visibility/Legibility – contrast and spatial frequency
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Discriminability – where details may be easily confused, the
important features should be highlighted
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Ex: Warning: If swallowed, DO NOT induce vomiting
Meaningfulness – avoid abbreviations and
icons whenever possible
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Labels are not effective if they can’t be read
Ex: Does this sign say go right or don’t go right?
Location – labels should be close to and unambiguously
related to the thing to which they
are associated
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Ex: difficult to tell what mode this radio is in
Color Coding
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Benefits
Color stands out against
monochrome background
Colors capitalize on established
meanings ex: red=danger
Color ties together elements of
different displays
Color can speed processing if
redundant with symbology or
text
Problems
Color discrimination difficult for
color blind, reduced illumination, etc.
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Can’t describe continuous data
well ex: too many colors on weather
map
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Must be consistent with user
stereotypes or may cause more
harm than good
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Irrelevant use of color for
aesthetics or preferences may be
confused with coding
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Monitoring Displays
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Legibility – contrast, spatial frequency, visual angle, etc
Analog vs. Digital – Analog’s advantage is ability to
estimate rate of change, while digital’s advantage is
precision of reading
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Display showing redundant
analog and digital signals
Prediction and Sluggishness – for some systems the
effects of input do not show up right away, (need prediction
displayed to compensate for lag)
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Ex:
Steering a large ship or turning on hot water in shower
Monitoring Displays
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Analog Form and Direction – scale and direction of
movement should be consistent with the user’s mental
model
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Requirement for higher numbers at top (or to right) and movement
of indicator up (or to right) for high may sometimes conflict (does
scale move or indicator?)
400
600
300
300
500
400
200
400
500
100
300
600
Pointer moves up to indicate
increasing value scale fixed
(consistent with pictorial realism and
moving parts, but space limitation)
Pointer fixed, scale moves down to
indicate increasing value (violates
moving parts principle, but
consistent with pictorial realism)
Pointer fixed, scale moves up to
indicate increasing value with low
numbers on top (consistent with
moving parts principle, but violates
pictorial realism)
Example of Bad Monitoring
Display
Not being one to read directions carefully, I waited 15
minutes for my son’s rubber bugs to cool because I
misinterpreted this poorly designed temperature
gauge. The oven was cool for some time, but like a
normal thermometer, I thought the arrow at the high
position meant hot.
Note how the pointer on this toy oven’s
temperature gauge goes up as the
temperature goes down (inconsistent with
user’s mental model of directionality).
Principles of Display Layout
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Frequency of Use – displays used most frequently
should be placed in the primary visual field (PVA)
Display Relatedness – related displays should be
placed close together
Consistency – placing displays in a standard position
eases the load on memory and attention
Organizational Grouping – displays spatially organized
to allow for patterns to emerge (pop-out)
Stimulus-Response Compatibility – displays should
be close to their associated controls
Clutter Avoidance – minimum spacing between
displays
Glass Cockpit
Glass cockpits allow the operator
the flexibility to place any display
in any CRT location at any time
Space Shuttle’s Glass Cockpit
Guidelines for using glass cockpit displays:
• Clearly indicate current display mode
• Use consistent formats
• Do not provide excessive flexibility
Head-Up Displays (HUD)
HUD Advantages
 Far and near info may be
monitored in parallel
 Imagery can be mapped onto
outside environment
 No need to frequently reaccommodate eyes when
switching from displays to
outside view
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Be careful to avoid excess
clutter
HUDs superimpose display
information on the PVA
Augmented Reality Displays
Augmented Displays - display that improves upon reality
by superimposing info over actual environment
ex: thermal imaging color codes objects by temperature
Navigation Displays & Maps
Navigation Displays & Maps:
 Direct user to destination (path)
 Facilitate planning
 Help recover from being lost
 Maintain situation awareness (build mental map)
Guidelines
 Legibility – adequate text size
 Avoid excessive clutter
 “You are here” personal-referenced view aids lost recovery
 Best if North-up and Nose-up options are available
Spatial Knowledge
Levels of Spatial Knowledge*
1. Landmark Knowledge (egocentric) – learned route by
landmarks
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2.
Route Knowledge (egocentric) –route list or commands
of how to get from point A to B.
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3.
Look for Hardees then turn right past the duck pond
Requires least mental effort, but useless when lost
Go 3 miles turn left, 4 miles then turn right, etc.
Survey Knowledge (exocentric) – map knowledge,
layout of environment
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Well developed mental map allows one to visual spatial relations
Requires most mental effort, but useful when lost
* Move from 1 to 2 to 3 with increased experience
Virtual Reality for Developing
Spatial Knowledge
Virtual Reality – “Fooling people into accepting as real
what is only perceived” (Karen Carr)
 Egocentric Navigation (may also provide exocentric)
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Proprioceptive cues
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Immersive (eye view) or tethered (view from outside body)
Head-tracking (with HMD)
3-D viewing
Dynamic
Interactive
Virtual Environments/Reality
Benefits/Costs
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Benefits of VE/VR
Telepresence
Hi Fidelity Training
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Military, medical applications
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3-D interaction with spaces
Escape from Reality
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On-line Comprehension
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Costs of VE/VR
Costly
Realistic motion is difficult
Distorted perception
Limited FOV
Disorientation
Cybersickness
Distraction from pain
Knowledge Elicitation
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Experts explain as they do
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Displays used for Training
Joint Combat Advanced Display and Debriefing System (JCADDS)