1. Human Factors Psychology Dr. Steve
Displays
Human Factors Psychology
Dr. Steve

2. Perceptual Principles of Display Design
Absolute Judgment Limits – avoid making the operator judge the represented variable level on the basis of a single sensory dimension (color, size, pitch, etc.)
Top-Down Processing – signals are perceived and interpreted based on operator’s past experience
Concentrate!
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3. Perceptual Principles of Display Design
Redundancy Gain – presenting a signal in more than one way increases the likelihood it will be interpreted correctly
ex: NO TURN ON RED
Discriminability – similar appearing signals are likely to be confused
ex: Speed or RPM?

4. Mental Model Principles of Display Design
Principle of Pictorial Realism – Display looks like the variable it represents
Principle of Configural Displays – elements are configured in same manner as environment it represents
Principle of the Moving Part – Moving elements should move consistently with the user’s mental model
Some “Door Ajar” indicators not only tell you that the door is open, but show you which one
The tape indicator moves in the same direction the tape is playing to make it easier to know whether to FF or REW

5. Mental Model Principles of Display Design
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
global optical flow – rate of optical flow in relation to ground (motion parallax)
edge rate – flow of parts w/in a texture (rumble strips as approach stop sign)
OZ display developed at IHMC
“Oz transforms the instrument flying process from one of complex mental modeling and slow sequential information gathering to one of instantaneous direct perception.”

6. Attention Principles of Display Design
Minimize Information Access Cost – frequently accessed sources of info should be readily available
Ex: right mouse button (PC) brings up menu of common commands
Proximity Compatible Principle – info that needs to be integrated or compared should be presented close together (allows for patterns to emerge)
Close spatial proximity increases the likelihood of parallel processing
Principle of Multiple Resources – facilitate processing of info by presenting via more than one medium
Click for example

7. Memory Principles of Display Design
Principle of Predictive Aiding – Displays that project into the future allow operator to be proactive, not reactive
Knowledge in the World – Make info visible when needed to minimize reliance on memory
Ex: Benefit of menus (Windows) over command language (DOS)
Principle of Consistency – Displays should present info in a consistent manner
Ex: All MicroSoft programs have same main menu (File Edit View)
Predictive display showing where aircraft are projected to be in a given time

8. 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?

9. Color-Coded Warning Scales
Asteroid Threat Scale
Terror Alert Scale
Severe
Critical
Serious
Guarded
Normal

10. Labels Labels – static displays of knowledge in the world
Visibility/Legibility – contrast and spatial frequency
Labels are not effective if they can’t be read
Discriminability – where details may be easily confused, the important features should be highlighted
Ex: Warning: If swallowed, DO NOT induce vomiting
Meaningfulness – avoid abbreviations and icons whenever possible
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
Ex: difficult to tell what mode this radio is in

11. Color Coding Problems Benefits
Color discrimination difficult for color blind, reduced illumination, etc.
Can’t describe continuous data well ex: too many colors on weather map
Must be consistent with user stereotypes or may cause more harm than good
Irrelevant use of color for aesthetics or preferences may be confused with coding
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

12. Monitoring Displays
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
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)
Ex: Steering a large ship or turning on hot water in shower

13. Monitoring Displays
Analog Form and Direction – scale and direction of movement should be consistent with the user’s mental model
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?)
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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)

14. 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).

15. Principles of Display Layout
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

16. 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

17. 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 re-accommodate eyes when switching from displays to outside view
Be careful to avoid excess clutter
HUDs superimpose display information on the PVA

18. Augmented Reality Displays
Augmented Displays - display that improves upon reality by superimposing info over actual environment
ex: thermal imaging color codes objects by temperature

19. 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

20. Spatial Knowledge Levels of Spatial Knowledge*
Landmark Knowledge (egocentric) – learned route by landmarks
Look for Hardees then turn right past the duck pond
Requires least mental effort, but useless when lost
Route Knowledge (egocentric) –route list or commands of how to get from point A to B.
Go 3 miles turn left, 4 miles then turn right, etc.
Survey Knowledge (exocentric) – map knowledge, layout of environment
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

21. 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)
Immersive (eye view) or tethered (view from outside body)
Proprioceptive cues
Head-tracking (with HMD)
3-D viewing
Dynamic
Interactive

22. Virtual Environments/Reality Benefits/Costs
Benefits of VE/VR
Telepresence
Hi Fidelity Training
Military, medical applications
On-line Comprehension
3-D interaction with spaces
Escape from Reality
Distraction from pain
Knowledge Elicitation
Experts explain as they do
Costs of VE/VR
Costly
Realistic motion is difficult
Distorted perception
Limited FOV
Disorientation
Cybersickness
Click button for Virtual Tour of Legoland

23. Displays used for Training
Joint Combat Advanced Display and Debriefing System (JCADDS)