Engineering Psychology

1
Engineering Psychology Human Performance

• Outline of Lecture 10
• Review of lecture 9
• Filters in perception
• Displays and Attention
• Perceptual Organization, Pre-attentive processing
  and displays
• Analog Judgments
• Depth perception and 3D displays

2
Perceptual Organization

• Demonstration of Preattentive (Global) vs.
  Attentive (local) Processes (Navon, 1977)
• Are the letters F or T

FFFFFFF F F FFFFF F F F F
TTTTTTT T T TTTTT T T T

• Report small letters response conflict between
  local (attentive) and global (preattentive)
  processes
• Report large letters much less conflict

3
Perceptual Organization

• Emergent features when stimuli are organized in
  a manner that facilitates understanding with low
  resource demand
• take advantages of preattentive processing
• typically features are global (course resolution)

4
Aiding Preattentive Processing Object Displays

• Examples of Object Displays
• Nuclear Power Plant StarGraph
• spokes represent values of 8 key parameters
• overall shape (emergent feature) represents
  overall system state

5
Aiding Preattentive Processing
Proximity-Compatibility

• Proximity Compatibility Principle
• if operator must integrate the information
  sources then integral (object) display formats
  are preferred
• produces emergent features
• enhances divided attention parallel processing
• if operator must respond based on a single
  dimension, variable or feature, then separable
  (uni-dimensional) display formats are preferred
• enhances focussed attention on the single
  dimension
• no parallel processing needed

6
Aiding Preattentive Processing
Proximity-Compatibility

• PCP can be achieved with multi-object displays
• spatial arrangement of indicators to produce
  emergent features
• proximity
• Close proximity favors organization of objects
  into a common group
• May foster preattentive processing and/or
  effective division of attention
• e.g., labels on lines of graph
• color coding
• integral elements should be coded with same color
• separated elements should be coded in unique
  colors (enhances preattentive pop-out effect)
• some natural (culturally accepted) meanings
• Problems Clutter and response conflict

7
Aiding Preattentive Processing Spatial Proximity

• Superimposed Displays Head-Up Displays (HUDs),
  Helmet-Mounted Displays (HMDs)

• Dont necessarily aid parallel processing of
  visual information
• Neisser and Becklan (1975)
• eye-movements, attention -- driven by mental
  models, expectations of one display
• Can result in increased clutter perceptual
  competition of non-attended stimuli

8
Aiding Preattentive Processing Spatial Proximity

• Limitations of Superimposed Displays (cont.)
• Close proximity can lead to confusion and
  conflict
• Eriksen Eriksen (1974) flanker task
• Target letter (H or F) flanked by two other
  letters
• Subject must identify the target letter as
  quickly as possible -- Reaction Time (RT) is
  measured
• 4 Conditions of flanker letters
• None
• Compatible
• Neutral
• Incompatible

9
Aiding Preattentive Processing Spatial Proximity

• No flanker letters
• H F
• Compatible flankers (C)
• H H H F F F
• Noise flankers (letters other than H or F)
• K H K S F S
• Incompatible flankers (IC)
• F H F H F H

10
Aiding Preattentive Processing Spatial Proximity

• Eriksen and Eriksen (1974) Results
• response conflict for IC and redundancy gain for
  C
• Size of conflict or gain depends on spatial
  proximity
• F H F
• worse performance than
• F H F

11
Analog Judgments

• How do they differ from absolute judgments?
• Continuous (magnitude) vs. categorical scale
• Often involve judgments of dynamic stimuli
  things that are constantly changing

12
Bias in Analog Judgments

• Psychological (F) vs. Physical Magnitude (P)
• Stevens Law F aP b
• a unit scaling factor
• Bias, b, varies depending on stimulus domain
• b lt 1 compression
• b 1 no bias
• b gt 1 expansion
• Typical b volume 0.6, area 0.8, length 1.0,
  finger span 1.3, electric shock 1.6

bgt1
b1
blt1
Perceived Magnitude
Physical Magnitude
13
Dynamic Analog Judgments

• Dials, meters, gauges, and other dynamic
  indicators
• Analog formats that change values over time
• Best display format for conveying a conceptual
  model of the state of a dynamic analog system to
  the operator
• Why best?
• Compatibility between actual system, the display,
  and the operators mental representation of the
  system
• Principle of Pictorial Realism (Roscoe, 1968)
• Example digital vs. analog speedometers

14
Dynamic Analog Judgments

• Meaning is conveyed by higher order time
  derivatives of dynamic indicators
• static position - space only, zero-order
• velocity - space/time, 1st-order
• acceleration - space/time2, 2nd-order
• and so on
• Example altitude indicator
• current altitude, change in altitude, and
  acceleration of altitude all have important
  consequences
• can we convey all in one indicator?

15
Dynamic Analog Judgments

• Sometimes static and dynamic aspects of
  indicators conflict
• Principle of the moving part (Roscoe, 1968)
• direction of movement of a display indicator
  should be compatible with the direction of
  movement in the operators mental model
• sometimes conflicts with the principle of
  pictorial realism
• Moving pointer vs. moving scale in altimeters

16
Dynamic Analog Judgments

• Attitude indicators
• Outside-in display (fixed ground-referenced)
• pictorial representation of foreground plane
  moves relative to background horizon
• Violates principle of pictorial realism
• Compatible with principle of the moving part
• Inside-out display (moving horizon)
• Horizon (background) moves relative to stationary
  foreground
• Compatible with principle of pictorial realism
• Violates principle of the moving part

17
Dynamic Analog Judgments

• Frequency Separated Display
• compromise between outside-in and inside-out that
  minimizes effect of violating display principles
• Takes advantage of different time scales for
  static and dynamic information
• dynamic -- short time scale
• static -- long time scale
• How?
• Short-term control inputs move foreground
  relative to background (outside-in)
• Over longer time periods, background and
  foreground both slowly counter-rotate (inside-out)

18
Dynamic Analog Judgments

• Attitude Displays
• inside-out outside-in
• good pictorial realism violates pictorial
  realism
• violates moving part consistent with moving
  part
• Frequency-separated
• sudden changes (high freq.)
• represented outside-in, then
• steady-state drift (low freq.)
• to inside-out representation

19
Depth Perception

• Fundamental Problem
• Three-dimensional (3D) world is projected onto 2
  two-dimensional (2D) images
• Our percept of the 3D world is constructed from
  these 2 2D images
• How is our percept constructed? From a variety
  of perceptual cues to depth

20
Depth Perception

• Object-centered cues Pictorial

• linear perspective
• interposition
• height in the plane
• light and shadow
• relative size
• textural gradients
• brightness/
• aerial perspective

21
Depth Perception

• Object-centered cues Motion parallax

22
Depth Perception

• Observer-centered cues Convergence
• motor feedback codes position of eyes

23
Depth Perception

• Observer-centered cues Binocular Disparity
• disparity in images codes depth

24
Depth Perception

• Observer-centered cues Accomodation
• strain of muscles controlling the shape of the
  lenses codes depth

25
Relative Usefulness of Depth Cues
26
Depth Perception

• Putting cues together
• most often multiple depth cues provide redundant
  information -- depth is overspecified
• sometimes depth cues are sparse or ambiguous
• perceptual hypotheses unconscious inference
• Metric properties of depth cues
• most cues provide ordinal depth information only
• metric information from disparity and motion
  parallax provides relative but not absolute depth
• depth perception is not veridical (accurate),
  spatial distortions result

27
3D Displays

• Advantages
• integrated display format represents integral
  dimensions in a manner compatible with operators
  mental model

28
Implications for 3D Displays

• Disadvantages
• Distortion of spatial dimensions makes precise
  readings difficult

29
Depth Perception

• Perspective vs. orthographic projections
• perspective projection image size of an object
  decreases with increased distance

30
Depth Perception

• Perspective vs. orthographic projections
• orthographic projection image size of an object
  is constant as distance changes

31
3D Displays

• Distortion of spatial dimensions can be overcome
  by augmenting depth information
• artificial frameworks
• stereoscopic or motion displays (motion parallax)

32
The Exam

• Features
• Will be given 1 hour 15 min to complete
• Will give you choice of items to answer
• Will consist of definitions, short-answer (4-6
  sentences), and longer-answer (essay) items
• To Prepare
• Read
• Wickens and Hollands chapters 1-4
• Norman chapters 1-2
• Review all lecture notes
• Review homeworks 1 and 2