VISUAL PERCEPTION & COGNITIVE PROCESSES

Transcription

1 VISUAL PERCEPTION & COGNITIVE PROCESSES Prof. Rahul C. Basole CS4460 > March 31, 2016

2 How Are Graphics Used? Larkin & Simon (1987) investigated usefulness of graphical displays Graphical visualization could support more efficient task performance by: Allowing substitution of rapid perceptual inferences for difficult logical inferences Reducing search for information required for task completion InfoVis is a useful tool for aiding comprehension, understanding and decision-making. This is not a surprise (we have been studying this all semester).

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5 Recall InfoVis Amplifies Cognition What is the process by which a person looks at a graphic and makes some use of it? What is your process?

6 Process Model I Navigation Process Model (by Robert Spence) Content is the display on screen User s modeling of visual image results in a cognitive map or cognitive model Interpretation (Aha!, variables x and y are related) leads to new cognitive map. In turn, generates idea for a new browsing strategy Spence 1999 Look at the display again with that strategy (Iterative)

7 Process Model II Knowledge Crystallization Model (by Card et al.) Overview Zoom Filter Details-on-demand Browse Search query Forage for data Task Author, decide or act Extract results Author report Reorder Cluster Class Average Promote Detect pattern Abstract Search for schema (representation) Instantiate schema Instantiate Problem-solve Reason about schema Facts Comparisons Patterns Iterate as needed

8 Process Model III Sensemaking Loop Model (by Pirolli and Card)

9 Process Model IV Information Design Model (by Fry) Benjamin Fry, Computational Information Design, Ph.D dissertation MIT 2004

10 Process Model V Visualization Reference Model (by Card et al.)

11 Process Model VI Visual Analysis Model (by Tableau)

12 So How Does Vis Amplify Cognition Again? Increases memory and processing resources available Reduces search for information Enhances the recognition of patterns Enables perceptual inference operations Uses perceptual attention mechanisms for monitoring Encodes info in a manipulable medium

13 Lots of Related Fields of Study Semiotics The study of symbols and how they convey meaning Classic book by J. Bertin (1983) The Semiology of Graphics Psychophysics Applying methods of physics to measuring human perceptual systems How fast must light flicker until we perceive it as constant? What change in brightness can we perceive? Cognitive psychology Understand how people think, and in our context, how it relates to perception

14 Perceptual Processing Seek to better understand visual perception and visual information processing Multiple theories or models exist Need to understand physiology and cognitive psychology

15 One (Simple) Model Two stage process Parallel extraction of low-level properties of scene Sequential goal-directed processing Stage 1 Stage 2 Early, parallel detection of color, texture, shape, spatial attributes Serial processing of object identification (using memory) and spatial layout, action Ware 2000

16 Stage 1: Low-level, Parallel Neurons in eye & brain responsible for different kinds of information Orientation, color, texture, movement, etc. Arrays of neurons work in parallel Occurs automatically Rapid Information is transitory, briefly held in iconic store Bottom-up data-driven model of processing Often called pre-attentive processing

17 Stage 2: Sequential, Goal-Directed Splits into subsystems for object recognition and for interacting with environment Increasing evidence supports independence of systems for symbolic object manipulation and for locomotion & action First subsystem interfaces to verbal linguistic portion of brain, second interfaces to motor systems that control muscle movements

18 Stage 2 Attributes Slow serial processing Involves working and long-term memory More emphasis on arbitrary aspects of symbols Top-down processing

19 Preattentive Processing How does human visual system analyze images? Some things seem to be done preattentively, without the need for focused attention Generally less than msecs (eye movements take 200 msecs) Seems to be done in parallel by low-level vision system

20 How Many 3 s?

21 How Many 3 s?

22 What Kinds of Tasks? Target detection Is something there? Boundary detection Can the elements be grouped? Counting How many elements of a certain type are present?

23 Example Determine if a red circle is present

24 Color (or Hue) Can be done rapidly (preattentively) by people Surrounding objects called distractors

25 Example Determine if a red circle is present

26 Shape Can be done preattentively by people

27 Example Determine if a red circle is present

28 Hue and Shape Cannot be done preattentively Must perform a sequential search Conjunction of features (shape and hue) causes it

29 Example Is there a boundary in the display?

30 Fill and Shape Left can be done preattentively since each group contains one unique feature Right cannot (but there is a boundary!) since the two features are mixed (fill and shape)

31 Example Is there a boundary in the display?

32 Hue versus Shape Left: Boundary detected preattentively based on hue regardless of shape Right: Cannot do mixed color & shapes together preattentively

33 Example Is there a boundary?

34 Hue versus brightness Left: Varying brightness seems to interfere Right: Boundary based on brightness can be done preattentively

35 Example Applet Nice on-line tutorial and example applet Chris Healey, NC State Prior examples taken from site

36 Remember Gestalt Principles Use visual structure to reinforce the underlying logical structure

37 Key Perceptual Properties Luminance Brightness Color Texture Shape

38 Luminance/Brightness Luminance Measured amount of light coming from some place Brightness Perceived amount of light coming from source Very different on screen versus paper

39 Color Sensory response to electromagnetic radiation in the spectrum between wavelengths micrometers gamma ultraviolet visible microwave tv

40 Color Models HVS model Hue - what people think of color Value - light/dark, ranges black<-->white Saturation - intensity, ranges hue<-->gray white black

41 Color Perception beau_lotto_optical_illusions _show_how_we_see?langua ge=en Seeing blue? Brand colors? m/what-is-blue-and-how-dowe-see-color

42 How Not to Use Color

43 Color Categories Are there certain canonical* colors? Post & Greene 86 had people name different colors on a monitor Pictured are ones with > 75% commonality *well recognized

44 Using Mechanical Turk

45 Please Read: Article Discussion Your thoughts?

46 Luminance Important for foreground-background colors to differ in brightness Hello, here is some text. Can you read what it says? Hello, here is some text. Can you read what it says? Hello, here is some text. Can you read what it says? Hello, here is some text. Can you read what it says? Hello, here is some text. Can you read what it says? Hello, here is some text. Can you read what it says? Hello, here is some text. Can you read what it says?

47 Color for Categories Can different colors be used for categorical variables? Yes (with care) Ware s suggestion: 12 colors red, green, yellow, blue, black, white, pink, cyan, gray, orange, brown, purple From Ware 04

48 Color for Sequences Can you order these (low à hi)?

49 Possible Color Sequences Gray scale Full spectral scale Single sequence part spectral scale Single sequence single hue scale Double-ended multiple hue scale

50 ColorBrewer Help with selecting colors for maps

51 Color Purposes Call attention to specific data Increase appeal, memorability Increase number of dimensions for encoding data Example, Ware and Beatty 88 x,y - variables 1 & 2 amount of r,g,b - variables 3, 4, & 5

52 Using Color Modesty! Less is more Use blue in large regions, not thin lines Use red and green in the center of the field of view (edges of retina not sensitive to these) Use black, white, yellow in periphery Use adjacent colors that vary in hue & value For large regions, don t use highly saturated colors (pastels a good choice) Do not use adjacent colors that vary in amount of blue Don t use high saturation, spectrally extreme colors together (causes after images) Use color for grouping and search Beware effects from adjacent color regions

53 Good Color Advice Maureen Stone s website Many references and links She frequently offers tutorials about color at conferences

54 Color Challenge

55 Texture Appears to be combination of orientation scale contrast Complex attribute to analyze

56 Shape, Symbol Can you develop a set of unique symbols that can be placed on a display and be rapidly perceived and differentiated? Application for maps, military, etc. Want to look at different preattentive aspects

57 Recall Encodings When you want to communicate one type of variable, which visual property should you use?

58 Optical Illusions

59 Great Book Information Visualization Perception for Design 2 nd edition Colin Ware Morgan Kaufmann