1. Visual Perception & Graphical Principles Seminar on Information Visualization Daniele Della Bruna winter 2006 @ university of Fribourg

2. Introduction Preattentive perception Introduction Demo preattentive Theories Postattentive vision Demo postattentive Demo visualization Demo postattentive Not lie with visualization Colour use guidelines Qualitative / Binary Diverging / Sequential Combinations Problems in colour appearance Questions Daniele Della Bruna – Visual Perception & Graphical Principles ; Seminar winter 2006 - Perception in visualization - Power of visualization - Color use guidelines

3. Introduction Preattentive perception Demo preattentive Theories Postattentive vision Demo postattentive Demo visualization Demo postattentive Not lie with visualization Colour use guidelines Qualitative / Binary Diverging / Sequential Combinations Problems in colour appearance Questions Daniele Della Bruna – Visual Perception & Graphical Principles ; Seminar winter 2006 - Eye movements take at least 200 msec to initiate -Tasks performed in less than 200-250 msec are considered preattentive -A limited set of visual properties are detected very rapidly by the low-level visual system

4. Introduction Preattentive perception Demo preattentive Theories Postattentive vision Demo postattentive Demo visualization Demo postattentive Not lie with visualization Colour use guidelines Qualitative / Binary Diverging / Sequential Combinations Problems in colour appearance Questions Daniele Della Bruna – Visual Perception & Graphical Principles ; Seminar winter 2006

5. Introduction Preattentive perception Demo preattentive Theories Postattentive vision Demo postattentive Demo visualization Demo postattentive Not lie with visualization Colour use guidelines Qualitative / Binary Diverging / Sequential Combinations Problems in colour appearance Questions Daniele Della Bruna – Visual Perception & Graphical Principles ; Seminar winter 2006 - Demo

6. Introduction Preattentive perception Theories Demo preattentive Theories Postattentive vision Demo postattentive Demo visualization Demo postattentive Not lie with visualization Colour use guidelines Qualitative / Binary Diverging / Sequential Combinations Problems in colour appearance Questions Daniele Della Bruna – Visual Perception & Graphical Principles ; Seminar winter 2006 -Feature integration theory: a set of feature maps ; each feature map registers in parallel activity in response to a specific feature -Texton Theory: a group of features ; only difference in textons or in their density can be detected -Similarity Theory: search time is based on T-N and N-N values -Guided Search Theory: features maps filtered into multiple categories (colour  red/green/blue/yellow)

7. Introduction Preattentive perception Postattentive vision Demo preattentive Theories Postattentive vision Demo postattentive Demo visualization Demo postattentive Not lie with visualization Colour use guidelines Qualitative / Binary Diverging / Sequential Combinations Problems in colour appearance Questions Daniele Della Bruna – Visual Perception & Graphical Principles ; Seminar winter 2006 -attention allow a viewer to learn what is it in a scene, but it does not allow the viewer to see the scene in a different manner -preattentive visual representation appears to be identical after the viewer studied it -What we see when confronted with a new scene depends as much on our expectations -an interruption in what is being seen renders us “blind” to significant changes

8. Introduction Preattentive perception Demo postattentive Demo preattentive Theories Postattentive vision Demo postattentive Demo visualization Demo postattentive Not lie with visualization Colour use guidelines Qualitative / Binary Diverging / Sequential Combinations Problems in colour appearance Questions Daniele Della Bruna – Visual Perception & Graphical Principles ; Seminar winter 2006

9. Introduction Preattentive perception Demo postattentive Demo preattentive Theories Postattentive vision Demo postattentive Demo visualization Demo postattentive Not lie with visualization Colour use guidelines Qualitative / Binary Diverging / Sequential Combinations Problems in colour appearance Questions Daniele Della Bruna – Visual Perception & Graphical Principles ; Seminar winter 2006

10. Introduction Preattentive perception Demo postattentive Demo preattentive Theories Postattentive vision Demo postattentive Demo visualization Demo postattentive Not lie with visualization Colour use guidelines Qualitative / Binary Diverging / Sequential Combinations Problems in colour appearance Questions Daniele Della Bruna – Visual Perception & Graphical Principles ; Seminar winter 2006

11. Introduction Preattentive perception Not lie with visualization Demo preattentive Theories Postattentive vision Demo postattentive Demo visualization Demo postattentive Not lie with visualization Colour use guidelines Qualitative / Binary Diverging / Sequential Combinations Problems in colour appearance Questions Daniele Della Bruna – Visual Perception & Graphical Principles ; Seminar winter 2006 - How data are represented visually has a powerful effect on how is perceived - It can significantly influence the user’s interpretation of the data

12. Introduction Preattentive perception Demo visualization Demo preattentive Theories Postattentive vision Demo postattentive Demo visualization Demo postattentive Not lie with visualization Colour use guidelines Qualitative / Binary Diverging / Sequential Combinations Problems in colour appearance Questions Daniele Della Bruna – Visual Perception & Graphical Principles ; Seminar winter 2006

13. Introduction Preattentive perception Colour use guidelines Demo preattentive Theories Postattentive vision Demo postattentive Demo visualization Demo postattentive Not lie with visualization Colour use guidelines Qualitative / Binary Diverging / Sequential Combinations Problems in colour appearance Questions Daniele Della Bruna – Visual Perception & Graphical Principles ; Seminar winter 2006 - Colours can help the understanding of a graph - 4 different colour schemes -Qualitative -Binary -Diverging -Sequential

14. Introduction Preattentive perception Qualitative / Binary Demo preattentive Theories Postattentive vision Demo postattentive Demo visualization Demo postattentive Not lie with visualization Colour use guidelines Qualitative / Binary Diverging / Sequential Combinations Problems in colour appearance Questions Daniele Della Bruna – Visual Perception & Graphical Principles ; Seminar winter 2006 -Qualitative: data of different categories are usually represented in an effective way by means of differences in hue - Binary: A binary scheme is a qualitative scheme where there are only two categories

15. Introduction Preattentive perception Diverging / Sequential Demo preattentive Theories Postattentive vision Demo postattentive Demo visualization Demo postattentive Not lie with visualization Colour use guidelines Qualitative / Binary Diverging / Sequential Combinations Problems in colour appearance Questions Daniele Della Bruna – Visual Perception & Graphical Principles ; Seminar winter 2006 - Diverging: In a diverging scheme data can be grouped in two sets that show two different trends around a balance or theshold point -Sequential: To represent ordered data in sequential form the common recommendation is using variations in lightness or saturation of a given hue

16. Introduction Preattentive perception Combinations Demo preattentive Theories Postattentive vision Demo postattentive Demo visualization Demo postattentive Not lie with visualization Colour use guidelines Qualitative / Binary Diverging / Sequential Combinations Problems in colour appearance Questions Daniele Della Bruna – Visual Perception & Graphical Principles ; Seminar winter 2006 - Finally these four possibilities can be combined among them to obtain up to 10 commendable bivariate schemes

17. Introduction Preattentive perception Problems in colour appearance Demo preattentive Theories Postattentive vision Demo postattentive Demo visualization Demo postattentive Not lie with visualization Colour use guidelines Qualitative / Binary Diverging / Sequential Combinations Problems in colour appearance Questions Daniele Della Bruna – Visual Perception & Graphical Principles ; Seminar winter 2006 - colorblind

18. Introduction Preattentive perception Questions Demo preattentive Theories Postattentive vision Demo postattentive Demo visualization Demo postattentive Not lie with visualization Color use guidelines Qualitative / Binary Diverging / Sequential Combinations Problems in color appearance Questions Daniele Della Bruna – Visual Perception & Graphical Principles ; Seminar winter 2006 ?