1. 1 ISE 412 Perception: Top-Down and Bottom-Up Processing Top ‑ Down Goal ‑ driven Processing dominated by context, expectations, hypotheses, "the big picture" Bottom ‑ Up Data ‑ driven Processing dominated by characteristics of stimulus, "details” Feature analysis Both types of processing occur simultaneously and are highly interactive.

2. 2 ISE 412 Some examples Problem-solving  Wheel of Fortune  Crossword puzzles  Design Hearing: conversation, listening to music, etc.

3. 3 ISE 412 An example … Listen to the song and write down the words as you hear them. To discuss …  What were doing during “bottom-up” processing (with and without visual cues?  What were you doing during “top-down” processing?

4. 4 ISE 412 Perception of print Feature analysis: Bottom-up, we perceive features of letters, letters, words Involves pattern matching Top-down, we use context of surrounding letters and words to limit alternative interpretations Sawple Sample Examples:

5. 5 ISE 412 Context-Data Tradeoff Assuming limited display size for text, trade off context and data quality: Many words:  High contextual redundancy (easy to comprehend)  Poor data quality (hard to read) Few words:  Good data quality (easy to read)  Low contextual redundancy (hard to comprehend)  Example: weather alerts on a heads-up display WEATHER Will encounter bad weather

6. 6 ISE 412 Creating context: Redundancy gain The information is presented in more than one way. If the viewer is not able to process the information in one mode (e.g., color blind) can rely on another. Reaction time is faster if information is presented redundantly. Promotes top-down processing.

7. 7 ISE 412 Object perception Objects are perceived holistically Empirical evidence on card ‑ sorting tasks: objects categorized more quickly and accurately than "separate" displays such as numbers or words 4 of Clubs ♣ Carrot Which is longer?

8. 8 ISE 412 Advantages & disadvantages … Advantages Disadvantages

9. 9 ISE 412 Object perception Wickens et al. studies:  object displays facilitate performance on information integration tasks  separable displays support diagnosis tasks GPM, yWt., tons 5.53.4 5.93.8 6.54.1 3.32.2 3.62.6 4.62.9 2 3.62.7 3.11.9 4.93.4

10. 10 ISE 412 Examples … Phone EasyDifficult A02 B12 C03

11. 11 ISE 412 Implications for display design Optimize bottom-up processing  size, contrast, font (for text), appropriate upper/lower case  raw data on object displays Optimize top-down processing  avoid abbreviations & acronyms whenever possible  provide context (more words in text, recognizable object displays)  restrict “vocabulary” (text and picture) and optimize distinction between words/pictures Evaluate tradeoffs Usability testing in context

12. 12 ISE 412 Some fun examples: http://exp.kyb.tuebingen.mpg.de/web-experiment/list.html http://www.grand-illusions.com/index.htm