1ISE 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.

2ISE 412

Some examples

Problem-solvingWheel of Fortune

Crossword puzzles

Design

Hearing: conversation, listening to music, etc.

3ISE 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?

4ISE 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

SawpleSampl

e

"The majority of people who take this class are Ixx majors."

Examples:

5ISE 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

WEATHERWill encounter bad weather

6ISE 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.

7ISE 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?

8ISE 412

Advantages & disadvantages …

Advantages

Disadvantages

9ISE 412

Object perception Wickens et al. studies:

object displays facilitate performance on information integration tasks

separable displays support diagnosis tasks

GPM, y Wt., tons5.5 3.45.9 3.86.5 4.13.3 2.23.6 2.64.6 2.92.9 23.6 2.73.1 1.94.9 3.4

0

2

4

6

8

0 1 2 3 4 5

Weight, tons

gpm

10ISE 412

Examples …

Easy

Easy

Easy

Diff icult

Diff icult

Diff icult

0

1

2

3

4

A B C

Phone

# E

rro

rs

Phone  Easy Difficult

A 0 2

B 1 2

C 0 3

0

2

1

2

0

3

0

1

2

3

4

A Easy A Difficult B Easy B Difficult C Easy C Difficult

Phone / Dialing Difficulty

To

tal

Err

ors

0

1

2

3

4

A Easy A Difficult B Easy B Difficult C Easy C Difficult

Phone / Dialing Difficulty

To

tal

Err

ors

11ISE 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

12ISE 412

Some fun examples:

http://exp.kyb.tuebingen.mpg.de/web-experiment/list.html

http://www.grand-illusions.com/index.htm