Jeffrey P. BighamAnna C. Cavender, Jeremy T. Brudvik, Jacob O. Wobbrock* and Richard E. Ladner

Computer Science & EngineeringThe Information School*University of Washington

A Comparison of Blind and Sighted Browsing Behavior

Study Overview Proxy-based observation for one week 10 Blind and 10 Sighted (Ages 18-63) Either Internet Explorer or Firefox Blind participants used JAWS

21,442 Pages 4,204,904 Events

Introduction

Geographic Diversity of Users

in situ StudyIntroduction

Valuable Qualities Participants use their own tools Familiar, preferred web pages Observe longer time periods

Usage Patterns in Usual Browsing Effects of web accessibility Coping strategies employed Differences in content chosen to view

Important Complement to Prior Work

Detail Researcher

Observation

Standard Tasks

User’s Tools

Longer Times

Lab1,2

Field3

Diary4

WebinSitu[1] Takagi et al. Analysis of navigability of Web applications for improving blind usability. 2007.

[2] Watanabe et al. Experimental evaluation of usability and accessibility of heading elements. 2007.[4] Coyne et al. Beyond alt text: Making the web easy to use for users with disabilities. 2001.[3] Lazar et al. Determining the impact of computer frustration on the mood of blind users. 2006.

Introduction

Outline

Introduction

Experimental Setup and Study Design

Browsing Differences

Effects of Content

A Proxy-Based System

Internet

UsageDBTracking Script

Augmented Page Original Page

Proxy

Used UsaProxy1

[1] Richard Atterer et al. Knowing the User's Every Move - User Activity Tracking for Website Usability Evaluation and Implicit Interaction. WWW 2007

Setup and Study Design

More than a regular proxySetup and Study Design

GET http://webinsight.cs.washington.edu/, 10 Oct 2007 04:12:30GET http://webinsight.cs.washington.edu/pics/web-eye.gif, 10 Oct 2007 04:12:30GET http://webinsight.cs.washington.edu/css/style.css, 10 Oct 2007 04:12:31…

Keypress, ctrl f, 10 Oct 2007 04:12:35Mouse, 540x232, 10 Oct 2007 04:12:36Focus, Text Box (name), 10 Oct 2007 04:12:36AJAX, url=“http://www.cs.washington.edu/.../foo.php, 10 Oct 2007 04:12:36Page Changed, 10 Oct 2007 04:12:39…

Image, alt=“Contact Us”, src=“http://www.washington.edu/pics/contact.gifLink, name=“University of Washington”, url=“http://www.washington.edu”…

Requests

Actions

Content

Easy Setup and DeploymentSetup and Study Design

No New Software to Install Works with Existing Tools

Outline

Background

Experimental Setup and Study Design

Browsing Behavior

Effects of Content

Using the Mouse Blind Users Don’t Use a Mouse

but, sometimes they have to100%

0%

50%

Blind SightedPages with Mouse Movements 25.9%

(n.s.)35.1%

Avg. Discrete Movements per Page

0.43(p < 0.0001)

8.21

% of Pages with Mouse Movements per Participant

Browsing Differences

Using the Mouse (why)

“…if there's a command in a form or shopping cart that says, ‘click here,’ with no labeled button, I must route my cursor to that position…”

Browsing Differences

Probing:

technical papers

technical program

Call for Papers

Technical Program

Browsing Differences

Following a link and returning in less than 30 seconds

Blind 1 out of 3 pages Sighted 1 out of 8 pages

Web Pages with Probes

0

5

10

15

20

Num

ber o

f pro

bes

1

100 200 300 400 500

Browsing Differences

(p < 0.01)

Ave

rage

tim

e pe

r pa

ge (

min

)

all pages

3

2

1

0

4

Browsing Efficiency

Blind Users Less Efficient Overall, ~2x longer per page

Contrast to 10x on completing tasks1

Why not more? Web pages, not tasks Accustomed to Web Pages “errors” (including probing)

[1] Takagi et al. Analysis of navigability of Web applications for improving blind usability. 2007.

Browsing Differences

(p < 0.1)

Using GoogleBrowsing Differences

Task Blind SightedEntering Query

74.6 sec.(p < 0.01)

34.5 sec.

Selecting Result

155.1 sec.(p < 0.0001)

34.8 sec.

Outline

Background

Experimental Setup and Study Design

Browsing Differences

Effects of Content

Images and Alternative Text

Proceed

Publish Bank Info

RESET

(empty)

http://www.domain.com/proceed.gifhttp://www.domain.com/pubbank-button.gifhttp://www.domain.com/239080s.gif

Blind Users are Smart

Effects of Content

Images and Appropriate Alt. Text

% of Images with App. Alt. Text Did not influence browsing behavior

Influenced Clicking Behavior:

100%

0%

50%

Blind Sighted72.2% 34.0%

Clicked Images with App. Alt. Text

% of Images Assigned Appropriate Alternative Text on Visited Pages

Effects of Content

(p < 0.01)

Skip Links“Skip top navigation and go to home page content”

822 Skip Links

Blind users clicked 5.6%

“Skip links are almost always broken.”

Effects of Content

Dynamic Content 15.0x fewer pages viewed (p < 0.07) 19.3x fewer interactions with dynamic content

(p < 0.01)

AJAX 7.5x fewer (p < 0.05)

Flash 44.1% were ads Blind participants used for sound content Only 5.6% were main content

Effects of Content

30%

20%

10%

0%

Summary and Future Work Main Points

Facilitated new type of study Confirmed anecdotal observations Interesting new directions

Many Remaining Questions Efficiency and experience Content requires using the mouse Annotation of dynamic content (ARIA) Extent of Flash accessibility MANY OTHERS

Effects of Content

WebInSight

webinsight.cs.washington.edu

Thanks to:National Science FoundationMax Aller, Richard Atterer, Darren Gergle, Steve Gribble, Sangyun Hahn, Scott Rose, Lindsay Yazzolino.

The End

Important Complement to Prior Work

Detai

l

Voice Output

No User Recordin

g

Standard Tasks

User’s

Tools

Longer

TimesLab1,2

Diary3

Field4

WebinSitu

[1] Takagi et al. Analysis of navigability of Web applications for improving blind usability. 2007.[2] Watanabe et al. Experimental evaluation of usability and accessibility of heading elements. 2007.[3] Lazar et al. Determining the impact of computer frustration on the mood of blind users. 2006.[4] Coyne et al. Beyond alt text: Making the web easy to use for users with disabilities. 2001.

Background and Motivation