eyetracking-methodology.pdf

Eyetracking Methodology

How to Conduct and Evaluate Usability Studies Using Eyetrackin g

Kara Pernice and Jakob Nielsen

August 2009

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To get your own copy, download from: http://www.useit.com/eyetracking/methodology

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Executive Summary

Contents

Executive Summary .......................................................................5

Should You Use Eyetracking in Your Usability Studies? .........................6

Eyetracking Method Tips ...............................................................7

Recruiting Users for Eyetracking Studies..................................... 13

Communicate to the Participant During the Screening Interview........13

How to Say It ......................................................................................14

What to Ask the User ..........................................................................15

Telephone is Easier than E-mail When Recruiting for Eyetracking

Studies ................................................................................................18

How Many Users to Include in a Study ........................................ 19

The Number of Test Participants Needed is Dictated by Desired

Output.................................................................................................19

Variablity in Heatmaps Depending on the Number of Users ................20

The Slowly-Diminishing Returns Curve ...............................................48

R 2 Explained ........................................................................................49

A Better Deliverable Than Heatmaps...................................................51

Eyetracking Studies in a Lab........................................................ 53

Eyetracking Lab Set-up Notes .............................................................53

Think Aloud Method..................................................................... 57

Benefits to Think Aloud in a Non-Eyetracking Study............................57

Drawbacks to using The think aloud Method in a Non-Eyetracking

Study...................................................................................................60

Drawbacks to Using The think aloud Method in an Eyetracking Study.60

Surveying is Common During Think Aloud...........................................67

Beginning the Session and Calibrating the User’s Eyes................ 72

What to Say to the User When Beginning the Sessions .......................72

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Impossible Eyetracker Calibration............................................... 87

Cannot be amended: These culprits really cannot be changed to

make calibration possible....................................................................87

Can be amended: These culprits usually can be changed to make

calibration possible .............................................................................88

Facilitating Test Sessions .......................................................... 104

Steps for making eyetracking test facilitation run smoothly .............104

Example of Facilitator’s Protocol Sheet .............................................110

Saving Files .......................................................................................111

Retrospective ....................................................................................112

Using the Right Eyetracking Analysis Tools ............................... 116

Gaze Replays.....................................................................................116

Gazeplots ..........................................................................................117

Heatmaps ..........................................................................................118

The Areas of Interest or LookZone Feature .......................................138

Analyzing Video and Animation .........................................................139

Using the Eyetracking Analysis Tools in the Best Way.......................143

Tasks Discussion ....................................................................... 145

The Scenic View: Show One Page and Interview Method .................145

Task-Based Testing ...........................................................................148

Variety in Tasks.................................................................................149

Should You Run Your Own Eyetracking Research Study?........... 152

Why Nielsen Norman Group Invests In Eyetracking..........................153

Technology-Related Notes......................................................... 155

About the Authors ..................................................................... 157

Acknowledgements ................................................................... 159

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Executive Summary

Executive Summary

In traditional usability testing without eyetracking there are many cues our test

users give us that help us evaluate designs, such as the time a person spends on a

page, the action he takes there, what he reads aloud, what he hovers the mouse

over, whether he smiles or grimaces, and what he comments on. These user

behaviors comprise, in our opinion, the most important aspects of learning about

usability. But eyetracking (ET) adds another dimension. Watching what people are

looking at adds a level of interest to usability studies. Following the eye at work

makes you feel as though you are in the user’s head, thinking with him. If nothing

else, the ET studies are more interesting and hold observers’ attention more easily.

Eyetracking technology also helps test facilitators avoid a major blunder: interrupting

the user when he is quiet for a long time. This is a huge benefit since interrupting

the participant too much or inappropriately is one of the greatest challenges for even

seasoned usability professionals.

In addition to helping to avoid a major facilitation gaffe, eyetracking technology

enables us to understand more than clicks and pauses. We learn finer points about

what draws attention and why. And by studying what people look at and do not look

at, we are able to glean more detailed insights about how the Web user works his or

her way through usable and unusable designs. Behaviors such as exhaustive review

(where people look repeatedly at areas that seem as though they’d be helpful but

are not) and selective disregard (where people purposefully tune out areas of the

website at given times) are very apparent when watching the user’s eye at work. We

see which interface items are miscues (erroneously calling attention) and which

areas trick users and are thus dropped like a hot potato. (All of these and more

behaviors are described in our book titled Eyetracking Web Usability , Nielsen and

Pernice, New Riders Publishing 2009.)

Conducting valid usability research calls for good planning and experience. But

conducting valid usability eyetracking research is on another plane, adding to the

preparation, facilitation, and analysis. Eyetracking technology takes a regular

usability test and makes it more difficult, more time-consuming, and more

expensive. Conducting or analyzing results of a research study erroneously is worse

than not doing any research at all. Unfortunately, ET technology makes it very easy

to get misleading results where you believe something that simply isn’t true about

your design.

In this report we discuss what we have learned about how to plan, conduct, and

analyze an eyetracking study that will produce sound results that you can trust and

use to improve your website. While we see many benefits to eyetracking research,

we also know that good usability studies do not call for high-tech solutions. Some of

the best, iterative tests are done with paper and pencil only, because the faster you

can run a study the sooner you can adjust the direction of your design project.

METHODOL OGY, NOT FINDINGS

This report does not present any of the findings from our ET projects—it’s purely

about methodology : giving advice for how you should run your own ET studies,

should you decide to do so.

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