3.1 Observation with Eye Tracking

Eye Tracking

凝視點 (Fixation)  「我癡癡地凝視著他，有好一段時間，我幾乎 忘了這個世界的存在」  定義  個體專注於視覺刺激中特定位置時  眼球相對固定不動時所停留的位置  兩項參數  ( 相對 ) 固定不動的最小時間 (e.g.,  80ms)  眼球轉動的最大視角 (e.g.,  0.5  )

Heatmap  Colored display for 2D data array  Advantages  Perceptual & locational  Parameters  # of users  Fixation length or # of fixations  Color scale

Two Types of Heatmaps Fixation count heatmapAbsolute gaze duration heatmap

Guidelines for Using Heatmaps (1) Used for visualizing quantitative data (2) Define the 2D-data represented (3) Define a fixation; e.g., 100ms, 0.5  (4) Define the upper bound for color scale (5) Describe the time duration when fixations were collected (X) let’s-track-and-see-what-happens approach

Case Study: ASCO Original ASCO homepageProposed ASCO homepage With which users can be quicker to find information?

Bad Examples of Visual Search Attention deploymentTarget processing     Visual designEase of understanding    

Participants and Apparatus  12 participants  Age:  ASCO member Recruited at 2005 ASCO Annual Meeting in Orlando  Use experience: once a month (mean)  Apparatus  17” monitor (1024 x 768 pixels)  a mouse  Tobii 1750 eye tracker

Procedures 25 tasks (Design 1) 20-min unrelated exercises 25 tasks (Design 2) Randomized Within-subjects design Counterbalanced against sequence effect 完全交互平衡法 Any confounding effect between old vs. new?

TASK I: Find a list of upcoming conferences Original webpageProposed webpage

Analysis Results

Task I in Original Design Too many link elements # of 目標凝視點 > 1: 4 Persons

Task I in Proposed Design Less apparent link elements # of 目標凝視點 = 1: All participants

TASK III: Find ASCO’s Position Statements Original webpageProposed webpage

Analysis Results

Task III in Original Design

What is Wrong With Proposed Design? 點選 “Legislative & Regulatory”: 9 participants Mean( 目標凝視點 ) = 2

What Color Scheme Is Better? Red-Orange-Yellow-Blue-GrayRed-Orange-Yellow-Green-Gray

Grayscale Scheme

White Background?

Gaze Plot & Gaze Replay  What they are?  Place  Order  Size  Limitations  有時候看不到數字  有時候看不到網頁  Time-consuming analysis  Gaze replay Qualitative nature

Areas of Interest (AOI)

F Pattern

3.2 Recruiting Participants

Communicate to the Participant  Disclose the exposure to eye tracking  Ethically  Ensure no surprise to subjects  Nothing fishy to subjects  Don’t over-explain eye tracking  Subjects too aware of eye movement ( 過度察覺 )  Subjects might quit the test  Ex: “is that infrared going to hurt me?”

How to Say It?  Simple introduction to eye tracking  在實驗過程中，我們會觀察你使用網頁的方式  我們會應用科技來追蹤眼睛的移動  接下來我們將請教一些關於眼睛的基本問題  以確定你適合進入這個實驗

Screener Questionnaire

Impossible Eyetracker Calibration Bifocals/Trifocals 白內障 (cataract)

Impossible Eyetracker Calibration 眼睛植入物 (eye implant)

Impossible Eyetracker Calibration Screen readerPermanently diluted pupil

Impossible Eyetracker Calibration Extreme heightBushy eyelashes

問卷後說明  正式表達邀請  說明酬勞 ( 如果有的話 )  說明實驗時間長度  告知受試者放鬆，而且實驗目的是為了瞭解互 動設計的優劣，與其個人能力高低沒有關係  詳述實驗過程中可能蒐集的所有行為項目  如果實驗不是即刻展開，與受試者約定時間  告知實驗地點  與受試者交換聯絡方式

3.3 Pre-experiment Preparation

Environmental Issues Avoid strong light over monitorAvoid eye dryness

Typical Eye-Tracking Lab Setup Stationary chair Clear desktop

3.4 Obstacles to Calibration

Some Behaviors Affecting Tracking Brimmed hatLooking over glasses

Some Behaviors Affecting Tracking DrinkingHand on the Chin

Some Behaviors Affecting Tracking Leaning on handHands up (in thinking aloud)

Some Behaviors Affecting Tracking Holding task sheet upLeaning back

Some Behaviors Affecting Tracking Leaning forwardSquinting