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Visual Attention in Newspaper versus TV-Oriented News Websites

William J. Gibbs and Ronan S. Bernas

Journal of Usability Studies, Volume 4, Issue 4, May 2009, pp. 147-165

Article Contents


Eye-tracking and Visual Attention Metrics

Diagnostic eye-tracking is becoming increasingly prevalent in interface usability testing (Duchowski, 2002). We used eye-tracking to study whether newspaper and TV-oriented sites influenced ocular behavior differently. Based on a review of literature, we selected several metrics to monitor visual attention: (a) number of fixations overall; (b) fixation duration, the average eye fixation duration; (c) gaze time, the percent of time participants spent fixating instead of saccade time; (d) saccade rate, the number of saccades per second; and (e) scan path analysis using a string-edit method and Optimal Matching Analysis (OMA). In the following paragraphs, we provide a brief overview of eye-tracking in general and then summarize the metrics used in this project.

Eye-tracking

It is not yet clear how users view Web pages (Pan et al., 2004) and what directs their attention, specifically visual attention. Eye movement studies on news sites can offer valuable information about visual attention during information seeking. Eye movements reveal moment-to-moment cognitive processes during task execution (Rayner, 1998) and provide reliable information about where one allocates attention when presented a visual stimulus (Pieters, Rosbergen, & Wedel, 1999). For instance, Pan et al. (2004) reported that participants fixated longer on the first page of a Website than on subsequence pages, and the type of Website being viewed influenced changes in eye movement direction and magnitude. Goldberg, Stimson, Lewenstein, Scott, and Wichansky (2002) found that when participants navigated portlets (screen areas) with at least two columns, they made more horizontal than vertical eye movements. They contend that between-column (horizontal search) preference should be used to determine screen layout to improve usability. The researchers also found that participants visited the body of pages prior to page headers, suggesting that the header bars were not viewed consistently for navigational cues. Similarly, the Stanford Poynter Project (2000) examined reading behavior on news sites and found that news readers preferred text over graphics, with most readers attending to text first rather than artwork.

With the exceptions of the Stanford Poynter Project and Josephson and Holmes (2002, 2008) few studies have examined eye movement behavior on newspaper and TV-oriented sites and, as Goldberg et al. (2002) pointed out, there has been insufficient work that links usability with eye-tracking results. Given the widespread use of newspaper and TV-oriented sites and the proliferation of media on them, “…it is imperative to understand how users view different Web pages in order to provide a cognitive basis for interface design” (Pan et al., 2004, p. 147).

Visual attention measures

When looking at a visual stimulus, the eyes make continuous and rapid movements known as saccades. With durations of roughly 150–200 milliseconds for planning and execution (Muir & Richardson, 2005), a saccade directs attention to the visual target and during which information processing is restrained (Pan et al., 2004; Rayner, 1998). Occurring between saccades, fixations are relatively motionless gazes associated with cognitive processing that take place over some minimum duration (Jacob & Karn, 2003; Josephson & Holmes, 2008). Viewers take in information when the eye is motionless, during fixations (Stanford Poynter Project, 2000). At least three processes take place while fixating: (a) visual stimulus encoding, (b) peripheral field sampling, and (c) preparation for the next saccade (Pan et al., 2004; Viviani, 1990). According to Pieters, Rosbergen, and Wedel (1999) fixations are an important characteristic of visual attention and their duration, position, and pattern should be determinants when assessing a visual display’s potential to gain attention.

The number of fixations in a particular area of a visual display is an indication of the importance a viewer affords to the display area. Conversely, a higher number of fixations overall suggests an inefficient information search that may be due to a poorly designed interface (Jacob & Karn, 2003).

Fixation duration is a brief glance lasting between 100-300 milliseconds, although some researchers (e.g., Bojko, 2006; Palmer, 2002; Rayner, 1998) document fixation ranges from ~50-~500 milliseconds. As noted by Josephson and Holmes (2002, 2008), researchers who study images in print and television (e.g., Baron, 1980; Fischer, Richards, Berman, & Krugman, 1989) classify a fixation as a pause in eye movement with a minimum duration of 100 milliseconds, although there is no definitive research that establishes 100 milliseconds as the minimum fixation duration. Fixation duration is a measure of information complexity and/or one’s difficulty discerning information from a display, and fixation patterns between displays indicate how efficiently visual elements are arranged (Fitts, Jones, & Milton, 1950; Jacob & Karn, 2003). Salvucci and Anderson (2001) point out that fixation durations are contingent on task difficulty and they can range from roughly 100 milliseconds to more than 1 second. In a Web search study, Cutrell and Guan (2007) reported mean fixation durations of over 2 seconds as participants viewed highly ranked search results on a search engine results page (SERP). The durations decreased as participants viewed search results ranked lower in the list.

Gaze time, or the portion of time spent looking at a display element, may suggest the importance a participant associates to an element. Similar to gaze time, ascertaining the percentage of participants who fixate in specific areas of a display can be indicative of an interface element’s ability to attract visual attention (Jacob & Karn, 2003).

Saccade rate and task difficulty are inversely related, signifying that as cognitive demands increase saccade rate decreases (Nakayama, Takahashi, & Shimizu 2002). When examining ocular behavior and task difficulty, Nakayama, Takahashi, and Shimizu found that the saccade rate (1.0 saccade/second) was similar when participants did not perform a mental task and when they responded quickly and correctly to a task. However, as participants responded slowly or incorrectly perhaps due to increased mental effort, saccade rate decreased (0.8 saccade/second). Pan et al. (2004) found that the first pages of business Websites were more cognitively demanding than second pages as indicated by an increased saccade rate on second pages. Conversely, they found that the second pages of search sites required more cognitive effort as indicated by a reduction in saccades.

A scan path is a repetitive succession of eye fixations (Brandt & Stark, 1997). Scan path theory (Brandt & Stark, 1997; Norton & Stark, 1971) purports that when a person is first presented a visual stimulus, he or she visually scans it and then retains in memory a spatial model of the succession of fixations that constitute the scan path. Upon re-exposure to the stimulus, the participant’s eye movements follow the scan path established during the initial viewing, facilitating recognition (Josephson & Holmes, 2002). Josephson and Holmes (2008) used string-edit method and OMA in which scan paths are assigned a code and then sequence pairs are compared to observe variations. They found that participants had preferred scan paths and that different participants exhibited similarities in eye movement sequences suggesting that features such as the complexity of the Web page design may be an important determinate in scan path variations.

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