# Assessing Interactive Web-Based Systems Using Behavioral Measurement Techniques
## 2 Literature Review
### Behavioral Measurements Techniques
#### 2.3.3. Eye Tracking  
Eye tracking is defined as \"the recording and study of eye movements when following a moving object, lines of text, or other visual stimuli; it is used as a means of evaluating and improving the visual presentation of information\" [59]. An eye-tracking device records the movements of users' eyes, and computer software analyzes how the gaze changes [48]. Eye-tracking tools help researchers register the required time for a task to be completed as well as analyze the first fixation duration and fixation time [29].  
In eye-tracking research, what the user looks at and the relevant mental processes are linked with the user's gaze. Perceptions of visual appeal are expressed through analyzing how users look at websites. This is achieved through various variables of gaze that are used to interpret the visual aesthetics' perception. Standard measures of eye-tracking based on cognitive load comprise a duration of fixations, pupil diameter, and saccadic length and speed [60]. When the eye is focused on a particular point on the screen, fixations occur and are collected as x and y coordinates [61]. When the eye moves from one fixation to the next fixation, saccades happen. Scanpaths are then composed of consecutive combinations of fixations and saccades. The output of the eye tracker may be a heatmap and eye movement trajectories. The heatmap depends on fixation counts or fixation duration [61].  
As with other evaluation methods, eye tracking has advantages and disadvantages. Eye tracking provides more information that helps in a deeper understanding of the causes of usability problems [58]. It also provides mental process-related information and reliable data because users focus their attention on where they are looking [62]. It is also easy to collect the data with no sacrifice of the study's ecological validity. It provides a better understanding of how the interaction happens through linking apparent events like clicking, typing, and scrolling with the attentional mental process's information [63]. Thus, it could be used to develop possible guidelines for fostering usability [58]. An additional advantage is the variety of ways and measures that the eye-tracking tool represents to researchers (and hence a multitude of measures) researchers can use to examine their data [64]. The eye-tracking methodology allows researchers to gather actual quantitative data: fixations, regressions, and saccades [65]. These data reveal attracting or distracting items on the web page, revealing indications about distinct user search strategies [61].  
However, with the ubiquity of eye tracking in usability research, it is essential to make sure that the methodology is used appropriately, ensuring the validity of research outcomes [64]. One drawback of eye-tracking research is the consideration that the gaze dot or cursor on the screen refers accurately to where a user is looking. Like other types of measurement devices, eye-trackers are prone to measurement errors, which in turn influence data interpretation [64]. Furthermore, in eye-tracking research, it is not possible to justify why a user fixates on a particular spot on a website [66]. In addition, the cost and the obstruction to the users are reported as issues when testing usability using eye-trackers [26].