# Cognitively Driven Arabic Text Readability Assessment Using Eye-Tracking
## 2 Background
### Eye-Tracking and Reading  
Eye-tracking is a technique performed by employing several concealed near-infrared illuminators that generate reflection configurations on the cornea. Image sensors can then detect the presence of the reader's eyes and acquire data at a rapid sampling speed. A three-dimensional model of the reader's eyes can be configured by processing the data, pinpointing the pupil's location, and recognizing apposite reflections from the illuminators, along with their accurate coordinates [38].  
Eye-tracking technology can be utilized to investigate a range of events relating to language processing. A number of the linguistic elements explored using eye-tracking include auditory, visual, and combined auditory and visual processing [39]. Since eye-tracking offers real-time information, it is the subject of expanding research, especially in applied linguistics and learning a second language. Eye-tracking has been deployed as an alternative to conventional assessments (e.g., cloze tests, think-aloud protocols, and interviews) [39].  
In studies relating to subjects' reading [8; 39; 40], eye-tracking data are often used to perceive and to interpret the following reading measures:  
1. Saccades: the participant's swift eye motions between areas of text. Longer saccades imply text that is straightforward and easily comprehended; short saccades suggest a greater challenge and time required to digest the language [40].
2. Fixations: points between saccades where the reader's eyes halt. Brief and infrequent fixations suggest text is readable; longer and numerous fixations are related to text difficulty and imply that the reader may be struggling with interpretation [12; 40].
3. Regressions: backward movements to return to earlier areas of text. Short regressions may imply local challenges, whereas more prolonged regressions may indicate the text's general level of difficulty and lack of clarity [12; 39].  
In common with other reaction time tests, eye-tracking employs two empirical theories during subjects' gaze data acquisition [39]. First, the time duration of gaze fixation represents the cerebral effort necessary for processing; that is, prolonged or more frequent fixations imply a higher degree of cognitive focus and vice versa. Second, the object of the subjects' gaze is the subject of concentration. In view of these assumptions and appreciating that the spectrum of fixations and saccades can offer significant information about both the reader and the words on the page [41], eye motion can be deployed to elucidate the cognitive processes related to reading [12].  
From a different perspective, the user should be aware of some limitations related to eye-tracking techniques that may influence their usefulness in studies [40]. Founded on the empirical assumptions relating to eye-tracking deployment, the gaze is linked to subjects' focus. Yet, realistically, focus can additionally be placed on items within the gaze periphery. This arises owing to the complexity of the human ophthalmic system. This restriction necessitates that the two options are embraced (i.e., the gaze does or does not correspond to the subject's precise focus). Additionally, information loss or inaccuracies may arise during eye-tracking experiments. Causes include physiological features of certain subjects (e.g., elongated eyelashes, make-up, or heavy eyelids), and external factors (e.g., reflective glasses or contact lenses). Moreover, since eye-tracking cameras operate with a set frequency, some eye motions may fail to be recorded. Furthermore, since the recorded signal is smoothed out to subtract anomalies such as blinking or peripheral eye deviations, some data could be erroneously deleted.