Table 2 The meanings of eye-tracking metrics.

Average fixation duration (ms)

AFD

The average time the subject spent looking at each fixation point. The more effort the subject put into recognizing the picture, the longer the average time they spent looking at the fixation point.

Fixation frequency (count/s)

FF

The ratio of the number of fixations to the duration of fixations is an indicator of the degree of attention paid to the evaluation area. A high fixation frequency indicates that the subject feels that the picture is important or is relatively interesting.

Saccade frequency (count/s)

SF

The number of saccades per unit time can reflect the search behavior of the subject. During the information search process, a high saccade frequency indicates that the subject’s search is extensive and the features of the images they are observing are not distinctive.

Average saccade amplitude (°)

ASA

Reflects the extent of information obtained. The smaller the average saccade amplitude, the more distinct the picture features and the more directly the subject can reach the target area.