# Effect of Stimulus Regularities on Eye Movement Characteristics
## 3 Results
### Saccade Number  
The saccade number is related to the number of fixations performed during the task. Figure 5 shows the distribution of the saccade number in each epoch. It shows that the saccade number has a skewed distribution. We tested three models for the effect of the stimuli and epochs on saccade number. The first uses all 72 stimuli, and thus, it assumes that the rotation angle and the position of the patterns affect the exploration activity of the participants. The second model assumes that the rotation angle is ineffective, but the position of the patterns (whether to the left or the right of the stimulus) changes the number of saccades. It includes 24 combinations of patterns. The third model assumes that neither the patterns' rotation nor position affects the saccade number. It includes 15 pairs of patterns. The cross-validation for model comparison implied a better fit of the data by the model that ignores the rotation angle and the pattern positions and thus regards only 15 combinations of the patterns. In contrast to the fixation duration, the saccade number varies with the stimulus type. We compared the saccade number for the three groups of patterns and the combinations of the same and the different patterns. The evidence strongly supports the hypothesis that for each group, the same patterns require more saccades than the different ones (Figure 6; Group 1: estimate = 0.26; 95% CI [0.20-0.32]; evidence ratio = Inf; probability = 1.0; Group 2: estimate = 0.08; 95% CI [0.00-0.15]; evidence ratio = 24.13; probability = 0.96; Group 3: estimate = 0.26; 95% CI [0.19-0.34]; evidence ratio = Inf; probability = 1.0). Moreover, the same patterns from the different groups elicited an unequal number of saccades--the largest for Group 1 and about the same for Groups 2 and 3. The analysis revealed an estimate of 0.15 and 95% credible intervals of 0.08-0.23 for the hypothesis A1A1 > A2A2 with an evidence ratio of 3332.33, and an estimate of 0.19 with 95% credible intervals for the hypothesis A1A1 > A3A3 and an evidence ratio of 9999. Based on the evidence ratio, the data provide strong evidence for more saccades elicited by the same patterns in Group 1 compared to the other groups. The evidence moderately supports the hypothesis that the saccade number for the same patterns in Group 2 exceeds those for the same patterns in Group 3 (hypothesis A2A2 > A3A3: estimate = 0.04; 95% CI [\(-\)0.05-0.13]; ER = 3.22; probability = 0.76). Figure 5: Distribution of the saccade number in the sequential epochs (1–6) of the experiment. Contrary to our expectations, the number of saccades increases in the different epochs (pd equals 100%; the evidence ratio for the hypothesis that the effect of epoch increases (epoch > 0) and equals Inf with an estimate 0.02; 95% CI [0.0-0.04]), providing strong support for the hypothesis of an increase in saccade number in the sequential blocks. The saccade number in our study reflects the exploratory eye movements. Its increase in the sequential blocks might represent the gained knowledge of the spatial structure of the stimuli. For example, in [8], the authors showed that both the exploratory and the confirmatory eye movements increased in the sequential trials when the participants had an explicit knowledge about the underlying structure of the visual scenes or during long implicit learning. In our understanding, however, the increase in saccade number in our experimental conditions and task should be considered in combination with the change in the other eye movement characteristics. This result is further discussed in the Section 4. We evaluated the trend of the epoch effect for the different combinations of patterns using the emtrends function [35]. For all combinations, the trend is positive. It is most prominent for the combination of the B and D patterns from Group 2, A and D from Group 1, and A and A for Group 3. The smallest increase in the saccade number was obtained for the AA pattern from Group 1 (Figure 7 and Figure S2 in the Supplementary File).