*3.1. Results of the Behavioral Data Analysis*

Contrasting subjects' DTs on four intervals, we observed significant changes among intervals, the effect of stimulus ambiguity, and the combined effect of ambiguity and orientation (see Table 1). Nevertheless, the experiment demonstrated that DT varies over the course of the experiment in the same way for all stimuli. We also found a significant effect of ambiguity on ER. At the same time, we observed a significant interaction effect of interval and ambiguity (see Table 2). These results suggest that ER differs for HA and LA stimuli regardless of their orientation. Moreover, ER changed differently during the experiment depending on the ambiguity.

**Table 1.** Median decision time to the current stimulus, DT [s] (ANOVA Summary).


Here, '\*' indicates the level of significance *p* < 0.05.



Here, '\*' indicates the level of significance *p* < 0.05.

The post hoc analysis revealed that subjects responded faster to LA stimuli than HA ones: *Z* = −3.724, *p* < 0.0001, Wilcoxon test (Figure 2A). For HA stimuli, DT was similar for the left- and right-oriented stimuli: *t*(17) = 0.383, *p* = 0.706, *t*-test (Figure 2B). For LA stimuli, subjects responded faster to the left-oriented stimuli: *Z* = −2.591, *p* = 0.01, Wilcoxon test (Figure 2C). Analysis of pairwise differences displayed that 12 subjects demonstrated effects in the same direction as the group. Finally, DT decreased with the

interval: *χ*2(3) = 12.218, *p* = 0.007, Friedman test (Figure 2D). The post hoc Wilcoxon test revealed higher ER for HA stimuli when compared to LA stimuli: *Z* = −3.29, *p* = 0.001 (Figure 2E). For HA stimuli, ER decreased during the course of the experiment: *χ*2(3) = 7.545, *p* = 0.056, Friedman test (Figure 2F). Finally, there was no correlation between age and DT to HA stimuli: *r*(20) = −0.24, *p* = 0.3 and LA stimuli: *r*(20) = −0.31, *p* = 0.17. DT was similar for males and females for both HA stimuli: *t*(18) = 0.79, *p* = 0.436 and LA stimuli: *t*(18) = 0.96, *p* = 0.348.

**Figure 2.** Results of the behavioral data analysis: (**A**) Median decision time, DT to HA and LA stimuli (∗ *p* < 0.0001 via Wilcoxon test, uncorrected). (**B**) Median DT to the left- and right-oriented HA stimuli (*p* = 0.706 via *t*-test, uncorrected). (**C**) Median DT to the left- and right-oriented LA stimuli (<sup>∗</sup> *p* = 0.01 via Wilcoxon test, uncorrected). (**D**) Median DT (group mean ± 95% CI) on four intervals (∗ *p* = 0.007 via Friedman test, uncorrected). (**E**) Percentage of erroneous responses (ER) to the HA and LA stimuli (<sup>∗</sup> *p* = 0.001 via Wilcoxon test, uncorrected). (**F**) ER (group means ± 95% CI) on all intervals separately for HA (*p* = 0.056 via Friedman test, uncorrected) and LA (*p* = 0.772 via Friedman test, uncorrected) stimuli.
