Supplementary Material for: Heterochronic development of the perception of different types of visual illusions

Introduction: The underlying neural and/or perceptual mechanisms of different visual illusions are still unknown; thus, they continue to be the focus of many ongoing studies. Inconsistencies persist in the empirical findings for understanding how the perception of these illusions evolves over the course of development.
Methods: We assessed 513 participants between 6.5 and 18.9 years of age, with 103 pairs of illusory and control images spanning five illusion types (Ebbinghaus, Müller-Lyer, Contrast, Moving Snake, and Subjective Contour). Misleading and helpful contexts were added when possible.
Results: In general, we found that, except for the Ebbinghaus illusion susceptibility changes with age: while for the Müller-Lyer it decreases, for the Contrast, Moving Snake, and Kanizsa susceptibility increases. Across all illusory conditions participants' decision time decreased with age. Context also influenced the performance and choice latency. We also found a gender difference: boys were less susceptible than girls on contrast and moving snake illusions and were faster to answer on Müller-Lyer illusion trials.
Conclusion: The current study found that susceptibility to illusions change in a manner that is age and in some cases sex specific. The different developmental trajectories of the perception of visual illusions support the idea of the lack of a common neural and/or perceptual process behind them. We can suggest that at least some of the cognitive processes and neural pathways involved develop in heterochronically.