The development of susceptibility to geometric visual illusions in children – A systematic review

Investigating children’s susceptibility to visual illusions (VIs) offers a unique window into the development of human perception. Although research in this field dates back to the seminal work of Binet in 1895, developmental trajectories for many VIs remain unclear. Here, for the very first time, we provide a comprehensive systematic review of research investigating children’s susceptibility to five of the most famous VIs: the Ebbinghaus, Ponzo, Müller-Lyer, Poggendorff, and Vertical-Horizontal illusions. Following PRISMA best-practice guidelines, 70 articles were identified across four databases (Scopus, PsycInfo, PsycArticles, and Web of Science). Our findings reveal opposing developmental trends across illusions; the magnitude of the Müller-Lyer, Poggendorff, and Vertical-Horizontal illusions tends to decrease with age, while the magnitude of the Ebbinghaus and Ponzo illusions typically increases with age. However, developmental trajectories identified by studies investigating the same illusion can vary dramatically due to substantial variability in methods and stimuli. Researchers are more likely to find decreasing VI magnitude with increasing age when employing the method of adjustment response paradigm, whereas the two-way alternative forced-choice paradigm typically reveals greater VI magnitude with increasing age. These findings suggest that conclusions regarding the development of VI susceptibility may be influenced by how they are studied and implicate the involvement of different cognitive abilities across response methods. These findings will benefit future research in dissociating the role of perceptual (e.g. the maturation of the brain's visual areas) and cognitive factors (e.g., attention span) in pinpointing the development trajectories for VI susceptibility.