Ruggero Micheletto¹ (), Taichi Umikawa¹, Kotaro Oikawa¹, Keiko Tsuchiya¹; ¹Yokohama City University

Character inversion, also known as “typoglycemia”, involves randomly swapping the letters within a word, while leaving the first and last letters of the word intact. We investigated the effect of reversing the hiragana characters in Japanese words and simultaneously examined the effect of this inversion on eye tracking behavior during reading. The experiment is performed by Japanese native speakers reading two passages containing words that are randomly affected by letter inversion. We used phrases of different complexity, an easier text extracted from a children's book and a more complex one from an adult novel. Regression analysis confirmed that, on average, the typoglycemia phenomenon is less probable than in the more complex text of the novel. Using an eye tracking system, we showed how the subjects skipped over the reversed words recording a heat map of eye movement. Also, analyzing the eye speed and direction of movement, we found that when the typoglycemya happens, the eye movements are faster than normal. Overall, this study shows how the complexity of a text affect the typoglycemia phenomenon, and correlate this with eye tracking behavior and eye movements speed. Our study is also confirming that people rely more heavily on the first and last letters than on the letters in the middle in order to gain reading comprehension even in Japanese characters context. Paradoxically, the analysis of reading speed suggests that letter reversals promote reading speed and text comprehension instead of hindering it.

Acknowledgements: We thank the Yokohama City University, "Basic Science 2024" grant