Fixations during recognition of rotated familiar and unfamiliar single characters

Character recognition forms the foundation of reading comprehension, yet the underlying visual processing mechanisms during single-character recognition are not fully understood. While character rotation is known to increase cognitive load, its effects on eye movement patterns and the role of language familiarity in these processes have not been systematically investigated. We hypothesized that character rotation would disrupt fixation patterns, with larger disruptions for familiar scripts due to interference with established recognition processes, while unfamiliar scripts would show smaller effects due to inherent processing difficulties. We examined fixation patterns during free-viewing of characters from six language categories (English, Japanese, Korean, Bengali, Arabic/Persian, digits) presented at 0° and 180° orientations. Fixation density maps and centroid movement analyses quantified rotation-induced changes in eye movement patterns across 19 Japanese university students. Results confirmed our predictions; rotation-induced fixation disruption showed different patterns depending on comparison method: no significant correlation in direct 0° vs. 180° comparison (r=0.252), but strong negative correlation when comparing orientation-adjusted patterns (r=-0.972). When comparing orientation-adjusted fixation patterns, familiar scripts showed larger differences between rotated and non-rotated conditions than unfamiliar scripts. Analysis of fixation point movements revealed directional patterns that suggest common visual processing mechanisms and familiarity-dependent modulations, with horizontal gaze shifts reflecting reading experience combined with stimulus-driven factors, and vertical shifts showing consistent tendencies across scripts. These findings reveal that character rotation systematically modulates fixation patterns in a familiarity-dependent manner, providing empirical evidence for the complex interaction between cognitive load and script familiarity in visual character processing.