<p>Selective attention typically becomes more refined with age, improving significantly from early to middle childhood. However, under certain conditions, such as the Ebbinghaus illusion task, younger children may display more focused selective attention than older children and adults. Cross-cultural differences have also been documented, with North American participants tending to focus selectively on central targets, while East Asian participants attending holistically and showing greater susceptibility to the illusion. Despite these findings, the physiological mechanisms underlying these age-related and cultural differences remain unclear. Specifically, does susceptibility to the illusion align with what we attend to? The present study investigated age-related and culture-related changes in susceptibility to the Ebbinghaus illusion among 3- to 8-year-old children in Japan and the U.S. using eye-tracking methods. The results revealed that older children and Japanese children were more susceptible to the Ebbinghaus illusion than younger children. Importantly, behavioral susceptibility was linked to gaze fixation patterns. In both cultures, the proportion of total fixation time on the correct target area, including target and distractor circles, rather than selective attention to targets alone, predicted susceptibility to the Ebbinghaus illusion. These findings highlight the role of gaze fixation in shaping perceptual experiences across developmental and cultural contexts.</p>