The effective fusional range for words in a natural viewing situation

We investigated the effective fusional range for written stimuli in children and adults in a natural viewing situation. We recorded binocular eye movements in children and adults during processing of stereoscopically presented words in a lexical decision task. The effect of disparity magnitude on ease of fusion caused decreased response accuracy, increasing numbers of fixations and increased trial viewing times when retinal disparity exceeded one character space. The data suggest that retinal inputs of a word that are disparate by up to one character (0.37°) fall within the effective fusional range such that lexical decisions are not impaired.