Young children often have a preference for auditory input, with auditory input often overshadowing visual input. The current research investigated the developmental trajectory and factors underlying these effects with 137 infants, 132 four-year-olds, and 89 adults. Auditory preference reverses with age: Infants demonstrated an auditory preference, 4-year-olds switched between auditory and visual preference, and adults demonstrated a visual preference. Furthermore, younger participants were likely to process stimuli only in the preferred modality, thus exhibiting modality dominance, whereas adults processed stimuli in both modalities. Finally, younger participants ably processed stimuli presented to the nonpreferred modality when presented in isolation, indicating that auditory and visual stimuli may be competing for attention early in development. Underlying factors and broader implications of these findings are discussed.