When presented simultaneously with equally discriminable, but unfamiliar, visual and auditory stimuli, 4-year-olds exhibited auditory dominance, processing only auditory information ( Sloutsky & Napolitano, 2003). The current study examined factors underlying auditory dominance. In 6 experiments, 4-year-olds (N181) were presented with auditory and visual compounds in which (a) the complexity and familiarity of stimuli were systematically varied (Experiments 15) and (b) participants were explicitly instructed to attend to a particular modality (Experiment 6). Results indicate that auditory dominance is a special case of flexible modality dominance, which may stem from automatic pulls on attention. Theoretical implications of these results for understanding the development of attention and cross-modal processing, as well as linguistic and conceptual development, are discussed.