Although it is well documented that language plays an important role in cognitive development, there are different views concerning the mechanisms underlying these effects. Some argue that even early in development, effects of words stem from top-down knowledge, whereas others argue that these effects stem from auditory input affecting attention allocated to visual input. Previous research (e.g., Robinson & Sloutsky, 2004a) demonstrated that non-speech sounds attenuate processing of corresponding visual input at 8, 12, and 16 months of age, whereas the current study demonstrates that words attenuate visual processing at 10 months but not at 16 months (Experiment 1). Furthermore, prefamiliarization with non-speech sounds (Experiment 2) resulted in able processing of visual input by 16-month-olds. These findings suggest that some effects of labels found early in development may stem from familiarity with human speech. The possibility of general-auditory factors underlying the effects of words on cognitive development is discussed. (Contains 5 figures and 2 tables.)