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We make a first attempt at distinguishing information-carrying visual signal by comparing visual characteristics of American Sign Language and everyday human motion, to identify what clues might be available in one but not in the other. The comparison indicated significantly higher fractal complexity in sign language across tested frequency bands (0.01-15 Hz), as compared to everyday motion. A comparison of our results with the work also showing high fractal complexity in the speech signal allows us to suggest the underlying properties of linguistic signals which allow babies to 'tune to' a specific channel, or modality, during language acquisition.