" A growing body of evidence suggests that teaching babies ASL may improve their ability to speak. Again, this indicates a link between manual signing and vocal speech. Babies express cognitive abilities through certain hand gestures (e.g., by pointing with the index finger) earlier than they do through articulated words (the latter require more refined oral motor skills, which very young babies do not yet possess). "

― David B. Givens , The NONVERBAL DICTIONARY of gestures, signs and body language cues