Babies get upset when they don't get what they need, whether that need is sleep, food, water or attention. However, many of the meltdowns that infants and toddlers have could be lessened, or even alleviated, through the power of communication. Sign language empowers children because it gives them the tools to express what they want without resorting to tantrums. For example, if a baby wants milk, he can sign his desire, rather than getting upset because he wants it but doesn't know how to get it. This also instills calm and confidence in the parents as they empower their child to tell them what he needs, and this builds trust in the relationship between parent and child.
Just because a baby can't speak doesn't mean she doesn't have a lot to say. She just needs to know how to do it. Babies acquire the ability to manipulate their hands and head before they possess the ability to manipulate speech. Thus, the tools learned through sign language are significant stepping stones to speaking, according to speech and language therapist Diane Ryan. Overall, babies learn that they can communicate and that it's effective. Because of this, they become confident in their abilities, which makes them more willing to experiment verbally further down the road.
Parents need not fear that signing will become a replacement for speech. Rather, it's a precursor. Babies who sign may even speak sooner than non-signing babies, using those first words that they had learned to sign. They may have a higher IQ, more interest in books and more vocabulary words than non-signers.