In all my workshops and parent training courses I emphasize the importance of “cause and affect” which are the fundamental building blocks for communication and verbal imitation. If your child does not understand cause and affect on a conscious level, he/she will have great difficulties communicating their needs and understanding what’s requested of them. Since the day we’re born, we are born with this innate ability, however, on a subconscious level. An infant soon “learns” by crying I get my basic needs met; I get changed, I get fed, I’m put in my bed to sleep, etc.
As children grow and enter the toddler age where communication is more purposeful, they learn “when they do something, something else happens.” As the rule of development goes, gross motor skills develop much faster than fine motor skills. Muscles necessary for speech are considered fine motor skills, which is why your child is able to move his/her arms and legs much sooner than they’re able to babble.
Teaching your child to sign, using “gross motor skills” is much easier than teaching them to say “mamma” or “dada” or “I want milk.” By teaching them sign language not are you teaching them the fundamental building blocks for communication, cause and affect and purposeful communication, but you’re also instilling in them early “language” building skills. It is not true that if your child learns to sign, he/she will not learn to talk because signing is easier. It’s especially helpful to “drag out” the beginning of each word as you’re signing it; ie. mmmmmmmmore while signing more. This helps “paring” speech with action which again helps with the building blocks and early language imitation and learning.
It is also not true that if your child does not learn to sign he/she will be a late talker. Some children are “early talkers” and talk much quicker than other children. These children may spontaneously start speaking without the need for learning sign language at all. Also keep in mind that girls speak sooner than boys do.
With all of that in mind, although sign language can be very helpful in early development of speech, language and motor skills, it is not necessary to learn language.