Baby sign language develops similar to spoken language development. First signs are recognized before they can be signed. That is, your baby will understand what a sign means when you do it, but it will take some time before your baby actually does the signs themselves. Next, signs begin as approximations to the real sign. They’ll have similar handshapes and follow similar placement and movement, but won’t be exact replicas of the real signs. Usually signs are copied at the early stages. Meaning a parent might ask if a baby would like a certain thing over another. This is entirely different from a baby who requests something when it’s not present. This takes some time and brainpower.
Your baby will initially begin to use similar signs for various things. For example, the sign for BALL is done by moving the hands closer together as if squishing a ball together. This is similar to the sign for MORE where the hands come together and the fingertips touch. Babies do a similar thing with language. Babies will say “bird”, “ball” and “blanket” by saying “bah.” Usually, it’s easy to know what a baby means based on the context in which baby signs the word. Babies also often use the same sign to mean more than one thing. For example, your baby might sign MORE for going OUTSIDE or going for WALK, or because baby wants to see the DOG again. With time, your baby will learn the differences between the words.
Finally, your baby will experience a signing explosion like they will a talking explosion. In the early stages your baby is just getting by, but when their mechanical abilities couple perfect with their mental ability, they will add signs at an explosive rate to the point where signs can be added in a matter of minutes.