What your baby sees versus what he perceives is very different. Not only this but your baby’s perception is also ever changing as your baby grows and develops. If you are attuned you can even see these changes before your very eyes. Try watching for this, it’s truly amazing. I remember telling my wife when she came home from work about all the wonderful new things our son was doing that he wasn’t doing the day before when she was home!
You know more or less that it’s time to introduce signs when your baby’s eyes begin to connect with yours. Newborns can’t see very clearly, but their vision improves all the time. So too does their longer term memory. Without a decent memory, signs can not be recalled for later. When your baby and you are able to share attention on an object, any object, you can introduce a sign for it. It will “stick” when your baby has both “receptive language” and “expressive language.” These are two entirely different things. Receptive language just means that your baby can hear a word and know what it means. Expressive language, means that your baby can say the word on their own – express it. You know your baby is getting close to signing when he or she understands what a word means.
There is an easy way to test this out. After you have said and signed the word for MILK by example for some time, place a cup or bottle of milk where your baby can see it, but away from you. To really test it, put it on the floor and leave it for a few minutes. Then sign and say the work MILK so your baby can see and hear you. Does your baby’s eyes drop to the milk? That means your baby understands the word. This means your are well on your way to hearing back from your baby in an expressive sense. Just continue signing and saying the word and soon enough your baby will sign back.
With time, your baby will begin to express all sorts of needs and desires. He will also strike up new conversations. When your child reaches about 20 months of age, he will also begin to recall things that happened the day before, or even the week previous. As your baby grows, he’s long term memory will grow too and he will add signs at an ever growing and increasing rate.