Nearly all babies who are signed to consistently will eventually sign, except for severely challenged babies and if you have concerns you should consult a local professional to rule this out. Only 1 out of 10 children have any sort of speech or language delay, but while rare, if you suspect that your baby is one of them, then please consult a speech and pathologist, for a professional opinion.
Most of the time baby not signing is due to either inconsistent signing or going for long stretches without signing to them. Taking long stretches without signing teaches to a baby that what they say may or may not be heard by the parent. If you do sign consistently and are following all the rules, then maybe your baby isn’t as talkative as other babies. Just like adults, some babies are introverted and others are extroverted. Introverted babies will tend to ponder things longer, will be shy around other people, especially adults, and will tend to keep to themselves. These babies will do well on their own, and not need to express themselves overtly preferring to think rather than act. As mentioned several times throughout the book, some babies will reduce signing when working on a milestone like crawling or walking. As soon as they have mastered this task all of the sudden they will begin to sign again. Other babies need more time to “get it” so be patient and continue. Other times, signing is erratic or inconsistent, again don’t worry, this can happen and in time your baby will catch up and sign more regularly.
If you think your baby should be signing, but isn’t, and you are only doing a few signs, then add even more signs and let them choose which signs are of value to them. Ramp up your efforts and sign more throughout the day, enlist the help of others, and tell them your goals so they can help. You should also turn signing into a priority by making sure it is done before, during and after the activity. Be sure to sign at least 20-30 times each day and really listen to your baby to discover their motivating signs. Focus on introducing these new signs, perhaps replacing old ones they haven’t picked up yet. Babies can have some pretty odd interests, so watch for things that seem to bring them amusement.
Finally, maybe your baby really is signing, but you’re so stressed he isn’t that you’re missing them! Watch your baby closely; sometimes even a very small movement is a sign even though it doesn’t look exactly how you’ve taught it. A lot of signs look confusingly similar and a lot of signs are also difficult for a baby to do perfectly so watch for micro-movement as clues. Maybe you are expecting signs to look too perfect from the start so aren’t looking for the right things. If your baby signs and you don’t encourage it with praise, they aren’t going to continue. Make sure you find those first attempts and make a big deal about them!