When John Thomas Neubauer of Lombard, IL, was 20 months old, he could stack cups into towers, do simple puzzles, and listen to stories attentively. But he didn't talk, and that worried his mom, Julie, since she noticed other children his age already could.

Kids who are John Thomas's age and who don't say a word, or 2-year-olds who say fewer than 50 words, are considered "late talkers." About 10 percent of toddlers are, says Maura Moyle, Ph.D., assistant professor of speech-language pathology at Marquette University in Milwaukee. About half catch up on their own  -- like John Thomas  -- and those kids often are:

Boys. They're three times more likely to be late talkers than girls, perhaps because they often focus on learning one skill at a time.

Preemies. They may need time to catch up.

Twins. Some experts think they communicate so well with each other without words that they catch on to speaking later.

Toddlers with talkative older siblings. They might find that they don't need to talk.

Speak directly to these kids  -- but don't use questions to prod them to speak. Saying words is a better way to teach language.

It can be difficult to know if your child is late to talk for one of these reasons or because of a hearing or cognitive problem. You can have him checked out, especially if any of these issues apply:

* You know your family has a history of speech problems.
* Your child doesn't interact well with you.
* He hasn't said a single word by 18 months.
* He doesn't seem to understand you.
* He doesn't babble or, if he does, doesn't use consonant sounds.
* He's had persistent ear infections.

Your child can get a free early-intervention evaluation under the Individuals with Disabilities Education Improvement Act. To find a specialist, ask your pediatrician, or call your local school district or a hospital's pediatrics department.