Q. My 15-month-old isn't talking yet and doesn't play with other children. Could he be autistic?
A. Does he say anything at all, like "Mama" or "Dada" or other simple words? Does he seem to want to communicate -- whether by pointing to things he wants or jabbering away at you in his own language? Does he appear to understand what you say to him -- getting his shoes when you ask him to, for instance, or responding appropriately when you ask him if he wants some milk? If the answers are yes, I wouldn't worry -- just give him some time. If not, or if within a couple months you haven't seen an improvement, talk to your doctor -- though hearing problems or language delays are far more common than autism.
As for playing with other children, 15-month-olds are more likely to play in the vicinity of other kids rather than with them. When considering if a child might be autistic, I look for whether a toddler makes eye contact, smiles at others, responds to his name, and has warm, loving relationships with parents and caregivers. If he doesn't, your doctor can refer him to be evaluated by specialists in child development.