Habits -- patterns of behavior that are repeated -- are common in a child's normal development process. Little kids have annoying habits, such as biting their nails, holding their breath, or picking their nose (or bellybutton). Of course, one of the most common childhood habits is thumb sucking. Thumb sucking probably starts accidentally, when an infant's thumb comes into contact with the mouth during random arm movements. While the thumb is typically the digit of choice, some kids suck multiple fingers or entire fists. So why does a child suck her thumb? Thumb sucking is a learned behavior that results in some sort of positive outcome for the child. She may suck her thumb:

• because of a stressful situation, to soothe and comfort herself
• when she's relaxed, such as before falling to sleep
• because it's associated with pleasurable things from infancy, like feedings and the end of hunger
• to attract attention -- even negative attention -- from parents

Most children stop sucking their thumb without the intervention of a parent, but what about those who don't, won't or can't? Frequent thumb sucking beyond the age of four can result in dental problems, thumb infections, and cruel teasing by peers. If your child doesn't seem to be outgrowing her thumb sucking, try positive reinforcement. Reward her when she doesn't suck her thumb. Praise her lavishly when you notice that she's not doing it. The old habit will not completely disappear until the replacement habit has been firmly established, so be consistent. Most childhood habits do not cause significant problems and improve as kids get older. If you're concerned about your child's habits, talk with your doctor. How did you get your child to stop thumb sucking? Read more:

• Thumb sucking at age 4
• Braces for you
• Serious increase in thumb sucking