With habits, as with many child health issues, there's a fine line between normal development and something that requires attention. While habits are normal, a tic might be a symptom of a health problem. So how do you tell them apart? For starters, a habit is more of a behavior or practice, while a tic is a repeated contraction of certain muscles and can't be voluntarily controlled much of the time. Most tics last for less than a year, but they affect up to 20 percent of kids -- boys much more frequently than girls. Sometimes tics come in the form of muscle patterns (excessive blinking, for example), and sometimes they can be verbal (the child making a certain sound over and over). After the age of two or three, echolalia -- when a child repeats sounds made by another person -- can be a sign of autism, Tourette's syndrome, or another disorder. However, it's quite normal for kids to repeat babbles and words earlier on, when they're starting to put words together.