why my child age 3yr is spitting at others

my daughter age 3yrs, very intelligent but newly got a habit of spitting in house and at school, at school she spitts on her table and cleans with rubber and at home she spitt on roof and at me and on her mother and on her younger sister.what to do  to remove this habit and what are the symptoms of this habit? please help me out  

[Richard B. Graff, PhD, BCBA-D]

Many problem behaviors in young children are learned behaviors.  There are several different possibilities as to why a 3-year-old may learn to spit-- for example, she may do it because she has learned that spitting gets attention form adults or other children.  It is also possible that she may do it to avoid doing things she doesn't like.  For example, at dinner you might ask her to eat her vegetables, but if she spits at you, you might then tell her that she doesn't have to eat them.  If something like this happened, she might learn that spitting gets her out of doing things she doesn't want to do.  Finally, it's possible that she enjoys the physical stimulation of spitting and then cleaning it up.

It's not possible for me to know why she may be doing this, but there are several things you should think about so you can try to figure out why she is doing it. First, ask yourself when she is doing it.  Is she more likely to get it when she is getting attention, or not getting attention.  when she spits, is she doing something she likes doing, is she doing something she doesn't like doing, or does she spit when she is not doing other things?  Most importantly, what do YOU do when she spits?  Do you give her attention by telling her not to spit?  Do you ignore her?  Do you give her a toy to play with?  What you do will give you some clues as to why she might be doing this.  For example, you if give her attention when she spits, give her attention when she is NOT spitting, and try to ignore the spitting.  If she gets out of doing things she doesn't like to do when she spits, son't let her, but teach her to ask appropriately to end that activity.  problem behavior such as spitting serve a function--you just need to try to figure out what it is, (attention, avoidance of nonprefered activities, access to stimulation), and provide those things before she starts spitting.

Best of luck.in the future!