Q. My 2-year-old loves her 11-month-old little sister and will play nicely with her most of the time. At times, however, she gets excited and becomes rough. She recently bit her three times while playing, and she will also try to wrestle her while hugging her and laughing! How do I discipline the rough behavior but encourage the affection and playfulness?

A. You may well be giving your daughter mixed signals about the roughhousing, acting upset on one occasion and then understanding and patient on the next. Your 2-year-old knows what she is doing, and she knows that she is causing pain to the baby. Your reaction, therefore, should be one of stern disapproval, and consistently so. Older sister needs to know exactly how you feel about her rough treatment of her little sister, and in no uncertain terms.

My standard recommendation as regards this situation, one that has solved the problem for lots and lots of parents, is to keep the older child completely away from the baby for a week. During this time, set a perimeter of approximately 10 feet around the baby and forbid the older child from entering that "safe zone."

Without communicating anger, make it clear to your toddler that this new rule exists because she hurts the baby when she plays with her. You cannot mince words about this. After a week of quarantine, begin to allow brief, supervised sessions where the 2-year-old can interact with the baby, first touching, then holding, and so on.

The week of deprivation causes the older child to want to be with the younger one, and she will figure out what she has to do to accomplish that. Over the next week, you gradually allow more and more interaction. If, however, the roughness starts again, you go back to square one. My experience is that within a week or two, the problem is solved.

Q: I have recently assigned dish-washing in the evening to our 3-year-old. He's quite capable of doing the job, the only problem being that he gets easily sidetracked. He quickly becomes caught up in some elaborate fantasy involving soap, water and the dishes. As a consequence, it takes him a long time to get the three plates, cups and silverware washed. I don't feel quite right punishing him, but I do tell him that he used up all his after-dinner playtime doing his chore and now it is time for bed. Will he get the hang of this in time, or should I do something different?

A. First, congratulations are in order. You are one of a dwindling minority of parents who actually believe that young children are capable. Most parents today think their children are gifted, but treat them like fools. You have proven that not only can 3-year-olds be trusted to do basic household chores, but also that there is hope still left in the world.

As for the "problem" of his imagination getting in the way of his focus, a child's imagination is in full flower during the fourth year of life. Three-year-olds can easily become lost in their imaginings no matter what they're doing. Since imagination is the root of all creativity, not to mention fun, I encourage you to be content with the fact that he eventually finishes his chore.

The fact that he's used up most of his evening by the time he finishes is of no consequence to him, by the way. After all, he's just had more fun than adults can imagine. Sometimes, one encourages growth in a child by simply staying out of it.

Family psychologist John Rosemond answers parents' questions at www.rosemond.com.