Sally's husband was often abusive. One morning, over breakfast, Hank began yelling at her because she was on the phone instead of keeping him company. Later, after Hank went to work, Sally picked up his shirts from the laundry, ran some other errands for him, and decided to cook his favorite dish for dinner.  Do you think Sally did the right thing?

Sally, alas, believed that if she could only create an ideal loving home atmosphere, her husband's abusiveness would stop. Unfortunately, she was in fact rewarding her husband's negative behavior. In response to his outbursts, Hank found his chores done for him and he was served his favorite dinner. Why would he change his treatment of his wife when she responds so positively?

The events that follow an action will weaken or strengthen the likelihood it will occur again. In behavioral psychology, this is called the "Law of Effect" and states that behavior varies as a function of its consequences.  Hence, if Sally is nice to Hank when he treats her badly, she is teaching him to continue being abusive. By putting up with Hank's abusive behavior, Sally gives him the message that it's okay to treat her that way. If she showed him instead that she was willing to be especially kind and helpful only when he was considerate and loving, a positive pattern would be more likely to develop.