The kind of parental inconsistency that undermines situational rules is accidental inconsistency — where you're too tired, or too busy, or you forget to supervise. Accidental inconsistency tells your son or daughter that you don't really care about the rule, and it encourages children to ignore it, too. So you forget to supervise the room cleaning this weekend and your child “forgets” to do it the next weekend. Accidental exceptions undermine normal expectations.

On the other hand, intentional inconsistency can strengthen a situational rule — when you let the child know in advance that you choose to make an exception due to a special circumstance. Intentional inconsistency shows that this exception “proves the rule.” “Normally you'd have to do your room next weekend, but because you'll be just getting back from your trip, you can wait a week.” The intentional exception puts the child on notice that the following week, chores will be back to business as usual. Intentional exceptions reinforce normal expectations.