A: Most 3-year-olds test limits and this is, while frustrating, also a natural part of their development. On the other hand, it’s completely reasonable for your son to know what’s expected of him, and it’s completely understandable that it’s getting you upset. The more we pay attention to behavior (wanted or unwanted), the more it’s reinforced. Unfortunately, when we react to things like screeching or spitting, we may be inadvertently increasing the likelihood that it will happen again. When diaper changing, try giving your son a job (eg “Can you hold this for me?”). Also I would turn your head away when he is doing unwanted things that can be ignored and give him lots of specific praise when he behaves (eg “Thanks so much for being still when I changed your diaper.”). Taking away toys may make sense, but it may not have the intended effect—he probably forgets about the toy quickly. Immediate reinforcers like specific praise for desired behavior and even small rewards (eg stickers) might help. For example, tell him that if he can be a good listener and be helpful when brushing teeth, he can get a sticker—and when he gets a few stickers, he can get a prize.