"The science also shows that corporal punishment is like smoking: It's a rare human being who can refrain from stepping up from a mild, relatively harmless dose to an excessive and harmful one. Three cigarettes a month won't hurt you much, and a little smack on the behind once a month won't harm your child. But who smokes three cigarettes a month? To call corporal punishment addictive would be imprecise, but there's a strong natural tendency to escalate the frequency and severity of punishment"