T he AMA recently published a study indicating that spanking might work in the short run, but it appeared to be associated with increased aggressive and anti-social behaviour on the part of the spankees. Habitual spanking is a likely indication that the parent or child or both are out of control.
Most medical studies have control groups that get placebos.
All kinds of people with various or no credentials have advice on raising children and parents pay more or less attention to the alternative notions. I recall a young couple who were intimidated by their toddler who could sustain an all night fit if he was not allowed to sleep in the bed with them. I don't know how the child turned out, but it is significant that he was an only child. I have known couples who tried to rely solely on reasoning with their offspring and ended up with bright children who delighted in quibbling with them continually over everything and often winning the argument when they should not have. Other parents can also frequently be smug about what you may or may not be doing right or wrong.