SOURCE : Pediatrics , online April 12 , 2010. sort of amazes me the bs that comes from the mouths of professionals. kids who grew up in the fifties as i did got their butts busted when they did something wrong. i nor any of my friends were bullies , but we got spanked , even in the class room. too little forgiveness , not enough discipline. my mom 's generation , everyone got spanked. so if this is true then everyone back then was a bully.but they aren 't. so if it 's not true then the researchers wouldn 't have seen kids twice as likely to develop aggressive behavior. therefore , the answer is that the level of aggression is so low , that what they measured are very small changes yet two fold relative differences. the contradiction of spanking and aggression is in the scientific interpretation of this data , and not in the history of human behavior .