I remember a while ago, there was a thread about corporal punishment, and in it some people got into a rather heated debate about spanking kids. At one point someone pulled the 'studies show' card, saying that it's ineffective, and someone else asked for specifics.
Well, the Yahoo! main page has an article about it right now, taken from Time::
http://news.yahoo.com/s/time/20100412/hl_time/08599198101900I haven't looked up the actual primary articles they're citing, but it's interesting. Especially to me, since I've always been in the 'a little spanking is ok' camp, though I don't plan on spanking my future kids. I may change my tune.