depends on what they mean by "works"
does it stop the behavior? eventually. So does GOYB.
To me the biggest problems with spanking aren't whether or not it "works" but the following: (quick thoughts off the top of my head)
It's lazy parenting. It's easy to just spank at eveything rather than actually problem solve.
It drives a wedge b/w the parent and child. The child isn't going to trust the adult as much b/c they will always be worried about getting a spanking. Any of the PP/GBD/GOYB parenting styles help prevent this b/c they take away punishment.
It doesn't show God to our kids. In spite what people like to say, God does NOT spank us when we misbehave. Natural consequences (which God is pretty expert at) is not the same as spanking.
Spanking drives the kids "underground". The sneakiest kids I've ever known were always spanked.
Spanking does not provide a better alternative to the child for the misbehavior.
It makes the parent feel good and like they are doing "something" so it sets up a false sense of "works". It also leaves no option when it isn't working except to spank harder, more often or for more things.
Finally, people who think it works are going to see that it works b/c that is what they expect, kwim?
---------- Post added at 09:41 AM ---------- Previous post was at 09:40 AM ----------
or what Allison said better and more consicely.