From Dr. Misty Hook, PhD, Spanking, Discipline and Physical Abuse:
Hundreds of studies on spanking spanning at least 75 years failed to provide evidence for the assertion that physical punishment improves children’s behavior in the long term (Gershoff 2008). Children who are spanked do not tend to internalize the value their parents want them to get (via the spanking) but instead are merely more likely to understand that they should not get caught.
Thus, the corrective outcome of spanking is short term at best (Larzelere 2000). In fact, one research study that followed children with serious behavior problems found that the children’s behavior actually improved after parents stopped spanking (Webster-Stratton 1990).
Moreover, the research shows that spanking is bad for kids. Spanking makes it more likely that children will be more defiant and aggressive (Taylor et al 2010), that they’ll be at risk for negative outcomes including mental health troubles (Strassberg et al 1994) and that they’re at greater risk for serious injury and physical abuse (Straus et al 1997).
I’ve heard spanking proponents dismiss this research stating that spanking is incredibly difficult to quantify and evaluate. This is definitely true, but even if you don’t believe the spanking research, all you have to do is look at other behavioral research to find corroborating justification for the spanking research conclusions.
Other research has consistently found that punishment is a vastly inferior method of behavior correction and that, put simply, violence begets violence. Per social learning theory, if you see someone use violence as a way to control another’s behavior, chances are you will too (ergo, the Cycle of Violence).
That’s one reason why it’s always astonished me when people use spanking as a way to teach children that they shouldn’t hit. The logical conclusion to that technique is: only hit those who are less powerful than you.