A few years ago I was on a train, traveling home from London, when I observed a mother with her children as they got on the train. One of them was misbehaving. The mother raised her voice and told the child that unless she behaved, she would be left there - alone on the station. They then boarded the train and sat close to where I was in the carriage.
A few minutes later, I heard the same mother proudly telling her neighbour that she never smacked her children because she thought it was wrong. It taught them violence - and violence wasn't the answer. It was clear from her language that she thought anyone who did smack their children was morally deficient.
Which leaves me wondering: does a slap on the wrist - clearly linked by explanation with the child's disobedience - cause more or less psychological damage than believing that bad behaviour will cause your mother to abandon you in the midst of a strange and hostile world?