A difficult topic because I dont think there is a single cause linked to a single effect.
The naughtiest children I have seen in school are those who have no discipline at all at home. However I would say the most agressive children I have seen are those that are disciplined at home with shouting and violence.
I still think smacking a child should be a last resort. I wouldnt rule it out completely, but I certainly would NEVER use it like an everyday thing, like it was used on me.
In fact I was thinking about this the other day, every time we went to the meeting when I was a kid I got taken to the back room and spanked. I wasnt a naughty kid at all. I used to get smacked for wriggling, or turning round and looking behind, or for drawing things instead of taking notes (this from the age of 4 mind you!). I was thinking how is giving me a smack every time I go to a meeting supposed to make me love jehovah??
I think all this smacking caused a great deal of anxiety in me that came out in nail biting, bed wetting, picking and scratching all the time to make myself bleed, and being very highly strung. Later in life I was a terrible flirt, and I think I was looking for some kind of positive regard, not this constant conditional regard based on my performance in the truth. (of course I was too young to work out this new attention was only based on my huge chest and big blue eyes). It was intoxicating to think that men just liked me for doing nothing inparticular. I was always in trouble for teenage flirting with workmen and people I met on holiday. I was too innocent to realise they wanted sex. I remember going for a walk once on holiday with a man twice my age (14 and 28) and being genuinely suprised when he took me to the beach and tried to get my clothes off. I was lucky he let me walk away in a huff, he must have thought I was a simpleton. I gave a 40 yr old man our home phone number once because I didnt know how to say no, then had to get my dad to tell him to stop phoning me up. I was 15. I had no idea he fancied me, I just thought he was being 'friendly'! Later on in life it affected my marriage this constant seeking attention from as many people as possible.
I know that seems like a very thin connection to smacking, but I think the constant anxiety of being smacked if I wasnt good enough, and also the weird dissonance of being smacked and told it was love ( and I was on about 2 a day!) caused a massive need and desire for positive attention and (what I thought was) love.