why spanking doesn't work

I don't often spank Dennis. I've done it less than 5 times in his entire life. Today was one of those times, and today I discovered that it's completely ineffective. He was practicing some of his best "menacing" today, running all over the house and grabbing all kinds of non-kid items and relocating them. I followed him at a jog all morning but couldn't prevent the widespread destruction of our home because his path was unpredictable. I had no idea where he was going to go next. After unloading his drawers and pulling them out of the wardrobe, pouring out all the Legos and Lincoln Logs and cars and trains and train tracks and every other thing that could possibly be used to cover his floor, he ran to the bathroom and flushed the toilet over and over again, then grabbed up the plunger and began plunging to the best of his ability. He ran to the kitchen while I was mopping up water in the bathroom and began systematically emptying the silverware drawer. He pushed the water dispenser button on the fridge and created a big puddle. Just as I arrived on this scene, he ran into the den and climbed up onto the pool table and began rolling balls all around. He got an umbrella and opened it and ran around twirling it dangerously close to our few breakables, and when I grabbed it and put it away, he ran into the front room and emptied an entire bag of cat food onto the dog's bed. This was the last straw and I gave him two little taps on the bottom and told him that emptying out all that food was bad and it made a big mess. The cat, meanwhile, was plastered to the window, looking in at all that bounty and meowing her loudest to try and get in. I scooped up most of the food back into the bag and let the dog take care of the rest. Dennis didn't care one whit about the spanking, but when I said "go to your room" in my sternest Mommy voice, his bottom lip began quivering and he started to wail and he ran into his room crying his heart out. I learned something here. He reinforced it later when we were sitting together on the couch and he spanked my arm and said "Bad, Mommy, that was very bad". So it's Time Outs for Dennis as long as they will work!