I've held on to a kindergarten memory that has had me confused until Psychology 1001 came into my life. I'm ashamed to admit I still have this memory, but the situation was distressing enough to stick. As a kindergartner, I was shy and well behaved. I had a classmate, Kyle, who was impulsive, loud and disrupted class frequently. Our teacher had a reward system know as "A pat on the back" that would go to the best behaved student that week. These "pats on the back" were the bees knees with special, pretty paper and a "give yourself a pat on the back" written on the paper hand. I now know why I NEVER got one and Kyle received one almost every other week.
My teacher was practicing positive reinforcement. She would present a pleasant stimulus, the pat on the back, to Kyle when he was acting the way she saw acceptable. She was encouraging him when she saw he was behaving. I on the other hand was always behaved and she didn't find reason to shape my behavior. I believe my teacher was also using the idea of variable ratio schedule. Instead of reinforcing the good behavior every time Kyle performed it, she did it randomly after an average number of good behavior, not after a fixed time or fixed number of good behaviors. This way, Kyle was constantly on edge, not knowing when the teacher was watching or noticing his bad behavior, making him behavior better for longer to get the "pat on the back". Ratio schedules have been found to be more effective and consistent than interval schedules due to the anticipation of random reinforcement.