Happiness is the resultant of the relative strengths of positive and negative feelings rather than an absolute amount of one or the other. ~Norman Bradburn
Positive Reinforcement VS Bribery
Some parents mistakenly associate positive reinforcement with bribing or giving material rewards. In bribery, you promise something bigger and more valuable than the behavior you are expecting. You also tend to negotiate or beg, even increasing the value of the prize, just to make sure that the behavior you wish is manifested. Giving a child verbal encouragement or small tokens after they exhibit a certain desirable behavior does not qualify for bribery.
Other parents steer clear from positive reinforcers for fear that they might spoil their child. However, it is far from spoiling if the reward given is commensurate to the positive behavior exhibited by the child. Material rewards need not be expensive things; small tokens like stickers or erasers are hardly decadent. Non-material reinforcers are highly recommended: a hug, a wink, and a compliment for a job well done.