Alfie Kohn, a former teacher and current educational critic and speaker, states in his book "Punished by Rewards" that offering rewards for specific behaviours, such as making good grades, is a form of manipulation that wipes out the potential for actual learning. Rewards systems may seem to work well for influencing learners, but many disadvantages exist that can compromise the goal of learning.
Abandonment of Learning
When someone offers a learner a reward to complete a task, the learner likely completes it because he wants the reward -- not because he wants to satisfy his internal curiosity. If a student does not derive something internally satisfying from a learning experience, once the external reward is removed, she will likely abandon the behaviour.
If an educator leads a learner to believe that learning reaps tangible rewards, then learning for the sake of learning loses its value. Students often will take the easiest path to success, such as rote memorisation of parts of a topic instead of trying to connect concepts and advance their knowledge. This diminishes the value of education, making learners feel as if it isn't worth doing without a reward.
Learners who regularly receive rewards for achieving set learning goals will eventually come to expect and even demand those rewards. It may even become an issue where students motivated by rewards systems want a reward for each task they complete. Eventually, the rewards become unsatisfactory over a period of time. Then, the educator is tasked with finding new and different rewards to entice the learners.
Not all learning experiences prove interesting. Educators should strive to find ways to improve the content of the educational material so that learners can experience internal, not external, motivation. If educators consistently turn to rewards systems for learners, instead of trying to make the content as interesting and motivating as possible, the students will miss out on valuable learning opportunities because they will focus on the reward. Instead of focusing on the reward, students could focus on interesting and engaging content that will serve as the basis of learning motivation.