Cognitive Evaluation Theory: This theory suggests that there are two motivation systems; intrinsic and extrinsic which correspond to two kinds of motivators.
Self-Perception Theory: The theory suggests that people develop attitudes by observing their own behavior and concluding what attitudes must have caused it.
Deci Effect: Named after Edward Deci who found through his studies that when money is used as an external reward for some activity, the subjects lose intrinsic interest for the activity.