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The remainder of the paper is the following. Section 2 surveys the different psychological theories that point out the detrimental effects of extrinsic motivation(s) on intrinsic motivation. In section 3 we present the different ways economists have championed the idea that incentives (positive as well as negative) and monitoring can undermine motivation. Section 4 presents the main critics opposed to the crowding out effect hypothesis. In section 5, we propose a revisited approach of this hypothesis, stressing that the SDT as well as some recent contribution in economics offer some interesting insights. Section 6 gives some concluding remarks. .
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2. Incentives and motivations in cognitive and social psychology. It has been shown in psychology that incentives and motivation are not necessarily evolving in the same way. It is difficult to provide an exhaustive presentation of the literature on this topic. However, Expectancy-Valence Theory (henceforth EVT), Self-Efficacy Theory (SET) Cognitive Evaluation Theory (CET), Self Perception (SP) and Self Determination Theory (SDT) in cognitive psychology are the main different approaches that analyze the relationships between rewards, punishment or monitoring and individual behavior. In social and behavioral psychology, there are also some important contributions on this topic. .
We will present these theories focusing on their conceptions of the relationships between rewards, sanctions or control and behavior and emphasizing the fact that they do not all share the idea that a crowding out effect is something effective, if relevant (see also section 4). .
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2.1. Expectancy-Valence Theory of Motivations .
This theory, developed by Vroom (1964), and extended by authors such as Fishbein (1967), Neider (1980), Porter and Lawler (1968), Campbell and Pritchard (1975) or Pritchard, DeLeo and Von Bergen (1976), is based on the idea that people are goal oriented and that they act on the basis of beliefs and values.