The economic literature attaches great importance to the analysis of “professional motivations”, in particular examining the possible crowding-out effects between extrinsic and intrinsic motivations. This article applies these questions to the healthcare professions with a view to providing a fair scaling of the implementation of pay-for-performance policies by public decision-makers. We assemble a panel of 528 independent general practitioners in the “Provence-Alpes-Côte d’Azur” region in France and provide an inter-personal statistical decomposition between extrinsic and intrinsic motivations with regard to preventive actions. The proportion of intrinsic motivations is relatively greater among physicians paid with fixed fees. The significant effect of age describes a U shape which can be interpreted as being the result of a “life cycle of medical motivations”. Finally, econometric estimations demonstrate a correlation between a small proportion of intrinsic motivation and a feeling of injustice with regard to the reforms. The cross-sectional nature of the data does not allow us to draw any conclusions concerning the direction of the causality. But the above correlation would seem to support the theory that the implementation of a policy based on monetary incentives towards performance is perceived as being offensive and may be accompanied by a reduction in intrinsic motivations in medical practice.