Students may learn their course material for different types of motives: because the material is interesting or because they aim at a good grade. A common intuition is that performing tasks because they are interesting (under intrinsic motivation) requires less effort than performing tasks because they are instrumental for obtaining some benefits (under extrinsic motivation). Yet, this notion is not incorporated in current effort allocation models, which were developed in the context of instrumental behaviour.
These same-cost models would consider intrinsic and extrinsic motivation as targeting two types of rewards through the same kind of effortful process. Here, we introduce a different-cost model, in which intrinsic motivation improves task performance by providing effortless direct drive, whereas extrinsic motivation improves performance through the exertion of effortful cognitive control. We tested the predictions of this model across a series of behavioural experiments, during which volunteers (n = 147 in total) memorized lists of information, with various levels of self-reported interest and various amounts of monetary reward associated to correct recall.
Behavioural results indicate that both interest and reward (intrinsic and extrinsic motivation) improve memory performance, with no interaction between the two effects. Computational analyses show that these behavioural effects are best captured by the different-cost model, rather than the same-cost model. Moreover, pupillometry validated the key prediction of the different-cost model: for a similar improvement in performance, increasing interest triggers lesser effort exertion compared to increasing reward.
Together, these findings suggest that working under intrinsic motivation might relax the demand on cognitive effort and help preventing fatigue and burnout syndromes. This work benefited from expertise of the staff (Karim N’Diaye and Gilles Rautureau) attached to the Prisme facility, where all experiments took place. The authors would like to thank Jean Daunizeau for his helpful advice regarding computational modelling.
The study was funded by the Paris Brain Institute and benefited from the Agence Nationale de la Recherche “Investissements d’avenir” (ANR-10- IAIHU-0006) program. J.S. received a PhD fellowship from the Brain, Behaviour and Cognition Doctoral School (ED3C). The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.
Motivation, Brain & Behavior team, Paris Brain Institute, Sorbonne Université, Inserm, CNRS, Pitié-Salpêtrière Hospital, Paris, France Swiss Center for Affective Sciences Campus Biotech, University of Geneva, Geneva, Switzerland Correspondence to Jade Seguin or Mathias Pessiglione. The authors declare no competing interests. Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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