According to the initial plan, the work performed during this shortened MSCA fellowship (8 months) mostly investigated questions related to the first objective (WP1). This resulted in several important developments.
1. The idea that two competing strategies (value-based and heuristics) might contribute to the final behavior has led the applicant to investigate the notion of Mixtures in Value-Based Decision-Making. This has taken the form of a collaboration with Dr. L van Maanen at the host institution, who develops methodologies to assess and test the presence of such mixtures. While adapting those methodologies to preference-elicitation tasks, important developments have been undertaken, which resulted in a methodological paper, published in PLoS one:
REF: van Maanen, L., Couto, J., & Lebreton, M. (2016). Three Boundary Conditions for Computing the Fixed-Point Property in Binary Mixture Data. PloS one, 11(11), e0167377.
2. A modified version of the main experimental test (initial proposal Part B - Section 2.1 - WP1) has been designed, and piloted. Data has been collected, the results are currently being analyzed, and a manuscript is under preparation. Preliminary results seem to reveal that individuals indeed implement heuristics, by increasing the decision-weight on their default-option. The manuscript will be uploaded on the preprint server when written, and will be submitted to an international peer-reviewed journal.
REF: Couto, J., van Maanen, L., Lebreton, M. (in prep). Investigating utility vs heuristics processes in value-based decision-making.
Ancillary projects: In addition, the applicant has contributed to the following project
1. The idea that people may use simple rules is not restricted to preference elicitation tasks, and can be applied to other decision situations, like in reinforcement –learning tasks. In a collaboration with Dr. S. Plaminteri, the applicant contributed to show that some individuals focus on positive reinforcements and tend to ignore negative reinforcement, generating an optimism bias. T
REF: Lefebvre, G., Lebreton, M., Meyniel, F., Bourgeois-Gironde, S. & Palminteri, S. Behavioural and neural characterization of optimistic reinforcement learning. Nature Human Behaviour. 1, 0067 (2017).
2. As mentioned in the initial proposal (Part B - Section 4.2) the applicant has leveraged the current framework to investigate the topic of “neuro-computational heterogeneity in value-based behavior”, i.e. brain-behavior individual difference. A first output, written as an important conceptual and opinion piece, has been uploaded on biorXiv, and is currently under review at international peer-reviewed journal.
Lebreton, M., & Palminteri, S. (2016). When are inter-individual brain-behavior correlations informative? bioRxiv, 036772.
All those results have been communicated using various media: published articles in international peer-reviewed journals, draft manuscripts uploaded on open access preprint servers (biorXiv), posters at conferences (Annual Meeting of the Society for Neuroeconomics 09/2015 Miami; Annual Meeting of the Organization for Human Brain Mapping 06/2015; Symposium on the Biology of Decision-Making 05/2015), invited talks at symposium (e.g. 2016 - Amsterdam Brain & Cognition Symposium), and invited talks at different labs.
