ORCID

Abstract

Value-based decision-making is a complex process that requires the integration of many pieces of information, or decision variables, to choose among several options. These decision variables include the expected value of an option, its associated risk, or the anticipation of the emotions that one could experience when seeing the outcomes of all possible options. In some cases, values attributed to options are learnt from experience, and additional strategies can be employed to refine them. One of them is to use information from the social environment in which decisions are made. Observational learning allows one to learn from observing others making decisions and from the outcome they obtain. However, observing others also elicits additional processes such as social comparison in which one compares its own aptitudes to the ones of others. In two studies, this thesis investigated the neural basis of social decision-making. We used behavioural tasks coupled with fMRI in healthy participants and used decoding analysis methods to refine our approach. To probe the causal role of specific brain circuits involved in social decisions, we used transcranial ultrasound stimulation (TUS). We found that the rostromedial prefrontal cortex (rmPFC) is involved in the integration of decision variables and that the precuneus/posterior cingulate cortex (PCC) is involved in the anticipation of regret, but not in its experience. We also found that social comparison is supported only by posterior brain areas, including the temporoparietal junction (TPJ), the posterior superior temporal sulcus (pSTS), and the precuneus, while observational learning additionally recruits the PCC and more anterior regions, including the rmPFC, the central orbitofrontal cortex (cOFC), and the dorsolateral prefrontal cortex (dlPFC). This work presents new evidence of the causal roles of rmPFC and precuneus/PCC in social decision-making, with a novel high spatial resolution provided by TUS. In addition, this work also disentangles for the first time the neural basis of observational learning and social comparison, two processes that are often confounded in decision-making and learning studies.

Awarding Institution(s)

University of Plymouth

Supervisor

Nadège Bault, Jérôme Sallet, Elsa Fouragnan

Document Type

Thesis

Publication Date

2026

Embargo Period

2026-01-20

Deposit Date

January 2026

Creative Commons License

Creative Commons Attribution-NonCommercial 4.0 International License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License

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