The first paper of Gaia her PhD has been published in Cognition! You can read the full paper here or read a brief summary in this post.

In this paper, we investigate the process of making decisions about future effort investments. We created a task in which we manipulated three objective parameters, motion coherence of a dot motion task, physical effort and reward prediction error all within one trial. Participants were then asked to rate their subjective experience (decision confidence, subjective physical effort, reward satisfaction). Subsequently, participants were asked to decide whether they wanted to repeat the trial during a second session. The analysis revolves around the comparison of two models: one where participants use the objective task parameters and another model where they use their own subjective experience to take this decision for their future effort investment.

As shown in the figure, our results show that participants use their subjective experience to decide on investments for future effort, since the subjective model provides the best fit to the data. Notably, through a mediation analysis, we discovered that the influence of objective parameters (here, objective EVC) on the decision to repeat a trial is almost entirely mediated by the corresponding subjective experiences (here, subjective EVC). 

Finally, we built two hierarchical drift-diffusion models (one with the objective parameters as predictors of the decision, the other with the subjective experiences). Upon comparison, the model including the subjective experiences as predictors of future effort investments was, again, the best fit to our data. Results from this model show an influence of subjective experiences on the accumulation of evidence (drift rate), not on the decision bias (z).