Vincent De Gardelle

Many studies report that following feedback, individuals do not update their beliefs enough (a conservatism bias), and react more to good news than to bad news (an asymmetry bias), consistent with the idea of motivated beliefs. In the literature on conservatism and asymmetric updating, however, only one prior study focuses on judgments on absolute performance (Grossman & Owens, 2012), which finds that belief updating is well described by the Bayesian benchmark in that case. Here, we set out to test the replicability of these results and their robustness across several experimental manipulations, varying the uncertainty of participants’ priors, the tasks to perform, the format of beliefs and the elicitation rules used to incentivize these beliefs. We also introduce new measures of ego-relevance of these beliefs, and of the credibility of the feedback received by participants. Overall, we confirm across various experimental conditions that individuals exhibit no conservatism and asymmetry bias when they update their beliefs about their absolute performance. As in Grossman & Owens (2012), most observations are well-described by a Bayesian benchmark in our data. These results suggest a limit to the manifestation of motivated beliefs, and call for more research on the conditions under which biases in belief updating occur.

In perceptual decision making, it is often found that human observers combine sensory information and prior knowledge suboptimally. Typically, in detection tasks, when an alternative is a priori more likely to occur, observers choose it more frequently to account for the unequal base rate but not to the extent they should, a phenomenon referred to as “conservative decision bias” (i.e., observers do not shift their decision criterion enough). One theoretical explanation of this phenomenon is that observers are overconfident in their ability to interpret sensory information, resulting in overweighting the sensory information relative to prior knowledge. Here, we derived formally this candidate model, and we tested it in a visual discrimination task in which we manipulated the prior probabilities of occurrence of the stimuli. We measured confidence in decisions and decision criterion placement in two separate experimental sessions for the same participants (N = 69). Both overconfidence bias and conservative decision bias were found in our data, but critically the link that was predicted between these two quantities was absent. Our data suggested instead that when informed about the a priori probability, overconfident participants put less effort into processing sensory information. These findings offer new perspectives on the role of overconfidence bias to explain suboptimal decisions.

The unified model of time processing suggests that the striatum is a central structure involved in all tasks that require the processing of temporal durations. Patients with Huntington’s disease exhibit striatal degeneration and a deficit in time perception in interval timing tasks (i.e. for duration ranging from hundreds of milliseconds to minutes), but whether this deficit extends to time production remains unclear. In this study, we investigated whether symptomatic patients (HD, N = 101) or presymptomatic gene carriers (Pre-HD, N = 31) of Huntington’s disease had a deficit in time production for durations between 4 and 10 s compared to healthy controls and whether this deficit developed over a year for patients. We found a clear deficit in temporal production for HD patients, whereas Pre-HD performed similarly to Controls. For HD patients and Pre-HD participants, task performance was correlated with grey matter volume in the amygdala and caudate, bilaterally. These results confirm that the striatum is involved in interval timing not only in perception but also in production, in accordance with the unified model of time processing. Furthermore, exploratory factor analyses on our data indicated that temporal production was associated with clinical assessments of psychomotor and executive functions. Finally, when retested twelve months later, the deficit of HD patients remained stable, although striatal degeneration was more pronounced. Thus, the simple, short and language-independent temporal production task may be a useful clinical tool to detect striatal degeneration in patients in early stages of Huntington’s disease. However, its usefulness to detect presymptomatic stages or for monitoring the evolution of HD over a year seems limited

The study of individual differences in rational decision-making has led to two close streams of research. While the study of scores to the Adult-Decision Making Competence (A-DMC) tasks has provided evidence in favor of a general decision-making competence (DMC) factor, studies investigating individual differences in performance on heuristics and biases tasks have challenged a one-factor model of rationality. Assuming that heuristics and biases are part of DMC and considering that the A-DMC assesses just a few of them, the aim of the present study was to test whether a general DMC factor still emerges when adding four heuristics and biases tasks to the six A-DMC tasks, while ensuring satisfactory levels of score reliability. Exploratory factor analyses revealed that while performance on the A-DMC tasks can be reasonably aggregated into a general DMC measure, a two-factor model provided the best statistical and conceptual fit of the 10 tasks combined, the two factors reflecting Mindware gaps and Contaminated mindware.