Julie Rosaz

Updating beliefs with imperfect signals: Experimental evidence

We conduct an experiment on individual choice under risk in which we study belief updating when an agent receives a signal that restricts the number of possible states of the world. Subjects observe a sample drawn from an urn and form initial beliefs about the urn’s composition. We then elicit how beliefs are modified after subjects receive a signal that restricts the set of the possible urns from which the observed sample could have been drawn. We find that this type of signal increases the frequency of correct assessments and that prediction accuracy is higher for lower levels of risk. We also show that prediction accuracy is higher after invalidating signals (i.e. signals that contradict the initial belief). This pattern is explained by the lower level of risk associated with invalidating signals. Finally, we find evidence for a lack of persistence of choices under high risk.

Quitting and peer effects at work

This paper studies the influence of peers on the extensive margin of effort at work by means of a real-effort experiment in which subjects have to decide on the intensity of effort and when to stop working. Participants perform a task alone or in the presence of a peer. The feedback on the co-workers output is manipulated and we vary whether the two workers can communicate. We find that when communication is allowed, the average productivity per unit of time and the quitting time are not increased but the presence of a peer causes workers to stay longer and to quit at more similar times. Peer effects on the extensive margin of effort derive more from a sociability effect, i.e. a reduction of the social distance between co-workers that could make the others presence more valuable, than from performance or quitting time comparisons.

Updating beliefs with imperfect signals: experimental evidence

This article analyses belief updating when agents receive a signal that restricts the number of possible states of the world. We create an experiment on individual choice under uncertainty. In this experiment, the subject observes an urn, containing yellow and blue balls, whose composition is partially revealed. The subject has to assess the composition of the urn and form an initial belief. Then, he receives a signal that restricts the set of the possible urns from which the initial observed sample is drawn. Once again, he has to estimate the composition of the urn. Our results show that, on the whole, this type of signal increases the frequency of correct assessment. However, differences appear between validating and invalidating signals (i.e. signals that either confirm or disprove the initial belief). The later significantly increase the probability to make a correct assessment whereas validating signals reduce the frequency of correct estimations. We find evidences of lack of persistence in choice under uncertainty. The literature shows that people may persist with their choice even when they are wrong. We show that they may also change even if they are right.