Participants are asked to attend two experimental sessions, approximately one week apart. During both sessions, they are asked to complete incentivized pairwise choices between different snacks, four healthy and four unhealthy. They are then asked to state the minimum payment they would need to be offered to not enter two effort tasks: 1) a real effort task; 2) a cognitive effort task [only in the second session]. The real effort task consists of two parts: two minutes of a slider task, in which participants are required to move as many sliders as possible to a specified position; and two minutes of a counting task, in which participants are asked to count the number of zeros in several matrixes of zeros and ones. Finally, they are asked to perform the real effort task, unless the minimum payment they require not to complete the real effort tasks is lower than 1 cent. In this case, participants will receive 1 cent and not complete the real effort task but will read a short text.
Using a 2x2 experimental design, the decision environment is exogenously varied between participants as well as between the first and second sessions attended by each participant. First, participants are assigned to complete an incentivized cognitive task aimed at inducing mild stress, either at the beginning of the first or the second session they attend. The stress task was adapted from a previous experimental study (Vitt et al., 2021) and has already been tested and validated using an online experiment (RCT ID: AEARCTR-0005946). This first experimental treatment introduces exogenous variation in the acute stress levels during the two sessions. The second experimental treatment introduces an additional element in the incentive structure for the stress task, a deduction from participants’ pay-off if they perform below an unknown threshold. Before the snack and effort decision-making tasks in the second session they attend, participants receive feedback about their performance relative to the threshold. The threshold level faced is varied by the second experimental treatment. Specifically, participants may face a low threshold level and receive success feedback or a high threshold level and receive failure feedback. This second experimental treatment introduces exogenous variation in perceived success or failure during the second session and has already been tested and validated using an online experiment (RCT ID: AEARCTR-0005946).
Subjects will receive a participation fee at the end of their second session. They will be paid a participation fee, and a varying amount either based on their performance in the stress task or based on their choices in one of the decision-making tasks. Finally, they receive a snack based on one of the pairwise choices in each session.