Cognitive load is induced throughout the treatment with Stroop tasks. There are three difficulty levels, baseline, congruent and dissimilar. In the baseline Stroop tasks, subject are presented with a name of a color, written in letters of that same color. To the right of the word there is a bullet where the name of the color, again, is written. Subject should simply choose the bullet to successfully complete a baseline Stroop task. In the congruent Stroop tasks, subjects are presented with a name of a color, written in letters of that same color. To the right of the word there is a list of six bullets, each representing a color. The subject should choose the bullet that corresponds to the word on the left. In the dissimilar Stroop tasks, subjects are presented with a name of a color, written in letters of a different color. To the right of the word there is a list of six colors. The subject should choose the color that corresponds to the color of the letters of the word on the left.
All subjects perform all tasks, time perception, time preferences elicitation and numeracy tasks with all three types of Stroop tasks (in a group of 2, 3 or 4 tasks at the time) generating a disturbing cognitive load.
In the time perception task, Stroop tasks are solved during the interval that is to be estimated. In the time preferences elicitation and the numeracy tasks, the screen is divided in two. The multiple price list/multiplication task appears on the left side while on the right side Stroop tasks (2, 3 or 4 at the time) pop up randomly (arrival determined by a poisson process).
The design is within-subject. Hence all subject do all tasks with all three levels of cognitive load.
Time perception is measured over three intervals. A random number between 7 and 12 seconds, a random number between 13 and 18 seconds and a random number between 19 and 24 seconds, all intervals with all three levels of cognitive load induced by Stroop tasks.
Time preferences are measured using a double multiple price list. There are 4 different versions of the MPL in terms of time: today vs. in one week, today vs. in three weeks, in one week vs. in three weeks and in three weeks vs. in six weeks. For each of the four time schemes, there are two versions of the MPL, one with a larger range than the other. In order to control for changes in concavity of the utility function as cognitive load increases, risk preferences are measured using MPL in the baseline Stroop condition and the dissimilar Stroop (high cognitive load). Here also, are two lists of different range presented in each of the two Stroop conditions.
Time preferences, time perception, performance on numeracy tasks and future time perspective are measured under two levels of arousal induced by external tempo generated by a metronome (in headphones).
The method for measuring time and risk preferences and numeracy are the same as in treatment 1, except that there is now no Stroop tasks popping up, instead, subjects listen two tempo of either 120 Bpm or 165 Bpm in headphones while solving the tasks.
Again, the design is within-subject, hence all subjects perform all tasks with both high and low tempo.
In order to avoid counting time during the time perception task, subjects solve a series of baseline Stroop tasks during the time intervals that are to be estimated.
The future time perspective is measured using a scrambled sentence task. Under time pressure the subject have to unscramble words and form sentences. In all tasks, one can either construct a future oriented sentence or a present oriented sentence. The share of future oriented sentences is the subjects measure of future time perspective. All subjects do two versions of the future time perspective task, one with 120 bpm in the headphones, the other with 165 bpm in the headphones. Which version is coupled with which beat is randomized.
For both treatment 1 and treatment 2, the order of tasks is randomized for each session.
Finally, at the end of the session, subjects are asked to estimate how long the experiment has taken.
Background questions that will be collected are individual information (age, gender, income, family status), self-reported attitudes towards risk preferences, time preferences and future time perception.