This is the project for **The effect of opportunity costs on mental fatigue in labor/leisure tradeoffs** The project contains one folder for each of the 4 studies. The folder for each study further contains up to 4 folders. **Analysis and results** contains the analysis script as well as the entire workspace for the study. For Study 2, there is an additional file reporting the preregistered analyses omitted from the manuscript. For Study 3, there is an additional file reporting information related to the assigned leisure tasks in both treatments. **Data** contains the data files for the study. For Study 1 and 2, these are the raw behavioural data and the ratings provided at the end of the study. For Study 3, there is an additional file for the ratings provided by each participant for the 6 leisure tasks before the study and a file containing the activity that was assigned to each participant. For Study 3, there is one more file containing the ratings the students in the lecture provided for the 13 initial leisure tasks. For Study 4, there is just one file containing all of the collected variables. **Materials** contains all the files that are needed to run the experiment (i.e., the python script, the stimuli, the instructions, etc). Many of these files are identical for the studies. To make it easy, I uploaded the files so that each materials folder contains all needed files (even those that are duplicates). **Power simulations** contains the power simulation script and workspace. For Study 1, it additionally contains the raw behavioural data and ratings from the pilot study (because in Study 2 [3] we used the data from Study 1 [2] as starting point, which can be found elsewhere)