In this project, we investigated the influence of complexity on risk preferences (complexity aversion). The project was preregistered with the OSF template. The data was collected in (1) a lab experiment with undergrads and (2) an online experiment via Prolific. The experiment was programmed in lab.js (https://lab.js.org/) and distributed via JATOS (https://www.jatos.org/). In case of questions, contact the first author via email. Folder contents: Analysis - Analysis Code: Analysis_from_scratch_1.R and Analysis_from_scratch_2.R, can be opened and run in R. - Completed Analysis: output_complexity_1.RData and output_complexity_2.RData, can be loaded into the workspace environment in R. Contains the output of the code in Analysis_from_scratch_1.R and Analysis_from_scratch_2.R. Can be used for quicker access to the results, as the brms analyses take a while otherwise. Data - Data: data_complexity_1.RData and data_complexity_2.RData, can be opened in R. - Data Documentation: complexity_short_documentation_1.xlsx and complexity_short_documentation_2.xlsc contains variable and explanations. Can be opened in Excel and R. Study - Study: complexity_study_1.json and complexity_study_2.json, can be run by loading it on https://labjs.felixhenninger.com/. The matrices task has been removed from complexity_study_2.json as it is copyright protected. It is available on request here: https://www.fernuni-hagen.de/hot-project/ contact: Dr. Timo Heydasch - Instructions: instructions_study_1.pdf and instructions_study_2.pdf contain an excerpt of the study instructions for easier access and can be opened in a PDF reader. - Lotteries: lotteries_study_1.csv, lotteries_study_2c.csv, and lotteries_study_2v.csv contain the stimuli (lotteries) used in the studies in CSV format. 2c contains the choice lotteries and 2v the valuation lotteries (all of the lotteries used in the valuation task are also used in the choice task). Version details: R version 4.0.1, RStudio version 1.3.959, RTools version 4.0