psiTurk, is an open-source platform which helps researchers develop experiment designs which can be conducted over the Internet. The tool primarily interfaces with Amazon’s Mechanical Turk, a popular crowd-sourcing labor market. psiTurk aims to reduce the technical hurdles for researchers developing online experiments while improving the transparency and collaborative nature of the behavioral sciences. psiTurk provides a Python-based web server and associated JavaScript library for conducting experiments on the web, saving experimental data to a database, and restricting the participant pool according to the experimenter’s needs (e.g., to prevent from repeating a study). It also provides a command-line interface with AMT to create and test new projects as well as to manage and pay participants. Finally, in the spirit of the recent “open science” movement (Open Science Collaboration 2012), it provides an open-source Experiment Exchange for sharing experiments that can be easily replicated and extended by other researchers.