OpenSesame is a free, open source experiment builder based upon the Python programming language. If you know how to use E-Prime already, moving to OpenSesame is very easy. That said, it is very easy to learn, even if you have no experience of using a computer package to create experiments. The video uses the same cat faces experiment as the E-Prime tutorial but if you haven't viewed that video then don't worry - the video begins with an explanation of what the experiment is trying to achieve. You can download the cat face photos used here, and the completed experiment can be downloaded here. OpenSesame itself can be downloaded from http://www.cogsci.nl/software/opensesame.