Jon Peirce is responsible for the creation of the bulk of the code in PsychoPy. The project arose out of his belief that programming psychophysics could, and should, be easier. If you use PsychoPy please acknowledge his efforts by citing one of the papers describing the library:
Psychtoolbox had already done a huge amount in making things easier, but was tied to Matlab which I find overly expensive and not as clean as Python. Also Matlab doesn't have a proper wrapper around OpenGL, so writing the equivalent code would require a great deal of C source as well which I didn't relish :) Nonetheless, PsychToolbox was a big influencing factor in the way PsychoPy was written. Thanks David Brainard, Denis Pelli and Mario Kleiner for that.
PsychoPy depends a great deal on the rest of the open-source community, people that give a great deal of time to making free software for you. You should be very grateful to them! PsychoPy has made use (directly or indirectly) of numpy, scipy, pyOpenGL, pygame, pyglet, matplotlib, wxpython, pyserial, pymedia, visionegg, and I'm sure there are more. Various members of the PsychoPy community have also contributed code, such as Konstantin Sering, Gary Strangman, Luca Citi, Yaroslav Halchenko
Thanks also to the University of Nottingham and the BBSRC for their support of the project.