PsyScope is a program to design and run psychological experiments, used by many experimental labs. It runs on Apple Macintosh computers. It has been developed at Carnegie Mellon by Jonathan Cohen, Matthew Flatt, Brian MacWhinney and Jefferson Provost for Mac OS 9 in the '90s. Thanks to its creators, its code has been made public, under the GNU GPL license. It has been ported to OS X thanks to a collective effort to which several labs kindly contributed. It is now being developed by the SISSA Language, Cognition and Development Lab at Sissa, the RICO group at the Universitat Pompeu Fabra, and many volunteers.

The current version of PsyScope X is an universal program. It runs natively on Intel processors, where it runs I would say pretty well, as well as on on PowerPc machines, where it runs I would say reasonably well — anyhow, better than most of the other commercial programs I know of. Furthermore, Psyscope X can allow you to have a control on several kinds of stimuli (movies, sounds) that other commercial programs running on other platforms cannot give you.