|Color-vision testing gear|
Signing up for such experiment is simple: just google "Universityof Washington Healthy Volunteer" and soon be looking at a page of experiments look for volunteers with particular characteristics.
What participation means varies widely, but it must be descibed to you in great detail so you can validly consent to it. Friday I was involved with an experiment about color vision: there were a half-dozen tasks I performed, including liningup colored disks in a spectrum (photo shown). As a result of this experiment, I learned that my color vision is absolutely normal; there was also a small financial compensation as well.
Earlier this month, I was involved in an experiment studying the mechanism underlying Snow World, a virtual reality game for helping burn victims ignore pain.
I'd suggest everyone with a bit of curiosity check out the possiblity of being a healthy volunteer for science. It can be an interesting process and who knows? you get to contribute to an increase in knowledge!