I too have heard that these studies are torturous-- which is why they pay so well and why you get the majority of the money only upon completion of the study. A huge number of people drop out before the end. In some sleep studies, for instance, you have to use a bed pan, stay in complete darkness for days at a time, stand staring at a wall for 12 hours, and other similarly unpleasant activities. Believe me, you will earn every penny of that "easy money".