I get the point that people may prefer external stimulation to internal thoughts. But I think the result of this study hinge on whether the electric shock was really all that unpleasant. For safety reasons, I'll assume the shock wasn't large enough to be harmful or create anything but a momentary sensation. People are curious, and it would seem a fairly safe environment. What's to stop them from simply experimenting…
Probably the worst was one I didn't expect, I slipped when opening a plastic case and caught my fingers over a fully charged high capacity 350v capacitor. The initial hit makes every muscle in your body hurt, then a wave of panic when you realize you could have died from the moment of stupidity.