The fact of the game never ending is what made the choice too easy, you're right.
EDITED
For this study you want sociopathy, not psychopathy. I can report from my wasted psych degree that sociopathy occurs in 1-2% of the population.
Binary probability tells us that if you repeat a 1% chance test 32 times, you have a 95% chance of never seeing it.
Don't pull the lever. Sorry for the ninja edit, I misread something.