Similar situation, with some added information. Everyone on earth who is capable of reading and thinking about the choice must push either a red button or a blue button - no babies will be given buttons! Everyone's buttons magically appear before you, all at the same time, and you're each shut off from everyone else until you push one or the other of the buttons. You're unable to discuss the matter with anyone else, and you can't see what anyone else has chosen; you're completely ignorant of everyone else's actions.
Anyone who is incapable of understanding the questions or is cognitively incapable of making an informed choice will live, regardless of the outcome of the button-pushers.
If less than half of the candidates push the blue button, everyone who pushed the blue button will die. If more than half of the candidates push the blue button, all of the candidates live.
Which button do you push?