Do we have autonomy, or are our choices preordained? Computer scientist Scott Aaronson has proposed a variation on the Turing Test that he calls the Envelope Argument or Prediction Game to address the question of free will, Scientific American blogger George Musser reports.

Someone poses questions to you and to a computer model of your brain, trying to figure out who’s the human. If a computer, operating deterministically, can reproduce your answers, then you, too, must be operating deterministically and are therefore not truly free. The output of this game, as Aaronson portrayed it, would be a level of confidence for whether your will is free or not.

Aaronson then posed the question: could a computer ever convincingly win the Prediction Game. The trouble is that a crucial step — doing a brain scan to set up the computer model — cannot be done with fidelity. Quantum mechanics forbids you from making a perfect copy of a quantum state—a principle known as the no-cloning theorem. The significance of this depends on how strongly quantum effects operate in the brain. If the mind is mostly classical, then the computer could predict most of your decisions….