I notice on occasions that once a decision is made and the corresponding action is somehow sufficiently initiated I can't stop myself even if I suddenly realise I really want to perform a different action. If the button I have decided to press lights up long enough before I actually start pressing it then I guess I will be able to stop myself but if the device waits to light the button until the last moment just before the initiating of the action then it'll be too late. But this is where I think some scientists may have their interpretation wrong.
EB
Why would the device wait? If the result is determined by prior factors such as brain state, environmental conditions, and so on, then it will know what you're going to do well before you do it, in plenty of time for you to press either button. Indeed, if your decision to press is determined, that decision must come before your action to press, with enough time for you to initiate either action.