I move to problem two. Here is a second problem that all three studies have in common. And it's a problem about the point of no return. So, I have given talks about this sort of thing and sometimes I do persuade people of my first point. That we don't have good evidence that decision or intentions are made at the early times and that they may well be made around 200 milliseconds before muscle motion. Sometimes I hear in response to that. Well okay, so maybe that's right but even so, the point of no return is hit at these early times. Now, the point of no return is a point such that once a process hits it, it's just going to roll on to completion unless there's some kind of special interference. So their claim then is that once the brain gets to that point, in the decision making process, the point of no return has been hit. But that would mean that the point of no return has been hit, before there's any consciousness of a decision, and before there's any real decision. And the thought is, well if the point of no return is hit back there, before conscious deciding, then free will really isn't involved in the production of the decision or the action that executes the decision. That's the claim, so what we want to know now is, is the point of no return hit that early? So, look at the purple box in the diagram and one thing we'd want to know then is whether we have good evidence that, thinking about Levitt's study in particular, that in that box, the point of no return has been hit. Now how would we get evidence of that? We'd want to be able to look and see whether we ever get a curve that has that shape in that part of the box but is not followed by muscle motion. So do you ever get a curve that looks like that but no muscle motion, that's what we need to look for. Now it turns out that given Libet's method in the main study, there's no way to look for that. And why is that? Because when you do EEG studies, you need to do something called back averaging. And so your computer needs to get a signal telling it to make a record of the preceding second or so of brain activity. And what Libet used as a signal to the computer to make a record of that activity was muscle motion. So it was only when there was muscle motion that you got these charts that you could read. But given that muscle motion is the trigger, you're precluded from looking for cases in which you get a curve that looks like that in the purple box but no muscle motion, and let me just read you a quotation. Sometimes people think this can't be right but it is. Here's the quotation from Libet and his method. In the absence of the muscle's electrical signal when being activated, there was no trigger to initiate the computers recording of any preceding brain activity. So in other words you can't look for what you want to look for in order to see whether the point of no return has been hit that early. Also you can look for independent evidence of when the point of no return is hit. Now my book Effective Intentions was published in 2009. In one study I suggested, in that book, was a stop signal study, and it was in connection with the point of no return. So, if you want to know when the point of no return is hit in a process of the kinds we're talking about. One way to get evidence about it is to issue stop signals to people and move them closer to or further from the time you're interested in. And see whether there's time for people to stop a process in response to the stop signal. And the simple sort of study I suggested was this. You could tell subjects to flex a wrist when the spot or hand hit the 9 o' clock point on the clock. Unless the clock face changed color from white to red. So at the start of the study, it's going to be white, and you can tell them, okay, now you can flex whenever you want, unless the clock face changes color to red, and then if it turns red, don't do it. Otherwise, do it. And what I predicted back then, because average stop signal reaction time is about 200 milliseconds is that if you gave them 200 milliseconds or a little more, they'd be able to stop. So just picture a clock, picture the 9 o'clock point, imagine putting a stop signal really close to that 9 o'clock point like a 100 milliseconds. That probably wouldn't do it, people are probably going to flex when it hits nine. But if you move it back to a little more than 200 milliseconds my prediction was, people will have time to stop. Now why is that relevant? Well, if they had time to stop, then they haven't really hit the point of no return in this process earlier. It can be stopped by an external signal. And if it can be stopped by an external signal, why not be stopped by an internal signal too, just telling yourself, no, don't do it. Wait for the next urge or whatever. So recently there is a study done by Schultze-Kraft and colleagues. It was published in 2016. It's way more sophisticated than the one I sort of made up as an example back in 2009. And in this study they use actual EEG readings to make predictions about when people will click when they'll move, and they designed a stop signal study that is sensitive to real time EEG. So they're predicting on the basis of the EEG when people will move and then they're using stop signals based on those predictions. Moving the signal around closer and farther from the predicted time. And the signal they used was a red light. So, the instruction was like driving a car, so this is foot motion this time. The instructions was, after you get the green light you can press that button on the floor whenever you want but don't do it if the light changes to red. And what they discovered with their red stop signal is that if there was no motion within 200 milliseconds of the red light showing up, in general there wasn't any motion. So that would be evidence that 200 milliseconds or so is enough to stop this process, which again, is evidence that the point of no return is not hit earlier than 200 milliseconds before muscle motion. Now recall that the claim here that I'm countering is that even though decisions maybe are not made at those early times, the point of no return is hit at the early times. At minus 550 milliseconds, at minus 800 milliseconds, at minus 7 to 10 seconds before muscle motion. And what we have here is evidence that the point of no return, is not hit until about 200 milliseconds before muscle motion and that as it happens is right around W time, the time of first awareness of the decision or intention to do the thing in question.
