If the 'state vector collapse' refers to quantum mechanics, it's the act of observation, not decision, that causes the system to adopt one of its eigenvalues and effect the so-called collapse. For that matter, an inanimate measuring device does the same thing. Personally, I consider the whole thing an artifact of an artifical dualism between experimenter and experiment. If you write a combined wavefunction of apparatus and system, the evolution of the combined system is purely deterministic.
If the act of decision is your criterion, of course, you must recognize that we don't generally recognize the ability of children to make free decisions. Will iself is a continuum, not a binary quantity.
I'll just echo Pinker's point that of course we have a revulsion towards the idea that what we are and what we do might be the result of the operation of a set of natural laws, because we evolved to act as if we have a control of our destiny. The people with the fatalistic genes saw a saber-toothed tiger coming and sighed 'que sera, sera', before letting kitty settle down to a nice meal. The free-will types picked up a rock, flung it, and then ran as fast as they could. But one's revulsion sould not be taken as prima facie evidence. I am revolted by broccoli, but I accept that it's good for me.
Yes, the act of decision would be my criterion, RightWingProfessor. For to "decide" requires that one select a particular choice from among a potentially very large set of competing alternatives, and once a decision is made, only one outcome is realized, and all the rest of the alternatives present in the probability amplitude remain unexpressed. I know that vector state collapse is a term normally associated with observations made within quantum systems, but as you'll recall I mentioned that effectively the same type of operation can be observed in "real-world systems," such as even a child making a decision.
Now you say that a child is incapable of making a "free" decision. I gather you do not spend much time observing children. Any child can select an alternative that he intends as a means of satisfying a perceived need or desire. All other potentially competing possibilities for the child's action remain unexpressed once the child fixes on one of them, and moves to realize it. This looks to me like an excellent example of the collapse of a probability amplitude to me. Whether or not a child is "competent" to make an informed choice, as presumably an adult would do, is beside the point. Even a mentally handicapped person can make a decision. And with the decision once made, all other possible decisions that person could make remain in the "netherworld of possibilities" that do not become reified. And this, to me, is the hallmark of state vector collapse.
Perhaps will may be a continuum; but an actual choice represents a "quantized" event. The choice or decision could have been otherwise, but it was not. Ergo, state vector collapse has occured.
I am revulsed by Pinker's idea that "of course we have a revulsion towards the idea that what we are and what we do might be the result of the operation of a set of natural laws, because we evolved to act as if we have a control of our destiny." Surely you see that this is mere opinion; for there's no way Pinker's insight could be falsified/validated. As an insight into human psychology, Pinker's statement is such that only an communist ideologue could love. To say that people have no control of their destiny because they are simply the sum-total of the operations of "natural laws" (what natural laws???) has been repeatedly invalidated throughout the course of human evolution, as any student of history is aware.
Or was there just something unique about the way the biochemistry worked out to produce a, say, Alexander the Great? Or a Hitler, for that matter?
Pinker's remark is an absurd reduction. It is a case of letting one's doctrinal tail wag the dog of reality. FWIW