I'm surprised at an article on free will that mentions neither Skinner nor Kahnemann. Skinner's studies on behaviourism and operational conditioning led him to question free will in quite a dramatic fashion - in some ways I think akin to how Darwin was able to reason from "reproduction with modification" to evolution, without ever having a mechanism for modification in mind (gene theory came along much later).
More recent studies of cognition and reaction have provided some of the counter-mechanisms, the things we do without deciding to do them, such as reflex arcs (the mechanism in action that causes us to withdraw our hands from something hot before our brains have realized it was hot, e.g.,), and, more importantly for the free-will discussion, Kahnemann's (and Tversky)'s two-systems model.
The basic idea of that model is that our body and brain do a lot of prefiltering, dealing with much of what we encounter and manage without ever involving the conscious mind. Think of driving on a familiar, quiet road. You never think about it, you might not even be aware of much of the drive, but you drove safely.
That "fast", low-energy-requirement system only flags things to the conscious mind - the slow, high-energy-system that we identify as ourselves - when it cannot make sense of what it encounters or when there are surprising happenings.
The workings of the fast (aconscious) system are inaccessible to the slow (conscious) system.
So we have within us a system that decides a great deal without our being involved, at least not consciously, and that only presents for our conscious consideration things it needs help with.
We make conscious, free-will-like decisions, based on filtered and reduced information. How free is that, really?
Of course, the definition of consciousness is a question all its own.