To most people, "how predictable you are" and "whether you have free will" are almost the same question.
Being quite unpredictable just means that you do a lot of random things -- but says nothing about how you came to will them.
If someone, for example, was threatened and ordered to follow for years what a program with millions of suggestions told him to do, he would be very unpredictable, but totally without free will.
And the inverse: one could choose to do the same routine all his life, and thus be very predictable, but it would still be his free choice.
But yeah, it's not the same as being unpredictable: that would look like seizures, not "gosh which ice cream flavor will he pick?:
RE free will itself, I'm thinking it has more to do with metacognition and general complexity of thoughts. People may have free will, but they're running the same "free will algorithm" - give them the same inputs, and most of the time you'll get the same outputs. A lot of people don't want to consciously accept that, but it's a fact. It's e.g. why economics works at all - because people are predictable at scale.
But when do we most often reference the concept of "free will" in practice? In evaluating degree of responsibility for decisions. "You did X, which was the most obvious and beneficial in the short-term option, but you could've done Y or Z, which would be better - therefore you will suffer consequences". Or, "I won't do X even though the situation tries to manipulate me into doing it; I notice I'm being manipulated so I'll do Y instead". Scenarios like these refer to the human ability of a) non-greedy optimization (long-term planning), and b) being able to go meta many levels up, to notice their own patterns of thoughts and use them as an input to the thinking process. A feedback loop over metacognition if you don't mind.
This is still all pretty deterministic. The apparent randomness - I think - comes from the fact that a) two people never have perfectly the same set of inputs, because the internal state is dependent on one's life history, and b) in some cases slight variations in those inputs cause huge variations in outputs (butterfly/hurricane and all that). In a way, the main connection between "free will" and randomness may be just that a human doesn't have capability to perfectly predict the thought process of another human. We can do that to inanimate objects, we can do that to algorithms we write - at least in principle. But we know that other humans will always suprise us (at least because they can notice we're trying to predict them and start acting random to mess with us).
That's not quite how economics work. It's more like, outputs from a given set of inputs can be characterized in a statistical way at scale (which is subtly different from saying that individuals are predictable at scale.) It's not that every person will choose to buy pizza if it's $11.99 but not if it's $12.00, but instead that if you offer pizza for $11.99 you'll generally get between X and Y sales per day, and if you increase that to $12.00 you can expect to lose about Z sales, and you can mess with that curve to try to maximize revenues or whatever.
I would say that what makes "free will" an interesting concept is that it's about how one chooses to prioritize different values -- how they express meaning by their choices. In the sense of a "free will algorithm", it's how you choose to weight different factors in your algorithm. How do you weight comfort, pleasure, stimulation, challenge, avoidance of pain, etc.? How do you weight those things for others? In practical usage, we talk about "free will" when someone makes a choice that surprises us, showing that their value system or their evaluation matrix is different from ours.
The former is the metaphysical idea that all events are causally linked, a belief which we can never confirm or refute. The latter describes something's observable degree of predictability.
They're not related concepts at all. This demo has nothing to do with free will, Determinism, or Compatibilism - but it's an interesting study in predictability.
If we are talking about an abstract computing device, and whether it is deterministic, we mean whether its next state is always uniquely logically determined by the current state, correct?
Hmm, if an abstract machine behaves in a way that is uniquely logically determined, but which is not computable, do we consider such machines to be deterministic? I would think so, but I am not sure. We would be unable to predict it, does that make it not deterministic(computing) ?
Ghost in the Quantum Turing Machine https://arxiv.org/abs/1306.0159
Did they predict which method I'd wire it up with and the exact source of the program I'd use to do so?
I'm going to hazard a 'no', so it looks like I have free will.