free will, whatever it is, is a pretty strange and elusive thing. The following speculation is not about determinism in relation to free will, but I think it sort of relates to our decision making and how "free" decisions are conventionally viewed - in the context of a currently popular TV game show! I hope it makes some sense and that you in particular, Compo, might find it interesting.
I wonder if anyone else has seen the ITV game show "The Tipping Point"? Contestants try to dislodge counters stacked towards the outer edges of two trays in a machine; the upper tray moves continuously backwards and forwards. The punter presses a button which releases a new counter onto the top, moving tray; when this tray moves back towards the new counter, some counters already on the tray are pushed off and tip onto the lower tray; then the bottom of the upper tray, as it moves out again from the back of the machine, may push some of these dislodged counters towards the existing counters on the edge of the lower tray. Any of these counters which tip off the lower tray wins money for the contestant.
Anyway, the winning contestant is, in the final part of the show, given a "jackpot" counter to release, and if he or she can eventually get this counter off the lower tray they will win the jackpot of £10K. Usually they fail to do this, and they are then given the choice of releasing three further counters or leaving with their money; they win the jackpot if these three new counters do the job of sending the jackpot counter over the tipping point, but if they still fail to do this then they lose all the money they have already won. Usually they decline the chance to win the £10K, but if they do opt to take the money already won they have to release the three counters anyway, and if these counters DO push the jackpot counter off the tipping point the contestant is invariably somewhat mortified at winning only a smaller amount of money!
But should they be mortified if this happens? What occurred to me was that this bit of psychological torture depends on the assumption that, if a person makes one or other of two stark choices which are significant to them (in this case because a lot of money is involved) then their states of mind in the two alternative scenarios will be the same; so that, whether they are releasing the three extra counters in the hope of winning £10K or just to see if they would have won this if they had opted to risk the money already won, their behaviour will be the same. But surely this is in fact unlikely. If they have been brave enough to go for the jackpot they will be in an excited and yet anxious state of mind and so they will attempt to be extra efficient in their timing of the button pressing. In contrast, if their fate is already determined, they will unmotivated to release the button in the most efficacious way and in fact may hope to mess up the last three drops! At any rate, their decision has led to two different futures, and I do not think that they can be compared. Once a decision has been made, and assuming that it cannot be reversed, the whole of life alters, so that, at least in the context I have described, it makes no sense to regret "losing" what appears to be better outcome if one had acted differently.