With all due respect, but this post reminds me of why I find the expectation-calculation kind of rationality dangerous.
IMO examples such as the first, with known probabilities and a straightforward way to calculate utility, are a total red herring.
In more realistic examples, you'll have to do many judgment calls such as the choice of model, and your best estimate of the basic probabilities and utilities, which will ultimately be grounded on the fuzzy, biased intuitive level.
I think you might reply that this isn't a specific fault with your approach, and th...
Sorry to hear about the drug problems, but how can you be sure they "destroyed" your dopamine neurons? Not all drugs that increase these neurons' activity kill them. Psychological changes might be a simpler explanation IMHO (but I don't know you, so that might be far off the mark).
[...] knock out the wanting to do drugs part of their brain...
Sounds draconian. That part isn't just there for drugs...
Seems like a pretty large leap from certain simple behaviours of rats to the natural-language meaning of "wanting" and "liking". Far-reaching claims such as this one should have strong evidence. Why not give humans drugs selective for either system and ask them? (Incidentally, at least with the dopamine system, this has been done millions of times ;) The opioids are a bit trickier because activating mu receptors (e.g. by means of opiates) will in turn cause a dopamine surge, too)
(Yes, I should just read the paper for their rationale, but can't be bothered right now...)
Kevin means this I suppose?