[fallingfrog]

And the part about the rats hitting the dopamine lever is wrong too. If the rats were in a rich environment with other rats to interact with they would overwhelmingly prefer straight water to water with cocaine. It was only rats in an empty box with literally nothing else to do that would get addicted- in other words rats which were already in significant psychological pain. I need to find the reference for that..

[neurosphere]

The idea of whether rats with exciting lives would indeed be less likely to become addicted to cocaine / morphine is quite controversial, and there have been some failures to replicate that original study (references here: 1. https://www.ncbi.nlm.nih.gov/pubmed/9148292?dopt=Abstract and 2. https://www.ncbi.nlm.nih.gov/pubmed/2616610?dopt=Abstract). I think the argument is that social isolation can and probably does make animals and humans more prone to drug addiction, but it's definitely not the only factor, and both animals and humans with good lives can still become hooked.

[pstuart]

This one? https://en.wikipedia.org/wiki/Rat_Park