I doubt that they addressed the general problem with this type of recreational drug experiment: the hypothesis that different brains and psychology cause differ

I doubt that they addressed the general problem with this type of recreational drug experiment: the hypothesis that different brains and psychology cause different behaviour is very plausible a priori, the reverse not so much. It would be good to test that with animals. You could control the alcohol consumption of rats in group A, let group B drink as much as they wanted to, and compare how the effects varied with consumption between the two groups. Has that experiment been done?