Scientists at the University of Washington (U.W.) in Seattle fed alcohol to a group of rats and found that their ability to make good decisions was impaired even long after they stopped consuming booze.
Researchers found that the tendency to make imprudent decisions did not fade for up to three months after the rats stopped consuming alcohol.
(from Scientific American’s report
In many ways, rats are nothing like humans, but I expect that whatever mechanism explains this in rats will also exist in us. The rats weren’t actually visibly drunk or addicted (displaying withdrawal) to the alcohol; they were just always slightly intoxicated for 20 days straight.
After ending alcohol consumption, the rats got to play with two reward-dispensing levers; one with a high expected reward but no extremely large “jackpot”, and the other with worse expected payoff, but larger payoff size (in both, I assume there’s some probability of receiving no reward).
I wouldn’t expect rats to correctly compute expected reward per trial, but nonetheless that rats who never got drunk preferred the higher-average lower-peak reward, while the drunk rats liked the bigger-jackpot less-rewarding lever, for up to 3 months of soberness
. We’ll assume the scientists randomized the positions of the jackpot and consistent levers between trials; otherwise the persistence of preference would be explained by habit.