A hundred college students were gathered for an audition at the University of Michigan. They had all responded to an advertisement asking human subjects to participate in a "psychological experiment".
When Professor Alexander Guiora and his colleagues made their way to the front of the room, they explained that one half of the audience, randomly divided, will go to room A, and the other half to room B. The ones in room A were given a small glass of punch; in the punch was one and a half ounces of vodka. Volunteers in room B got the same punch, but without the vodka. After a short period of time the participants in both rooms were led to a large language laboratory, where they simultaneously took a recorded test in which they were invited to try to pronounce words in the Thai language (which none of the subjects knew). After the test they were dismissed, with thanks and a token payment for their trouble.
Later, the results of the experiment were published. Guiora announced that group A did a significantly better job of pronouncing words in Thai than group B. Conclusion: the alcohol lowered the students' inhibitions, giving group A the advantage.
There is plenty to quibble about in this experiment, but it has been shown via other methods that one of the greatest blocks to adult second-language success is fear: fear of failing, fear of making a fool of yourself in front of others, fear of falling flat on your face. Children are far less inhibited linguistically than adults. Beyond a certain sensitivity to in-group slang, children don’t pay much attention to grammatical correctness and linguistic forms.
Much like inebriated adults.