When a single fish gets tipsy, it swims faster than usual. This was already known. But what happens when it is thrown into a tank with sober fish? The fish swims even faster than when it is alone, and, furthermore, the whole school speeds up. The sober fish may take the soused swimmer's speed and uninhibited fin-flapping for leadership.
"These results were very surprising," said NYU researcher Maurizio Porfiri (one of PopSci's Brilliant 10 class of 2010), who led the study, in a statement. "It is clear that the untreated [sober] fish were matching the swimming speed of the alcohol-exposed fish, and this correlation was especially strong at an intermediate level of alcohol exposure. At very high or low levels, the influence decreases." Especially at high concentrations, the very drunk fish are sluggish, and have trouble keeping up with the rest of the school.
What does it all mean? It shows the effects of alcohol are different in a solitary verses a social setting in zebrafish, and that boozy behavior of a single individual can affect the whole group–of interest to researchers studying alcoholism and sociality. It also shows how disinhibited, aggressive behavior can in this species resemble leadership. Are you my leader, or are you just drunk as a fish? It's thought that the individual swims faster around its shoalmates in part because it has increased interest in interacting with them–kind of the way the bottle can bring out a shy human.
In related drunk-fish science news, a study (also by Porfiri) found that normally zebrafish are afraid of a robotic fish that looks like one of their predators. But not when they're drunk–then do not appear to be afraid of the artificial aliens.