SCOTT DETROW, HOST:
Brain scientists are finding that a mouse's brain can be primed for battle simply by watching others duke it out. As NPR's Pien Huang reports, their findings come from a series of mouse cage fights.
PIEN HUANG, BYLINE: Two mice swipe at each other in a cage. Another one watches from the top.
ANNEGRET FALKNER: We set this up to look a little bit like a gladiator arena, so the mouse is kind of above the two mice fighting on a platform.
HUANG: Annegret Falkner is an associate professor at the Princeton Neuroscience Institute.
FALKNER: Mice fight a lot in the wild. You know, mice form hierarchies, normally. They defend their territories.
(SOUNDBITE OF MICE SQUEAKING)
HUANG: But here in the lab, these fights are a kind of performance - a rodent wrestling match, if you will.
FALKNER: The fight is always fixed. So we have these mice that are sort of trained to be losers. They perform loser-y (ph) behavior, and then we have mice that are very experienced. They do a lot of winner-y (ph) behaviors.
HUANG: The mouse on the platform observes a series of live, four-minute cage fights over about a week. It's purely a spectator. At the end of it, the spectator mice try their skills in their own cage fights.
(SOUNDBITE OF MICE SQUEAKING)
HUANG: Jorge Iravedra Garcia, a postdoctoral researcher in Falkner's lab, says the mice that watched fights mimicked what they saw.
JORGE IRAVEDRA GARCIA: They were the ones that were starting the fights. They were pushing back. And in between, they held these sorts of postures that meant that they were ready to engage.
HUANG: In other words, the observer mice learned to be more vigilant and aggressive. The researchers tracked their brain activity through the training and the fighting.
IRAVEDRA GARCIA: When we did this in fighters and watchers alike, the way that activity lights up across this suite of brain regions was actually very similar.
HUANG: Which means simply watching fights rewired mouse brains to look like that of a fighter. Brains have excitatory neurons and inhibitory neurons, like the gas and the brakes in a car.
IRAVEDRA GARCIA: There's this population of inhibitory neurons whose job when it comes to aggression is to brake - it's to stop.
HUANG: He says all mice, including those that had never even seen fighting, were gassed up and ready to go when placed in a brawl. But those that had fought or had watched fights before had fewer inhibitions, fewer brakes. Iravedra Garcia says the observers moves weren't as smooth or as regular as those with real fighting experience, but they did have a sense of strategy and retreated less.
IRAVEDRA GARCIA: They don't fully recapture the sort of behavioral effects of experience, but it gets you somewhere in the middle.
HUANG: The paper is published in the journal Nature. Moriel Zelikowsky is a neurobiologist at the University of Utah, not affiliated with the paper.
MORIEL ZELIKOWSKY: A very creative work by the authors there. I'm staging these kinds of fight club and even observers of the fight club.
HUANG: She says their findings shed light on how animals learn by watching.
ZELIKOWSKY: It really goes beyond just kind of mirroring what you're seeing or hearing and, instead, takes us to this next level of how the brain might be reshaped by these observational experiences that then will maximize an animal's chance of increased survival.
HUANG: She says this type of learning may extend to other behaviors, like mating and feeding, which are critical to get right. Falkner, the Princeton researcher, says humans can also learn physical skills by watching others, like in sports.
FALKNER: The question is not whether you can be a professional athlete by watching the NFL, but are you better at football for watching sports than if you had never watched anything? And the answer is absolutely yes.
HUANG: In the study, the observer mice fought with a mix of aggressive and defensive behaviors, like they had learned tactics from both sides.
FALKNER: Which is something that might not happen with experience, right? You only have your own perspective and experience.
HUANG: So at least for mouse fights, watching others pummel others is a safer and maybe smarter way to learn.
Pien Huang, NPR News.
(SOUNDBITE OF A.V. HAMILTON & HIJINX SONG, "DOWN!") Transcript provided by NPR, Copyright NPR.
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