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When we humans encounter an unconscious person, we might spring into action and try to revive them. Well, a new study in the journal Science hints that lab mice might do something similar. NPR's Jonathan Lambert has more.
JONATHAN LAMBERT, BYLINE: Neuroscientist Li Zhang has anesthetized a lot of mice for his research. Several years ago, as he brought these knocked-out mice back to their cages, he started noticing that the mice around them were acting strangely.
LI ZHANG: Then we noticed, OK, its cagemate has shown very strong social interaction with this anesthetized partner.
LAMBERT: At first, the mouse would just sniff its cagemate, but as the cagemate remained unresponsive, the behaviors would escalate to things that seemed almost like first aid, says Zhang's colleague at the University of Southern California, Huizhong Whit Tao.
HUIZHONG WHIT TAO: No behaviors like this has been reported before.
LAMBERT: The fact that lab mice seemed to be doing this offered a rare opportunity to study this in more detail. First, the team presented a subject mouse with an unconscious cagemate or an active mouse. The subject mouse spent a lot more time engaging with the anesthetized mouse.
TAO: So it seems that the mouse can perform deliberately this whole set of behaviors, escalating from sniffing, grooming, to more forceful actions such as tongue biting, mouth biting and tongue pulling.
LAMBERT: Those behaviors turned out to help the mice regain consciousness. When mice pulled out the tongues of their cagemates, that actually expanded the airways of the unconscious mouse and helped dislodge foreign objects that the researchers had placed there. What's more, it turned out that mice didn't just help any old mouse but favored helping mice that they knew.
TAO: Familiarity is a very important factor, so it plays the major role.
LAMBERT: These results led the researchers to think that maybe the mice are actually trying to help their friends. But they also might just be curious. To test that possibility, they repeated the experiment over five days. It turned out that the mice actually became a bit more interested in their unconscious cagemates over that time period.
TAO: This type of experiment can exclude the possibility of curiosity as a driving force.
LAMBERT: Finally, the researchers studied the mouse's brains and found that oxytocin circuits were crucial for the behavior. Oxytocin plays a key role in helping behaviors across all sorts of animals. Altogether, Tao and Zhang say that the evidence supports the idea that the mice are actually trying to help their friends, even perhaps out of a sense of empathy. Peggy Mason, a neuroscientist at the University of Chicago, isn't so convinced.
PEGGY MASON: They found a great behavior. I don't dispute that. I dispute the interpretation of it.
LAMBERT: Specifically, she doesn't buy that the mice actually intend to help. She offers this analogy.
MASON: So if I drop $20 by mistake, somebody else picks it up - that person has been helped, but I have not helped them.
LAMBERT: She thinks that curiosity about this weird, unconscious mouse could still be driving these behaviors. But James Burkett, a neuroscientist at the University of Toledo, thinks that it might be an instinctual helping behavior.
JAMES BURKETT: To me, this looks very much like a behavior that's driven by what I would call the altruistic impulse.
LAMBERT: The fact that even lab mice might be behaving in this altruistic way suggests to him that the inner lives of many animals may be much richer than humans have realized. Jonathan Lambert, NPR News.
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