Wednesday, March 31, 2010

Family matters

If you’re a pet owner, chances are you believe your pet has a personality, recognizes you, loves you, feels your pain. Who hasn’t heard a story about a girl who’s crying over a heart break, and her dog comes over to cuddle with her and lick her tears away? On the other hand, many firmly believe that animals are just friendly when they want food, and that they don’t have the kind of intelligence needed for emotions such as empathy. For example, my dad likes to claim that cats have a “smooth brain”, a reference to the fact that the brains of cats are not folded as much as those of humans, and therefore, the 16 pounds of fluff sleeping in my living room can’t possibly experience more than “hungry”, “sleepy” and “farty”. The thing is, it’s hard to tell, because we can’t ask animals how they feel. Faced with this difficulty, a team of researchers recently devised a method to determine if the lowly mouse is capable of complex emotions.

The researchers initially wanted to see if mice could learn to fear something without experiencing it. They put two mice in a cage and separated them by a see-through wall. The researchers then proceeded to give mild electrical shocks to the feet of one of the mice. Interestingly, the observing mouse (who wasn’t getting shocked) also displayed signs of fear (which is expressed mostly by a freezing behavior). What’s more, when the observing mouse was put back in the same experimental cage later, it still displayed signs of fear, meaning it remembered the experience of watching the other mouse get shocked. However, if you put the observer mouse in a different cage or different environment, it behaved normally. These results indicate that the observing mouse learned to fear a specific context without experiencing the pain it fears.

So what, you say? The mouse could just be mimicking the fear behavior, or experiencing “emotional contagion”. But there’s more. The researchers tried the same experiment, but this time, they used a pair of siblings instead of two random mice. Surprisingly, the effect they observed in the first experiment was now much stronger: the observer mice displayed significantly more freezing behavior, as if they could relate more to the pain of a sibling mouse than to that of a random mouse. The freezing effect was also stronger when the two mice were unrelated but had been sharing a cage for more than 10 weeks (mice in common-law). Overall, the more familiar the observer mouse is with the mouse getting the shocks, the better the observer mouse can feel the pain of the other mouse.

Are the mice really feeling empathy, or are they simply sensing a danger? While this study can’t tease those two possibilities apart, the fact that the response is much stronger when the mice are related definitely raises the interesting hypothesis that, pardon the cliché, “animals have feelings too”. What is your experience with animal intelligence? Share in the comments!

Reference: Observational fear learning involves affective pain system and Cav1.2 Ca1+ channels in ACC. (2010) Jeon et al. Nature Neuroscience 13(4):482-8.

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