Show Me How You FeelĪnimals use facial expressions mainly to communicate with one another, says Bridget Waller of the United Kingdom's University of Portsmouth. “These days, there’s no shortage of hard data showing that animals experience rich and deep emotions,” says Marc Bekoff, emeritus professor of animal behavior at the University of Colorado, Boulder. (Related: " Do Animals Laugh? Tickle Experiments Suggest They Do.") And since mammals share many brain functions and chemistry, emotions that stimulate brains in the same way may be experienced similarly. What scientists can do is look at what parts of the brain are activated and which chemicals are released during emotional situations, he says. “While it’s likely that animals do feel emotions, it is unknown if they feel them the same way we do,” says Melotti. Ears of the happy rats turned pink due to increased blood flow, though it's not clear if that was because the rats were happy, or just that they got more exercise during tickling.Īs for what exactly “happy” feels like to a rat, it’s hard to know precisely. The team compared the facial expressions of rats after being tickled-and thus happy-and after being exposed to an uncomfortable white noise. (Also see "Rats Show Regret After Wrong Choices, Scientists Say.")
Melotti has become a “rat-tickling master” and says that he has also seen that individual rats have different personalities animals that are shy and anxious tend to prefer less rough-and-tumble tickling. Previous research has shown that rats enjoy being tickled-they’ll run over to a person’s hand to get tickled some more, and emit a “laughing” sound that’s too high-pitched for humans to hear without special equipment. To see if rats have “happy” faces, researchers tickled rats to get them in a good mood and then immediately photographed their facial expressions. Ultimately, he hopes to develop an automated system for monitoring an animal’s emotional state by watching its expressions. Recognizing when an animal is happy or in pain could help people give captive animals a better quality of life, says Luca Melotti, an animal-behavior expert at the University of Bern in Switzerland and an author of the recent study, published in the journal PLOS ONE. (Related: “ The Surprisingly Humanlike Ways Animals Feel Pain”) There’s even a rat "grimace scale" to measure pain levels.
Other research on rat facial expressions has focused mainly on pain, showing that suffering rats narrow their eyes or squeeze them shut, flatten their nose and cheeks, and curl their ears forward.
The study is the first to look for signs of positive emotions on rats’ faces, such as pleasure or happiness. They found that happy laboratory rats not only can be literally tickled pink, but they relax their ears so that they hang loosely to the side. Do rats feel joy? It can be hard to tell, since they can’t exactly greet us with a grin.īut now, for the first time, scientists have spotted the rat equivalent of a smile-and it’s all in the ears.
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