Happy Rats? New Study Suggests They Smile With Their Ears

Is that a smile you see on that rat's face? The ears tell the story, according to a new study published by scientists on Plos One. The team of researchers with the University of Bern in Switzerland revealed that rats actually express their happiness by "smiling" through their ears.

A report from Phys.Org revealed that the scientists were able to discover that rats experiencing happiness or pleasure tend to have their ears become droopier and pinker. The lowered ears indicated a relaxed state, while there has been no clear-cut explanation yet for the noticeable change in color. It was suggested that it may have been an effect of increased blood flow due to the physical exertion of laughing.

The researchers of this new study took their cues from a previous research published in Science Magazine that explained that rats liked being tickled - not unlike rubbing a dog's belly, perhaps. This study showed that the small animals were shown to have sought out the researcher's hand to get tickled some more and they also emitted ultra-sonic sounds that are considered to be the equivalent to giggles in humans, according to a report from the New York Times.

With this in mind, the team from the more recent study designed two environmental experiences to observe the rats' reaction: tickling for a positive experience and white noise for a negative experience.

While there have been multiple studies observing pain and other negative emotions in rats, this is the first to delve into positive emotions such as happiness.

In a report from National Geographic, Luca Melotti, one of the authors of the new study and an animal behavior expert from the University of Bern, explained that recognizing animals' different emotions - pleasure or pain - could help people give pet or laboratory animals a better quality of life.