As social creatures, we subconsciously match moods with those around us—and not just when a cranky supervisor darkens your day (Editor’s Note: Is it something I said?). The scientific term for the spread of feelings is “emotional contagion,” a term that may feel particularly appropriate when it comes to grumpiness. But as is so often the case with human psychology, this very human behavior does not appear to be unique to our species.
Studying emotions and their contagious nature in other animals can be tricky. Relying on outward displays runs the risk of conflating a simple emotion with some overt rowdiness that makes it visible. Getting at that underlying emotion requires understanding how critters act in varying moods. A team led by the University of Vienna’s Jessie Adriaense tried to do that with ravens by designing a test to reveal whether they were feeling optimistic.
The first goal of the experiment was to induce a positive or negative emotional state in a raven. To do so, the raven was shown a pair of food items: dog kibbles (a highly rated treat) and some raw carrot (a hard pass). One of the food items would then be taken away. When the tasty treat remained in view, the raven should be enthused; it responded by walking up to that side of the cage and focusing its attention on the snack. When the carrot was left, the bird gave it a dominantly left-side side-eye (the left eye and right brain hemisphere are linked to negative stimuli) and scratched at the ground in frustration.