Our undertsanding and reaction to another's emotions may be partly dictated by our genes, according to a novel study on mice.
In the University of Wisconsin-Madison and Oregon Health and Science University (OHSU) study, a highly social strain of mice learned to associate a sound played in a specific cage with something negative simply by hearing a mouse in that cage respond with squeaks of distress.
A genetically different mouse strain with fewer social tendencies did not learn any connection between the cues and the other mouse's distress, showing that the ability to empathise may have a genetic basis.
The study has been published in the Public Library of Science ONE journal.
Like humans, mice can automatically sense and respond to others' positive and negative emotions, such as excitement, fear or anger.
Understanding empathy in mice may lead to important discoveries about the social interaction deficits seen in many human psychosocial disorders, including autism, schizophrenia, depression and addiction, the researchers say.
"The core of empathy is being able to have an emotional experience and share that experience with another," says UW-Madison graduate student Jules Panksepp, who led the work along with undergraduate QiLiang Chen.
"We are basically trying to deconstruct empathy into smaller functional units that make it more accessible to biological research," the researcher added.
In the experiments, one mouse observed as another mouse was placed in a test chamber and trained to associate a 30-second tone with a mild foot shock. Upon experiencing the shock, the test mouse emitted a short distress call or squeak.
Though having no direct knowledge of the foot shock, observers from a very social mouse strain learned from the distress calls to associate the test chamber and tone with something negative.
When later placed in the test chamber and presented with the tone, they exhibited clear physiological signs of aversion, such as freezing in place, even though no shock was delivered.
In contrast, observer mice from a less gregarious strain - less likely to seek the company of other mice - showed no response to the tone when they were placed in the test chamber.