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.
"The question is, can the mouse identify the emotions of another animal as a predictor of environmental cues?" says Garet Lahvis, a professor of behavioral neuroscience at OHSU. "The social strain learned from the distressed mouse that the tone predicted distress. The nonsocial strain couldn't make that [association]."
The differences exhibited by the two strains show that there is a genetic component to the ability to perceive and act based on another's emotional state, the researchers say. Future studies will focus on the genetic differences between the mouse strains to try to identify some of the specific genes that may be involved.
While it may come as no surprise to pet owners or those who work with animals that animals are able to pick up on the emotional states of those around them, this type of effect has not been rigorously demonstrated in a scientific context, the researchers say.
"Mice are capable of a more complex form of empathy than we ever believed possible," says Lahvis. "We
|Contact: Jules Panksepp|
University of Wisconsin-Madison