The (Un)surprising Empathic Abilities of Rodents

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Regrettably, it has taken a very long time for psychologists and neuroscientists to take the leap towards investigating empathy in non-primate mammals. Of course, why should sociobiology get in the way of politics and religion?

The study that had perhaps the biggest impact in this field, was conducted by Langford et al. (2006), entitled "Social modulation of pain as evidence of empathy in mice". The simple yet ingenious design included placing two mice, which were either strangers or cage mates, into transparent Plexiglas cylinders, such that they could see one another. Either one or both mice received an injection of 0.9% acetic acid into the stomach cavity and their pain response (writhing behavior) was measured. Remarkably, mice appeared to be in more pain when they saw another mouse also in pain, but only when that mouse was their cage mate or sibling, not when it was a stranger. Their pain was amplified by seeing familiar individuals in pain.

Pain, Rejection, and the Optimal Calibration Hypothesis

A paper by Chester et al. was published in the July 2012 issue of Frontiers in Evolutionary Neuroscience under the title:

"The optimal calibration hypothesis: how life history modulates the brain's social pain network."

This work presents a novel way of looking at adaptations in the sensitivity of the "social pain network" throughout the human lifespan.

The authors start out by reviewing the evidence of overlap between the brain networks involved in pain perception, and the neural substrates of the affective response to social threats, such as rejection. Reviewed are the two neocortical structures which appear to be involved in both. The anterior cingulate cortex (ACC) is thought to support the affective features of pain, but activation in this region is also observed in response to perceived social rejection. Similarly, the anterior insula appears to be involved in affective responses to both physical pain and social rejection.