Neuroscience is uniquely suited to investigate the biological underpinnings of the features and traits that make us human, including morality, complex emotions and higher-order cognition. However, as we continually learn more about our behaviour and its origins, one unavoidable and startling possibility is frequently made clear; many quintessentially 'human' characteristics may not be unique to ourselves. One recent example is empathy, the experience of feeling and understanding the state of another agent. Empathy may cause one to respond altruistically; for example, to relieve the suffering or discomfort of another in unfortunate circumstances. Biologists have found evidence of altruistic behaviour across the animal kingdom, presumably due to evolutionary pressures favouring those behaviours that promote species survival and not due to active cognition. However, recent studies have raised the startling possibility that the experience of empathy may be older (evolutionarily) than we think, that we may not be alone in our understanding of the states of others, and that our own understanding of the mental states of animals may be even more primitive than we hold them to be.
Some of the recent evidence suggesting that rodents may have the capacity for empathy comes from pain research here at McGill. Mice in the presence of another mouse in pain are more sensitive to pain themselves, but only if the mouse is familiar (a 'roommate', essentially), and not if the alternate mouse is unfamiliar. To put it another way, if a mouse sees a 'friend' in pain, their understanding (such as it is) of the familiar mouse's experience can affect their own perception of pain, as part of a phenomenon termed “emotional contagion” that is believed to be a precursor to empathic behaviour.
A brand-new study has potentially added some exciting insight to the issue of empathy precursors in animals. A team from the University of Chicago developed a novel method of examining empathy-related behaviour, in which one rat is held in a restraining device that can be released by another rat. After learning how to open the restraining cage, the freely-moving rat chose to free its restrained companion, but not empty restrainers or those containing a toy rat. Notably, female rats seemed to show more altruistic behaviour than males. In a subsequent experiment, this team showed that if a second restrainer containing chocolate was placed alongside a trapped rat, the free rat was equally likely to initially open the chocolate restrainer (and enjoy the chocolate alone) or to open the rat restrainer and share the chocolate, suggesting that freeing the trapped companion is as motivating to the rat as a tasty treat. The authors of this study suggest that these results indicate empathy on the part of the freely-moving rat, in that it is highly motivated to rescue a companion animal that it perceives as distressed, even when doing so costs the rat resources (in terms of sharing the chocolate).
However, is this really the case? In the scant time since this article was published, alternative explanations for the rats' behaviour have arisen. One possibility is that the freely-moving rat becomes distressed by the trapped rat (either by their vocal cries, a released scent, or another signal), and the free rat is opening the restrainer to extinguish these cues and reduce its own distress, as opposed to 'helping' the other rat. Supporting this hypothesis, the animals emitted more frequent 'alarm calls' when an animal was trapped, explaining why the free animals were more motivated to open only those cages containing a trapped companion. This would not be empathic behaviour, as the freely-moving rat is merely acting to reduce its own distress, rather than altruistically 'rescuing' the trapped rat. In addition, the evolutionary advantages of empathic experiences in rodents are unclear.
So the animal empathy issue, new as it is, remains somewhat murky. It seems that rodents possess the capacity for emotional contagion, a primitive precursor for actual empathy. The more recent research raises the possibility for empathy underlying altruistic behaviour in rats, although the evidence so far is insufficient to conclude that this is the case. However, these studies provide clear research directions for future studies investigating the origins of our own uniquely human condition. We already know that human infants display empathy- and morality-related behaviour, as well as a basic understanding of the mental experiences of others (“theory of mind”), as early as one to two years of age. Taken together, these avenues of research bring us closer to understanding the evolutionary and developmental origins of those traits that make us human, to whatever extent we can say they remain uniquely ours.
[Adapted from a post originally posted here.]