Mice help their colleagues when they are in difficulty

One of the possibly most exciting characteristics of humans is the willingness we show to help when someone is in difficulty, especially, but not only, if they are friends or if we have previously met. It is a prosocial capacity related to empathy that favors the survival of the species and has been shown to also benefit the person who helps, as it receives approval from the environment, fosters reciprocal social relationships, and improves their status within the community. However, it is known that we are not the only species that exhibits this behavior.

To demonstrate how far this help can go in other species, three research groups have published their work in the journals Science and Science Advances in which they have analyzed the behavior of domestic mice (Mus musculus) to help their unconscious companions recover. These three studies, led by neurologists and neurobiologists Pen Cao, Wenjian Sun, and Fangmiao Sun and their research teams, have shown that these animals not only recognize when a companion is immobile, but also actively attempt to resuscitate it. This finding opens new perspectives on social behavior in mammals and could have important implications for understanding empathy and altruistic helping.

Empathetic and altruistic?

In one experiment, the behavior of 200 pairs of mice was analyzed in four different situations: when their partner was active, naturally asleep, unconscious due to light anesthesia, or dead. The results revealed that the mice spent almost 50% of their time interacting with the unconscious individual, trying to bring it back to life, especially if they had met it before, but also, although less intensely, if it was a stranger. Furthermore, mice resuscitated by their partners recovered more quickly than those that woke up from anesthesia on their own. The partner approached and licked the mouse vigorously. If the mouse didn't respond, the partner would bite its snout and extend its tongue to revive it. This behavior, however, did not occur when the other mouse was awake, simply asleep naturally, or had recently died, indicating that these rodents clearly distinguish between a normal sleep state and an emergency situation.

Another study analyzed the neural basis of this prosocial behavior. Researchers found that tongue manipulation by the partner activates a specific neural circuit between the tongue and the brain that helps restore consciousness in the affected animal. This circuit connects the so-called trigeminal mesencephalic nucleus, which is involved in proprioception of the masticatory muscles, and the locus coeruleus, which modulates states of alertness and attention. They observed that mechanical stimulation of the tongue has a direct effect on the breathing and heart rate of unconscious mice, increasing the chances of recovery and speeding up the process.

By chance, in one of these experiments, the researchers observed that one of the unconscious mice had a small expanded polystyrene (Styrofoam) ball in its mouth, which further hindered its breathing. To see how well its companion was able to detect this situation and remove it to facilitate its recovery, they designed another set of experiments. The unconscious mice had a Styrofoam ball deliberately inserted into their mouths, or alternatively, as a control, into their anus or vagina, where it did not hinder breathing. The helping companions only attempted to remove the ball they had in their mouths, but in no case did they attempt to remove the ball that the control mice had in their anus or vagina.

It should be noted that these experiments, which have been carried out on sensitive animals, must be approved in advance by animal experimentation ethics committees, which assess the degree of animal suffering in relation to the knowledge expected to be obtained from the studies. This does not prevent some aspects, such as the introduction of Styrofoam pellets, from being open to criticism.

Finally, it was found that, in terms of hormones, mice that helped their peers experienced increased levels of oxytocin, a neurohormone that, among other functions, is involved in empathy and socialization. This suggests that helping behavior is not merely reflexive, but may be related to a social reward that promotes cooperation within the group. According to the researchers, this discovery has important implications in the fields of neuroscience and social psychology, for example in conditions such as autism, where the mechanisms of empathy and helping may be impaired. Understanding how this behavior works in mice may provide clues about the neural circuits involved in human prosociality.