Rat Empathy and Brain Evolution

Current theories of the brain’s evolution attempt to correlate mental ability with the evolutionary age and sophistication of its structures. The older and more primitive the structure, the less emotional and cognitive abilities should be present. However, recent studies are shaking the brain-behavioral evolutionary tree.  Amoebas, which have no brain, have been observed sacrificing themselves for other amoebas. In fact, they do so more frequently the closer they’re related. Lizards, who have only a primitive midbrain, have shown decision-making abilities better than that of most birds. Studies of apes now show that they consider the thoughts of other apes when giving warnings, an advanced trait thought to only exist in humans.

All these new findings are difficult to explain. But, perhaps the most surprising one has to do with empathy in rats.

 Mammalian Empathy

Empathy is an advanced emotion; it is a capacity that includes both recognizing another’s condition and sharing some aspect of their feelings. While primates and humans have often shown empathy, a recent study places empathy much further down the mammalian evolutionary ladder. According to current theory, pro-social behavior, where an animal acts solely to benefit another, should not occur in animals with small brains.

Rats prove the theory wrong. As social animals, it has been known that they experience emotional contagion; they share the excitement and distress of other rats. In fact, rats often freeze when observing the suffering of another rat. But they are not supposed to demonstrate empathy and act upon it.

 Experimental Rat Helps Mate

In an experiment, a rat was placed in a large cage with another rat trapped in a restrainer device. The free rat became excited at witnessing the distress of its comrade but did not freeze.  Instead, it gnashed at the restraint box, trying to open it. After a week of hourly visits to the trapped rat’s cage, the free rat finally figured out that by lifting the door with its head it could open its friend’s restraint. From then on, every day, it always freed the restrained rat as soon as it could. After each liberation, the pair celebrated by running around the cage together.

In a further experiment, the free rat chose to liberate the distressed mate even before opening a trap containing chocolate.  Remarkably, the liberating rat would share the chocolate each time with the newly freed rat. This daily rat liberation occurred even when the freed rat was routed to a separate cage that could be seen by the hero rat but there was no contact allowed. In other words, rats are shockingly empathetic.

 Evolutionary Roots

Advanced abilities like empathy are better correlated with evolutionarily younger brain structures, such as those in the cortical and subcortical regions. We associate the subcortical amygdala with emotional learning and cortical mirror neurons with awareness of others’ experience. Previous evolutionarily theory assumed that the midbrain, associated with instinct, couldn’t produce deep empathy in rats or advanced decision-making in lizards. That theory is now called into question.

Of course, all such theories are speculative because real neuro-biological evolutionary information doesn’t exist. There is still strong resistance in some scientists to the notion that animals, especially rodents, have emotions at all.

The question still remains: what can altruism in microbes, complex decision-making in lizards, and empathy in rats tell us about the brain’s evolution? What does it say about mind in evolution?

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  • neuromusic

    One shortcoming of this approach is the assumption that the evolutionary age of a certain brain *structure* has anything at all to do with the modern, evolved role it plays in an animal’s behavior.

    Referring to the midbrain as “primitive” because the macro structure is phylogenetically old is like referring to hands as “primitive” because metacarpals are phylogenetically old. However, metacarpals have adapted differently based on the needs of different animals and the same can be expected true for the brains of different animals.

    If we can shed this idea of “evolutionarily younger brain structures” and instead recognize that the same structure may have evolved to do different things in different animals (based in part on the connectivity *within* the structure), then a “neocortex” is no longer a prerequisite for “higher cognition” and the idea that a lizard or octopus might have empathy is no longer so crazy. The really interesting question (once behavioral experiments demonstrate such cognitive processes are taking place) then becomes: what is the circuitry necessary to support such cognitive processes and how did they emerge across different brain structures?

    And I’m very curious what you mean when you say that “real neuro-biological evolutionary information doesn’t exist”… because it seems to me that there is a host of developmental and comparative neurobiology and neuroethology that is precisely that. See, for example, http://www.pnas.org/content/107/28/12676.short

    • Jonlieff

      I completely agree with your view.

      The reasons that I think we do not understand as much about regions in the brain and behavior are expressed in two other posts, one about imaging studies, decision making and free will, http://bit.ly/Ka9InK, and another about interpretations of behavior and circuits in the brain http://bit.ly/L3U4fA.

      It appears to me that interpretations of many such studies are over interpreted.