Reading other individuals’ emotions allows animals to obtain knowledge about potential threats in the surrounding environment, and adjust their own behaviour accordingly. Scientists from the Nencki Institute argue, that empathy can be evolutionary advantageous, as it makes use of cooperation with other individuals to increase the chance of survival.

Traditionally, empathy – the ability to read the emotions of others – was considered a purely human ability. However, more recent research indicates that also animals possess this skill. The current definition of empathy, proposed by Dutch scientist Frans de Waal, includes both very basic, primitive responses for the emotions of others, as well as higher processes such as sympathetic concern and perspective taking. The former can be observed even in fish – says Prof. Ewelina Knapska, the leader of Emotions Neurobiology Laboratory at the Nencki Institute of Experimental Biology in Warsaw.

Until recently, most scientists believed that these are automatic reactions, based on imitation. If one of the animals suddenly stopped moving, the other one would do that as well. – Yet our newest study demonstrates that it is more complicated than this. Animals categorize received information and, depending on the situation, react in a different manner. Completely automatic imitation would not be beneficial for them – says Kacper Kondrakiewicz, graduate student in the Emotions Neurobiology Laboratory.

Prof. Knapska’s team studies a phenomenon known as ‘emotional contagion’, a process in which, if one animal from a studied pair gets scared, the other one shares this emotion, despite not being directly exposed to the same threat. Karolina Andraka and Kacper Kondrakiewicz are the first authors of a paper on this topic, published in the newest issue of ‘Current Biology’.

The scientists examined the behaviour of rats in two fear provoking situations. In the first one, called the immediate threat model, both animals were tested in the same apparatus and could see, hear, and smell each other. One of them, called the demonstrator, received mild electric shocks, which are not strong enough to cause pain, but evoke fearful responses, such as bouts of immobility, which are a standard defensive reaction. The observer rat that witnessed the whole situation also ceased to move.

In the second condition, called the remote threat model, the demonstrator rat was alone in the cage during electric stimulation. Afterwards it was returned to the home cage, and met with the observer. In this situation, the demonstrator behaved normally, but it’s partner became more aroused, performed more rearing, and explored the cage more intensely, collecting more information about the surrounding environment.

- In the first condition we observed a defensive response, which in a natural environment would be executed after a predator attack; in the second, the observer was more focused on localizing the source of threat, a reaction adequate to the whole situation. – says Prof. Knapska.

Throughout the experiment, the scientists also recorded ultrasonic vocalization emitted by the animals. Rats communicate using two types of such calls. Low frequency, c.a. 20kHz calls are considered alarm calls – they are long and very repetitive. The second type of ultrasonic calls have a much higher frequency, oscillating around 50kHz. These vocalizations are shorter, much more complex and diverse. They are usually observed in situations which are pleasant for the animals – for example, when they meet after being separated for some time.

- In the immediate threat model we have seen the ‘twenties’ (20kHz calls), but in case of remote threat, when the observer did not directly observe the threatening stimulation, we unexpectedly saw the ‘fifties’ (50kHz calls). Maybe, in this way, the rats soothed each other. – says Kacper Kondrakiewicz

The probable function of these vocalizations is to reduce the stress. A similar mechanism can be observed in humans – tension rapidly goes down if we can share our feelings, or if someone strokes our hand. – Other experiments that we conduct suggest that the rats release stress quicker if they touch each other more. – says Prof. Knapska.

The research conducted by scientists from the Nencki Institute, also demonstrated that the social signals of these two types of threats – imminent versus remote – activate different types of neurons in the rat amygdala. This brain structure is evolutionary very old, and it controls basic reactions to threats. – The same structures are activated in humans also, on which we conduct similar studies. However, in humans, we cannot perform as detailed neuroimaging as with rats. We can do it in rodents, which allowed us to show that there are neural circuits specific for these two types of emotional contagion – says Prof. Knapska.

Emotional contagion – the ability to share the emotions of others in various situations – is at the core of empathy. Prof. Knapska thinks that it is an evolutionary adaptation found among various species, not only in primates. It allows to communicate efficiently, and avoid potential threats. Rats can categorize social information because, from their perspective, it is crucial to discern whether they should run immediately, or if they can continue foraging, just paying more attention to potential predators.

- Common experience proves that empathy is helpful in real life. In the past, there was some evolutionary pressure which stimulated development and propagation of the ability to read emotions – says Prof. Knapska.

Individuals with higher ability to recognize the state of conspecifics had a higher chance to survive and produce offspring. Also today, empathy is a key factor in initiating help in everyday life. Some therapeutical approaches which target social interaction difficulties are based on teaching soft skills, for example, understanding others’ point of view.