There are a handful of traits that scientists and philosophers would argue would make us human, including self-awareness and language. Another key part of being human is thought to be our ability to empathize (although I sometimes find myself doubting some humans’ abilities to empathize). I also doubt that we are the only animal that has empathy. However, this can be tricky to test. If we define empathy as Franz de Waal does as ‘‘the capacity to be affected by and share the emotional state of another, assess the reasons for the other’s state and identify with the other, adopting his or her perspective’’ how would we go about testing this in a non-human animal?

Take, for example, pigs. We know that pigs are ‘intelligent’ animals (whatever that word really means) and that they feel emotions such as stress. They are also social animals, and so presumably if other animals do empathise with one another, then a pig might be a likely candidate.

Well, scientists at Wageningen University in the Netherlands recently carried out an experiment to determine whether pigs might empathise with each other as part of a larger study looking at a number of aspects of pig empathy. This question is particularly pertinent to farming practices, as pigs are often kept in close quarters with fellow pigs, many of which are likely to be stressed.

To look at this, the researchers housed pigs in 16 groups of six. They then took two of the pigs from each of these groups and either trained them to anticipate that something good would happen, or that something bad would happen. They did this by playing the pigs some music and then either giving them a good experience (food) or a stressful experience (social isolation and handling) in a pen next door. The idea of this stage was to train pigs that the music predicted food or stress.

The researches then took two of the pig’s penmates (‘naïve’ pigs) and put them with the pig that had either been trained to one of these two things. All the pigs were then played the music that held meaning to the trained pigs (which, incidentally, was Bach or a military march). A few of the trained pigs showed that they learned what the music predicted for them, showing either ‘happy’ behaviours (play behaviour, wagging their tail and barking) or stress (standing ‘alert’, put their ears back, urinated and defecated). However, on the whole the trained pigs did not seem to anticipate what was ahead.

Despite this, the naïve pigs still experienced their penmates going into a neighbouring pen to experience something good or bad, even though they had never experienced this themselves. The researchers wanted to see if the naïve pigs would show ‘emotional contagion’ (sharing the emotional response someone else is having), as it is one key aspect of the ability to empathize. They found that the pigs did indeed react to the behaviour of the other pig: when a naïve pig was near a trained pig that was acting stressed, the naïve pig also became more alert and also put their ears back. This happened to a much greater degree than when naïve pigs were paired with pigs that acted ‘happy’. The researchers could be sure that the naïve pigs were reacting to the behaviour of the other pigs and not just the sound of the music because when they just played naïve pigs music this had no effect on their behaviour at all.

Now this experiment might seem cruel, as it both involved stressing pigs and showed that the stress of pigs likely affects other pigs. However, practices much worse than those used in the current experiment are common in pig farming, and without experiments like this investigating pig ‘emotion’ current practices are unlikely to change.

References

de Waal FBM (2008) Putting the altruism back into altruism: the evolution of empathy. Annu Rev Psychol 59:279–300

Reimert, I., Bolhuis, J. E., Kemp, B., & Rodenburg, T. B. (2014). Emotions on the loose: emotional contagion and the role of oxytocin in pigs. Animal cognition. DOI 10.1007/s10071-014-0820-6 (Main article).

Photo Credits

Child: Eugene Hamil

Piglets: Silke

Pigs from experiment: Monique Ooms