Do pigs anticipate positive and negative emotions?

Imfeld-Muellera, S., Van Wezemaela, L., Stauffachera,M., Gygaxb, L., Hillmanna, E. (2011). Do pigs distinguish between situations of different emotional valences during anticipation? Applied Animal Behaviour Science, 131, 86-93

Distinguishing between positive and negative emotions in animals is necessary to ensure good welfare. This study aimed to assess the emotional responses of pigs during anticipation of positive and negative situations.

Using Pavlovian conditioning, weaned pigs were trained to expect a positive or negative situation depending on a sound played in a pen. Half of the group were trained to anticipate a bowl of popcorn (positive) upon hearing the ringing of a phone, and to anticipate a task, where they had to cross a ramp (negative) upon hearing a harmonic four-note cord. The sounds and corresponding situations were reversed for the rest of the group. Physiological and behavioural measurements were recorded throughout the trials.

Pigs squeal less when anticipating popcorn

Physiological measurements of heart rate and heart rate variability did not differ depending on whether the situation was positive or negative. However, significantly fewer squeal vocalisations and avoidance behaviours were observed during anticipation of the positive situation. The results indicate that pigs do indeed show emotional responses during anticipation of situations of positive and negative valence. Frequency of vocalisations were shown to be a suitable indicator for the emotional valence of particular situations for pigs.

World Animal Protection’s view

There are often inconsistencies in the way people view and treat companion animals compared to farm animals. We believe that it is very important to better understand how farm animals display their emotional states. That way, the varying approaches towards the welfare of some species compared to others can then be overcome.