Emotional contagion is when emotions influence more than one individual in a group. An emotion is aroused after witnessing that emotion in another individual. It is a simple form of empathy. Emotional contagion has been seen in many socially complex species such as dogs, wolves, great apes and a few other nonhuman species, including pigs.
According to Marino and Colvin:
“In one study, naïve test pigs were exposed to pen mates who had been trained to anticipate upcoming rewarding events (receiving straw and chocolate raisins) or aversive events (social isolation). When the naïve pigs were placed in the company of the trained pigs they adopted the same emotional anticipatory behaviors (eg ear and tail postures, increased cortisol) as the trained pigs with the direct experience. These findings show that not only can pigs connect with the emotions of other pigs, but they can also do so with pigs who are responding emotionally in anticipation of future events” (32).