Some pigs tend to be optimistic while others have a more pessimistic view, according to new research that has implications for animal welfare.
The study, published in the journal Biology Letters, is the first to show that mood and personality interact in an animal, impacting judgement. This happens to humans all the time, but the effect had never been documented in another species, much less pigs.
"We find that pigs, which have more outgoing personalities, are generally quite optimistic most of the time, whereas the less outgoing pigs are only optimistic when they have a nice home pen with lots of straw to play with," lead author Lucy Asher told Seeker. "In a less nice pen they are quite pessimistic."
RELATED: Is Your Dog a Pessimist?
Asher, a researcher at the University of Newcastle's Institute of Neuroscience, and her team housed groups of pigs in the two types of environments. One reflected standard commercial conditions and the other was cushier with more space and plenty of fluffy, deep straw. After the pigs got used to these new digs over a few weeks, the researchers picked 18 pigs from each type of housing arrangement to train and test their judgment.
"To do this, we trained each pig that in one corner of a training room there would be a bowl with chocolate sweets - specifically M&Ms, pigs love M&Ms - and in a bowl at the opposite side of the room there would be a bowl that would contain coffee beans, which pigs find bitter-tasting," senior author Lisa Collins of the University of Lincoln's School of Life Sciences said, adding that coffee does not harm pigs; they just do not like it.
Over a number of training trials, pigs learned to go to the bowl reliably when it was in the corner where they had figured out to expect M&Ms. Conversely, they quickly learned to avoid the bowl when it was in the corner where they would expect to find the coffee beans.
The researchers next placed an unfamiliar bowl in different locations, to see how the pigs would react. Some gleefully high-tailed it to the bowl no matter what, exhibiting optimism that it would contain their favorite sweets. Others, however, behaved as though they expected it to contain coffee beans, exemplifying pessimism.
The pigs that the scientists observed were upbeat most of the time remained optimistic, no matter their housing conditions. The pessimists, on the other hand, only became optimistic after they were housed for some time in the ultra-comfy pen. These animals are considered to be more "reactive," and vulnerable to change, whereas the happier-go-lucky pigs seem to have more of an inner reserve that serves as a buffer to life's challenges.
RELATED: Surfing Pig? Animals Catch Waves
It could be that optimism and pessimism are far more common traits in the animal kingdom - including insects - than thought.
"Previous research in other species has identified that mood in animals can be influenced by a variety of different things, including the environment the animals are kept in," Collins said. "Personality, on the other hand, is likely to be due to a combination of genetics and environment."
The findings suggest that a one-size-fits-all answer to animal welfare issues does not exist.
"Different individuals, even those that have been bred to share many of the same features for the purposes of commercial farming, are exactly that - individual," Collins explained. "And changes that work to improve the conditions for one may not necessarily work for all. So it is important to maintain an eye on the individual, even while making decisions at a level that affects whole populations."
Even if pigs just equate to bacon or other meat for some people, there is still cause for concern. Studies have suggested that how an animal is treated during its lifetime can directly affect meat quality and taste.
WATCH: Is Your Dog a Pessimist?