The depressing thing that humans and pigs have in common

Enlarge / That'll do, pig.

It turns out that pigs make arbitrary decisions for some of the same reasons humans do. They get moody and peevish, and they allow those feelings to dictate judgement. By subjecting pigs to a series of experiments involving chocolate candies and uncomfortable beds, a group of UK researchers determined that pigs have some of the same psychological blind spots as humans.

Scientists have long known that humans suffer from cognitive biases that stem from our fundamental personalities interacting with more transient moods. University of Newcastle neuroscientist Lucy Asher and colleagues explain in a Biology Letters paper that pig personalities can be grouped into two groups: proactive and reactive. Proactive pigs tend to be extroverted, inflexible, and optimistic, while reactive ones are neurotic and easily affected by their environments. The researchers did personality tests on 36 pigs to determine whether they were proactive or reactive and then put them in a variety of situations where they had to make split-second decisions about whether to seek out a hidden treat.

Here's how it worked. For several days in a row, the pigs were given a dish with a false bottom that contained three delicious chocolate candies. The dish would always be put in the exact same spot. At the same time, the pigs were given a similar dish with much-loathed (among pigs) coffee beans under the false bottom. The disgusting coffee dish was also placed in a distinctive spot. After a while, the pigs learned to make a beeline for the dish in the chocolate spot and ignore the dish in the coffee spot. (Both dishes had been coated in sugar, so they smelled the same.) These learning sessions also gave the researchers a sense of how quickly the pigs would move toward the dish if they felt optimistic about finding a hidden tasty treat.