A pig poking its head out of a fence.

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Pessimist pigs are positive if they have nice digs

Your personality and your mood determine how you will react to an uncertain situation. If you’re an optimist, chances are you’ll respond positively no matter the circumstances. But if you’re a pessimist, your reaction is far more dependent on your mood. It turns out that other animals share this personality and mood-based decision-making process. To find out how optimistic—and pessimistic—pigs reacted to uncertain situations, researchers raised 27 young pigs in either spacious pens with deep straw or smaller areas with little straw. They then ranked the animals’ personalities based on their reaction to novel situations. More optimistic pigs were more daring, whereas more pessimistic pigs were more cautious. The scientists then trained the animals to feed from a bowl in a test arena. If the bowl was in one corner, it held three sweets, but if it was in the opposite corner, it contained three bitter coffee beans. All of the pigs quickly learned which corner was the positive one, and made a beeline whenever the bowl was there. But when the scientists slightly altered the setup, placing the bowl somewhere in the middle, pessimist pigs that lived in better pens were more curious about what the bowl might contain, hustling to find out even when the bowl was in the middle or close to the negative corner. But pessimist pigs that lived in shabbier pens were less interested about what they would find, and dawdled. What about the optimist pigs? Regardless of their housing conditions, most happily approached all the bowls, a response that fits with what’s known about animals with this personality trait, the researchers report today in Biology Letters. The study shows that the judgments of pigs—like those of humans—are shaped by both their basic personality traits and their mood.

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