Pigs have personalities that can be trough half-full or trough half-empty, a study shows.
Scientists tested 36 domestic pigs, some of which were treated to enriched living conditions with extra space and layers of deep straw.
Their personalities were investigated by offering them food bowls in two fixed locations and containing sugar-coated chocolates or disappointing coffee beans.
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Pro-active, optimistic pigs were more likely to investigate a bowl placed between the two locations that might or might not be filled with delicious sweets.
They always looked on the bright side, whatever environment they had to live in.
Moody reactive animals with less space and no straw tended to be negative and pessimistic, but were cheered up by an improvement in living conditions.
The findings are published in the Royal Society journal Biology Letters.
Dr Lisa Collins, from the University of Lincoln, and colleagues wrote: "Reactive pigs in the less enriched environment were more pessimistic and those in the more enriched environment more optimistic.
"These results suggest that judgment in non-human animals is similar to humans, incorporating aspects of stable personality traits and more transient mood states."
