Pampered pigs 'feel optimistic'
Pigs feel optimistic or pessimistic about life depending on how pleasant their environment is, researchers at Newcastle University have found.
A technique has been developed to "ask" the animals about their mood.
They were put in two groups, one with more space and toys, then taught to associate one noise with a treat and another with something less pleasant.
When a new noise was played, pigs in the better environment were more likely to approach expecting a treat.
Half the pigs were placed in an enriched environment - more space, freedom to roam in straw and play with "pig" toys - while the other half were placed in a smaller, boring environment - no straw and only one non-interactive toy.
In both cases, a note from a glockenspiel was followed by an apple but a dog training clicker led to something mildly unpleasant - the rustling of a plastic bag.
The new and ambiguous sound was a squeak.
Dr Catherine Douglas, who led the experiment, said: "We found that almost without exception, the pigs in the enriched environment were optimistic about what it could mean and approached expecting to get the treat.
"In contrast, the pigs in the boring environment were pessimistic about this new strange noise and, fearing it might be the mildly unpleasant plastic bag, did not approach for a treat."
She said the results were similar to a "glass half empty versus glass half full" interpretation of life, where feelings affect judgement of events.
"For example, if you're having a bad day, feeling stressed and low, and you're presented with an ambiguous cue such as your boss calling you into their office, the first thing that goes through your head is what have I done wrong?", she said.
"But on a good day you greet the same ambiguous event far more positively, you might strut in expecting a slap on the back and a pay rise."
Although techniques exist to measure stress, it has not been possible to directly assess whether or not a pig is happy, and the results, which Dr Douglas described as "compelling" will have implications for animal welfare.
The research, from the School of Agriculture, Food and Rural Development, was funded by the Universities Federation for Animal Welfare.