If you’ve ever bought a lottery ticket on a day everything seemed to be going your way or found yourself inhaling a pint of ice cream after a breakup, you’re well aware that your mood can influence your behavior.
But we’re not the only species whose emotions affect our decisions. Researchers have determined that primates, cats, dogs, mice, horses, pigs and even honeybees also display some degree of mood-congruent judgment.
In other words, just like us, these animals view the world through a rose-colored lens when they’re happy and a darker, gloomier lens when they’re unhappy, and this plays a role in whether they expect negative or positive things to happen to them.
It appears hamsters do this as well, according to new research by scientists from Liverpool John Moores University.
To determine if hamsters’ decisions could be influenced by mood, the researchers taught 30 captive-bred Syrian hamsters to associate a container on the right side of their cage with sugary water and a container on the left side of their cage with bitter water.
Then they divided the animals into separate cages. One group lived the hamster high life in cages decked out with extra bedding, wheels, chew toys, huts and hammocks, while the other group received only some light Aspen-chip bedding.
The researchers then began adding new containers to the hamsters’ cages and randomly filling them with either the bitter or sweet-tasting water. The new containers spaced throughout the cage were intended to encourage exploration and provide the animals with opportunities to take a chance on a container that might offer a sweet treat.
Scientists found that the hamsters living in the more luxurious cages were 12 percent more likely to try the water in the new containers than the hamsters living in the more minimal cages. They also found that when they swapped the animals’ cages, the hamsters’ behavior also switched.
The researchers concluded that the hamsters in the cages with more toys and bedding were more optimistic about the chances of being rewarded than their counterparts in the other cages.
“We cannot say whether the hamsters in our study felt happy in their enriched housing, but the changes in cognitive processing of ambiguous cues certainly suggests enriched hamsters became more optimistic about the likelihood of future reward when faced with uncertain information,” the researchers wrote.
So if you want your pet hamster to see his water bowl as half full, be sure to fill his cage with toys and treats.