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How do you know if your hamster is happy?

29 July 2015

Title: Happy hamsters? Enrichment induces positive judgement bias for mildly (but not truly) ambiguous cues to reward and punishment in Mesocricetus auratus

Authors: Emily J. Bethell, Nicola F. Koyama

Journal: Royal Society Open Science

A study published in Royal Society Open Science has found that hamsters with extra toys and cosier bedding in their cages are more likely to make optimistic decisions than those with fewer luxuries. Optimistic judgements are an indicator of positive wellbeing in humans and could potentially indicate wellbeing in hamsters.

Researchers from Liverpool John Moores University tested 30 hamsters to determine if enriching their environment by adding toys and bedding to their cages would change the decisions they made when faced with an uncertain choice.

To begin with, hamsters were offered the choice of two water bottles at either end of a wall in a test cage. One was filled with sweet sugary water and one with bitter quinine water. The hamsters learnt to drink from the sugar water bottle and avoid the quinine.

In the second phase of testing, researchers gave half the hamsters extra luxuries in their cages e.g. a better running wheel, chew sticks, extra bedding and toys. The other half had toys removed from their cages.

The hamsters were tested again. This time only one water bottle was placed in the test cage somewhere between where the sugar water and quinine drink had been. The researchers found hamsters who had been in cages with lots of toys were more likely to approach the mystery bottle to drink from it than the hamsters who’d been in the barer cages.

The team say this shows that the hamsters who had more toys were prone to making choices that were more ‘optimistic’ than the ones who had had less enrichment.

These sorts of biases in decision-making can indicate different states of mind in humans. In people, low mood might result in increased expectation of negative events while a positive mood might lead people to see things in a sunnier light and act more optimistically. The team suggest the same might be true for hamsters.

The test, called a judgement bias test, only shows that the decisions the hamsters made changed in response to how many extra toys they had. It’s difficult to know for certain what an animal’s emotion is but behavioural changes could be an indicator.

‘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,’ say they team.