A little more than a decade ago, Mike Mendl developed a new test for gauging a laboratory rat’s level of happiness. Mendl, an animal welfare researcher in the veterinary school at the University of Bristol in England, was looking for an objective way to tell whether animals in captivity were suffering. Specifically, he wanted to be able to measure whether, and how much, disruptions in lab rats’ routines—being placed in an unfamiliar cage, say, or experiencing a change in the light/dark cycle of the room in which they were housed—were bumming them out.
He and his colleagues explicitly drew on an extensive literature in psychology that describes how people with mood disorders such as depression process information and make decisions: They tend to focus on and recall more negative events and to judge ambiguous things in a more negative way. You might say that they tend to see the proverbial glass as half-empty rather than half-full. “We thought that it’s easier to measure cognitive things than emotional ones, so we devised a test that would give us some indication of how animals responded under ambiguity,” Mendl says. “Then, we could use that as a proxy measure of the emotional state they were in.”
[Read the story at Nautilus // April 13, 2017]