To what extent do we have evidence that animals have emotions?

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• breeder
• cow
• mammals
• behavior
• psychology

A dog barks fearfully at a possible intruder. A cat strolls disdainfully past, paying no attention to the people around it. The cow mooses contentedly as it licks its cud. At least, that's how it seems to us when we see animal behavior. To connect to and comprehend the creatures we come across, we draw on our own experiences and fill in the blanks with our imaginations.

Our presumptions are often incorrect. Consider the game of "horse." Many people think these powerful and magnificent creatures are only playing rough. However, mature horses seldom play in the wild. Martine Hausberger, an animal biologist at the CNRS at the University of Rennes in France, believes that the fact that we observe them playing in captivity is not always a positive indicator.

After seeing that horse keepers often misinterpret their charges' body language, horse breeder and breeder Hausberger started researching horse welfare about three decades ago on her property in Brittany.

Does one's disposition really make a difference?

Mendl, together with fellow psychologist Elizabeth Paul of the University of Bristol, zeroed focused on a commonplace aspect of human nature. Negative or good, people's emotions affect their judgment. These pervasive emotional experiences are collectively referred to as "affect" in the field of psychology.

One's perspective on the world is tinted by one's affect, which may be likened as wearing rose-colored or turd-smeared spectacles depending on one's past experiences. In the early 2000s, Mendl, Paul, and graduate student Emma Harding conducted an experiment to disentangle whether or not a rat's emotional state may be altered by its environment.

First, the rats were conditioned to link a certain tone with a reward (food), and another tone with a punishment (aversive sound) (an unpleasant noise). The rats were trained to push a lever in response to a positive tone and to refrain from doing so in response to a negative tone. The researchers separated the animals into two groups, one living in a pleasant, predictable environment, and the other in a frustratingly changeable one.

A few days later, for each animal, the researchers played a beep with a wavelength exactly between the positive and the negative tones. The animals who had lived in the attractive cage pushed the lever, signaling that they were hopeful that pushing the lever would produce a reward. People in the unpredictable cage either didn't use the lever at all or took longer to push it than those in the stable cage, indicating that the latter group was more pessimistic.

Mendl states that they believe their test may reveal whether or not an animal is in a favorable or negative emotional state. Put another way, the rats' actions may be seen as evidence that they evaluate tones according to whether or not they make the listener feel optimistic about the state of the world. At least 22 other species, including mammals, birds, and insects, have been tested using this task or variants thereof since that study.

But, as Mendl points out, there is a major catch. The outcome of the experiment, known as a judgment bias task, might reveal whether an animal is having a pleasant or bad experience. However, the assignment fails to show that the animal can have subjective sensations to begin with.

According to Mason, if animals weren't conscious, then it wouldn't make sense to study their wellbeing. "But none of the measurements we employ can verify or confirm that assumption, since we just don't yet know how to assess sentience," she says.