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Is Your Dog’s Food Bowl Half Full or Half Empty?

How to tell if your dog is a pessimist or optimist.

Artwork: Sarah Alsmiller

Guest post by Sky Sobol

We all know people who are optimists. The glass is always half-full, and they see the bright side of everything. We also all know some pessimists — people that see  the glass half-empty and read doom and gloom into the most neutral events. In humans, it is easy to tell how optimistic someone is, but what about your dog? Does your dog see the food bowl half-empty or half-full? Fortunately, science can help answer this question. 

In human psychology a person’s tendency towards optimism or pessimism is called judgment bias (Roelofs and van de Staay 2017).  Optimistic people have positive judgment bias and pessimistic people have negative judgment bias.  Optimism and pessimism are not fixed traits, and in humans, these traits shift based on positive and negative life experiences and reflect emotion (Schwaba et al 2019). The ability to measure someone’s judgment bias can give us a window into a person’s emotional state and well-being. 

Animals also have judgment biases. In animal welfare research, we can measure judgment bias in animals using something called a “judgment bias test” (Mendl et al 2009). This test has been used on a variety of animals, including dogs (Mendl et al 2010), and can tell us if animals are feeling optimistic or pessimistic. Just like with humans (Conversano et al 2010), levels of optimism can tell us a lot about an animal’s well-being, so the judgment bias test can, in essence, measure an animal’s welfare. 

Initially, this test was created using rats (Harding et al 2004), and rats are a great model to show how this test works. I’ll explain the test using two rats. One rat is named Zelda, and the other is named Zoe.

In order to start the test, Zelda and Zoe begin a training phase. Zelda and Zoe are individually placed in a room with a lever. They are trained that when they hear a musical tone (let’s call this tone A-sharp) they will get a treat if they push the lever. Alternatively, Zelda and Zoe also learn that every time they hear another musical tone (we’ll call this one D-flat), they will get shocked if they push the lever. Both the rats learn this quickly. But what happens when we introduce a new musical tone (this tone will be a B)? Will Zelda and Zoe push the lever?

Rats are taught to discriminate between tones that mean cheese or no cheese
Rats are taught to discriminate between a musical tone that predicts a treat (left) when a lever is pressed and another musical tone that predicts a shock (middle) when the lever is pressed. What happens when an ambiguous tone is played? (right). Image: Sky Sobol.

That is where the test begins. When Zelda hears the new tone she runs quickly to push the lever. We can assume that Zelda is more optimistic because she probably thinks that she is going to get a treat when she hears the B note. However, Zoe shows a lot of hesitation and it takes her a lot longer to push the lever, if she even pushes the lever at all.  Zoe is likely more pessimistic since she probably thinks she is going to get a shock from the middle lever when she hears the B note.

The optimistic rat thinks they will get cheese, while the pessimistic one does not, when they hear the ambiguous tone
The optimistic Zelda assumes that the tone is going to produce a treat. The pessimistic Zoe assumes the tone is going to produce a shock. Sky Sobol.

Training dogs with electric shock negatively impacts dog welfare (Ziv 2017). Since we do not want to shock our dogs, the test looks a little bit different from how it is conducted in rats. We have two dogs, Rufus and Rainy, that will help us explain this test. Rufus and Rainy are individually placed in a room where they are taught that the left location contains a bowl with a treat, and that the right location contains an empty bowl. 
A dog learns that a bowl on the left always has food whereas the one on the right is empty
Dogs are taught to discriminate between a treat and no treat. Sky Sobol. 

A dog decides what they think the bowl in the ambiguous location will contain
Like in the rat experiment, a middle ambiguous bowl is introduced. Sky Sobol.

Once the two dogs learn the difference between the two locations, an ambiguous bowl is introduced in the middle. Like Zelda, if Rufus runs quickly to the bowl, we can assume that Rufus is more optimistic because he probably assumes he is going to get a treat. On the other hand, Rainy shows a lot of hesitation towards the ambiguous bowl and might not even approach the bowl at all.  We can assume Rainy is more pessimistic since he probably thinks that he is not going to get a treat.

The optimistic dog thinks the bowl will contain food, while the pessimistic dog doesn't
This optimistic dog assumes that the food bowl is going to produce a treat. The pessimistic dog assumes that the middle bowl will have no treat. Sky Sobol.

While it is great that we can quantify optimism and pessimism in animals, this test also has even broader uses. We can look at the optimism and pessimism levels between different groups of dogs by comparing the average time it takes for both groups to get to the middle bowl. For example, this test has helped us find that owned dogs are generally more optimistic than shelter dogs (Burani et al 2020). This makes sense as shelter dogs often experience high levels of stress and uncertainty.

An optimistic dog at a viewpoint at the top of a mountain
Photo: Sky Sobol

Since optimism and pessimism are not fixed traits and can be influenced by life experiences, the judgment bias test is useful in illuminating what sort of life conditions can impact our dogs’ welfare. Using this knowledge, we can make changes to help our pups learn to see the food bowl as half-full instead of half-empty. 

Sky Sobol pictured with her dog.
Sky Sobol with her dog

Sky Sobol is an Ecology, Evolution, and Behavior P.hD. student at Boise State University, and she studies dog welfare and behavior. When she started her research, she found that there were not many ways to measure a dog’s emotional state. Fortunately, she discovered the judgment bias test, and she is here to help you understand how this test works and what it can tell us. 


Burani, C., Barnard, S., Wells, D., Pelosi, A., & Valsecchi, P. (2020). Using judgment bias test in pet and shelter dogs (Canis familiaris): Methodological and statistical caveats. Plos one, 15(10), e0241344.

Conversano, C., Rotondo, A., Lensi, E., Della Vista, O., Arpone, F., & Reda, M. A. (2010). Optimism and its impact on mental and physical well-being. Clinical practice and epidemiology in mental health: CP & EMH, 6, 25.

de Castro, A. C. V., Fuchs, D., Morello, G. M., Pastur, S., de Sousa, L., & Olsson, I. A. S. (2020). Does training method matter? Evidence for the negative impact of aversive-based methods on companion dog welfare. Plos one, 15(12), e0225023.

Fernandes, J. G., Olsson, I. A. S., & de Castro, A. C. V. (2017). Do aversive-based training methods actually compromise dog welfare?: A literature review. Applied Animal Behaviour Science, 196, 1-12.

Harding, E. J., Paul, E. S., & Mendl, M. (2004). Cognitive bias and affective state. Nature, 427(6972), 312-312.

Mendl, M., Brooks, J., Basse, C., Burman, O., Paul, E., Blackwell, E., & Casey, R. (2010). Dogs showing separation-related behaviour exhibit a ‘pessimistic’cognitive bias. Current Biology, 20(19), R839-R840.

Mendl, M., Burman, O. H., Parker, R. M., & Paul, E. S. (2009). Cognitive bias as an indicator of animal emotion and welfare: Emerging evidence and underlying mechanisms. Applied Animal Behaviour Science, 118(3-4), 161-181.

Roelofs, S., & van der Staay, F. J. (2017). Judgment bias. Encyclopedia of Animal Cognition and Behavior, 7.

Schwaba, T., Robins, R. W., Sanghavi, P. H., & Bleidorn, W. (2019). Optimism development across adulthood and associations with positive and negative life events. Social Psychological and Personality Science, 10(8), 1092-1101.

Ziv, G. (2017). The effects of using aversive training methods in dogs—A review. Journal of Veterinary Behavior, 19, 50-60.


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