Do animals enjoy solving puzzles like people do?

Reference: McCoy, D.E., Schiestl, M., Neilands, P., Hassall, R., Gray, R.D., & Taylor, A.H. (2019). New Caledonian crows behave optimistically after using tools. Current Biology, 29, 2737 – 2742.

Smart cat doing sudoku
(1) Cat “solving” a Sudoku puzzle

Do animals enjoy solving puzzles like people do?

Do you have a favorite hobby? Do you paint, play the piano, or dance simply for the fun of it? People find joy and happiness from activities such as playing sports or working towards a goal. Can animals also find joy from performing certain activities? Researchers investigate this question using the cognitive bias test. This test observes how animals react to an ambiguous stimulus, or an object that evokes either a positive or negative emotion. If an animal is in a good mood, they will react to the ambiguous stimulus positively; if they’re in a bad mood, they’ll react to that same stimulus negatively. To understand this task, imagine looking at a doll’s face. Even though the face is neutral and doesn’t change, you may think it’s cute if you’re happy but disturbing if you’re upset.

Past research has focused on how changing the environment an animal is in affects their cognitive state, or whether they are in a good mood or a bad mood. For example, adding fluffy bedding or fun toys to an animal’s house typically leads to a positive state, much like you would be in a good mood if someone put a spa in your house. But can an animal’s activities put them in a good mood? Do animals find joy from solving puzzles like people often do?

Are tools fun to use?

juvenile New Caledonian crow probing in a tree hole with a tool
(2) New Caledonian crow using a stick as a tool to search for insects

Previous research with chimpanzees and New Caledonian crows (a crow species known for their use of tools) suggest that these animals are extremely motivated to use tools to solve problems. But do these animals also feel happier after solving problems? Researchers McCoy and colleagues conducted an experiment to see whether New Caledonian crows feel happier after using tools to get food.


Crows were brought into the laboratory and trained to expect food after opening a box. If the box was on one side of the cage, the box contained a lot of food and if it was on the other side of the cage, the box contained very little food. This setup trained the crows that the location of the box would indicate how large of a food reward they would receive. In half of the trials, the crows were given a stick to help them open the box, whereas in the other half of the trials, the crows had to open the box using only their beak.
(3a) Location of large and small rewards (meat cubes) during training

After the food reward was successfully retrieved, the researchers used a cognitive bias test to see if and how tool use influenced the cognitive state of the crows. The task went as follows: Researchers first placed the box used to hold the food reward in an ambiguous location — halfway between where the boxes were placed during training. Because the box was in a new location that was halfway between the previous locations of the large versus small food rewards, presumably the crows would not know if the box contained a large or small amount of food. Then, the researchers measured the speed at which the crows approached the box (i.e., the ambiguous stimulus). If the crows approached the box quickly, the researchers concluded that the crows were in a better mood and thought there might be a lot of food in the box than if they approached the box slowly.
(3b) Location of ambiguous stimulus during the cognitive bias test. The box is between where the large and small reward boxes were, so the crows don’t know how much meat reward is in this box

Does tool use make crows happier?

Adule and juvenile wild New Caledonian crows, with a tool (juvenile)
(4) New Caledonian crows, one of which is holding a tool used to get food

The crows approached the ambiguous stimulus faster after using tools than if they did not use tools, suggesting that the crows enjoyed using tools and were in a more positive mood and optimistic as a result. In addition, this positive mood was not a result of how easy or hard retrieving the food reward was: crows seem to specifically improve their mood after tool use itself. According to author Dakota McCoy, “our research suggests that animals do not only need to have their basic needs met, but they also benefit from enriching, challenging, complex actions. To truly give animals a fulfilling life, especially smart animals, they need complex, species-specific enrichment.”

So, what?

Because we can’t directly ask animals how they are feeling, the cognitive bias test is a creative way to test an animal’s cognitive state. However, the results from this task are based on an inference that a particular behavior is associated with a specific feeling – in this case, that approaching an ambiguous stimulus is associated with optimism. Given our inability to ask a crow in words if they’re happier after using tools, the cognitive bias test allows us to glean a crow’s mood indirectly.

On a larger scale, this study has a few implications on how tool use may have evolved in crows and other animals, potentially even humans. Tool use clearly serves a practical purpose, helping animals like crows get food. Beyond just their utility, though, this study suggests that tool use itself is rewarding. Crows in this study presumably felt rewarded by using tools; they appeared to be in a better mood afterward as a result.

Emotions and pleasure are found across the animal kingdom, not just in humans. Positive emotions are often found linked with behaviors that are also useful. As brains get more complex, relationships between emotion and behavior emerge. We love solving crosswords and playing bridge even though they don’t help us get food or live longer.

Maybe we originally evolved puzzle-solving and tool-use abilities to find food, but the positive emotions we get from these behaviors lead us to solve puzzles without an immediate reward. We enjoy some things just for their own sake. This study shows that like us, crows enjoy doing things simply because they are fun. Enjoyment from activities may shape the evolution of behaviors like tool use not just in crows, but in many animals.

The next time you feel pleased after solving a brain teaser, think about how that feeling may have led to the evolution of us using tools as a species. Our use of tools has allowed us to shape our world into the technologically-rich place it is today. Technology has allowed us to expand our experiences and knowledge into places we’d never before known existed, and will allow expansion to occur as long as we continue to create the tools to take us there. 


(1) Photo by ringogoingo on Flickr. Accessed 10.06.2019. Link.

(2) Photo by Natalie Uomini on Flickr. Accessed 10.06.2019. Link.

(3) Crow image from Public Domain Pictures. Accessed 10.10.2019. Link. 

(4) Photo by Natalie Uomini on Flickr. Accessed 10.06.2019. Link.