Can Dogs Use Human Emotional Expressions to Identify Which Box Contains Food?

Do expressions of happiness and disgust on a person's face tell dogs which box contains tasty food?

A labrador retriever with a rope toy in its mouth, looking at the camera
Labrador Retrievers were one of the breeds to take part in the study
Photo: Carolyn Brule / Shutterstock

By Zazie Todd, PhD

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Dogs are very aware of human emotional states. An earlier blog post looked at how dogs respond to a crying stranger. This week’s post is about whether or not dogs can use human emotional cues to tell them which of two boxes contains a tasty treat.

The research was conducted by David Buttelmann and Michael Tomasello in Germany. They compared two sets of human emotional expressions: Happy vs Neutral; and Happy vs Disgust. They tested 58 domestic dogs (Siberian Huskies, Labrador Retrievers, Golden Retrievers, Border Collies and German Shepherds). The Siberian Huskies were tested at the open air enclosure where they lived, and the other dogs were all tested in a room, mostly with the owner present.

The experimental set-up involved two cardboard boxes, each containing an item that acted as a clue to the experimenter as to which emotion they should display: sausage for the happy condition, wood shavings for the neutral condition, and garlic for disgust.  

The dogs were given a warm-up in which they were shown a pair of boxes and learned that they would receive any food that was in the box they chose. Then a screen was put up, and the experimenter pretended to be busy while an assistant placed items in the boxes.

When the screen was removed, the experimenter came to the table and called the dog over to watch. The experimenter lifted the lid of each box in turn and acted out the appropriate emotion. There were two boxes in each condition, so they acted either Happy and Neutral, or Happy and Disgust, depending on the condition. For the Happy and Disgust emotions, they also said the German word for nightingale in an appropriate tone of voice. This word had no meaning for the experiment, so only the tone of voice was relevant to the dogs.

The dogs were given a chance to choose a box, and then shown the contents. If it was sausage, they were allowed to eat it. Then the whole procedure was repeated. If the dogs showed a bias to a particular side (e.g. they always chose the box on the left), there was another warm-up session in which they were shown that either box might contain food.

The results showed that in the Happy-Neutral condition, the dogs chose the Happy box 52.1% of the time. In the Happy-Disgust condition, they chose the Happy box 54.9% of the time. In each case, this was significantly better than chance, suggesting that they were using the human expressions as a clue.

Some individual dogs performed exactly at chance levels. This was because they chose a side and stuck to it throughout the experiment, despite the warm-up session designed to show that the box on either side could contain food.

For some reason the Siberian Huskies performed better than the other dogs. Since the huskies were tested outside, they may have been able to use smell to distinguish between the boxes, especially since they were tested on a windy day. 

So a control condition was done with just Siberian Huskies, outside. This had the same procedure, i.e. one box contained sausage and the other contained either wood shavings or garlic, but the experimenter always had a neutral expression. In this case, where the dogs had no emotional expression to help them, they did not perform significantly better than chance. However, they also did not perform significantly better than in the earlier experiment.

These results suggest that dogs can distinguish human emotions, and use them to help identify which of two boxes contains food. However, the reason why the Siberian Huskies performed better than the other dogs is unexplained, which suggests that further research is needed before we can draw a definite conclusion. 

One thing missing from this research report is a consideration of what a social scientist would call the lived experience of the dog. What I mean is that a dog’s experience of observing human emotions may not show them to be a reliable indicator of whether or not something is tasty. Some dogs have a habit of finding things to eat that cause a look of disgust on their owner’s face, even though the dog likes it very much.

This is a fascinating piece of research despite the fact there are a few things to tease out.  I look forward to seeing the follow-up studies. 

If you liked this post, check out my book Wag: The Science of Making Your Dog Happy. Modern Dog magazine calls it "The must-have guide to improving your dog's life."

What disgusting things does your dog like to eat? As always, feel free to leave any other comments you have about this research.

Zazie Todd, PhD, is the award-winning author of Wag: The Science of Making Your Dog Happy and Purr: The Science of Making Your Cat Happy. She is the creator of the popular blog, Companion Animal Psychology, and also has a column at Psychology Today. Todd lives in Maple Ridge, BC, with her husband, one dog, and two cats. 

Buttelmann, D., & Tomasello, M. (2013). Can domestic dogs (Canis familiaris) use referential emotional expressions to locate hidden food?. Animal Cognition, 16, 137-145.

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