Domestication constrains the ability of dogs to convey emotions via facial expressions in comparison to their wolf ancestors

Abstract:

Dogs (Canis lupus familiaris) are the domestically bred descendant of wolves (Canis lupus). However, selective breeding has profoundly altered facial morphologies of dogs compared to their wolf ancestors. We demonstrate that these morphological differences limit the abilities of dogs to successfully produce the same affective facial expressions as wolves. We decoded facial movements of captive wolves during social interactions involving nine separate affective states. We used linear discriminant analyses to predict affective states based on combinations of facial movements. The resulting confusion matrix demonstrates that specific combinations of facial movements predict nine distinct affective states in wolves; the first assessment of this many affective facial expressions in wolves. However, comparative analyses with kennelled rescue dogs revealed reduced ability to predict affective states. Critically, there was a very low predictive power for specific affective states, with confusion occurring between negative and positive states, such as Friendly and Fear. We show that the varying facial morphologies of dogs (specifically non-wolf-like morphologies) limit their ability to produce the same range of affective facial expressions as wolves. Confusion among positive and negative states could be detrimental to human–dog interactions, although our analyses also suggest dogs likely use vocalisations to compensate for limitations in facial communication.

Significance:

We demonstrate that identifiable combinations of facial movements relate to nine specific affective states in wolves, whereas divergent head and facial feature morphologies among domestic dog breeds limit their ability to produce the same affective facial expressions. It is well known that selective breeding has led to a wealth of physical health problems in many domestic dog breeds. Here we show that selective breeding also generates social communicative limitations in dogs, potentially impacting dog–human interactions. Quantifying associations between facial expressions and affective states may provide a foundation for monitoring welfare in wild and captive canids and allows for cross-species comparisons to yield insight into the emotional evolution in Canidae.

About the study:

This study provides the first measurable evidence that domestic dogs are limited in their ability to produce the same emotional facial expressions as their wolf ancestors, in particular dog breeds with non-wolf-like head and facial feature morphologies. However, we also provide evidence that dogs with the more limiting (non-wolf-like) morphologies actually vocalise more than wolves and wolf-like dogs for any given social situation, which suggests that non-wolf-like dogs use vocalisations to convey their emotions as a compensatory affect for their lack of facial communication.

It is important to understand what your companion dog is trying to convey for welfare purposes and humans tend to look to facial expressions to gather information about emotional states. However, many dog breeds, in particular those with brachycephalic faces (short, broad heads and short muzzles) and flopped ears such as ‘bully-breeds’ are the most limited in their ability to express their emotions via facial expressions. This study shows that confusion often occurs between positive and negative emotions in domestic dogs, which is concerning. For example, a large proportion of the non-wolf-like dogs used in this study that displayed fear facial expressions were misinterpreted as displaying friendly facial expressions. Many dogs can become ‘fear aggressive’ and will bite in defence when scared. If a human or another dog misinterpreted fear as friendly it would increase the risk of being bitten or indeed a fight breaking out between dogs. It is well known that many dogs are bred with debilitating physical health issues (such as breathing problems seen in bulldogs) but, this study also shows that selective breeding may be producing dogs with communicative issues.

Note from Elana Hobkirk:

This research also demonstrates for the first time that wolves are capable of producing a wide range of emotional facial expressions, which gives insights into their sentience. It is my hope that this research allows wolves to be viewed in a more positive light and will aid conservation efforts by showing just how complex, charismatic and relatable wolves truly are. This research opens a door into a vast, relatively unstudied (certainly unquantified) area that I aim to pursue further and build a career on. I have been obsessed with wolves, dogs and other canids my entire life, I came to Durham University to study Zoology and I conceived this research as an undergraduate student while writing my final year literature review on wolf behaviour. I conducted this research for my Masters by Research degree and now I plan to continue this research for a PhD and build my academic career upon it.

Further Information:

• Read the full publication in Nature Scientific Reports here
• Find out about the Department of Biosciences at Durham University
• Learn more about the work of Dr Sean Twiss here at Durham University and Elana's work here on Facebook.
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Image Credit: Elana Hobkirk