What Is Written on a Dog’s Face? Evaluating the Impact of Facial Phenotypes on Communication between Humans and Canines

Abstract

Facial phenotypes are significant in communication with conspecifics among social primates. Less is understood about the impact of such markers in heterospecific encounters. Through behavioral and physical phenotype analyses of domesticated dogs living in human households, this study aims to evaluate the potential impact of superficial facial markings on dogs’ production of human-directed facial expressions. That is, this study explores how facial markings, such as eyebrows, patches, and widow’s peaks, are related to expressivity toward humans. We used the Dog Facial Action Coding System (DogFACS) as an objective measure of expressivity, and we developed an original schematic for a standardized coding of facial patterns and coloration on a sample of more than 100 male and female dogs (N = 103), aged from 6 months to 12 years, representing eight breed groups. The present study found a statistically significant, though weak, correlation between expression rate and facial complexity, with dogs with plainer faces tending to be more expressive (r = −0.326, p ≤ 0.001). Interestingly, for adult dogs, human companions characterized dogs’ rates of facial expressivity with more accuracy for dogs with plainer faces. Especially relevant to interspecies communication and cooperation, within-subject analyses revealed that dogs’ muscle movements were distributed more evenly across their facial regions in a highly social test condition compared to conditions in which they received ambiguous cues from their owners. On the whole, this study provides an original evaluation of how facial features may impact communication in human–dog interactions.

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

“…This implies that domestic dogs (across breed-types) are inconsistent in the way they convey affective states via facial expressions. Such high levels of confusion between positive and negative affective states is potentially detrimental to dog–dog and dog–human communication 91 . For example, many dogs that are fearful can become ‘fear aggressive’ and will bite to defend themselves from potential threats 92 , 93 .…”

What does that head-tilt mean? Brain Lateralization and Sex Differences in the Processing of Familiar Human Speech by Domestic Dogs

“…Due to the COVID-19 pandemic, data were collected via community science, using owner-submitted videos. See Sexton et al 13 for details.…”

“…Data collection was done throughout the COVID-19 pandemic utilizing community science, meaning no in-person collection could be performed. See Supplementary Materials and Sexton et al 13 .…”