Dogs Evaluate Threatening Facial Expressions by Their Biological Validity – Evidence from Gazing Patterns

Abstract

Appropriate response to companions’ emotional signals is important for all social creatures. The emotional expressions of humans and non-human animals have analogies in their form and function, suggesting shared evolutionary roots, but very little is known about how animals other than primates view and process facial expressions. In primates, threat-related facial expressions evoke exceptional viewing patterns compared with neutral or positive stimuli. Here, we explore if domestic dogs (Canis familiaris) have such an attentional bias toward threatening social stimuli and whether observed emotional expressions affect dogs’ gaze fixation distribution among the facial features (eyes, midface and mouth). We recorded the voluntary eye gaze of 31 domestic dogs during viewing of facial photographs of humans and dogs with three emotional expressions (threatening, pleasant and neutral). We found that dogs’ gaze fixations spread systematically among facial features. The distribution of fixations was altered by the seen expression, but eyes were the most probable targets of the first fixations and gathered longer looking durations than mouth regardless of the viewed expression. The examination of the inner facial features as a whole revealed more pronounced scanning differences among expressions. This suggests that dogs do not base their perception of facial expressions on the viewing of single structures, but the interpretation of the composition formed by eyes, midface and mouth. Dogs evaluated social threat rapidly and this evaluation led to attentional bias, which was dependent on the depicted species: threatening conspecifics’ faces evoked heightened attention but threatening human faces instead an avoidance response. We propose that threatening signals carrying differential biological validity are processed via distinctive neurocognitive pathways. Both of these mechanisms may have an adaptive significance for domestic dogs. The findings provide a novel perspective on understanding the processing of emotional expressions and sensitivity to social threat in non-primates.

Decoding Human Emotional Faces in the Dog’s Brain

“…Although we cannot determine the degree of attention that dogs paid to our stimuli, this interpretation is compatible with the fact that happy faces are salient for dogs. Several behavioral studies in dogs have not found differences between happy and neutral human faces 5,6,28,33 , yet we found differences in brain activity related to these two types of stimuli. Our results suggest that the specific brain activity to happy human faces reflects that these stimuli are important for dogs.…”

“…An interesting study showed that once dogs learn from images of their owners' faces to discriminate a smiling face from a neutral face, they can generalize their learning to other humans of the same gender as their owners 2 . An eye-tracking study 6 found that dogs use a conjunction of information from eyes, midface, and mouth (i.e., inner face) to process faces in general; however, when looking at a pleasant human face, dogs spend significantly more time looking at the eyes in comparison to the mouth. The same authors also found different gazing patterns when dogs looked at threating and pleasant human faces, but not between pleasant and neutral faces.…”

Human Empathy, Personality and Experience Affect the Emotion Ratings of Dog and Human Facial Expressions

“…a toaster, a coffee maker, a wall clock, a backpack) from the BOSS database [63]. The face stimuli were characterized with facial action coding system (FACS, [64]) and dog-FACS [8], and they were first used in a study examining dogs’ gazing patterns; for more details of the human and dog faces, see [12]. …”

“…Furthermore, dogs have many of the same muscles that produce facial expressions in humans [8], and their facial expressions are connected to the affective situation [9]. Dogs can differentiate emotions displayed by either human or dog facial expressions [10–12], and they also show rapid facial mimicry in response to a conspecific expression during play [13]. Facial expressions thus provide important information of conspecific emotions also for dogs; they reflect at least some of their emotional states by the face and react to others’ expressions accordingly.…”

Vegetative symptoms and behaviour of the therapy-accompanying dog of a chronically suicidal patient

“…Incidentally, the same held true for the patient’s dog in the presented case. Findings of a study with voluntary eye gaze of domestic dogs suggest that dogs evaluate social threat rapidly and that they do not base their perception of facial expressions on the viewing of a single structure, but on the interpretation of a constellation of areas comprising eyes, mid-face and mouth 13. Huber et al 14 showed that dogs expressed more behavioural indicators for arousal and negatively valenced states after hearing negative emotional sounds from humans or conspecifics, which indicates that dogs recognised the different valences of the emotional sounds.…”