Nasal Oxytocin Treatment Biases Dogs’ Visual Attention and Emotional Response toward Positive Human Facial Expressions

Abstract

The neuropeptide oxytocin plays a critical role in social behavior and emotion regulation in mammals. The aim of this study was to explore how nasal oxytocin administration affects gazing behavior during emotional perception in domestic dogs. Looking patterns of dogs, as a measure of voluntary attention, were recorded during the viewing of human facial expression photographs. The pupil diameters of dogs were also measured as a physiological index of emotional arousal. In a placebo-controlled within-subjects experimental design, 43 dogs, after having received either oxytocin or placebo (saline) nasal spray treatment, were presented with pictures of unfamiliar male human faces displaying either a happy or an angry expression. We found that, depending on the facial expression, the dogs’ gaze patterns were affected selectively by oxytocin treatment. After receiving oxytocin, dogs fixated less often on the eye regions of angry faces and revisited (glanced back at) more often the eye regions of smiling (happy) faces than after the placebo treatment. Furthermore, following the oxytocin treatment dogs fixated and revisited the eyes of happy faces significantly more often than the eyes of angry faces. The analysis of dogs’ pupil diameters during viewing of human facial expressions indicated that oxytocin may also have a modulatory effect on dogs’ emotional arousal. While subjects’ pupil sizes were significantly larger when viewing angry faces than happy faces in the control (placebo treatment) condition, oxytocin treatment not only eliminated this effect but caused an opposite pupil response. Overall, these findings suggest that nasal oxytocin administration selectively changes the allocation of attention and emotional arousal in domestic dogs. Oxytocin has the potential to decrease vigilance toward threatening social stimuli and increase the salience of positive social stimuli thus making eye gaze of friendly human faces more salient for dogs. Our study provides further support for the role of the oxytocinergic system in the social perception abilities of domestic dogs. We propose that oxytocin modulates fundamental emotional processing in dogs through a mechanism that may facilitate communication between humans and dogs.

The Way Dogs (Canis familiaris) Look at Human Emotional Faces Is Modulated by Oxytocin. An Eye-Tracking Study

“…A possible solution to this methodological problem is to train the dogs to lie still for the purpose of an eye-tracking study. For example, in a recent study in which dogs were specifically trained to meet the requirements of eye-tracking (Somppi et al, 2017 ) 43 of the 46 recruited subjects successfully completed the experiment. However training dogs for such a task might heavily influence their looking pattern as well as their cognitive processes during image viewing, as training has been shown to modulate attention in general (Vas et al, 2007 ).…”

Perception of dynamic facial expressions of emotion between dogs and humans

“…Similar to humans, dogs prefer to fixate on internal facial features (especially the eyes, Somppi et al 2014), but other eye-tracking studies show that fixations on facial elements depend on the facial expression, with the specifics relating to gaze allocation being somewhat inconsistent. In some studies (Barber et al 2016;Somppi et al 2017), dogs fixated more on the mouth and eyes in negative expressions and the forehead in positive expressions; whereas in another study (Somppi et al 2016), dogs fixated more on the eyes and midface than the mouth in negative facial expressions and more on the eyes in pleasant faces, but attended more to the mouth of negative dog faces compared to positive ones. Somppi et al (2017) suggest that enhanced gaze towards the eyes of emotional faces is related to the dog observer's emotional state; a perceptual bias induced by the emotional content of the face may help to focus observation on the signalling areas of greatest biological relevance (Albuquerque et al 2018).…”

“…In some studies (Barber et al 2016;Somppi et al 2017), dogs fixated more on the mouth and eyes in negative expressions and the forehead in positive expressions; whereas in another study (Somppi et al 2016), dogs fixated more on the eyes and midface than the mouth in negative facial expressions and more on the eyes in pleasant faces, but attended more to the mouth of negative dog faces compared to positive ones. Somppi et al (2017) suggest that enhanced gaze towards the eyes of emotional faces is related to the dog observer's emotional state; a perceptual bias induced by the emotional content of the face may help to focus observation on the signalling areas of greatest biological relevance (Albuquerque et al 2018). Nonetheless, in general, dogs tend to look more towards negative dog faces than positive human faces (Somppi et al 2016).…”

Low-dose intranasal oxytocin delivered with Breath Powered device modulates pupil diameter and amygdala activity: a randomized controlled pupillometry and fMRI study

“…Direct administration of oxytocin and arginine vasopressin into the eye has also been reported to constrict the rabbit pupil, both in vitro and in vivo, suggesting that oxytocin may act directly on iris sphincter muscles [36]. Intranasal oxytocin administration in dogs was shown to constrict the pupils in response to the presentation of angry human faces compared to happy human faces, however, the opposite effect was found after placebo administration [37]. Of note, prior human pupillometry research has not included non-social stimuli, so it is unclear if the effects of oxytocin on pupil activity are exclusive to social stimuli or if they also modulate pupil activity during the processing of non-social stimuli.…”