'Puppy Dog Eyes' Are Associated With Eye Movements, Not Communication.

Annika Bremhorst,Stefanie Riemer,Daniel S Mills,Lisa Stolzlechner,Hanno Würbel

doi:10.3389/fpsyg.2021.568935

Annika Bremhorst, Stefanie Riemer + Show 3 more

Open Access

https://doi.org/10.3389/fpsyg.2021.568935

Copy DOI

Abstract

The inner brow raiser is a muscle movement that increases the size of the orbital cavity, leading to the appearance of so-called ‘puppy dog eyes’. In domestic dogs, this expression was suggested to be enhanced by artificial selection and to play an important role in the dog-human relationship. Production of the inner brow raiser has been shown to be sensitive to the attentive stance of a human, suggesting a possible communicative function. However, it has not yet been examined whether it is sensitive to human presence. In the current study, we aimed to test whether the inner brow raiser differs depending on the presence or absence of an observer. We used two versions of a paradigm in an equivalent experimental setting in which dogs were trained to expect a reward; however, the presence/absence of a person in the test apparatus was varied. In the social context, a human facing the dog delivered the reward; in the non-social context, reward delivery was automatized. If the inner brow raiser has a communicative function and dogs adjust its expression to an audience, we expect it to be shown more frequently in the social context (when facing a person in the apparatus) than in the non-social context (when facing the apparatus without a person inside). The frequency of the inner brow raiser differed between the two contexts, but contrary to the prediction, it was shown more frequently in the non-social context. We further demonstrate that the inner brow raiser is strongly associated with eye movements and occurs independently in only 6% of cases. This result challenges the hypothesis that the inner brow raiser has a communicative function in dog-human interactions and suggests a lower-level explanation for its production, namely an association with eye movements.

Highlights

Facial expressions accompany emotional states in humans and non-human animals and can provide information about an individual’s intentions and potential future behavior (Waller et al, 2017), both in positive contexts such as signaling playful intent (Fox, 1970) and in negative contexts such as predicting aggression (Camerlink et al, 2018)
The frequency of the inner brow raiser was unrelated to sample order both within the non-social context and the social context
13 1,214 to the prediction, dogs performed the inner brow raiser more frequently in the non-social context, regardless of the expected reward type, trial valence, subject sex, or age. This direction of effect challenges the assumption that the inner brow raiser is used functionally by dogs for communication with humans, and alternative explanations for the production of the inner brow raiser need to be considered

Summary

Introduction

Facial expressions accompany (putative) emotional states in humans and non-human animals (reviewed by Descovich et al, 2017) and can provide information about an individual’s intentions and potential future behavior (Waller et al, 2017), both in positive contexts such as signaling playful intent (Fox, 1970) and in negative contexts such as predicting aggression (Camerlink et al, 2018). While facial expressions have often been considered to be mainly reflexive and invariable, AU101 Not for Communication when linked to emotional states (see e.g., Liebal et al, 2014; Scheider et al, 2016; reviewed by Jones et al, 1991; Kaminski et al, 2017), for humans and several nonhuman primate species there is evidence of audience effects on the production of facial expressions: individuals will adjust their facial displays depending on the presence or attentive state of an observer (e.g., Kraut and Johnston, 1979; Jones et al, 1991; Liebal et al, 2004; Poss et al, 2006; Demuru et al, 2015; Waller et al, 2015; Scheider et al, 2016) This sensitivity to an audience suggests a communicative function of the respective expression (Leavens et al, 1996), which may constitute a ’signal,’ i.e., a behavior evolved for the purpose of information conveyance (Laidre and Johnstone, 2013). The visibility of the food item, did not significantly affect the dogs’ facial display, suggesting that it does not primarily constitute an emotional expression (Kaminski et al, 2017)

Objectives

Results

Conclusion