Evaluating the accuracy of facial expressions as emotion indicators across contexts in dogs

A Bremhorst,D S Mills,H Würbel,S Riemer

doi:10.1007/s10071-021-01532-1

A Bremhorst, D S Mills + Show 2 more

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https://doi.org/10.1007/s10071-021-01532-1

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Journal: Animal cognition	Publication Date: Aug 2, 2021
Citations: 12	License type: open-access

Affiliation: University of Bern, University of Lincoln

Abstract

Facial expressions potentially serve as indicators of animal emotions if they are consistently present across situations that (likely) elicit the same emotional state. In a previous study, we used the Dog Facial Action Coding System (DogFACS) to identify facial expressions in dogs associated with conditions presumably eliciting positive anticipation (expectation of a food reward) and frustration (prevention of access to the food). Our first aim here was to identify facial expressions of positive anticipation and frustration in dogs that are context-independent (and thus have potential as emotion indicators) and to distinguish them from expressions that are reward-specific (and thus might relate to a motivational state associated with the expected reward). Therefore, we tested a new sample of 28 dogs with a similar set-up designed to induce positive anticipation (positive condition) and frustration (negative condition) in two reward contexts: food and toys. The previous results were replicated: Ears adductor was associated with the positive condition and Ears flattener, Blink, Lips part, Jaw drop, and Nose lick with the negative condition. Four additional facial actions were also more common in the negative condition. All actions except the Upper lip raiser were independent of reward type. Our second aim was to assess basic measures of diagnostic accuracy for the potential emotion indicators. Ears flattener and Ears downward had relatively high sensitivity but low specificity, whereas the opposite was the case for the other negative correlates. Ears adductor had excellent specificity but low sensitivity. If the identified facial expressions were to be used individually as diagnostic indicators, none would allow consistent correct classifications of the associated emotion. Diagnostic accuracy measures are an essential feature for validity assessments of potential indicators of animal emotion.

Highlights

Emotions are relatively short-term affective responses (Mendl et al 2010) triggered by events or stimuli of personal relevance (Gygax 2017)
If specific facial or body expressions are reliably associated with a variety of situations in which a particular emotion is likely experienced, they could have potential as indicators of the respective emotional state (Paul et al 2005)
We found that the positive condition was associated with a higher incidence of the Ears adductor action (DogFACS Ear Action Descriptor (EAD) 102 (Waller et al 2013))

Summary

Introduction

Emotions are relatively short-term affective responses (Mendl et al 2010) triggered by events or stimuli of personal relevance (Gygax 2017). Different emotions are presumably elicited when a reward or punisher is anticipated, delivered, omitted, or terminated (Mendl et al 2010; Rolls 2013) Physiological measurements such as heart rate and heart rate variability (e.g., Beerda et al 1998; Gygax et al 2013; Zupan et al 2016), body temperature (e.g., Moe et al 2012; Part et al 2014; Riemer et al 2016; Travain et al 2016; but see Proctor and Carder 2016), or hormone levels (e.g., Part et al 2014) can give some information about. This suggests that facial expressions of (at least some) animals have potential as honest signals of internal states (see Descovich et al 2017)

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