Table 4.

DogFACS²⁶ variables used as outcome measures in this study (AU = Action Unit; AD = Action Descriptor; EAD = Ear Action Descriptor).

Category	AU/AD/EAD	Number	Variable name	Definition*
Upper Face Action Units	AU	101	Inner brow raiser	Protuberance above the eye moves dorsally and obliquely towards the midline.
		143	Eye closure	Both eyelids move towards and touch each other, covering the eye for at least 0.5 s.
		145	Blink	Both eyelids move towards and touch each other, covering the eye for less than 0.5 s.
Lower Face Action Units		109 + 110	(Nose wrinkler & Upper lip raiser)**	Nose and upper lip move dorsally and wrinkles appear on the dorsal muzzle part.
		110	(Upper lip raiser)**	Upper lip moves dorsally.
		12	Lip corner puller	Lip corners move caudally.
		116	Lower lip depressor	Lower lip moves ventrally.
		118	Lip pucker	Lip corners move rostrally.
		25	Lips part	Any lip separation.
		26	Jaw drop	Lower jaw moves ventrally in a relaxed manner (i.e. absence of tension signs) and teeth are separated.
		27	Mouth stretch	Lower jaw moves ventrally in an actively stretching manner and teeth are separated; lower teeth, tongue and oral cavity are visible.
Action Descriptors	AD	19	Tongue show	Tongue is protruded at least until the inner lower lip.
		33	Blow	Lips expand due to air being expelled from the mouth.
		35	Suck	Upper lip is sucked into the mouth.
		37	Lip wipe	Tongue moves on the outer part of the upper lips from the midline of the mouth to one corner.
		137	Nose lick	Tongue moves out of the mouth towards the nose and wipes it.
Gross Behaviour		126	Panting	Mouth is open (AU26), tongue is protruded (AD19), and dog breathes shortly and quickly.
Ear Action Descriptors	EAD	101	(Ears forward)**	Ears move rostrally.
		102	Ears adductor	Ears move dorsally towards the midline of the head; bases of both ears come closer together.
		103	Ears flattener	Ears move caudally.
		104	Ears rotator	Ears move laterally and externally.
		105	Ears downward	Ears move ventrally.

DogFACS²⁶ variables with bold letters occurred with a prevalence of at least 10% in either all positive or all negative samples. *Definitions were obtained from the DogFACS manual²⁶ (www.dogfacs.com) and were partly adapted for this Table. **DogFACS²⁶ variables in brackets were excluded from the analysis as the strength of the intercoder reliability was below a substantial agreement⁶¹.