... There exists a close relationship between emotions and physiology, more particularly the autonomic nervous system (ANS) and the hypothalamic-pituitary-adrenal (HPA) axis activity (Sander and Scherer, 2014). Therefore, biomarkers play an important role and serve as a proxy when assessing emotion and positive well-being in animals (e.g.,von Borell et al., 2007;Schmied et al., 2008Schmied et al., , 2010Reefmann et al., 2009a,b;Coulon et al., 2013Coulon et al., , 2015Briefer et al., 2015;Kowalik et al., 2017). Heart rate (HR) (Csoltova et al., 2017), heart rate variability (HRV) (Bergamasco et al., 2010;Katayama et al., 2016;Travain et al., 2016), surface temperature (Travain et al., 2015(Travain et al., , 2016Csoltova et al., 2017), oxytocin (Odendaal and Meintjes, 2003;Mitsui et al., 2011;Rehn et al., 2014;Nagasawa et al., 2015), vasopressin (Hydbring-Sandberg et al., 2004;MacLean et al., 2017aMacLean et al., ,b, 2018Pirrone et al., 2019), cortisol (Hennessy et al., 1998(Hennessy et al., , 2006Coppola et al., 2006;Bergamasco et al., 2010;Shiverdecker et al., 2013), and alpha-amylase (Contreras-Aguilar et al., 2017;Hong et al., 2019) have been implemented and showed potential usefulness in indirect and noninvasive assessment of positiveemotion in dogs. ...