The study of animal emotions is a field of interest in expansion since several years, but the challenges have stayed the same: how to determine these emotions in a reliable way with other measures than physiological ones due to their difficulties to perform and usually higher costs. But there is a rather efficient way to obtain a reliable image of one state of mind by using cognitive biases, and more precisely cognitive judgement bias (CJB).
 

The CJB has been defined as the tendency of an individual to display an anticipation regarding the possible positive or negative outcome of ambiguous stimuli, thereby to show a behavior stated as more "optimistic" or "pessimistic" (Mendl et al., 2009).

The study of affective state and more precisely CJB is of an important matter in relation to animal welfare considering the opportunities to access the emotional valence, along with the cognitive faculties, and to link it to bad or good living conditions. For instance, chronic stress has been linked to a decreased learning capacity (Hiby, 2005), and poor welfare can cause reduced health (Clark et al., 1997).
However, dogs have an important inter-individual variability for the suffering signs, therefore a well-defined list of stress behaviors is not achievable (Rooney et al., 2007a; Hiby et al., 2006). That is why expanding the methodological knowledge for testing CJB in dogs is important, because of this difficulty to see clearly stress behaviors that might be camouflaged by the dog. A CJB test being able to assess signs of compromised welfare (depressive and anxious states).

This study is thus investigating a new method based on innate reactions to certain stimuli and got its inspiration from a study of Salmeto et al. (2010). A CJB test was performed on chicks but this time using ecologically relevant stimuli (Chick/Owl morphs) and similar results, within less time, were obtained than if a more common CJB test was used.
Thus for the ecologically relevant stimuli, a smiling human face was chosen because of its positive stimulus for the dog (Albuquerque et al., 2016; Racca et al., 2012) and an aggressive dog face as a negative stimulus (Racca et al., 2012) and make a morph 50/50% out of these two faces for it to be an ambiguous sitmulus.

The aim of this study was to see if individuals were consistent in their response/judgement bias when comparing the tCJB and nCJB, meaning that a dog showing optimism in the tCJB should show the same bias in the nCJB.