Using judgment bias test in pet and shelter dogs (Canis familiaris): Methodological and statistical caveats

Modifying the Attention Bias Test to Assess the Emotional State of Dogs

The attention bias test is an established cognitive method used to evaluate emotional states in farm animals by examining their response to a stimulus under varying emotional conditions. This study adapted this test for dogs, utilizing naturally induced emotional states in place of pharmacological interventions. Dogs were emotionally primed into positive, neutral or negative emotional states through interactions with their owners before encountering a novel, mildly threatening stimulus (a fan with colorful streamers attached) in a controlled arena. Behavioral responses were observed and recorded, revealing distinct patterns linked to emotional states. Notably, dogs in the negative condition exhibited increased pacing, reduced vocalizations, and a tendency to remain near the exit door-behaviors consistent with heightened anxiety. In contrast, dogs in the positive and neutral conditions showed less pronounced behavioral differentiation. These findings highlight the potential of the attention bias test as a valuable tool for assessing emotional states in dogs. This application underscores the importance of further research to refine methodologies, deepen our understanding of canine emotions and enhance animal welfare practices.

Effect of pre-session discrimination training on performance in a judgement bias test in dogs

Spatial judgement bias tests (JBTs) can involve teaching animals that a bowl provides a reward in one location but does not in another. The animal is then presented with the bowl placed between the rewarded and the unrewarded locations (i.e., ambiguous locations) and their latency to approach reflects expectation of reward or 'optimism'. Some suggest that greater 'optimism' indicates better welfare. Performance in JBTs, however, may also indicate a learning history independently from welfare determinants. We hypothesized that dogs' 'optimism' in a follow-up JBT may be impacted by a learning treatment involving additional trials of a different discrimination task. Once enrolled, companion dogs (n = 16) were required to complete three study phases: (1) a pre-treatment JBT, (2) a learning treatment, and (3) a post-treatment JBT. During the JBTs, dogs were presented with five locations: one rewarded, one unrewarded, and three ambiguous (all unrewarded). Dogs were randomly assigned to a trial-based learning task-a nose-touch to the palm of the hand. In the Experimental discrimination treatment phase (n = 8), dogs were presented with two hands in each trial and only rewarded for touching one specific hand. In the Control treatment phase (n = 8), dogs were presented with one hand per trial in alternating sequence and were yoked to dogs in the Experimental group to receive the same number of rewarded and unrewarded trials (to control for possible frustration). Using a repeated measures mixed model with JBT repeated within dog, we found no difference in the change in approach latency to the ambiguous locations between the dogs across treatments. 'Optimism' as measured in this JBT was not altered by the additional discrimination trials used in our study.

The Role of Life History and Familiarity in Performance of Working and Non-Working Dogs (Canis lupus familiaris) in a Point-Following Task

Domestic dogs are very successful at following human communicative gestures in paradigms such as the object-choice task. Pet dogs also prefer responding to cues given by a familiar cue-giver and this had not been found in working dogs. Therefore, we tested three groups of dogs in the object-choice task (n = 54): the groups were "Actively working" dogs from working dog breeds, pet dogs from "Non-working breeds" and pet dogs from "Working breeds". We found that "Actively working" and "Working breeds" dog groups outperformed "Non-working breeds" in following a point in the object-choice task. We also found that both "Actively working" and "Working breeds" preferred a familiar cue-giver over an unfamiliar one, in contrast to previous findings. Therefore, we conclude that dogs' abilities to perform well in the object-choice task is influenced by the selective history of the breed, and this is then increased by life experience and training.

The effect of repeated testing on judgement bias in domestic dogs (Canis familiaris)

Judgement bias paradigms are increasingly being used as a measure of affective state in dogs. Approach to an ambiguous stimulus is commonly used as a measure of affect, however, this may also be influenced by learning. This study directly measured the impact of learning on a commonly used judgement bias paradigm in the absence of an affective state manipulation. Dogs (N = 15) were tested on a judgement bias task across five sessions. The dogs' latency to approach a bowl placed in one of three ambiguous locations between non-baited (negative) and baited (positive) locations was measured. Results show that session number had a significant effect on the dogs' latencies to reach the ambiguous bowl locations, with post-hoc tests revealing that dogs were significantly slower to approach the locations as the number of sessions increased. Session number also had a significant effect on the number of times the dogs did not approach the bowl within 30 s of being released, with the number of no approaches generally increasing across sessions. When dog identity was included as a fixed effect, a significant effect on latency to approach was found, suggesting that some dogs were consistently faster than others across sessions. To assess whether the paradigm produced repeatable results, Intraclass Correlation Coefficients were used. A low degree of reliability was found between latencies to approach each bowl position across sessions. This study demonstrates that dogs learned that the ambiguous locations were not rewarded with repeated exposures, and that this impacted their responses. We conclude that this judgement bias paradigm may require further consideration if applied across multiple exposures and that repeated results should be interpreted with caution as they are likely impacted by learning.

Negative expectations and vulnerability to stressors in animals

Humans express stable differences in pessimism that render some individuals more vulnerable to stressors and mood disorders. We explored whether non-human animals express stable individual differences in expectations (assessed via judgment bias tests) and whether these differences relate to susceptibility to stressors. Judgment bias tests do not distinguish pessimism from sensitivity to reinforcers; negative expectations are likely driven by a combination of these two elements. The available evidence suggests that animals express stable individual differences in expectations such that some persistently perceive ambiguous situations in a more negative way. A lack of research prevents drawing firm conclusions on how negative expectations affect responses to stressors, but current evidence suggests a link between negative expectations and the adoption of avoidance coping strategies, stronger responses to uncontrollable stressors and risk of mood-related disorders. We explore implications for animals living in captivity and for research using animals as models for human disorders.