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

Abstract

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.

Keywords: Affective state; Animal welfare; Canine; Cognition; Discrimination; Learning.

Fig. 1

Before each experiment, five circles with a diameter of 1 m were drawn on the floor in chalk; the centre of each circle was 3.5 m from the starting position, represented by the dotted grey lines. These circles were 1.2 m and 20^O from the adjacent circle. At its centre, each circle had a 5 cm piece of adhesive hook and loop tape. The letters P, NP, M, NN, N indicating the location were drawn on the circle with chalk. The Timer was seated (next to the stopwatch, coloured black), the dog’s owner was seated (coloured blue), The Handler was next to the dog, and The Experimenter was standing behind the middle position

Fig. 2

The Handler and the dog faced The Experimenter at a distance of 1.5 m, represented by the grey dotted line. The Timer was seated (next to the stopwatch, coloured black), the dog’s owner was seated (colored blue), The Handler walked the dog, and The Experimenter was seated in front of the dog

Fig. 3

Dogs’ average latency to approach the five locations. Circles and triangles represent JBT1 and JBT2, respectively. Colour represents treatment. Error bars represent standard error of the mean

Fig. 4

Points represent average change in the pooled latency to the ambiguous locations (NP, M, NN) from JBT1 to JBT2 per dog. Colours represent match-paired dogs. Black points represent means and error bars represent standard error of the means. The dashed line represents no change across JBT1 and JBT2