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

We tested dogs (N=10) on a judgement bias task once a week, for five weeks, to investigate whether there was an effect of repeated testing on their responses. Judgement bias was assessed based on the dogs’ latency to approach a bowl placed in one of three ambiguous locations (Near Negative, Middle, Near Positive) between non-baited (Negative) and baited (Positive) bowl locations. Generalized Linear Mixed Model Analyses revealed that the week number (1, 2, 3, 4 or 5) had a significant effect on the dogs’ latencies to reach the ambiguous bowl locations (F = 16.072, p <.001), with visualisation of the data revealing that dogs were slower to approach the ambiguous locations as the number of test sessions increased. Week number also had a significant effect on the number of times the dogs did not approach the bowl (F = 14.748, p <.001), with the number of no approaches increasing with each session. Results suggest that, over repeated exposure, the dogs learned that the ambiguous locations were not rewarded. We conclude that this judgement bias task is limited in its application across multiple exposures and repeated results should be interpreted with caution as they may reflect learning rather than affective state.