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

Abstract

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.

Does the odour of human stress or relaxation affect dogs’ cognitive bias?

“…These ndings suggest a learning effect that may have occurred due to our repeated testing design. This effect has previously been shown to occur in sheep 76 and in dogs 77 where Wilson et al (2023), found that repeated cognitive bias testing (up to ve sessions) resulted in an increase in latency to approach ambiguous locations and a decrease in the number of approaches. This is likely due to animals learning that the ambiguous locations are not rewarded, and therefore beginning to treat them as negative cues.…”

“…Although we observed a signi cant decrease in the likelihood of approaching NN between baseline and session 3, we did not see a decrease in the likelihood of approaching between baseline and session 2 or between session 2 and 3. Neither did we see a signi cant effect of session at the NP or M locations as observed by Wilson et al (2023) 77 , suggesting our modi cation may have been effective at minimising learning effects at these two ambiguous locations. Although the effects at N and P were not reported by Wilson et al (2023), the signi cant decrease in likelihood of approaching N and the signi cant increaseinlikelihood of approaching P between session 1, 2 and 3 in the current study is likely also due to a learning effect.…”

“…Neither did we see a signi cant effect of session at the NP or M locations as observed by Wilson et al (2023) 77 , suggesting our modi cation may have been effective at minimising learning effects at these two ambiguous locations. Although the effects at N and P were not reported by Wilson et al (2023), the signi cant decrease in likelihood of approaching N and the signi cant increaseinlikelihood of approaching P between session 1, 2 and 3 in the current study is likely also due to a learning effect. This suggests that dogs continued to learn about these reinforced locations during the testing period.…”

“…This is likely due to animals learning that the ambiguous locations are not rewarded, and therefore beginning to treat them as negative cues. To ameliorate this effect, in the current study, we reduced the number of presentations at each ambiguous location from three (as used traditionally and in the Wilson et al (2023) study 77 ) to two per session. This provided a balance between reducing the learning effect whilst minimising the risk of spurious results from a single presentation.…”

Fearful snake pictures make monkeys pessimistic

“…This outcome is consistent with several studies that have indicated that the impact of learning on animals’ responses to ambiguous stimuli can represent a significant confounding factor that affects the interpretation of results from judgment bias tests. 19 , 26 , 27 It is worth mentioning that we detected a learning effect despite having reduced the ratio of ambiguous stimulus trials relative to reference stimulus trials in each session (274:10) and having implemented a variable reinforcement schedule (80%) following prior research. 19 , 20 , 28 Nevertheless, despite the learning effect, the tendency for response times to be prolonged in the snake condition relative to the control condition was persistent even in later trials, as depicted in Figure 3 .…”