Moods influence cognitive processes in that people in positive moods expect more positive events to occur and less negative ones (“optimistic bias”), whereas the opposite happens for people in negative moods (“pessimistic bias”). The evidence for an effect of mood on cognitive bias is also increasing in animals, suggesting that measures of optimism and pessimism could provide useful indicators of animal welfare. For obvious ethical reasons, serious poor treatments cannot be easily replicated in large mammals in order to study their long-term effects on moods. In this study, we tested the long-term effects (>2 years) of prior poor welfare on the moods of rescued goats at an animal sanctuary, using a spatial judgement bias experiment. A group of goats that had experienced poor welfare before arriving at the sanctuary (“poor welfare group”; n = 9 goats) was compared with another group of goats that had experienced generally good care (“control group”; n = 9 goats). We first trained the goats to discriminate between a rewarded and a non-rewarded location. We then compared the responses of the two groups of goats to ambiguous locations situated between the two reference locations. Our results showed that, after three days of training, both groups could equally discriminate rewarded and non-rewarded locations. There was no overall effect of the welfare group during the test, but there was an interaction effect between sex and welfare group. Surprisingly, females from the poor welfare group (n = 4) reacted in the opposite way to that predicted, and showed a more optimistic bias than control females (n = 5). This suggests that these females could be experiencing long-term optimistic bias triggered by release from stress. They were also more optimistic than males from the same group (n = 5). Male judgement bias did not differ between the poor welfare and control groups (n = 4 controls). Therefore, our results show that after several years of good care, rescued goats displayed optimistic moods (females) or similar moods as controls (males). This suggests that goats probably recover from neglect, and that sex differences in mood potentially exist. The optimistic or pessimistic biases experienced by domestic animals are likely to have a strong impact on their abilities to cope with their environment, and more generally on their welfare.
Briefer, E. F., & McElligott, A. G. (2013). Rescued goats at a sanctuary display positive mood after former neglect. Applied Animal Behaviour Science, 146(1), 45-55.