Environmental complexity buffers against stress-induced negative judgement bias in female chickens

Abstract

Cognitive processes are often biased by emotions. In humans, affective disorders are accompanied by pessimistic judgement, while optimistic judgement is linked to emotional stability. Similar to humans, animals tend to interpret ambiguous stimuli negatively after experiencing stressful events, although the long-lasting impact on judgement bias has rarely been investigated. We measure judgement bias in female chicks (Gallus gallus domesticus) after exposure to cold stress, and before and after exposure to additional unpredictable stressors. Additionally, we explore if brain monoamines can explain differences in judgement bias. Chicks exposed to cold stress did not differ in judgement bias compared to controls, but showed sensitivity to additional stressors by having higher motivation for social reinstatement. Environmental complexity reduced stress-induced negative judgement bias, by maintaining an optimistic bias in individuals housed in complex conditions even after stress exposure. Moreover, judgement bias was related to dopamine turnover rate in mesencephalon, with higher activity in individuals that had a more optimistic response. These results demonstrate that environmental complexity can buffer against negative effects of additive stress and that dopamine relates to judgement bias in chicks. These results reveal that both internal and external factors can mediate emotionally biased judgement in animals, thus showing similarities to findings in humans.

The relationship between learning speed and personality is age- and task-dependent in red junglefowl

“…It is possible that explorative chicks are less distracted by that they are alone in a test arena than less explorative ones. It has, for example, been shown that stressed chicks can have higher motivation for social reinstatement (Zidar et al 2018 ) and that longer latencies in tonic immobility positively correlate with motivation for social reinstatement (Marin et al 2001 ). In this scenario, slow-exploring chicks, which according to coping style theory are also easily stressed and fearful (Koolhaas et al 2010 ), may actually be inherently better learners, as in adults, but their learning ability might be masked by motivational differences.…”

Symposium review: Scientific assessment of affective states in dairy cattle

“…Mood states are increasingly viewed as important for animal welfare (Paul et al, 2005). Studies have attempted to assess changes in mood associated with housing conditions (Zidar et al, 2018), painful procedures (Neave et al, 2013), and chronic stress (Destrez et al, 2013) in farm animals. The majority of these studies have relied on cognitive approaches to assess these states.…”

The role of personality, cognition, and affective state in same-sex contests in the red junglefowl

“…To assess affective state and optimism, we conducted a judgement bias test (Harding et al 2004). In this test, we presented the birds with five different cues, one at a time, in a pseudo-random order (Sorato et al 2018;Zidar et al 2018a). These cues again consisted of a bowl (5 × 3 cm, Ø × H) and a laminated card (9 cm 2 ) in matching colors.…”

“…As this test required birds to have passed the discriminative learning test, only females participated in it. To obtain a measure of a bird's optimism towards ambiguous cues, we recorded their average latency (in seconds) to approach each of these cues; a shorter latency indicated higher optimism and a more positive affective state (Mendl et al 2010;Sorato et al 2018;Zidar et al 2018a). Birds were given a maximum latency of 60 s if they did not approach within 60 s.…”