Daros Rolnei R, Costa João H C, von Keyserlingk Marina A G, Hötzel Maria J, Weary Daniel M
Animal Welfare Program, Faculty of Land and Food systems, University of British Columbia, Vancouver, Canada; Laboratório de Etologia Aplicada e Bem-Estar Animal, Departamento de Zootecnia e Desenvolvimento Rural, Universidade Federal de Santa Catarina, Florianópolis, Brazil.
Animal Welfare Program, Faculty of Land and Food systems, University of British Columbia, Vancouver, Canada.
PLoS One. 2014 May 21;9(5):e98429. doi: 10.1371/journal.pone.0098429. eCollection 2014.
Negative emotional states in humans are associated with a negative (pessimistic) response bias towards ambiguous cues in judgement tasks. Every mammalian young is eventually weaned; this period of increasing nutritional and social independence from the dam is associated with a pronounced behavioural response, especially when weaning is abrupt as commonly occurs in farm animals. The aim of the current study was to test the effect of separation from the cow on the responses of dairy calves in a judgement task. Thirteen Holstein calves were reared with their dams and trained to discriminate between red and white colours displayed on a computer monitor. These colours predicted reward or punishment outcomes using a go/no-go task. A reward was provided when calves approached the white screen and calves were punished with a timeout when they approached the red screen. Calves were then tested with non-reinforced ambiguous probes (screen colours intermediate to the two training colours). "GO" responses to these probes averaged (± SE) 72±3.6% before separation but declined to 62±3.6% after separation from the dam. This bias was similar to that shown by calves experiencing pain in the hours after hot-iron dehorning. These results provide the first evidence of a pessimistic judgement bias in animals following maternal separation and are indicative of low mood.
人类的负面情绪状态与判断任务中对模糊线索的负面（悲观）反应偏差有关。每只哺乳动物幼崽最终都会断奶；从母亲那里逐渐增加营养和社交独立性的这段时期与明显的行为反应有关，尤其是当断奶很突然时，就像农场动物中常见的那样。本研究的目的是测试与母牛分离对奶牛犊牛在判断任务中的反应的影响。13头荷斯坦犊牛与它们的母亲一起饲养，并接受训练以区分电脑屏幕上显示的红色和白色。这些颜色通过一个“是/否”任务来预测奖励或惩罚结果。当犊牛接近白色屏幕时会得到奖励，而当它们接近红色屏幕时会被暂停一段时间作为惩罚。然后用无强化的模糊探测（屏幕颜色介于两种训练颜色之间）对犊牛进行测试。在与母亲分离前，对这些探测的“是”反应平均（±标准误）为72±3.6%，但在与母亲分离后降至62±3.6%。这种偏差与热烙铁去角后数小时内经历疼痛的犊牛所表现出的偏差相似。这些结果首次证明了动物在与母亲分离后存在悲观判断偏差，表明情绪低落。
