Department of Ethology, Eötvös Loránd University, Budapest, 1117, Hungary.
HAS University of Applied Sciences, 's-Hertogenbosch, 5223DE, The Netherlands.
Sci Rep. 2019 Dec 27;9(1):20201. doi: 10.1038/s41598-019-56636-z.
Age-related changes in the brain can alter how emotions are processed. In humans, valence specific changes in attention and memory were reported with increasing age, i.e. older people are less attentive toward and experience fewer negative emotions, while processing of positive emotions remains intact. Little is yet known about this "positivity effect" in non-human animals. We tested young (n = 21, 1-5 years) and old (n = 19, >10 years) family dogs with positive (laugh), negative (cry), and neutral (hiccup, cough) human vocalisations and investigated age-related differences in their behavioural reactions. Only dogs with intact hearing were analysed and the selected sound samples were balanced regarding mean and fundamental frequencies between valence categories. Compared to young dogs, old individuals reacted slower only to the negative sounds and there was no significant difference in the duration of the reactions between groups. The selective response of the aged dogs to the sound stimuli suggests that the results cannot be explained by general cognitive and/or perceptual decline. and supports the presence of an age-related positivity effect in dogs, too. Similarities in emotional processing between humans and dogs may imply analogous changes in subcortical emotional processing in the canine brain during ageing.
大脑的衰老变化会改变情绪的处理方式。在人类中，随着年龄的增长，注意力和记忆力的效价特异性变化已经被报道，即老年人对负面情绪的注意力降低，体验也较少，而对正面情绪的处理则保持完整。关于非人类动物的这种“正性效应”，我们知之甚少。我们用人类的笑声、哭声和打嗝、咳嗽等中性声音来测试年轻（n=21，1-5 岁）和年老（n=19，>10 岁）的家庭犬，并研究了它们在行为反应上的年龄相关差异。只有听力正常的狗才被分析，所选的声音样本在效价类别之间具有平均频率和基频的平衡。与年轻的狗相比，年老的狗对负面声音的反应较慢，而且两组之间的反应持续时间没有显著差异。老年犬对声音刺激的选择性反应表明，这些结果不能用一般的认知和/或感知下降来解释。并且支持狗也存在与年龄相关的正性效应。人类和狗在情绪处理方面的相似性可能意味着犬类大脑在衰老过程中，与情绪相关的皮质下处理也发生了类似的变化。
