Laboratoire de Psychologie Cognitive UMR7290, CNRS, Aix-Marseille Université, 3 Place Victor Hugo, 13331, Marseille Cedex 3, France.
Station de Primatologie, CNRS, Rousset-sur-Arc, France.
Sci Rep. 2020 Jul 3;10(1):11036. doi: 10.1038/s41598-020-68020-3.
About 66-72% of human mothers cradle their infants on their left side. Given that left-cradling exposes the baby's face to the mother's left visual field (i.e., mainly projected to her right hemisphere) and is altered by emotional states such as stress, maternal left-cradling was interpreted as reflecting right-hemispheric dominance for emotional processing. Whether this phenomenon is unique to human evolution is still in debate. In the present study we followed 44 olive baboon (Papio anubis) mothers and their infants in different social groups. We found that a maternal cradling bias exists and is predominantly towards the left in a similar proportion as in humans, but shifts toward a right bias in mothers living in high density groups. The sensitivity of left-cradling to social pressure highlights its potential links with the mother's stress as reported in humans. Our finding clearly illustrates the phylogenetic continuity between humans and Old-World monkeys concerning this lateralization and its potential links with hemispheric specialization for emotions, inherited from a common ancestor 25-35 million years ago.
大约 66-72%的人类母亲会将婴儿放在左侧怀抱。鉴于左侧怀抱会使婴儿的脸朝向母亲的左视野（即主要投射到她的右半球），并且会受到情绪状态（如压力）的影响，因此母亲的左侧怀抱被解释为反映了右半球在情绪处理方面的优势。这种现象是否是人类进化所特有的，目前仍存在争议。在本研究中，我们跟踪了 44 只橄榄狒狒（Papio anubis）母亲及其在不同社会群体中的婴儿。我们发现，存在一种母亲怀抱的偏向，而且与人类相似，主要偏向左侧，但在生活在高密度群体中的母亲中，偏向会向右侧转移。左侧怀抱对社会压力的敏感性突出了其与人类报告的母亲压力之间的潜在联系。我们的发现清楚地说明了人类和旧世界猴子在这种偏侧性及其与情绪的半球专门化之间的系统发育连续性，这种专门化是从 2500 万到 3500 万年前的共同祖先那里遗传下来的。
