Young children frequently report imaginary scary things in their bedrooms at night. This study examined the remembrances of 140 preschool children and 404 adults selecting either above, side, or below locations for a scary thing relative to their beds. The theoretical framework for this investigation posited that sexual-size dimorphism in Australopithecus afarensis, the presumed human ancestor in the Middle Pliocene, constrained sleeping site choice to mitigate predation. Smaller-bodied females nesting in trees would have anticipated predatory attacks from below, while male nesting on the ground would have anticipated attacks from their side. Such anticipation of nighttime attacks from below is present in many arboreal primates and might still persist as a cognitive relict in humans. In remembrances of nighttime fear, girls and women were predicted to select the below location and males the side location. Following interviews of children and adult questionnaires, multinomial log-linear analyses indicated statistically significant interactions (p < 0.001) of sex by location for the combined sample and each age class driven, in part, by larger frequencies of males selecting the side location and females selecting the below location. Data partitioning further revealed that males selected the side location at larger frequencies (p < 0.001) than the below location, whereas female selection of side and below locations did not differ significantly. While indicative of evolutionary persistence in cognitive appraisal of threat locations, the female hypothesis did not consider natural selection acting on assessment of nighttime terrestrial threats following the advent of early Homo in the Late Pliocene.

幼儿经常在晚上报告自己卧室中的假想的可怕事物。这项研究调查了140名学龄前儿童和404名成年人的记忆，这些人选择相对于其床而言，在上方，侧面或下方的位置放置一件恐怖的东西。这项研究的理论框架认为，Afaruslopithecus afarensis中的性大小双态性，是上新世中期的人类祖先，它限制了睡眠场所的选择，以减轻掠食。身材矮小的雌性筑巢在树上时，会预料到会从下面掠夺性攻击，而雄性筑巢在地上筑巢时，会预见到它们会从侧面进攻。在许多树栖灵长类动物中都存在这种对来自夜间的夜间袭击的预期，并且可能仍会继续作为人类的认知遗迹。为了纪念夜间恐惧，预计女孩和妇女选择以下位置，而男性选择侧面位置。在对儿童和成人问卷进行访谈之后，多项对数线性分析显示出统计学上的显着相互作用（p 组合样本和每个年龄段的性别按位置划分的性别差异均小于0.001），部分原因是男性选择侧边位置的频率较高，而女性选择以下位置的频率较高。数据划分进一步显示，男性选择侧边位置的频率 高于下方位置（p <0.001），而女性选择侧边位置和下方位置的频率没有显着差异。尽管在威胁位置的认知评估中显示出进化上的持久性，但女性假说并未考虑自然选择是对上新世晚期早期人类出现后对夜间陆地威胁的评估。