Roots of primate cognition: the Primate Cognition Test Battery applied to three species of lemurs (Microcebus murinus, Varecia variegata and Lemur catta)

与其他哺乳动物相比，灵长类动物，尤其是人类的大脑相对较大。由于大脑在能量上是非常昂贵的，所以主要的问题是哪些因素可能有利于这么大的大脑的进化。灵长类认知测试组合(PCTB)代表了一种系统的方法来寻找人类学中这个中心问题的答案。它由一系列标准化和综合性的认知实验组成，涉及认知技能的物理和社会领域。PCTB已经用于人类、猿类和两个东半球猴子物种的实验(Herrmann等人。2007年；施密特等人。2012年)。这些研究表明，儿童在社会认知技能方面胜过所有非人类灵长类动物。在物理领域，不同物种之间只有很小的差异，尽管他们的大脑相对大小不同。这些结果表明，社会认知技能对大脑大小的进化具有决定性的影响。为了验证这一假设，并充分了解灵长类和人类智力的进化，我们提出了对其他灵长类物种的比较研究。链鼻灵长类特别适合于这种比较方法，因为它们属于代表与其他哺乳动物进化联系的祖先灵长类动物，因此，它们可以作为灵长类祖先认知技能的活模型。因此，我们将把PCTB应用于三种狐猴：Microcebus Murinus、Varecia varegata和Lemur Catta，这三种狐猴在社会组织和复杂性上表现出多样性。此外，我们将检验一个特定假说(即合作育种假说)的预测。它指出，在子女养育过程中，异体母亲的投入水平对社会认知技能有影响。由于这三种狐猴的繁殖策略不同，因此将在此背景下对它们的性能进行比较。因此，这项研究代表了对狐猴认知技能的第一次系统调查，并将为整个灵长目动物的认知进化提供重要的比较洞察。

Compared to other mammals, primates, and especially humans, have relatively large brains. Since the brain is energetically very costly, the major question is which factors might have favoured the evolution of such large brains. The Primate Cognition Test Battery (PCTB) represents one systematic approach to finding answers to this central question in anthropology. It consists of a standardized and comprehensive series of cognitive experiments addressing the physical and social domain of cognitive skills. The PCTB has already been used in experiments with humans, apes and two Old World monkey species (Herrmann et al. 2007; Schmitt et al. 2012). These studies revealed that children excel all non-human primates concerning their social cognitive skills. In the physical domain, there were only minor differences across species, although they differ in relative brain size. These results suggest that social cognitive skills have had a decisive influence on brain size evolution. To test this hypothesis and to fully understand the evolution of primate and human intelligence, comparative studies of additional primate species are indicated. Strepsirrhine primates are especially suitable for such a comparative approach, since they belong to the phylogenetically ancestral primates that represent the evolutionary link to other mammals, and, hence, they can serve as living models of the ancestral cognitive skills of primates. Therefore, we will apply the PCTB to three lemur species, Microcebus murinus, Varecia variegata and Lemur catta, which exhibit variation in social organization and complexity. Furthermore, we will test the predictions of one particular hypothesis (i.e. the cooperative breeding hypothesis). It states that the level of allomaternal investment during offspring rearing has an influence on social cognitive skills. Since the three lemur species have different breeding strategies, their performances will be compared in this context. Thus, this study represents the first systematic investigation of the cognitive skills of lemurs and will provide important comparative insights into the cognitive evolution across the entire order Primates.