Abstract
Primates have relatively larger brains than other mammals even though brain tissue is energetically costly. Comparative studies of variation in cognitive skills allow testing of evolutionary hypotheses addressing socioecological factors driving the evolution of primate brain size. However, data on cognitive abilities for meaningful interspecific comparisons are only available for haplorhine primates (great apes, Old- and New World monkeys) although strepsirrhine primates (lemurs and lorises) serve as the best living models of ancestral primate cognitive skills, linking primates to other mammals. To begin filling this gap, we tested members of three lemur species (Microcebus murinus, Varecia variegata, Lemur catta) with the Primate Cognition Test Battery, a comprehensive set of experiments addressing physical and social cognitive skills that has previously been used in studies of haplorhines. We found no significant differences in cognitive performance among lemur species and, surprisingly, their average performance was not different from that of haplorhines in many aspects. Specifically, lemurs’ overall performance was inferior in the physical domain but matched that of haplorhines in the social domain. These results question a clear-cut link between brain size and cognitive skills, suggesting a more domain-specific distribution of cognitive abilities in primates, and indicate more continuity in cognitive abilities across primate lineages than previously thought.
Highlights
One central question in comparative cognition is why primates have evolved larger brains and enhanced cognitive skills compared to other -sized mammalian species (Shettleworth2010)
Only chimpanzees performed significantly better than ruffed lemurs, and chimpanzees and orangutans outperformed ring-tailed and mouse lemurs
We applied the Primate Cognition Test Battery to three lemur species differing in socioecological traits and brain size and compared their performance with that of four haplorhine species tested in previous studies with the exact same methods
Summary
One central question in comparative cognition is why primates have evolved larger brains and enhanced cognitive skills compared to other -sized mammalian species (Shettleworth2010). One central question in comparative cognition is why primates have evolved larger brains and enhanced cognitive skills compared to other -sized mammalian species Because larger brains are energetically more expensive 1995), they are assumed to confer benefits with regard to enhanced cognitive abilities that compensate this additional investment (Navarrete et al 2011; Reader and Laland 2002; Reader et al 2011). Several non-mutually exclusive hypotheses on the evolution of brain size have been proposed to account for the distinctive cognitive abilities of primates (Dunbar and Shultz 2017). According to the General intelligence hypothesis, larger brains are thought to confer an advantage because of faster learning and larger memory capacities (Spearman 1904).
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