Logical inferences from visual and auditory information in ruffed lemurs and sifakas

Inference by exclusion, or the ability to select a correct course of action by systematically excluding other potential alternatives, is a form of logical inference that allow individuals to solve problems without complete information. Current comparative research shows that several bird, mammal, and primate species can find hidden food through inference by exclusion. Yet there is also wide variation in how successful different species are, as well kinds of sensory information they can use to do so. An important question is therefore why some species are better at engaging in logical inference than others. Here, we investigate the evolution of logical reasoning abilities by comparing two strepsirrhine primate species that vary in dietary ecology: frugivorous ruffed lemur (Varecia spp.) and folivorous Coquerel’s sifakas (Propithecus coquereli). Across two studies, we examined their abilities to locate food using direct information versus inference from exclusion and using both visual and...