Inferring the evolutionary history of cognitive abilities requires large and diverse samples. However, such samples are often beyond the reach of individual researchers or institutions, and studies are often limited to small numbers of species. Consequently, methodological and site-specific-differences across studies can limit comparisons between species. Here we introduce the ManyPrimates project, which addresses these challenges by providing a large-scale collaborative framework for comparative studies in primate cognition. To demonstrate the viability of the project we conducted a case study of short-term memory. In this initial study, we were able to include 176 individuals from 12 primate species housed at 11 sites across Africa, Asia, North America and Europe. All subjects were tested in a delayed-response task using consistent methodology across sites. Individuals could access food rewards by remembering the position of the hidden reward after a 0, 15, or 30-second delay. Overall, individuals performed better with shorter delays, as predicted by previous studies. Phylogenetic analysis revealed a strong phylogenetic signal for short-term memory. Although, with only 12 species, the validity of this analysis is limited, our initial results demonstrate the feasibility of a large, collaborative open-science project. We present the ManyPrimates project as an exciting opportunity to address open questions in primate cognition and behaviour with large, diverse datasets.

From early on in ontogeny, young children hear things being said about particular individuals. Here we investigate the ways in which testimony with social content, that is, gossip, influences children's decision-making. We explored whether five-year-old (N 5 72) and seven-year-old (N 5 72) children trust gossip or firsthand observation in a partner choice setting. Seven-year-old children preferentially trusted what they had seen firsthand over gossip; five-year-old children, in contrast, did not differentiate between these two sources of information. However, five-year-old children (but not seven-yearolds) generally gave negative information more weight, that is, they showed a "negativity bias." These results suggest that at around school age, young children become more "epistemically vigilant" about gossip. K E Y W O R D Sdecision-making, social behavior, social cognition, social learning

No abstract

Psychologists disagree about the development of logical concepts such as or and not. While some theorists argue that infants reason logically, others maintain that logical inference is contingent on linguistic abilities and emerges around age 4. In this Registered Report, we conducted five experiments on logical reasoning in chimpanzees. Subjects (N = 16; 10 females; M = 24 years) participated in the same setup that has been administered to children: the two‐, three‐, and four‐cup‐task. Chimpanzees performed above chance in the two‐cup‐, but not in the three‐cup‐task. Furthermore, chimpanzees selected the logically correct option more often in the test than the control condition of the four‐cup‐task. We discuss possible interpretations of these findings and conclude that our results are most consistent with non‐deductive accounts.

No abstract