a b s t r a c tResearch on the relationship between the representation of space and time has produced two contrasting proposals. ATOM posits that space and time are represented via a common magnitude system, suggesting a symmetrical relationship between space and time. According to metaphor theory, however, representations of time depend on representations of space asymmetrically. Previous findings in humans have supported metaphor theory. Here, we investigate the relationship between time and space in a nonverbal species, by testing whether non-human primates show space-time interactions consistent with metaphor theory or with ATOM. We tested two rhesus monkeys and 16 adult humans in a nonverbal task that assessed the influence of an irrelevant dimension (time or space) on a relevant dimension (space or time). In humans, spatial extent had a large effect on time judgments whereas time had a small effect on spatial judgments. In monkeys, both spatial and temporal manipulations showed large bi-directional effects on judgments. In contrast to humans, spatial manipulations in monkeys did not produce a larger effect on temporal judgments than the reverse. Thus, consistent with previous findings, human adults showed asymmetrical space-time interactions that were predicted by metaphor theory. In contrast, monkeys showed patterns that were more consistent with ATOM.

Transitive Inference is a form of deductive reasoning that has been suggested as one cognitive mechanism by which animals could learn the many relationships within their group's dominance hierarchy. This process thus bears relevance to the social intelligence hypothesis which posits evolutionary links between various forms of social and nonsocial cognition. Recent evidence corroborates the link between social complexity and transitive inference and indicates that highly social animals may show superior transitive reasoning even in nonsocial contexts. We examined the relationship between social complexity and transitive inference in two species of prosimians, a group of primates that diverged from the common ancestor of monkeys, apes, and humans over 50 million years ago. In Experiment 1, highly social ring-tailed lemurs, Lemur catta, outperformed the less social mongoose lemurs, Eulemur mongoz, in tests of transitive inference and showed more robust representations of the underlying ordinal relationships between the stimuli. In Experiment 2, after training under a correction procedure that emphasized the underlying linear dimension of the series, both species showed similar transitive inference. This finding suggests that the two lemur species differ not in their fundamental ability to make transitive inferences, but rather in their predisposition to mentally organize information along a common underlying dimension. Together, these results support the hypothesis that social complexity is an important selective pressure for the evolution of cognitive abilities relevant to transitive reasoning. KeywordsSocial Intelligence; Social Brain; Transitive Inference; Prosimian; Primate; Cognition; Cognitive Evolution; Evolution; Species Difference Social Complexity Predicts Transitive Reasoning in Prosimian Primates Explaining the emergence of generalized forms of intelligence is among the greatest challenges in evolutionary psychology and biological anthropology. In the primate literature, considerable attention has been given to the social intelligence hypothesis which suggests that life in complex social environments was the primary selective pressure for primate cognitive evolution (Jolly © 2008 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.*Corresponding author, Department of Biological Anthropology and Anatomy, Box 90383-0383, Duke University, Durham, NC 27708, E-mail: E-mail: maclean@duke. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. 1966b;Humphrey 1976;Byrne and Whiten 1988;Kummer et al. 1997). Although the s...

Do young children understand the numerical value of empty sets prior to developing a concept of symbolic zero? Are empty sets represented as mental magnitudes? In order to investigate these questions, we tested 4-year old children and adults with a numerical ordering task in which the goal was to select two stimuli in ascending numerical order with occasional empty set stimuli. Both children and adults showed distance effects for empty sets.. Children who were unable to order the symbol zero (e.g., 0 < 1), but who successfully ordered countable integers (e.g., 2 < 4) nevertheless showed distance effects with empty sets. These results suggest that empty sets are represented on the same numerical continuum as non-empty sets and that children represent empty sets numerically prior to understanding symbolic zero.

The goal of the current research was to explore whether monkeys possess conceptual precursors necessary for understanding zero. We trained rhesus monkeys on a nonsymbolic numerical matching-to-sample task, and on a numerical ordering task. We then introduced nondifferentially reinforced trials that contained empty sets to determine whether monkeys would treat empty sets as numerical values. All monkeys successfully matched and ordered the empty sets without any training. Accuracy showed distance effects, indicating that they treated empty sets as values on a numerical continuum.