, 2007; Paz-Y-Miño et al.,

2004). While perceptual cues may provide a useful, but relatively imprecise, heuristic with which to rapidly evaluate an unfamiliar individual (e.g., an intruder: Marsh et al., 2009; Todorov et al., 2008; Whalen, 1998), specific knowledge of the rank position of a fellow group member is needed to support more accurate judgments of rank (Cheney and Seyfarth, 1990; Tomasello and Call, 1997). Indeed, considerable Rucaparib price evidence indicates that humans and nonhuman primates possess such knowledge, and are able to rank each other within linear hierarchies that are stable over long periods of time (Byrne and Bates, 2010; Cheney and Seyfarth, 1990; Savin-Williams, 1990).

For instance, primates spontaneously discriminate images of individuals based on their rank status (Deaner et al., 2005) and are able to identify third-party relations that exist between their companions—when engaged in a competitive interaction (e.g., a duel) individuals will typically recruit allies that outrank both themselves and their opponents (e.g., favoring the 3rd ranked individual over the fifth ranked) (Cheney and Seyfarth, 1990; Tomasello and Call, 1997). According to psychological theories grounded in research in animals, individuals acquire knowledge Metformin nmr about social hierarchies by experiencing encounters between pairs of conspecifics, with such dyadic interactions either being experimentally enforced (Grosenick et al., 2007; Paz-Y-Miño et al., 2004) or occurring through the course of natural behavior (Cheney and Seyfarth, 1990; Tomasello and Call, 1997). Notably, however, individuals must confront whatever a thorny obstacle during learning: the number of possible dyadic interactions scales

exponentially with group size, thereby placing prohibitive demands on memory capacity (Byrne and Bates, 2010; Cheney and Seyfarth, 1990). Evidence suggests that individuals solve this problem in an elegant fashion—by restricting their observations to a small subset of all possible dyadic interactions, and then using a highly developed capacity for transitive inference to deduce the remaining rank relations between group members (i.e., if P1 > P2 & P2 > P3, then P1 > 3, where P1 denotes the highest ranking individual) (Byrne and Bates, 2010; Cheney and Seyfarth, 1990; Grosenick et al., 2007; Paz-Y-Miño et al., 2004). Indeed, it has been argued that the pressures of living in large social groups may have driven the evolution of sophisticated abilities for transitive inference, based on the finding that the more highly social of two closely related primate species exhibit superior capacities in this regard (e.g., Maclean et al., 2008).