Spontaneous voice–face identity matching by rhesus monkeys for familiar conspecifics and humans

Abstract

Recognition of a particular individual occurs when we reactivate links between current perceptual inputs and the previously formed representation of that person. This recognition can be achieved by identifying, separately or simultaneously, distinct elements such as the face, silhouette, or voice as belonging to one individual. In humans, those different cues are linked into one complex conceptual representation of individual identity. Here we tested whether rhesus macaques (Macaca mulatta) also have a cognitive representation of identity by evaluating whether they exhibit cross-modal individual recognition. Further, we assessed individual recognition of familiar conspecifics and familiar humans. In a free preferential looking time paradigm, we found that, for both species, monkeys spontaneously matched the faces of known individuals to their voices. This finding demonstrates that rhesus macaques possess a cross-modal cognitive representation of individuals that extends from conspecifics to humans, revealing the adaptive potential of identity recognition for individuals of socioecological relevance.cross-species | vocal communication | nonhuman primates | picture recognition I n humans, both faces and voices convey information about identity, providing some of the many cues we use to recognize individuals we know (1). The multifaceted nature of identity code suggests that a complex cognitive representation binds semantic information with information of different sensory modalities. In rhesus monkeys, however, it has typically been assessed only via single-modality information. For instance, rhesus monkeys can discriminate between calls of two conspecifics in a playback experiment using a spontaneous habituation-discrimination paradigm (2). They are also able to discriminate faces of two conspecifics in a match-to-sample task (3) and monkey faces or human faces in visual paired comparison tasks (4-6). These observations demonstrate that monkeys can discriminate idiosyncratic characteristics ("individual A is different from B") for their own or other species. However, they do not provide evidence of individual recognition ("this is individual A, this is B"). In comparison with discrimination, individual recognition requires an additional associative level that allows retrieval of information belonging to a specific individual. In rhesus monkeys, coarse recognition processes such as of their own species, kin, gender, reproductive status, or hierarchy are well documented (2, 7-12). However, these rudimentary recognition abilities fail to account for some sophisticated behaviors that are observed in rhesus macaques' societies. In particular, rhesus macaques live in large groups and maintain elaborate social relations involving, e.g., nonkin alliances during aggressive interactions, fight interference, reciprocal support, friendly grooming, and reconciliation (13-15). Such an organization would benefit well from the finest-grain individual recognition based on a cognitive multimodal representation of identity.Individu...

Cross-modal individual recognition in wild African lions

“…Recent advances in the cognitive sciences have resulted in growing evidence for individual recognition in non-human animals by virtue of demonstrating cross-modal processing of information on identity [7,8]. Cross-modal sensory perception is the ability to integrate information from multiple senses-in the case of individual recognition, this often involves matching vocal and visual cues, which may be demonstrated through experiments in which subjects detect a mismatch when the cues do not correspond [5,7].…”

“…Cross-modal sensory perception is the ability to integrate information from multiple senses-in the case of individual recognition, this often involves matching vocal and visual cues, which may be demonstrated through experiments in which subjects detect a mismatch when the cues do not correspond [5,7]. While there is now direct evidence for cross-modal recognition in a range of species tested in captive or domestic settings [5,[7][8][9], this ability has not been directly shown in the wild during natural social communication among conspecifics [6]. Such investigations are facilitated by a study species where repeated social interactions lead to important long-term social relationships, in which communication involves multiple sensory modalities, and where communication signals are known to provide familiarity cues as well as potential cues to identity.…”

Cross-modal individual recognition in domestic horses ( Equus caballus ) extends to familiar humans

“…We recently used an expectancy violation paradigm to demonstrate that domestic horses are capable of spontaneous cross-modal individual recognition of conspecifics [3]. The ability to match the sight of familiar individuals with their voice, without explicit training, has also since been demonstrated in non-human primates (Lophocebus albigena, Macaca mulatta) and crows (Corvus macrorhynchos), indicating that the ability is likely to have a long phylogenetic history [4][5][6].…”

Elephants can determine ethnicity, gender, and age from acoustic cues in human voices

“…Furthermore, these cues are available when the predator is still out of sight, potentially providing an important early warning system. Until now, however, studies of animal responses to human voices have focused on demonstrating skills in recognizing individual humans (17)(18)(19)(20)(21) rather than investigating specific abilities to identify particular human subgroups that have functional relevance in the natural environment.…”