Social and Emotional Values of Sounds Influence Human (Homo sapiens) and Non-Human Primate (Cercopithecus campbelli) Auditory Laterality

Abstract

The last decades evidenced auditory laterality in vertebrates, offering new important insights for the understanding of the origin of human language. Factors such as the social (e.g. specificity, familiarity) and emotional value of sounds have been proved to influence hemispheric specialization. However, little is known about the crossed effect of these two factors in animals. In addition, human-animal comparative studies, using the same methodology, are rare. In our study, we adapted the head turn paradigm, a widely used non invasive method, on 8–9-year-old schoolgirls and on adult female Campbell's monkeys, by focusing on head and/or eye orientations in response to sound playbacks. We broadcast communicative signals (monkeys: calls, humans: speech) emitted by familiar individuals presenting distinct degrees of social value (female monkeys: conspecific group members vs heterospecific neighbours, human girls: from the same vs different classroom) and emotional value (monkeys: contact vs threat calls; humans: friendly vs aggressive intonation). We evidenced a crossed-categorical effect of social and emotional values in both species since only “negative” voices from same class/group members elicited a significant auditory laterality (Wilcoxon tests: monkeys, T = 0 p = 0.03; girls: T = 4.5 p = 0.03). Moreover, we found differences between species as a left and right hemisphere preference was found respectively in humans and monkeys. Furthermore while monkeys almost exclusively responded by turning their head, girls sometimes also just moved their eyes. This study supports theories defending differential roles played by the two hemispheres in primates' auditory laterality and evidenced that more systematic species comparisons are needed before raising evolutionary scenario. Moreover, the choice of sound stimuli and behavioural measures in such studies should be the focus of careful attention.

Interaction of music and emotional stimuli in modulating working memory in macaque monkeys

“…Monkeys have a highly developed auditory system for detecting and discrimination of acoustic information, which is closely similar to humans (Basile, Lemasson, & Blois‐Heulin, ; Rauschecker, ). Some studies have suggested that macaque monkeys have difficulties in using auditory stimuli to drive their behavior (Fritz, Mishkin, & Saunders, ; Scott, Mishkin, & Yin, ) and compared to visual stimuli, longer training might be needed to make monkeys put attention to auditory stimuli to perform a task (Gámez et al, ; Merchant et al, ).…”

Campbell's monkeys concatenate vocalizations into context-specific call sequences

“…In terms of comprehension, primates and possibly many other species are able to assign meaning to different calls if there is a strong relation between a call's acoustic morphology and its eliciting context (11)(12)(13)(14). In some species, there is some evidence for hemispheric specialization when processing conspecific calls [e.g., horses (15), Campbell's monkeys (16), rhesus macaques (17), starlings (18), and sea lions (19)]. …”

Brain Functional Asymmetry of Chimpanzees (Pan troglodytes): the Example of Auditory Laterality

“…Depending on the species, the animals in these studies demonstrated the dominance of the left or right hemisphere. Thus, Japanese macaques (Macaca fuscata) (Petersen et al, 1978), California sea lions (Zalophus californianus) (Boye et al, 2005), and dogs (Siniscalchi et al, 2008), processed the stimuli associated with vocalization by the left hemisphere, while starlings (Sturnus vulgaris) and chimpanzees -by the right hemisphere (Basile et al, 2009).…”