• There is no Other Monkey in the Mirror for Spider Monkeys (Ateles geoffroyi)

      Murray, Lindsay; Schaffner, Colleen; Aureli, Filippo; Amici, Federica; University of Chester, Adams State University, Universidad Veracruzana, Liverpool John Moores University, Max Planck Institute for Evolutionary Anthropology (American Psychological Association, 2020-06-18)
      Mirror self-recognition (MSR), usually considered a marker of self-awareness, occurs in several species and may reflect a capacity that has evolved in small incremental steps. In line with research on human development and building on previous research adopting a gradualist framework, we categorized the initial mirror responses of naïve spider monkeys (Ateles geoffroyi) according to four levels. We compared social, exploratory, contingent and self-exploratory responses to a mirror and faux mirror during three short trials. If spider monkeys respond as most monkey species, we predicted they would perform at level 0, mainly showing social behavior toward their mirror-image. However, because spider monkeys show enhancement of certain cognitive skills comparable to those of great ape species, we predicted that they would perform at level 1a (showing exploratory behavior) or 1b (showing contingent behavior). GLMMs revealed that monkeys looked behind and visually inspected the mirror significantly more in the mirror than the faux mirror condition. Although the monkeys engaged in contingent body movements at the mirror, this trend was not significant. Strikingly, they showed no social behaviors toward their mirror-image. We also measured self-scratching as an indicator of anxiety and found no differences in frequencies of self-scratching between conditions. Therefore, in contrast to most findings on other species, spider monkeys did not treat their image as another monkey during their initial exposure to the mirror. In fact, they reached at least level 1a within minutes of mirror exposure. These responses recommend spider monkeys as good candidates for further explorations into monkey self-recognition.
    • Video-mediated behavior in gorillas (G. g. gorilla): A stage in the development of self-recognition in a juvenile male?

      Murray, Lindsay; University of Chester (American Psychological Association, 2020-03-12)
      The anomalous position of gorillas (G. g. gorilla) in the capacity for self-recognition remains puzzling. The standard measure of self-recognition is Gallup’s (1970) mark test that assesses an individual’s ability to recognize its altered image in a mirror following the application of paint marks to visually inaccessible areas. Here, the results of a small-scale pilot study are presented, utilizing video playback through a television monitor, to examine behavioural differences indicative of developing self-recognition. The behaviors of four Western lowland gorillas at Bristol Zoo, UK were observed while watching a TV screen during five conditions: blank screen, white noise interference, footage of unfamiliar gorillas, self previously recorded, and self-live. Differences were predicted in the frequency of the gorillas’ observed behaviors when viewing each of the conditions: specifically, that there would be more visual inspection, contingent body and facial movements, and self-exploration in the self-recorded and self-live conditions compared to the other conditions. These predictions were partially supported. No agonistic or fear responses were observed and self-exploration was only seen in the self-live condition. During live playback, contingency-checking movements and self-exploration of the mouth were observed, particularly in the youngest gorilla, providing important video evidence of a close parallel to the mouth exploratory behavior witnessed in self-recognizing chimpanzees. On the basis of these preliminary findings of differentiated spontaneous behaviors, a tentative framework is proposed for categorizing gorillas according to levels of developing self-recognition along a continuum.