An infant chimpanzee (Pan troglodytes) follows human gaze

Okamoto, Sanae; Tomonaga, Masaki; Ishii, Kiyoshi; Kawai, Nobuyuki; Tanaka, Masayuki; Matsuzawa, Tetsuro

doi:10.1007/s10071-002-0133-z

Cited by 73 publications

(66 citation statements)

References 19 publications

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“…Similarly, apes may not show basic co-orienting responses when others move the direction of their gaze, nor more complex forms of reasoning about others' line of sight (e.g. accounting for barriers and distractors) until they are several years old [24,[32][33][34][35][36]. Overall, this evidence supports the proposal that gaze following in non-human primates requires more extensive experience with relevant social interactions than is necessary for humans (e.g.…”

Section: Introductionsupporting

confidence: 73%

Rhesus monkeys show human-like changes in gaze following across the lifespan

et al. 2016

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Gaze following, or co-orienting with others, is a foundational skill for human social behaviour. The emergence of this capacity scaffolds critical humanspecific abilities such as theory of mind and language. Non-human primates also follow others' gaze, but less is known about how the cognitive mechanisms supporting this behaviour develop over the lifespan. Here we experimentally tested gaze following in 481 semi-free-ranging rhesus macaques (Macaca mulatta) ranging from infancy to old age. We found that monkeys began to follow gaze in infancy and this response peaked in the juvenile periodsuggesting that younger monkeys were especially attuned to gaze information, like humans. After sexual maturity, monkeys exhibited human-like sex differences in gaze following, with adult females showing more gaze following than males. Finally, older monkeys showed reduced propensity to follow gaze, just as older humans do. In a second study (n ¼ 80), we confirmed that macaques exhibit similar baseline rates of looking upwards in a control condition, regardless of age. Our findings indicate that-despite important differences in human and non-human primate life-history characteristics and typical social experiences-monkeys undergo robust ontogenetic shifts in gaze following across early development, adulthood and ageing that are strikingly similar to those of humans.

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Section: Introductionsupporting

confidence: 73%

Rhesus monkeys show human-like changes in gaze following across the lifespan

et al. 2016

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“…Macaques and chimpanzee infants do not respond reliably before the age of 5-6 and 36 -48 months, respectively (Tomasello, Hare, & Fogleman, 2001). Although Okamoto et al (2002) also found a developmental change, the age of emergence in their subject was much earlier-they detected reliable gaze-following responses to head orientation and eye orientation alone at the age of 11 and 13 months, respectively. Okamoto et al (2002) pointed out that a possible explanation for this discrepancy between studies was that, in their study, the experimenter always looked at a target that was in the subject's view, whereas the experimenter in the Tomasello et al (2001) study always looked into empty space outside the visual field of the subject.…”

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confidence: 92%

All Great Ape Species Follow Gaze to Distant Locations and Around Barriers.

Bräuer

Call

Tomasello

2005

Journal of Comparative Psychology

252

199

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Following the gaze direction of conspecifics is an adaptive skill that enables individuals to obtain useful information about the location of food, predators, and group mates. In the current study, the authors compared the gaze-following skills of all 4 great ape species. In the 1st experiment, a human either looked to the ceiling or looked straight ahead. Individuals from all species reliably followed the human's gaze direction and sometimes even checked back when they found no target. In a 2nd experiment, the human looked behind some kind of barrier. Results showed that individuals from all species reliably put themselves in places from which they could see what the experimenter was looking at behind the barrier. These results support the hypothesis that great apes do not just orient to a target that another is oriented to, but they actually attempt to take the visual perspective of the other.

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“…We used MRI technology to examine the developmental changes of the SVT shape in three living chimpanzee infants, named Ayumu (male), Cleo (female), and Pal (female). They were born in 2000 and were reared by their biological mothers in the Kyoto University Primate Research Institute (KUPRI) (20,21). Care and use of the chimpanzees adhered to the guidelines of the KUPRI, and the protocol for the MRI examination was approved by the Ethics Panel of the KUPRI (22,23).…”

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confidence: 99%

Descent of the larynx in chimpanzee infants

Nishimura

Mikami

Suzuki

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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The human larynx descends during infancy and the early juvenile periods, and this greatly contributes to the morphological foundations of speech development. This developmental phenomenon is believed to be unique to humans. This concept has formed a basis for paleoanthropological studies on the origin and evolution of human speech. We used magnetic resonance imaging to study the development of three living chimpanzees and found that their larynges also descend during infancy, as in human infants. This descent was completed primarily through the rapid descent of the laryngeal skeleton relative to the hyoid, but it was not accompanied by the descent of the hyoid itself. The descent is possibly associated with developmental changes of the swallowing mechanism. Moreover, it contributes physically to an increased independence between the processes of phonation and articulation for vocalization. Thus, the descent of the larynx and the morphological foundations for speech production must have evolved in part during hominoid evolution, and not in a single shift during hominid evolution. In the human neonate, the hyoid bone and larynx are positioned as high as in other mammals (1-3). However, they descend gradually during postnatal life (1-6). This descent is completed through the descent of the laryngeal skeleton relative to the hyoid and the descent of the hyoid relative to the mandible and cranial base (4-6). Thus, the human supralaryngeal vocal tract (SVT) develops to form a double resonator system with equally long horizontal [SVT H , from the posterior oropharyngeal wall (POW) to the lips] and vertical (SVT V , from the vocal folds to the velum) components (2, 6). Acoustically, such a configuration, in combination with the tongue's mobility, enables humans to produce complex speech sounds (7,8).It is commonly assumed that this developmental descent evolved as an adaptation for speech in a single shift in the human lineage, in combination with decreased prognathism and flexure of the cranial base (2, 9, 10). This concept has formed a basis for paleoanthropological studies on the origin and evolution of human speech, in which the ''unique'' morphological features related to speech have been examined through comparisons with extant primates (2,(11)(12)(13)(14)(15)(16). Thus, the evolution of the morphological basis for human speech has been regarded as synonymous with the evolution of the developmental descent of the larynx. Nonetheless, there are few comparative studies on the developmental changes of humans and non-human mammals (17-19), and it is unclear how and when the unique features of the speech apparatus of adult humans appear and develop during growth. Subjects and MethodsMagnetic Resonance Imaging (MRI) Procedures. We used MRI technology to examine the developmental changes of the SVT shape in three living chimpanzee infants, named Ayumu (male), Cleo (female), and Pal (female). They were born in 2000 and were reared by their biological mothers in the Kyoto University Primate Research Institute (KUPRI) (20,2...

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An infant chimpanzee (Pan troglodytes) follows human gaze

Cited by 73 publications

References 19 publications

Rhesus monkeys show human-like changes in gaze following across the lifespan

Rhesus monkeys show human-like changes in gaze following across the lifespan

All Great Ape Species Follow Gaze to Distant Locations and Around Barriers.

Descent of the larynx in chimpanzee infants

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