Gibbons exploit information about what a competitor can see

Sánchez-Amaro, Alejandro; Tan, Jingzhi; Kaufhold, Stephan P.; Rossano, Federico

doi:10.1007/s10071-019-01333-7

Cited by 10 publications

(9 citation statements)

References 80 publications

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“…So far, most information on gaze and glance cue understanding in apes derive from studies in which human experimenters signal to an ape subject in a captive setting (Barth et al, 2005;Tomasello et al, 2007;Caspar et al, 2018;Sanchez-Amaro et al, 2020). It is important to note that responsiveness to human eye orientation by habituated animals does not equate with the usage of glance cues among conspecifics, as for instance the successful exploitation of human glances by Californian sea lions (Zalophus californianus) demonstrates (Arkwright et al, 2016).…”

Section: Is Ocular Pigmentation Linked To Specific Sociocognitive Tramentioning

confidence: 99%

“…Despite their phylogenetic position and resulting relevance to understand the evolution of hominoid cognitive traits, gibbons are widely ignored in primate behavioral research (excluding acoustic communication), so that little is known about their sociocognitive traits (Butler & Suddendorf, 2014;ManyPrimates et al, 2019). However, there currently is consensus that glancing does not carry noteworthy communicative value to them (Caspar et al, 2018;Sanchez-Amaro et al, 2020). In line with this, gibbon gaze following is less sophisticated than in their large-bodied relatives.…”

Section: Introductionmentioning

confidence: 99%

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Ocular pigmentation in humans, great apes, and gibbons is not suggestive of communicative functions - having an eye on the ‘cooperative eye hypothesis’

Caspar

Biggemann

Geissmann

et al. 2021

Preprint

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Pigmentation patterns of the visible part of the eyeball, encompassing the iris and portions of the sclera, have been discussed to be linked to social cognition in primates. In the context of the cooperative eye hypothesis, the white sclera of humans has been viewed as a derived adaptive trait, enhancing communication via glance cueing. Here, we provide a comparative analysis of ocular pigmentation patterns in 15 species of hominoids (humans, great apes & gibbons) representing all extant ape genera, based on photographs and literature data. Additionally, we quantify hominoid scleral exposure on the genus level during different glancing situations. Our data reveals a continuum of eye pigmentation traits among the studied taxa. Gibbons display darker, more uniformly colored eyes than great apes and expose less sclera, particularly during averted glancing. Iridoscleral contrasts in orangutans and gorillas approach the human condition but differ between congeneric species. Contrary to recent discussions, we found chimpanzee eyes to exhibit a cryptic coloration scheme that resembles gibbons more than other great apes and that does not enhance glance cueing or gaze following. We critically evaluate the evidence for links between social cognition and eye pigmentation in primates, concluding that the cooperative eye hypothesis cannot convincingly explain the patterns observed. Although the human eye exhibits unique traits that are likely linked to social communication, high iridoscleral contrast is not one of them. Differences in scleral pigmentation between great apes and humans are gradual and might have arisen via genetic drift and sexual selection.

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Section: Is Ocular Pigmentation Linked To Specific Sociocognitive Tramentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ocular pigmentation in humans, great apes, and gibbons is not suggestive of communicative functions - having an eye on the ‘cooperative eye hypothesis’

Caspar

Biggemann

Geissmann

et al. 2021

Preprint

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“…Despite their phylogenetic position and resulting relevance to understand the evolution of hominoid cognitive traits, gibbons are widely ignored in primate behavioral research (excluding acoustic communication), so that little is known about their socio-cognitive traits 19 , 20 . However, there currently is consensus that glancing does not carry noteworthy communicative value to them 21 , 22 . In line with this, gibbon gaze following is less sophisticated than in their large-bodied relatives.…”

Section: Introductionmentioning

confidence: 99%

Ocular pigmentation in humans, great apes, and gibbons is not suggestive of communicative functions

Caspar

Biggemann

Geissmann³

et al. 2021

Sci Rep

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Pigmentation patterns of the visible part of the eyeball, encompassing the iris and portions of the sclera, have been discussed to be linked to social cognition in primates. The cooperative eye hypothesis suggests the white sclera of humans to be a derived adaptive trait that enhances eye-mediated communication. Here, we provide a comparative analysis of ocular pigmentation patterns in 15 species of hominoids (humans, great apes & gibbons) that show marked differences in social cognition and quantify scleral exposure at the genus level. Our data reveals a continuum of eye pigmentation traits in hominoids which does not align with the complexity of gaze-mediated communication in the studied taxa. Gibbons display darker eyes than great apes and expose less sclera. Iridoscleral contrasts in orangutans and gorillas approach the human condition but differ between congeneric species. Contrary to recent discussions, we found chimpanzee eyes to exhibit a cryptic coloration scheme that resembles gibbons more than other apes. We reevaluate the evidence for links between social cognition and eye pigmentation in primates, concluding that the cooperative eye hypothesis cannot explain the patterns observed. Differences in scleral pigmentation between great apes and humans are gradual and might have arisen via genetic drift and sexual selection.

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“…In the case of gaze-following studies, researchers have found that gibbons are able to shift their gaze in response to a previous experimenter gaze shift but it remains unclear whether gibbons are taking the perspective of the experimenter into account, including her mental states. However, a recent study found that when gibbons were presented with a competitive scenario in which they could only retrieve uncontested rewards-when the experimenter did not orient his body, head or eyes towards the rewards, gibbons avoided the contested table by paying attention to the orientation of the body and the head of the experimenter but not to his eyes 43 . This later result suggests that, in line with previous socio-cognitive studies in other primate species [44][45][46] , gibbons may perform better in competitive settings compared to neutral ones.…”

Section: Introductionmentioning

confidence: 99%

“…However, in previous gaze-following studies the interaction only occurred between the human experimenter and the ape and not between conspeci cs. Considering the competitive task presented by Sánchez-Amaro and colleagues 43 as an example, the experimenter and the gibbon faced a con ict of interest every time the gibbon approached the contested table since the experimenter and the gibbon competed for the same food reward. Therefore, one open question is how pairs of gibbons would solve con icts of interest in a more naturalistic context.…”

Section: Introductionmentioning

confidence: 99%

How do gibbons solve social dilemmas?

Sánchez-Amaro¹,

Ball²,

Rossano³

2020

Preprint

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Social primates face conflicts of interest with other partners when their individual and collective interests collide. Despite living in small, primarily dyadic, groups compared to other social primates, gibbons are not exempt from these conflicts in their everyday lives. In the current task, we asked whether pairs of gibbons would solve a conflict of interest over food rewards. We presented pairs of gibbons with a situation in which one pair member, the actor, could release food rewards at a distance, giving the passive partner a chance to take an advantageous position to obtain the rewards. Gibbons participated in three conditions: A No Food control, an Altruistic situation in which the actor could not obtain a direct reward from the cooperative act and a Test condition in which the actor could secure a small fraction of the total rewards. We found that gibbons acted more often in the two conditions involving food rewards, and waited longer when no direct rewards were available for the actor, thus suggesting that they understood the mechanism and that they faced a social trade-off between making the rewards available and waiting for each other to act. However, we found that in a majority of pairs, acting individuals benefitted more than the passive partners in both altruistic and test conditions. Furthermore, in some occasions actors actively refused to approach the location where the food was released. These results suggest that while gibbons strategize to solve the social dilemmas, they often allowed their partners to obtain better rewards. Our results highlight the importance of social tolerance and motivation as drivers promoting cooperation in these pair-living species.

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Gibbons exploit information about what a competitor can see

Cited by 10 publications

References 80 publications

Ocular pigmentation in humans, great apes, and gibbons is not suggestive of communicative functions - having an eye on the ‘cooperative eye hypothesis’

Ocular pigmentation in humans, great apes, and gibbons is not suggestive of communicative functions - having an eye on the ‘cooperative eye hypothesis’

Ocular pigmentation in humans, great apes, and gibbons is not suggestive of communicative functions

How do gibbons solve social dilemmas?

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