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Li Z, Zhao S, Yang J, Murai T, Funahashi S, Wu J, Zhang Z. Is P3 amplitude associated with greater gaze distraction effect in schizotypy? Schizophr Res 2024; 267:422-431. [PMID: 38640853 DOI: 10.1016/j.schres.2024.04.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Revised: 02/27/2024] [Accepted: 04/03/2024] [Indexed: 04/21/2024]
Abstract
A recently proposed "Hyperfocusing hypothesis" suggests that schizotypy is associated with a more narrow but more intense way of allocating attention. The current study aims to test a vital prediction of this hypothesis in a social context, that schizotypy may be related to greater difficulty overcoming the distracting effects of gaze. This could cause a longer time to respond to targets that are invalidly cued by gaze. The current study tested this prediction in a modified Posner cueing paradigm by using P3 as an indicator for attentional resources. Seventy-four young healthy individuals with different levels of schizotypy were included, they were asked to detect the location of a target that was cued validly or invalidly by the gaze and head orientation. The results revealed that (a) schizotypy is associated with hyperfocusing on gaze direction, leading to greater difficulty overcoming the distracting effect of gaze. The higher the trait-schizotypy score, the more time needed to respond to targets that were invalidly cued by gaze (b) schizotypy is associated with reduced P3 which is directed by social communicative stimuli. The higher the trait-schizotypy score, the smaller the amplitude of P3 (c) the relationship between schizotypal traits and response times of the gaze-invalid condition is fully intermediated by P3. The findings of the current study suggest the P3 component may be a crucial neural mechanism underlying joint attention deficits in schizophrenia.
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Affiliation(s)
- Zimo Li
- Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, Okayama, Japan; Research Center for Medical Artificial Intelligence, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Shuo Zhao
- School of Psychology, ShenZhen University, ShenZhen, GuangDong, China.
| | - Jiajia Yang
- Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, Okayama, Japan
| | - Toshiya Murai
- Department of Psychiatry, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Shintaro Funahashi
- Research Center for Medical Artificial Intelligence, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Jinglong Wu
- Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, Okayama, Japan; Research Center for Medical Artificial Intelligence, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Zhilin Zhang
- Research Center for Medical Artificial Intelligence, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China; Department of Psychiatry, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
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2
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Konno A, Aoki H, Suzuki E, Furuta S, Ueda S. Are dark-eyed dogs favoured by humans? Domestication as a potential driver of iris colour difference between dogs and wolves. ROYAL SOCIETY OPEN SCIENCE 2023; 10:230854. [PMID: 38126061 PMCID: PMC10731317 DOI: 10.1098/rsos.230854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Accepted: 11/27/2023] [Indexed: 12/23/2023]
Abstract
Comparative studies have shown that the eye morphology of primates has been shaped by a variety of selection pressures (e.g. communication, environmental factors). To comprehensively elucidate the complex links between ocular morphology and its evolutionary drive, attention should be paid to other phylogenetic groups. Here, we address a new question regarding the evolution of eye colour patterns in the oldest domesticated animal, namely, the domestic dog (Canis familiaris). In this study, we conducted an image analysis of dogs and their closest relatives, grey wolves (Canis lupus), to compare the colours of their irises, with the aim of assessing whether eye colours of dogs affect how humans perceived dogs. We found that the irises of dogs were significantly darker than those of wolves. We also found that facial images of dark-eyed dogs were perceived as more friendly and immature, potentially eliciting caregiving responses from humans. Our findings are consistent with our expectation that humans favour dark-eyed dogs over light-eyed ones and provide an updated hypothesis that dogs with dark eyes may have evolved by acquiring a facial trait that sends a non-threatening gaze signal to humans.
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Affiliation(s)
- Akitsugu Konno
- Department of Animal Sciences, Teikyo University of Science, Yamanashi, Japan
| | - Hitomi Aoki
- Department of Animal Sciences, Teikyo University of Science, Yamanashi, Japan
| | - Emiri Suzuki
- Department of Animal Sciences, Teikyo University of Science, Yamanashi, Japan
| | - Seiya Furuta
- Department of Animal Sciences, Teikyo University of Science, Yamanashi, Japan
| | - Sayoko Ueda
- The Mt. Fuji Institute for Nature and Biology, Showa University, Yamanashi, Japan
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3
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Clark IR, Lee KC, Poux T, Langergraber KE, Mitani JC, Watts D, Reed J, Sandel AA. White sclera is present in chimpanzees and other mammals. J Hum Evol 2023; 176:103322. [PMID: 36706647 PMCID: PMC9998187 DOI: 10.1016/j.jhevol.2022.103322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 12/22/2022] [Accepted: 12/23/2022] [Indexed: 01/27/2023]
Affiliation(s)
- Isabelle R Clark
- Department of Anthropology, University of Texas at Austin, 2201 Speedway, Austin, TX 78712, USA
| | - Kevin C Lee
- School of Human Evolution and Social Change and Institute of Human Origins, Arizona State University, 900 S. Cady Mall, Tempe, AZ 85281, USA
| | - Tucker Poux
- Tufts University, 419 Boston Ave, Medford, MA 02155, USA
| | - Kevin E Langergraber
- School of Human Evolution and Social Change and Institute of Human Origins, Arizona State University, 900 S. Cady Mall, Tempe, AZ 85281, USA
| | - John C Mitani
- Department of Anthropology, University of Michigan, 1085 S. University Ave., Ann Arbor, MI 48109, USA
| | - David Watts
- Department of Anthropology, Yale University, P.O. Box 208277, New Haven, CT 06520, USA
| | - James Reed
- Underdog Films Ltd, 2 St. Paul's Road, Bristol, BS8 1LT, UK
| | - Aaron A Sandel
- Department of Anthropology, University of Texas at Austin, 2201 Speedway, Austin, TX 78712, USA.
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Wolf W, Thielhelm J, Tomasello M. Five-year-old children show cooperative preferences for faces with white sclera. J Exp Child Psychol 2023; 225:105532. [PMID: 35988359 DOI: 10.1016/j.jecp.2022.105532] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 07/29/2022] [Accepted: 07/29/2022] [Indexed: 11/25/2022]
Abstract
The cooperative eye hypothesis posits that human eye morphology evolved to facilitate cooperation. Although it is known that young children prefer stimuli with eyes that contain white sclera, it is unknown whether white sclera influences children's perception of a partner's cooperativeness specifically. In the current studies, we used an online methodology to present 5-year-old children with moving three-dimensional face models in which facial morphology was manipulated. Children found "alien" faces with human eyes more cooperative than faces with dark sclera (Study 2) but not faces with enlarged irises (Study 1). For more human-like faces (Study 3), children found human eyes more cooperative than either enlarged irises or dark sclera and found faces with enlarged irises cuter (but not more cooperative) than eyes with dark sclera. Together, these results provide strong support for the cooperative eye hypothesis.
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Affiliation(s)
- Wouter Wolf
- Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA; Department of Developmental Psychology, Utrecht University, 3584 CS Utrecht, the Netherlands.
| | - Julia Thielhelm
- Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA
| | - Michael Tomasello
- Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA; Department of Developmental and Comparative Psychology, Max Planck Institute for Evolutionary Anthropology, 04103 Leipzig, Germany
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Kano F. Evolution of the uniformly white sclera in humans: critical updates. Trends Cogn Sci 2023; 27:10-12. [PMID: 36229339 DOI: 10.1016/j.tics.2022.09.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Revised: 09/19/2022] [Accepted: 09/20/2022] [Indexed: 12/24/2022]
Abstract
The human eye characteristically has exposed and uniformly white sclera, which is hypothesized to have evolved to enhance eye-gaze signaling for conspecific communication. Although recent studies have put this hypothesis into question, current morphological and experimental evidence supports its key premise, albeit with recommendations for critical updates.
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Affiliation(s)
- Fumihiro Kano
- Centre for the Advanced Study of Collective Behaviour, University of Konstanz, 78464, Konstanz, Germany; Max-Planck Institute of Animal Behavior, 78315, Radolfzell, Germany.
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Li K, Lu A, Deng R, Yi H. The Unique Cost of Human Eye Gaze in Cognitive Control: Being Human-Specific and Body-Related? PSICHOLOGIJA 2022. [DOI: 10.15388/psichol.2022.59] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
This study investigated the eye gaze cost in cognitive control and whether it is human-specific and body-related. In Experiment 1, we explored whether there was a cost of human eye gaze in cognitive control and extended it by focusing on the role of emotion in the cost. Stroop effect was found to be larger in eye-gaze condition than vertical grating condition, and to be comparable across positive, negative, and neutral trials. In Experiment 2, we explored whether the eye gaze cost in cognitive control was limited to human eyes. No larger Stroop effect was found in feline eye-gaze condition, neither the modulating role of emotion. In Experiment 3, we explored whether the mouth could elicit a cost in Stroop effect. Stroop effect was not significantly larger in mouth condition compared to vertical grating condition, nor across positive, negative, and neutral conditions. The results suggest that: (1) There is a robust cost of eye gaze in cognitive control; (2) Such eye-gaze cost was specific to human eyes but not to animal eyes; (3) Only human eyes could have such eye-gaze costs but not human mouth. This study supported the notion that presentation of social cues, such as human eyes, could influence attentional processing, and provided preliminary evidence that the human eye plays an important role in cognitive processing.
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Zeiträg C, Jensen TR, Osvath M. Gaze following: A socio-cognitive skill rooted in deep time. Front Psychol 2022; 13:950935. [PMID: 36533020 PMCID: PMC9756811 DOI: 10.3389/fpsyg.2022.950935] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Accepted: 10/07/2022] [Indexed: 11/07/2023] Open
Abstract
Social gaze has received much attention in social cognition research in both human and non-human animals. Gaze following appears to be a central skill for acquiring social information, such as the location of food and predators, but can also draw attention to important social interactions, which in turn promotes the evolution of more complex socio-cognitive processes such as theory of mind and social learning. In the past decades, a large number of studies has been conducted in this field introducing differing methodologies. Thereby, various factors influencing the results of gaze following experiments have been identified. This review provides an overview of the advances in the study of gaze following, but also highlights some limitations within the research area. The majority of gaze following studies on animals have focused on primates and canids, which limits evolutionary interpretations to only a few and closely related evolutionary lineages. This review incorporates new insights gained from previously understudied taxa, such as fishes, reptiles, and birds, but it will also provide a brief outline of mammal studies. We propose that the foundations of gaze following emerged early in evolutionary history. Basic, reflexive co-orienting responses might have already evolved in fishes, which would explain the ubiquity of gaze following seen in the amniotes. More complex skills, such as geometrical gaze following and the ability to form social predictions based on gaze, seem to have evolved separately at least two times and appear to be correlated with growing complexity in brain anatomy such as increased numbers of brain neurons. However, more studies on different taxa in key phylogenetic positions are needed to better understand the evolutionary history of this fundamental socio-cognitive skill.
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Affiliation(s)
- Claudia Zeiträg
- Department of Philosophy and Cognitive Science, Lund University, Lund, Sweden
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Wacewicz S, Perea-García JO, Lewandowski Z, Danel DP. The adaptive significance of human scleral brightness: an experimental study. Sci Rep 2022; 12:20261. [PMID: 36424405 PMCID: PMC9691750 DOI: 10.1038/s41598-022-24403-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 11/15/2022] [Indexed: 11/27/2022] Open
Abstract
Homogeneously depigmented sclerae have long been proposed to be uniquely human-an adaptation to enable cooperative behaviour by facilitating interpersonal coordination through gaze following. However, recent evidence has shown that deeply pigmented sclerae also afford gaze following if surrounding a bright iris. Furthermore, while current scleral depigmentation is clearly adaptive in modern humans, it is less clear how the evolutionarily intermediate stages of scleral pigmentation may have been adaptive. In sum, it is unclear why scleral depigmentation became the norm in humans, while not so in sister species like chimpanzees, or why some extant species display intermediate degrees of pigmentation (as our ancestors presumably did at some point). We created realistic facial images of 20 individually distinct hominins with diverse facial morphologies, each face in the (i) humanlike bright sclera and (ii) generalised apelike dark sclera version. Participants in two online studies rated the bright-sclera hominins as younger, healthier, more attractive and trustworthy, but less aggressive than the dark-sclera hominins. Our results support the idea that the appearance of more depigmented sclerae promoted perceived traits that fostered trust, increasing fitness for those individuals and resulting in depigmentation as a fixed trait in extant humans.
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Affiliation(s)
- Slawomir Wacewicz
- grid.5374.50000 0001 0943 6490Center for Language Evolution Studies, Nicolaus Copernicus University, Toruń, Poland
| | - Juan Olvido Perea-García
- grid.5132.50000 0001 2312 1970The Cognitive Psychology Unit, Faculty of Social Sciences, Leiden University, Leiden, The Netherlands
| | - Zdzisław Lewandowski
- grid.8505.80000 0001 1010 5103Department of Human Biology, Wroclaw University of Health and Sport Sciences, Wroclaw, Poland
| | - Dariusz P. Danel
- grid.413454.30000 0001 1958 0162Department of Anthropology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wroclaw, Poland
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9
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Perea-García JO, Ramarajan K, Kret ME, Hobaiter C, Monteiro A. Ecological factors are likely drivers of eye shape and colour pattern variations across anthropoid primates. Sci Rep 2022; 12:17240. [PMID: 36243745 PMCID: PMC9569326 DOI: 10.1038/s41598-022-20900-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Accepted: 09/20/2022] [Indexed: 01/06/2023] Open
Abstract
External eye appearance across primate species is diverse in shape and colouration, yet we still lack an explanation for the drivers of such diversity. Here we quantify substantial interspecific variation in eye shape and colouration across 77 primate species representing all extant genera of anthropoid primates. We reassess a series of hypotheses aiming to explain ocular variation in horizontal elongation and in colouration across species. Heavier body weight and terrestrial locomotion are associated with elongated eye outlines. Species living closer to the equator present more pigmented conjunctivae, suggesting photoprotective functions. Irises become bluer in species living further away from the equator, adding to existing literature supporting a circadian clock function for bluer irises. These results shift the current focus from communicative, to ecological factors in driving variation in external eye appearance in anthropoid primates. They also highlight the possibility that similar ecological factors contributed to selection for blue eyes in ancestral human populations living in northern latitudes.
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Affiliation(s)
- Juan Olvido Perea-García
- grid.4280.e0000 0001 2180 6431Department of Biological Sciences, National University of Singapore, Singapore, 117557 Singapore ,grid.5132.50000 0001 2312 1970Institute of Psychology, Cognitive Psychology Unit, Leiden University, Wassenaarseweg 52, 2333 AK Leiden, The Netherlands
| | - Kokulanantha Ramarajan
- grid.462738.c0000 0000 9091 4551School of Applied Sciences, Republic Polytechnic, Singapore, Singapore
| | - Mariska E. Kret
- grid.5132.50000 0001 2312 1970Institute of Psychology, Cognitive Psychology Unit, Leiden University, Wassenaarseweg 52, 2333 AK Leiden, The Netherlands
| | - Catherine Hobaiter
- grid.11914.3c0000 0001 0721 1626Centre for Social Learning and Cognitive Evolution and Scottish Primate Research Group, School of Psychology and Neuroscience, University of St Andrews, Fife, Scotland, UK
| | - Antónia Monteiro
- grid.4280.e0000 0001 2180 6431Department of Biological Sciences, National University of Singapore, Singapore, 117557 Singapore ,grid.463064.30000 0004 4651 0380Science Division, Yale-NUS College, Singapore, Singapore
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10
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Mearing AS, Burkart JM, Dunn J, Street SE, Koops K. The evolutionary drivers of primate scleral coloration. Sci Rep 2022; 12:14119. [PMID: 35982191 PMCID: PMC9388658 DOI: 10.1038/s41598-022-18275-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Accepted: 08/08/2022] [Indexed: 11/09/2022] Open
Abstract
The drivers of divergent scleral morphologies in primates are currently unclear, though white sclerae are often assumed to underlie human hyper-cooperative behaviours. Humans are unusual in possessing depigmented sclerae whereas many other extant primates, including the closely-related chimpanzee, possess dark scleral pigment. Here, we use phylogenetic generalized least squares (PGLS) analyses with previously generated species-level scores of proactive prosociality, social tolerance (both n = 15 primate species), and conspecific lethal aggression (n = 108 primate species) to provide the first quantitative, comparative test of three existing hypotheses. The 'self-domestication' and 'cooperative eye' explanations predict white sclerae to be associated with cooperative, rather than competitive, environments. The 'gaze camouflage' hypothesis predicts that dark scleral pigment functions as gaze direction camouflage in competitive social environments. Notably, the experimental evidence that non-human primates draw social information from conspecific eye movements is unclear, with the latter two hypotheses having recently been challenged. Here, we show that white sclerae in primates are associated with increased cooperative behaviours whereas dark sclerae are associated with reduced cooperative behaviours and increased conspecific lethal violence. These results are consistent with all three hypotheses of scleral evolution, suggesting that primate scleral morphologies evolve in relation to variation in social environment.
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Affiliation(s)
- Alex S Mearing
- Department of Archaeology, Fitzwilliam Street, University of Cambridge, Cambridge, CB2 1QH, UK.
| | - Judith M Burkart
- Department of Anthropology, University of Zurich, 8057, Zurich, Switzerland
| | - Jacob Dunn
- Department of Archaeology, Fitzwilliam Street, University of Cambridge, Cambridge, CB2 1QH, UK.,School of Life Sciences, Anglia Ruskin University, Cambridge, CB1 1PT, UK.,Department of Cognitive Biology, University of Vienna, 1090, Vienna, Austria
| | - Sally E Street
- Department of Anthropology, University of Durham, Durham, DH1 3LE, UK
| | - Kathelijne Koops
- Department of Archaeology, Fitzwilliam Street, University of Cambridge, Cambridge, CB2 1QH, UK.,Department of Anthropology, University of Zurich, 8057, Zurich, Switzerland
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