Mariska Kret

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Papers by Mariska Kret

No immediate attentional bias towards or choice bias for male secondary sexual characteristics in Bornean orang-utans (Pongo pygmaeus)

Scientific reports, May 27, 2024

Primate faces provide information about a range of variant and invariant traits, including some t... more Primate faces provide information about a range of variant and invariant traits, including some that are relevant for mate choice. For example, faces of males may convey information about their health or genetic quality through symmetry or facial masculinity. Because perceiving and processing such information may have bearing on the reproductive success of an individual, cognitive systems are expected to be sensitive to facial cues of mate quality. However, few studies have investigated this topic in non-human primate species. Orang-utans are an interesting species to test mate-relevant cognitive biases, because they are characterised by male bimaturism: some adult males are fully developed and bear conspicuous flanges on the side of their face, while other males look relatively similar to females. Here, we describe two non-invasive computerised experiments with Bornean orang-utans (Pongo pygmaeus), testing (i) immediate attention towards large flanges and symmetrical faces using a dot-probe task (N = 3 individuals; 2F) and (ii) choice bias for pictures of flanged males over unflanged males using a preference test (N = 6 individuals; 4F). In contrast with our expectations, we found no immediate attentional bias towards either large flanges or symmetrical faces. In addition, individuals did not show a choice bias for stimuli of flanged males. We did find exploratory evidence for a colour bias and energy efficiency trade-offs in the preference task. We discuss our null results and exploratory results in the context of the evolutionary history of Bornean orang-utans, and provide suggestions for a more biocentric approach to the study of orang-utan cognition. Primates have a highly specialized visual system that helps them navigate their social environment 1,2 . For example, primates attend to faces of conspecifics 3 and discriminate faces based on different characteristics, such as emotional expressions 4 and familiarity . Importantly, primate faces can also signal cues that are relevant for mate choice, such as health or dominance 8 . Consequently, primates might have cognitive biases related to sexually relevant facial characteristics. Examples of such traits are sexually dimorphic characteristics and facial symmetry . However, previous work on this topic has mostly focused on rhesus macaques, and very few studies have studied cognitive biases to sexually relevant facial characteristics in great apes. Therefore, the present paper aims to investigate whether Bornean orang-utans (Pongo pygmaeus) have cognitive biases for such facial characteristics using an immediate attention task and a preference task. Cognitive processes are strongly influenced by evolutionarily relevant contexts, such as mate choice . Mate choice is one of the most important aspects of a sexually reproducing animal's life: choosing a suitable mate might ensure a good representation of the individual's genes in the next generation. Because of this strong incentive to choose a suitable mate, many species have evolved specific mate preferences that guide individuals during the mate choice process . For humans, it has been established that preferences affect social cognition: several cognitive processes, such as attention , memory 17 , and motivational drive 18 , are modulated by physical attractiveness. For non-human primates, research on this topic is still relatively scarce. While previous work has

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Sharing of science is most likely among male scientists

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Experimental evidence for yawn contagion in orangutans (Pongo pygmaeus)

Scientific Reports, Dec 17, 2020

Yawning is highly contagious, yet both its proximate mechanism(s) and its ultimate causation rema... more Yawning is highly contagious, yet both its proximate mechanism(s) and its ultimate causation remain poorly understood. Scholars have suggested a link between contagious yawning (CY) and sociality due to its appearance in mostly social species. Nevertheless, as findings are inconsistent, CY's function and evolution remains heavily debated. One way to understand the evolution of CY is by studying it in hominids. Although CY has been found in chimpanzees and bonobos, but is absent in gorillas, data on orangutans are missing despite them being the least social hominid. Orangutans are thus interesting for understanding CY's phylogeny. Here, we experimentally tested whether orangutans yawn contagiously in response to videos of conspecifics yawning. Furthermore, we investigated whether CY was affected by familiarity with the yawning individual (i.e. a familiar or unfamiliar conspecific and a 3D orangutan avatar). In 700 trials across 8 individuals, we found that orangutans are more likely to yawn in response to yawn videos compared to control videos of conspecifics, but not to yawn videos of the avatar. Interestingly, CY occurred regardless of whether a conspecific was familiar or unfamiliar. We conclude that CY was likely already present in the last common ancestor of humans and great apes, though more converging evidence is needed. Yawning is an evolutionarily old phenomenon as its associated motor features can be recognized in different groups of animals 1 . It follows a stereotyped pattern that, once started, is unstoppable 2 . Apart from its spontaneous form, it is also notoriously contagious, at least for some species; i.e. individuals yawn as an unconscious and automatic response to seeing or hearing other individuals yawn 3 . While a yawning-like pattern is observed in a wide range of vertebrates 1 , contagious yawning (CY) is less wide-spread. To date, CY appears to be present in only a few, generally social species, including tonkean macaques 4 (and possibly stumptail macaques 5 ), gelada baboons 6 , chimpanzees 7-14 , bonobos , dogs and wolves , sheep 20 , elephant seals 21 , budgerigars 22 , and rats 23 . In contrast, studies failed to show CY in grey-cheeked mangabeys and long-tailed macaques 24 , mandrills 1 , common marmosets 25 , lemurs 26 , horses 27 , lions 1 , tortoises 28 , and fish 1 , even though some of these species are also very social. Despite growing interest in CY, both its proximate mechanisms (how it functions and develops) and ultimate causes (why and how it evolved) currently remain unclear. Several hypotheses have been put forward, following a Tinbergian approach 29 . One view on the proximate mechanism underlying CY is that it is an automatic form of physiological or emotional state-matching between individuals. This synchrony of states between individuals may work via a perception-action mechanism (PAM), an adaptive mechanism that serves to create and maintain relationships in highly social species and that can give rise to higher-order cognitive phenomena such as empathy 30 . Some scholars argue that CY taps into the same PAM as emotion contagion (e.g. ), which is the tendency to automatically synchronize emotional states with another individual 33 . Following this line of thought, CY can thus potentially be a proxy for empathy (i.e. the CY-empathy hypothesis) . Indeed, neuroimaging studies have shown increased brain activity during CY in areas involved in theory of mind and social cognition , corroborating the idea that CY is linked with emotional state-matching and perhaps even empathy. Furthermore, individuals who score low on empathy scales (e.g. individuals on the autism spectrum) are less likely to engage in CY 39 , and females yawn more frequently in response to seeing others yawn than males do, reflecting the idea that females show higher levels of empathy than males because of their investment in offspring care . Nevertheless, there are some studies that do not find such a clear link between CY and empathy. For instance, when people with autism spectrum disorder (ASD) are

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Parental Support for Drawing Questionnaire

PsycTESTS Dataset

Sex differences in ocular morphology in Caucasian people: a dubious role of sexual selection in the evolution of sexual dimorphism of the human eye

Behavioral Ecology and Sociobiology, 2020

The horizontal size of the exposed depigmented sclera in Caucasians has been previously suggested... more The horizontal size of the exposed depigmented sclera in Caucasians has been previously suggested to be sexually dimorphic, and the significance of this phenomenon remains unclear. Here we build on a previous study and extend it by (i) examining sex differences in other measures of ocular morphology and (ii) exploring the link between eye morphology and biometric markers of facial attractiveness. We used facial photographs of 100 Caucasians (50 men) from Eastern-Central Europe and digitally measured four ocular features. Eye measurements were tested for sex differences and associations with morphometric data on facial averageness and sexual shape dimorphism. We found that sclera surface is more horizontally exposed in men, even though the total surface area is similar in both sexes. We also found that eye fissures are rounder (less rectangular) in women than in men and that irises are brighter in women. We did not find any relationship between the examined eye features and two aspec...

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Photopic factors influence external eye appearance in parrots (Psittaciformes)

Research Square (Research Square), Apr 25, 2023

External eye appearance in diverse avian taxa has been proposed to be driven by social and ecolog... more External eye appearance in diverse avian taxa has been proposed to be driven by social and ecological functions in different studies. Recent research using quantitative measurements and phylogenetically informed analyses in primates suggest that instead photoprotective functions are important drivers of external eye appearance. Using similar methods, we examine the variation in external eye appearance of 132 parrot species (Psittaciformes) in relation to their ecology and sociality. Breeding systems, ock size and sexual dimorphism, as well as species' latitude and maximum ying altitude were used to explore the relative contribution of social and ecological factors in driving external eye appearance. We measured the hue and brightness of visible parts of the eye and the difference in measurements of brightness between adjacent parts of the eye. While we found no link between social variables and our measurements, we found a signi cant negative association between the brightness of the inner part of the iris and latitude and altitude. Darker inner parts of the irises were more prevalent farther away from the equator and with higher ying altitudes. Because the amount of UV radiation varies according to these factors, our results suggest that irises are at least partially adapted for photoprotective functions. The results inform our growing understanding of the drivers of external eye appearance across land vertebrates, highlighting the importance of photopic factors across such distantly related taxa as anthropoid primates and psittaciformes. ED looked up and measured photographs, coordinated data collection, and contributed towards writing the manuscript; JOPG measured photographs, ran statistical analyses, contributed towards writing the MS, and conceived the study; DP and CV looked up and measured photographs; MEK conceived the study and contributed towards revising the manuscript JJMM looked up photographs, found species-level data

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The ontogeny of human laughter

Biology Letters, Sep 1, 2021

Human adult laughter is characterized by vocal bursts produced predominantly during exhalation, y... more Human adult laughter is characterized by vocal bursts produced predominantly during exhalation, yet apes laugh while exhaling and inhaling. The current study investigated our hypothesis that laughter of human infants changes from laughter similar to that of apes to increasingly resemble that of human adults over early development. We further hypothesized that the more laughter is produced on the exhale, the more positively it is perceived. To test these predictions, novice (n = 102) and expert ( phonetician, n = 15) listeners judged the extent to which human infant laughter (n = 44) was produced during inhalation or exhalation, and the extent to which they found the laughs pleasant and contagious. Support was found for both hypotheses, which were further confirmed in two pre-registered replication studies. Likely through social learning and the anatomical development of the vocal production system, infants' initial ape-like laughter transforms into laughter similar to that of adult humans over the course of ontogeny.

format_quoteInfant laughter occurs during exhalation significantly less (M=0.62) than adult laughter (M=0.74), indicating a developmental progression in laughter production.format_quote

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Multimodal mate choice: Exploring the effects of sight, sound, and scent on partner choice in a speed-date paradigm

Evolution and Human Behavior, Sep 1, 2021

Abstract When people meet a potential partner for the first time, they are confronted with multip... more Abstract When people meet a potential partner for the first time, they are confronted with multiple sources of information, encompassing different modalities, that they can use to determine whether this partner is suitable for them or not. While visual attractiveness has widely been studied with regard to partner choice, olfactory and auditory cues have received less attention, even though they might influence the attitudes that people have towards their partner. Therefore, in this study, we employed a combination of pre-date multimodal rating tasks followed by speed-date sessions. This offered a naturalistic setup to study partner choice and disentangle the relative effects of a priori attractiveness ratings of sight, scent and sound on date success. Visual attractiveness ratings showed a strong positive correlation with propensity to meet the partner again, while the effects of olfactory and auditory attractiveness were negligible or not robust. Furthermore, we found no robust sex differences in the importance of the three modalities. Our findings underscore the relative importance of visual attractiveness in initial mate choice, but do not corroborate the idea that static pre-date measures of auditory and olfactory attractiveness can predict first date outcomes.

Chimpanzees and Humans Mimic Pupil-Size of

Group-living typically provides benefits to individual group members but also confers costs. To a... more Group-living typically provides benefits to individual group members but also confers costs. To avoid incredulity and betrayal and allow trust and cooperation, individuals must understand the intentions and emotions of their group members. Humans attend to other’s eyes and from gaze and pupil-size cues, infer information about the state of mind of the observed. In humans, pupil-size tends to mimic that of the observed. Here we tested whether pupil-mimicry exists in our closest relative, the chimpanzee (P. troglodytes). We conjectured that if pupil-mimicry has adaptive value, e.g. to promote swift communication of inner states and facilitate shared understanding and coordination, pupil-mimicry should emerge within but not across species. Pupillometry data was collected from human and chimpanzee subjects while they observed images of the eyes of both species with dilating/constricting pupils. Both species showed enhanced pupil-mimicry with members of their own species, with effects be...

format_quoteThe interaction of pupil-size and species significantly affects mimicry outcomes (F = 13.124, p < .0005), supporting the study's core hypothesis.format_quote

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Attitudes Toward the Islam Questionnaire

PsycTESTS Dataset, 2012

Functional neuroanatomy of emotional body language

Ecological factors are likely drivers of eye shape and colour pattern variations across anthropoid primates

Scientific Reports

External eye appearance across primate species is diverse in shape and colouration, yet we still ... more 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 s...

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Automatic Change Detection of Emotional and Neutral Body Expressions: Evidence From Visual Mismatch Negativity

Frontiers in Psychology, Aug 23, 2019

Rapidly and effectively detecting emotions in others is an important social skill. Since emotions... more Rapidly and effectively detecting emotions in others is an important social skill. Since emotions expressed by the face are relatively easy to fake or hide, we often use body language to gauge the genuine emotional state of others. Recent studies suggest that expression-related visual mismatch negativity (vMMN) reflects the automatic processing of emotional changes in facial expression; however, the automatic processing of changes in body expression has not yet been studied systematically. The current study uses an oddball paradigm where neutral body actions served as standard stimuli, while fearful body expressions and other neutral body actions served as two different deviants to define body-related vMMN, and to compare the mechanisms underlying the processing of emotional changes to neutral postural changes. The results show a more negative vMMN amplitude for fear deviants 210-260 ms after stimulus onset which corresponds with the negativity bias that was obtained on the N190 component. In earlier time windows, the vMMN amplitude following the two types of deviant stimuli are identical. Therefore, we present a two-stage model for processing changes in body posture, where changes in body posture are processed in the first 170-210 ms, but emotional changes in the time window of 210-260 ms.

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Emotional expressions beyond facial muscle actions. A call for studying autonomic signals and their impact on social perception

Frontiers in Psychology, May 27, 2015

Humans are well adapted to quickly recognize and adequately respond to another's emotions. Differ... more Humans are well adapted to quickly recognize and adequately respond to another's emotions. Different theories propose that mimicry of emotional expressions (facial or otherwise) mechanistically underlies, or at least facilitates, these swift adaptive reactions. When people unconsciously mimic their interaction partner's expressions of emotion, they come to feel reflections of those companions' emotions, which in turn influence the observer's own emotional and empathic behavior. The majority of research has focused on facial actions as expressions of emotion. However, the fact that emotions are not just expressed by facial muscles alone is often still ignored in emotion perception research. In this article, I therefore argue for a broader exploration of emotion signals from sources beyond the face muscles that are more automatic and difficult to control. Specifically, I will focus on the perception of implicit sources such as gaze and tears and autonomic responses such as pupil-dilation, eyeblinks and blushing that are subtle yet visible to observers and because they can hardly be controlled or regulated by the sender, provide important "veridical" information. Recently, more research is emerging about the mimicry of these subtle affective signals including pupil-mimicry. I will here review this literature and suggest avenues for future research that will eventually lead to a better comprehension of how these signals help in making social judgments and understand each other's emotions.

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Liking your eyes: pupil size and gaze orientation shape person impressions

Proceedings of the 14th NVP Winter Conference on Cognition, Brain, and Behaviour of the Dutch Psychonomic Society

Pupil responses to dynamic negative facial expressions of emotion in infants and parents

Developmental Psychobiology, Sep 21, 2021

Observing others’ emotions triggers physiological arousal in infants as well as in adults, reflec... more Observing others’ emotions triggers physiological arousal in infants as well as in adults, reflected in dilated pupil sizes. This study is the first to examine parents’ and infants’ pupil responses to dynamic negative emotional facial expressions. Moreover, the links between pupil responses and negative emotional dispositions were explored among infants and parents. Infants’ and one of their parent's pupil responses to negative versus neutral faces were measured via eye tracking in 222 infants (5‐ to 7‐month‐olds, n = 77, 11‐ to 13‐month‐olds, n = 78, and 17‐ to 19‐month‐olds, n = 67) and 229 parents. One parent contributed to the pupil data, whereas both parents were invited to fill in questionnaires on their own and their infant's negative emotional dispositions. Infants did not differentially respond to negative expressions, while parents showed stronger pupil responses to negative versus neutral expressions. There was a positive association between infants' and their parent's mean pupil responses and significant links between mothers’ and fathers’ stress levels and their infants’ pupil responses. We conclude that a direct association between pupil responses in parents and offspring is observable already in infancy in typical development. Stress in parents is related to their infants’ pupillary arousal to negative emotions.

How do babies laugh?

Journal of the Acoustical Society of America, Sep 1, 2018

Laughter occurs across all great ape species, yet human laughter differs from that of other prima... more Laughter occurs across all great ape species, yet human laughter differs from that of other primates: Human laughter is primarily produced on the exhale, whereas other primates laugh on both the inhale and exhale. In the current study, we asked whether human infants laugh in a similar manner to apes, given that human infants, like non-human primates, tend to laugh in the context of tickling or rough-and-tumble play. Human adults, in contrast, laugh across many different kinds of social interactions. To test this hypothesis, we examined whether human infant laughter is acoustically more similar to non-human apes' laughter. Laughter clips from infants aged 3 to 18 months were annotated by phoneticians and evaluated by two listener samples (naïve listeners and phoneticians, respectively). The results provide support for the prediction that the proportion of infants’ laughter produced on the exhale increases with age. These results suggest that at younger ages, human infants’ laughter is more similar to that of other great apes. These findings are discussed in the context of vocal control maturation and social learning.

Emotion recognition from faces with in- and out-group features in patients with depression

Journal of Affective Disorders, Feb 1, 2018

License: Article 25fa pilot End User Agreement This publication is distributed under the terms of... more License: Article 25fa pilot End User Agreement This publication is distributed under the terms of Article 25fa of the Dutch Copyright Act (Auteurswet) with explicit consent by the author. Dutch law entitles the maker of a short scientific work funded either wholly or partially by Dutch public funds to make that work publicly available for no consideration following a reasonable period of time after the work was first published, provided that clear reference is made to the source of the first publication of the work. This publication is distributed under The Association of Universities in the Netherlands (VSNU) 'Article 25fa implementation' pilot project. In this pilot research outputs of researchers employed by Dutch Universities that comply with the legal requirements of Article 25fa of the Dutch Copyright Act are distributed online and free of cost or other barriers in institutional repositories. Research outputs are distributed six months after their first online publication in the original published version and with proper attribution to the source of the original publication. You are permitted to download and use the publication for personal purposes. All rights remain with the author(s) and/or copyrights owner(s) of this work. Any use of the publication other than authorised under this licence or copyright law is prohibited. If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons.

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The role of pupil size in communication. Is there room for learning?

Cognition & Emotion, Aug 31, 2017

The eyes are extremely important for communication. The muscles around the eyes express emotional... more