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Humans, great apes and old world monkeys show selective attention to faces depending on conspecificity, familiarity, and social status supporting the view that primates share similar face processing mechanisms. Although many studies have been done on face scanning strategy in monkeys and humans, the mechanisms influencing viewing preference have re...
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... In accordance with previous work on the concept of familiarity in other species (Sugita, 2008;Coulon et al., 2010;Meary et al., 2014), we expected a spontaneous preference for photos of familiar conspecifics in the pretest. During training, we expected Group A to show higher learning performance than Group B because this group had to discriminate the photo of a known goat, whereas for Group B the rewarded photo was an unknown goat. ...
To study individual recognition in animals, discrimination tasks are often conducted by presenting 2D images of real conspecifics. However, animals may discriminate the images merely as visual stimulus combinations without establishing referential relationships to the individuals depicted. In the current study, we investigated whether goats are able to discriminate photos of familiar and unfamiliar conspecifics, whether they not only process the photos as visual stimuli, but also understand them as virtual copies of real conspecifics and whether they grasp the concept of familiarity. Using a computer-controlled learning device, in three tests, goats of two experimental groups (A and B) had to discriminate portrait (Te1), profile (Te2) or headless body photos (Te3) of conspecifics. Tests were presented as 4-choice tasks, with one photo from Group A (rewarded) plus three photos from Group B (distractors). That is, the rewarded photo was familiar to Group A, but unfamiliar to Group B. Finally, in a reversal test (Te4) we reversed this principle. The goats learned the discriminations in Te1 to Te3 within two (Te1 and Te2) and three training days (Te3), respectively, and they needed between 91 [CL (66, 126)] and 174 [CL (126, 241)] trials to reach the learning criterion, with no statistically significant differences between the groups. In Te4, in contrast, the animals took 403 [Group A; CL (291, 557)] and 385 [Group B; CL (286, 519)] trials, respectively, to learn the task. The lack of spontaneous preferences for the photo of the familiar conspecific in the pretests of Te1 to Te3 in Group A, as well as the lack of differences in the number of trials to learn the discriminations between both groups, do not at first glance suggest that the goats established a correspondence between real conspecifics and their 2D representations. However, the higher number of trials in Te4 suggests that both groups formed the learning rule of choosing either the known (Group A) or the unknown goat (Group B) over the course of Te1 to Te3 and then failed after the rule was reversed, providing evidence that goats can associate 2D photos of conspecifics with real animals.
... Originally tested on an infant chimpanzee [Pan troglodytes, Fantz (1958a)] then with human infants (Fantz, 1958b), the method's simplicity and adaptability to different environments has made it popular amongst researchers working with animals. While indicating discrimination between stimuli (Koba and Izumi, 2008;Pfefferle et al., 2014), the goal of studies using this paradigm vary, with some aiming to uncover social orientations (Craighero et al., 2011;Franchini et al., 2017) or preferences (Paukner et al., 2017;Adams and Macdonald, 2018), recognition (Fujita, 1987;Schell et al., 2011;Méary et al., 2014;Rakotonirina et al., 2018) as well as memory for stimuli (Gothard et al., 2004;Howard et al., 2018) and shifts in underlying affective states (Bethell et al., 2012). The term preferential looking is synonymous with looking time, attention, and gaze. ...
... That is, preferential looking paradigms only demonstrate that a pair of stimuli can be discriminated, not why the stimuli are discriminated (Aslin, 2007;Tafreshi et al., 2014;Wilson et al., 2021). A study group might look longer at images of out-group members because to different individuals they are novel, threatening or attractive (Fujita, 1987;Méary et al., 2014). Or they might look longer at images of group members because they, again, frontiersin.org ...
The study of gaze responses, typically using looking time paradigms, has become a popular approach to improving our understanding of cognitive processes in non-verbal individuals. Our interpretation of data derived from these paradigms, however, is constrained by how we conceptually and methodologically approach these problems. In this perspective paper, we outline the application of gaze studies in comparative cognitive and behavioral research and highlight current limitations in the interpretation of commonly used paradigms. Further, we propose potential solutions, including improvements to current experimental approaches, as well as broad-scale benefits of technology and collaboration. Finally, we outline the potential benefits of studying gaze responses from an animal welfare perspective. We advocate the implementation of these proposals across the field of animal behavior and cognition to aid experimental validity, and further advance our knowledge on a variety of cognitive processes and welfare outcomes.
... Findings of similar preferences in human and nonhuman primates have also been reported for curved contours (humans and chimpanzees: Munar et al. 2015), and for prototypicality (human and macaque infants: Damon et al. 2017b), further highlighting shared underlying face/object processing mechanisms. Interestingly, face familiarity further shows differential impact on face preference in humans and rhesus macaques (Méary et al. 2014). When two faces of different species/races were presented side-by-side, Caucasian humans demonstrated clear visual preference for Caucasian faces over Asian faces (own-race bias), and human faces (regardless of races) over nonhuman primate (e.g., chimpanzee, Barbary, and rhesus macaque) faces (own-species bias). ...
... The argument that visual selective attention can bias yawn contagion rates in a specific direction (subjects responding more to family than strangers) is also undermined by the absence of any specific pattern of social attention in human and non-human primate. Via eyetracking (applied to measure the viewing time) and by showing unknown faces to their experimental subjects, Méary et al. (2014) observed that humans were skewed toward own-race faces whereas rhesus macaques' attention was more attracted by new than by same species faces. Kawakami et al. (2014) observed that human subjects paid more attention to the eyes of ethnic in-group members and to nose and mouth of ethnic out-group members. ...
Contagious yawning differs from spontaneous yawning because it occurs when an individual yawns in response to someone else’s yawn. In Homo sapiens and some non-human primates contagious yawning is higher between strongly than weakly bonded individuals. Up to date, it is still unclear whether this social asymmetry underlies emotional contagion (a basic form of empathy preferentially involving familiar individuals) as predicted by the Emotional Bias Hypothesis (EBH) or is linked to a top-down, selective visual attention bias (with selective attention being preferentially directed toward familiar faces) as predicted by the Attentional Bias Hypothesis (ABH). To verify whether the visual attentional bias explained the yawn contagion bias or not, in this study, we considered only yawns that could be heard but not seen by potential responders (auditory yawns). Around 294 of auditory yawning occurrences were extrapolated from over 2000 yawning bouts collected in free ranging humans for over nine years. Via GLMM, we tested the effect of intrinsic features (i.e., gender and age) and social bond (from strangers to family members) on yawn. The individual identity of the subjects (trigger and potential responder) was included as random factor. The social bond significantly predicted the occurrence of auditory yawn contagion, which was highest between friends and family members. A gender bias was also observed, with women responding most frequently to others’ yawns and men being responded to most frequently by others. These results confirm that social bond is per se one of the main drivers of the differences in yawn contagion rates between individuals in support of the EBH of yawn contagion.
... As such, care needs to be taken in interpreting these biases and there remains substantial debate over how to do so. For example, it has been argued that both the tendency for children with ASD to be less prone to contagious yawning [83] and the familiarity bias [37,84,85] can be explained in terms of differences in attending to yawners rather than differences in empathetic response. Similarly, the gender bias reported in humans [29] is not straightforward to interpret and there is debate over whether it simply reflects a false positive in the literature [33,34]. ...
Contagious yawning has been suggested to be a potential signal of empathy in non-human animals. However, few studies have been able to robustly test this claim. Here, we ran a Bayesian multilevel reanalysis of six studies of contagious yawning in dogs. This provided robust support for claims that contagious yawning is present in dogs, but found no evidence that dogs display either a familiarity or gender bias in contagious yawning, two predictions made by the contagious yawning-empathy hypothesis. Furthermore, in an experiment testing the prosociality bias, a novel prediction of the contagious yawning-empathy hypothesis, dogs did not yawn more in response to a pro-social demonstrator than to an antisocial demonstrator. As such, these strands of evidence suggest that contagious yawning, although present in dogs, is not mediated by empathetic mechanisms. This calls into question claims that contagious yawning is a signal of empathy in mammals.
... Regarding the first condition, literature shows that, in human and non-human primates, social attention does not follow a unique trend. By using the viewing time measured via eye-tracking and showing unknown faces to the experimental subjects, Méary et al. (2014) found that humans had a strong bias towards own-race faces whereas, in rhesus macaques, novel species faces attracted more attention than same species faces. This study did not address the effect of social bonding on attention patterns. ...
Spontaneous mimicry appears fundamental to emotional perception and contagion, especially when it involves facial emotional expressions. Here we cover recent evidence on spontaneous mimicry from ethology, psychology and neuroscience, in non-human and human animals. We first consider how mimicry unfolds in non-human animals (particularly primates) and how it relates to emotional contagion. We focus on two forms of mimicry-related phenomena: facial mimicry and yawn contagion, which are largely conserved across mammals and useful to draw evolutionary scenarios. Next, we expand on the psychological evidence from humans that bears on current theoretical debates and also informs non-human animal research. Finally, we cover the neural bases of facial mimicry and yawn contagion. We move beyond the perception/expression/experience trichotomy and from the correlational to the causal evidence that links facial mimicry to emotional contagion by presenting evidence from neuroimaging, direct manipulation, neuro-stimulation and lesion studies. In conclusion, this review proposes a bottom-up, multidisciplinary approach to the study of spontaneous mimicry that accounts for the evolutionary continuity linking non-human and human animals.
... Furthermore, when presented with a conspecific or heterospecific face alone picture (i.e. without body and background scene) with neutral facial expression, both humans and monkeys tended to show a face-specific directional gaze bias towards the left hemiface (Guo et al. 2009) and stereotypical gaze allocation at socially informative local facial features with a strong preference towards the eyes (Guo et al. 2006;Dahl et al. 2009;Méary et al. 2014). These similarities in social attention behaviour (i.e. ...
... This sample size was determined based on previous research in the same field and was comparable to the published reports (e.g. Guo et al. 2003Guo et al. , 2006Guo 2007;McFarland et al. 2013;Méary et al. 2014). All the monkeys were born in captivity and socially housed indoors. ...
... monkey and chimpanzee faces). This finding is in agreement with previous observation that humans, chimpanzees and rhesus monkeys showed qualitatively similar face-scanning pattern when viewing conspecific and other primates' faces with relaxed expressions (Guo et al. 2003;Kano and Tomonaga 2010;Méary et al. 2014; see also Dahl et al. 2009), indicating the homologous nature of face-viewing gaze behaviour in primates which is probably driven by the crucial role of eye detection in face reading and associated behavioural responses (e.g. towards the approach of a potential mate, competitor or predicator) (Emery 2000). ...
Common facial expressions of emotion have distinctive patterns of facial muscle movements that are culturally similar among humans, and perceiving these expressions is associated with stereotypical gaze allocation at local facial regions that are characteristic for each expression, such as eyes in angry faces. It is, however, unclear to what extent this ‘universality’ view can be extended to process heterospecific facial expressions, and how ‘social learning’ process contributes to heterospecific expression perception. In this eye-tracking study, we examined face-viewing gaze allocation of human (including dog owners and non-dog owners) and monkey observers while exploring expressive human, chimpanzee, monkey and dog faces (positive, neutral and negative expressions in human and dog faces; neutral and negative expressions in chimpanzee and monkey faces). Human observers showed species- and experience-dependent expression categorization accuracy. Furthermore, both human and monkey observers demonstrated different face-viewing gaze distributions which were also species dependent. Specifically, humans predominately attended at human eyes but animal mouth when judging facial expressions. Monkeys’ gaze distributions in exploring human and monkey faces were qualitatively different from exploring chimpanzee and dog faces. Interestingly, the gaze behaviour of both human and monkey observers were further affected by their prior experience of the viewed species. It seems that facial expression processing is species dependent, and social learning may play a significant role in discriminating even rudimentary types of heterospecific expressions.
... 94 Differences in looking time between classes of stimuli can be difficult to interpret due to various 95 and often unpredictable novelty and familiarity effects [37], however primates reliably exhibit a 96 visual bias (i.e. greater looking time) toward images of conspecifics compared to those of 97 heterospecifics [38][39][40][41][42]. We follow the interpretation that longer looking time at a particular face 98 reflects level of interest. ...
Discriminating between conspecifics and heterospecifics potentially challenging for closely related sympatric species. The guenons, a recent primate radiation, exhibit high degrees of sympatry and form multi-species groups in which hybridization is possible but rare in most populations. Guenons have species-specific colorful face patterns hypothesized to function in species discrimination. Here, we apply a novel machine learning approach to identify the face regions most essential for correct species classification across fifteen guenon species. We then demonstrate the validity of these computational results using experiments with live guenons, showing that facial traits identified as critical for accurate classification do indeed influence selective attention toward con- and heterospecific faces. Our results suggest variability among guenon species in reliance on single-trait-based versus holistic facial characteristics when discriminating between species, and differences in behavioral responses to faces can be linked to whether discrimination is based on a single trait or whole-face pattern. Our study supports the hypothesis that guenon face patterns function to promote species discrimination and provides novel insights into the relationship between species interactions and phenotypic diversity.
... Furthermore, if human ratings of attractiveness are the product of mechanisms shared among primates, they might also predict visual face preferences in monkeys. Although the issue of how much a monkey evaluates a face as attractive is a question difficult to address (if even possible), implicit face preferences can be inferred from looking-time measures (Méary, Li, Li, Guo, & Pascalis, 2014). ...
... If so, triggering attractiveness-based visual preferences might necessitate prior categorization of a face as own-species. Human adults (Méary et al., 2014) and infants (Di Giorgio, Méary, Pascalis, & Simion, 2013;Heron-Delaney, Wirth, & Pascalis, 2011) preferentially allocate visual attention toward own-species faces over other-species faces, and similar findings have been reported in nonhuman primates (Fujita, 1987;Sugita, 2008, but see Méary et al., 2014). Moreover, other face processing tasks also reflect an attentional advantage for own-species faces, such as detection (e.g., in humans, Crouzet, Kirchner, & Thorpe, 2010) and visual search (e.g., in humans, Simpson, Husband, Yee, Fullerton, & Jakobsen, 2014;in macaques, Simpson et al., 2017). ...
... If so, triggering attractiveness-based visual preferences might necessitate prior categorization of a face as own-species. Human adults (Méary et al., 2014) and infants (Di Giorgio, Méary, Pascalis, & Simion, 2013;Heron-Delaney, Wirth, & Pascalis, 2011) preferentially allocate visual attention toward own-species faces over other-species faces, and similar findings have been reported in nonhuman primates (Fujita, 1987;Sugita, 2008, but see Méary et al., 2014). Moreover, other face processing tasks also reflect an attentional advantage for own-species faces, such as detection (e.g., in humans, Crouzet, Kirchner, & Thorpe, 2010) and visual search (e.g., in humans, Simpson, Husband, Yee, Fullerton, & Jakobsen, 2014;in macaques, Simpson et al., 2017). ...
Studies on facial attractiveness in human adults, infants, and newborns have consistently reported a visual preference for faces rated as attractive compared with faces rated as unattractive. Biological accounts of facial attractiveness have typically presented such preferences as arising from adaptations for mate choice or as by-products of general sensory bias. In this cross-species study, we examined whether explicit ratings of attractiveness made by human judges would predict implicit visual preferences in other humans and also in rhesus macaques and, if they do, whether such preferences would extend beyond conspecific faces. Results showed that human ratings of attractiveness can predict implicit preferences in nonhuman primates (macaque monkeys; Macaca mulatta ). However, we also found a species-specific effect of face attractiveness in which humans showed a visual preference for human faces (but not macaque faces) rated as attractive, and macaques displayed a visual preference for macaque faces (but not human faces) rated as attractive. Overall, the findings suggest that attentional bias toward attractive faces arises neither from an exclusive operation of mate choice adaptation mechanisms nor from the sole influence of a general sensory bias, but rather reflects their interaction. The influence of a general sensory bias may be modulated by the categorization of a face as conspecific or heterospecific, leading to species-specific preference for attractive faces.
... Other studies have also shown that adult macaques and humans are sensitive to specific facial features. Rhesus macaques are sensitive to face identity 32,33 , they show preferences for conspecifics' faces compared to other species [34][35][36] , although being also interested by human faces. ...
