Exploring the morphological and emotional correlates of infant cuteness

Examining infantile facial features and their influence on caretaking behaviors in free-ranging Japanese macaques (Macaca fuscata)

Facial features of immature individuals play a pivotal role in eliciting caretaking behaviors in humans. It has been posited that non-human animals share particular infantile facial features with humans, which can elicit caregivers' attention and caretaking behaviors. Nevertheless, the empirical examination of this hypothesis is extremely limited. In this study, we investigated infantile facial features in Japanese macaques (Macaca fuscata), their developmental processes, and their correlation with caretaking and infant behaviors, based on 470 facial photographs from one free-ranging group. We measured the size of facial parts and evaluated these features using non-contact procedures with the animals. The results indicated that, although some partial species differences were observed, the infantile facial features in Japanese macaques were broadly consistent with those previously observed in humans and great apes. Furthermore, half of the infant subjects displayed non-linear developmental trajectories of infantile faces, similar to those suggested in humans. However, unlike previous studies in humans, infantile faces were not significantly associated with maternal or non-maternal caretaking behaviors, nor were their developmental changes correlated with infant behavioral development. These findings indicate that while many aspects of infantile facial features are shared among particular primates, humans may have evolved a uniquely elevated preference for selecting such features among the primate lineage.

Lorenz's classic 'baby schema': a useful biological concept?

Konrad Lorenz introduced the concept of a 'baby schema', suggesting that infants have specific physical features, such as a relatively large head, large eyes and protruding cheeks, which function as an innate releaser to promote caretaking motivation from perceivers. Over the years, a large body of research has been conducted on the baby schema. However, there are two critical problems underpinning the current literature. First, the term 'baby schema' lacks consistency among researchers. Some researchers use the term baby schema to refer to infant stimuli (often faces) in comparison with adults (categorical usage), while others use the term to refer to the extent that features contribute to cuteness perception (spectrum usage). Second, cross-species continuity of the 'baby schema' has been assumed despite few empirical demonstrations. The evolutionary and comparative relevance of the concept is, therefore, debatable, and we cannot exclude the possibility that extreme sensitivity to the baby schema is a uniquely human trait. This article critically reviews the state of the existing literature and evaluates the significance of the baby schema from an evolutionary perspective.

The Relative Contribution of Facial and Body Information to the Perception of Cuteness

Faces and bodies both provide cues to age and cuteness, but little work has explored their interaction in cuteness perception. This study examines the interplay of facial and bodily cues in the perception of cuteness, particularly when these cues convey conflicting age information. Participants rated the cuteness of face-body composites that combined either a child or adult face with an age-congruent or incongruent body alongside manipulations of the head-to-body height ratio (HBR). The findings from two experiments indicated that child-like facial features enhanced the perceived cuteness of adult bodies, while child-like bodily features generally had negative impacts. Furthermore, the results showed that an increased head size significantly boosted the perceived cuteness for child faces more than for adult faces. Lastly, the influence of the HBR was more pronounced when the outline of a body's silhouette was the only available information compared to when detailed facial and bodily features were presented. This study suggests that body proportion information, derived from the body's outline, and facial and bodily features, derived from the interior surface, are integrated to form a unitary representation of a whole person in cuteness perception. Our findings highlight the dominance of facial features over bodily information in cuteness perception, with facial attributes serving as key references for evaluating face-body relationships and body proportions. This research offers significant insights into social cognition and character design, particularly in how people perceive entities with mixed features of different social categories, underlining the importance of congruency in perceptual elements.

Face inversion effect on perceived cuteness of infant faces

Research has demonstrated that attractiveness evaluations of adult faces were less accurate when faces were inverted than upright. It remains unknown, however, whether a similar effect applies to perceived cuteness of infants, which is assumed to be based on elemental facial features called the "baby schema." In this research, we studied the face inversion effect on perceived cuteness of infant faces in a rating task and a two-alternative forced-choice (2AFC) task. We also examined beauty as a control dimension. Although the rating task revealed no inversion effect, the 2AFC task showed poorer discrimination performance with inverted faces than with upright faces in both evaluations. These results indicate that infant cuteness and beauty dimensions are correlated well with each other, and their perception not only relies on elemental features that are not strongly affected by inversion but is also affected by holistic facial configurations when a detailed comparison is required.

Revisiting the baby schema by a geometric morphometric analysis of infant facial characteristics across great apes

Infants across species are thought to exhibit specific facial features (termed the "baby schema", such as a relatively bigger forehead and eyes, and protruding cheeks), with an adaptive function to induce caretaking behaviour from adults. There is abundant empirical evidence for this in humans, but, surprisingly, the existence of a baby schema in non-human animals has not been scientifically demonstrated. We investigated which facial characteristics are shared across infants in five species of great apes: humans, chimpanzees, bonobos, mountain gorillas, and Bornean orangutans. We analysed eight adult and infant faces for each species (80 images in total) using geometric morphometric analysis and machine learning. We found two principal components characterizing infant faces consistently observed across species. These included (1) relatively bigger eyes located lower in the face, (2) a rounder and vertically shorter face shape, and (3) an inverted triangular face shape. While these features are shared, human infant faces are unique in that the second characteristic (round face shape) is more pronounced, whereas the third (inverted triangular face shape) is less pronounced than other species. We also found some infantile features only found in some species. We discuss future directions to investigate the baby schema using an evolutionary approach.

That brachycephalic look: Infant-like facial appearance in short-muzzled dog breeds

Brachycephalic dog breeds are highly popular, yet their conformation-related disorders represent a major welfare concern. It has been suggested that the current popularity of such breeds can be explained by their cute, infant-like facial appearances. The concept of 'kindchenschema' refers to the observation that certain physical features of infant humans and other animals can automatically stimulate positive and nurturant feelings in adult observers. But the proposal that brachycephalic dogs possess heightened 'kindchenschema' facial features, even into adulthood, has never been formally investigated. Here, we hypothesised that relative muzzle shortening across a range of breeds would be associated with known 'kindchenschema' facial features, including a relatively larger forehead, larger eyes and smaller nose. Relative fronto-facial feature sizes in exemplar photographs of adult dogs from 42 popular breeds were measured and associated with existing data on the relative muzzle length and height-at-withers of the same breeds. Our results show that, in adulthood, shorter-muzzled breeds have relatively larger (taller) foreheads and relatively larger eyes (i.e. area of exposed eyeball relative to overall face area) than longer-muzzled breeds, and that this effect is independent of breed size. In sum, brachycephalic dog breeds do show exaggeration of some, but not all, known fronto-facial 'kindchenschema' features, and this may well contribute to their apparently cute appearance and to their current popularity as companion animals. We conclude that the challenge of addressing conformation-related disorders in companion dogs needs to take account of the cute, 'kindchenschema' looks that many owners are likely to be attracted to.

Changes in Cat Facial Morphology Are Related to Interaction with Humans

We aimed to clarify the changes in facial morphology of cats in relation to their interactions with humans. In Study 1, we compared the facial morphology of cats (feral mixed breed, owned domestic mixed breed, and owned domestic purebreds) with that of African wildcats. After collecting 3295 photos, we found that owned domestic cats' noses were significantly shorter than those of African wildcats and feral mixed breed, and there were no significant differences between the latter two. The eye angles were significantly more gradual in owned domestic purebreds than in the other groups. In Study 2, we examined the correlation between facial morphology and years with the owner, and found that the former is not affected by the latter. This suggests that changes in facial morphology are possibly transgenerational changes. The difference in facial morphology between wildcats and owned cats might be caused by domestication, and that between feral cats and owned cats might be due to feralization. In Study 3, we investigated whether cats' facial features affect cuteness ratings. We asked human participants to evaluate the cuteness of cats' face images and found that faces with shorter nose lengths were considered cuter. This suggests that owned domestic cats' facial morphology is preferred by humans.

Examination of morphological traits of children's faces related to perceptions of cuteness using Gaussian process ordinal regression

Konrad Lorenz, an ethologist, proposed that certain physical elements are perceived as cute and induce caretaking behavior in other individuals, with the evolutionary function of enhancing offspring survival. He called these features Kindchenschema, baby schema. According to his introspection, these include a large forehead, chubby round features, and chubby cheeks. Previous studies are limited to examining the effects of these facial features on perceived cuteness. However, other morphological factors may be related to perceived cuteness. This study uses Bayesian optimization, one of the global sequential optimization methods for estimating unknown functions, to search for facial morphological features that enhance the perceptions of facial cuteness. We applied Bayesian optimization incorporating Gaussian process ordinal regression (GPOR), which allows an estimation of the latent cuteness function based on evaluations using the Likert scale. A total of 96 preschool children provided the facial images used in this study. We summarized the facial shape variations using methodologies of geometric morphometrics and principal component analysis (PCA) up to the third principal component (PC), which we refer to as the face space. A total of 40 participants evaluated the images created by warping the average facial texture of the children's faces with randomly generated parameters in the face space. Facial traits related to perceived cuteness were estimated based on the averaged cuteness function. Perceived cuteness was linked to the relative lower position of facial components and narrower jawline but not to the forehead height.

The Influence of Infant Schema Cues on Donation Intention in Charity Promotion

This research performed four experiments to investigate the influence of infant schema cues on charitable donation intention and examine the moderating effect of gender. The results indicate that: (1) individuals stimulated by infant schema (vs. adult schema) cues had a higher willingness to donate when facing charity promotion; (2) the main effect was not due to the perceived cuteness of character in posters; (3) empathy played an entirely mediating role in the relationship between infant schema cues and donation intention; (4) gender moderated the influence of infant schema on donation intention: infant schema cues are effective for improving females’ donation intention, but ineffective for males. These findings contributed to the literature on infant schema and provide practical significance for introducing infant schema in charity promotion.

The Effect of Baby Schema in Cats on Length of Stay in an Irish Animal Shelter

Simple Summary

Several factors may influence cats’ length of stay (LoS) within the shelter environment. The aim of this study was to investigate the potential influence that ‘cuteness’ has on cats’ length of stay (LoS) in an animal shelter. Other factors such as paired-homing requirements, adoption profile (advertisements to encourage the adoption of a specific animal) wording, coat colour, sex and age were also explored. ‘Cuteness’ was measured in two ways; 1. Facial characteristics which characterise human infants, such as big eyes and a round head, were measured from images of cats to create an objective cuteness score. 2. Subjective cuteness scores were developed by participants rating the ‘cuteness’ of the cat images from ‘1-Not very cute’ to ‘5-Extremely cute’ through two online surveys; survey 1 investigated the cats’ social nature as well as cuteness while the second only looked at cuteness. The subjective cuteness scores were used to validate the objective cuteness scores. The analysis found that subjective cuteness influenced cats’ length of stay during the analysis of the first survey with no effect of other variables such as adoption profile language, homing requirements, coat colour, sex and age. Analysis of the data from the second survey found that none of the variables influenced the cats’ LoS. A novel objective measurement for cuteness in cats was developed which reflects the shape of the eyes and is associated with subjective cuteness scores. This research looks to understand factors that influence LoS to help identify potential methods to reduce time spent in shelters and improve the welfare of cats within these environments.

Abstract

Several factors may influence cats’ length of stay (LoS) within the shelter environment. The aim of this study was to investigate the potential influence that baby schema (characteristic facial features of infants, related to perceived ‘cuteness’) has on cats’ length of stay (LoS) in an animal shelter. Other factors such as paired-homing requirements, adoption profile (adverts to encourage the adoption of a specific animal) wording, coat colour, sex and age were also explored. Objective ‘cuteness’ scores were created by measuring specific facial features of 165 shelter cats. Several proportions of the cats’ faces were explored to identify the best objective measure of cuteness, including elements which have been found to associate with cuteness in cats and humans and new exploratory eye measurements. Subjective cuteness scores were developed by participants rating the ‘cuteness’ of the cat from ‘1-Not very cute’ to ‘5-Extremely cute’ through two online surveys; survey 1 investigated the cats’ social nature as well as cuteness while the second only looked at cuteness. The subjective cuteness scores were used to validate the objective cuteness scores. The analysis found that subjective cuteness in survey 1 was the only variable of influence on LoS. A novel objective cuteness measurement was developed which reflects the eye shape associated with subjective cuteness scores. The current study found that cuteness may not be as influential on cats’ LoS in shelters as hypothesised. This research looks to understand factors which influence LoS to help identify potential methods to reduce time spent in shelters and improve the welfare of cats within these environments.

Creation and Validation of the Japanese Cute Infant Face (JCIF) Dataset

Research interest in cuteness perception and its effects on subsequent behavior and physiological responses has recently been increasing. The purpose of the present study was to produce a dataset of Japanese infant faces that are free of portrait rights and can be used for cuteness research. A total of 80 original facial images of 6-month-old infants were collected from their parents. The cuteness level of each picture was rated on a 7-point scale by 200 Japanese people (100 men and 100 women in their 20s–60s). Prototypical high- and low-cuteness faces were created by averaging the top 10 and bottom 10 faces according to the mean cuteness ratings. Then, 50 composite faces were made by mixing two faces randomly chosen from the 60 unused middle-cuteness faces. The normative cuteness ratings of these composite faces were obtained from 229 Japanese men and women in their 20s–60s. The shape of each composite face was transformed to be cuter (+50%) or less cute (–50%) along a continuum between the high- and low-cuteness prototypical faces. A two-alternative forced-choice task (N = 587) confirmed that cuteness discrimination was better than the chance level for all 50 face pairs. Moreover, the results showed that young men had poorer sensitivity to cuteness differences in infant faces than older men and women of any age. This Japanese Cute Infant Face (JCIF, “jay-sif”) dataset, including composite face images and normative rating scores, is publicly available online.

Eye Size Affects Cuteness in Different Facial Expressions and Ages

Researchers have suggested that infants exhibiting baby schema are considered cute. These similar studies have mainly focused on changes in overall baby schema facial features. However, whether a change in only eye size affects the perception of cuteness across different facial expressions and ages has not been explicitly evaluated until now. In the present study, a paired comparison method and 7-point scale were used to investigate the effects of eye size on perceived cuteness across facial expressions (positive, neutral, and negative) and ages (adults and infants). The results show that stimuli with large eyes were perceived to be cuter than both unmanipulated eyes and small eyes across all facial expressions and age groups. This suggests not only that the effect of baby schema on cuteness is based on changes in a set of features but also that eye size as an individual feature can affect the perception of cuteness.

Secure Attachment Priming Amplifies Approach Motivation for Infant Faces Among Childless Adults

Existing studies have indicated that priming secure attachment alters adults' neural responses to infant faces. However, no study has examined whether this effect exists for motivational behavioral responses, and none of the previous studies included adult faces as a baseline to determine whether the security prime enhances responses to human faces in general or infant faces alone. To address this limitation, the current study recruited 160 unmarried and childless adults in the first phase, and all of them completed a battery of questionnaires, including the Interest in Infants, the Experiences in Close Relationships (ECR), and State Adult Attachment Measure (SAAM). A week later, after priming, 152 (76 security-primed vs. 76 neutrally primed) participants completed the SAAM and a behavioral program assessing their motivational responses to both adult and infant faces (i.e., liking, representational, and evoked responses). A manipulation check showed that the security prime was effective. Then, generalized linear mixed-effects models (GLMMs) showed that security priming enhances adults' liking, representational, and evoked responses (three components of the motivational system) only to infant faces and not to adult faces. Moreover, hierarchical regression analysis indicated that, even after security priming, there was a substantial linear relationship between positive motivation toward infant faces and the state of adult secure attachment. In summary, this study demonstrated for the first time that promoting the state of adult secure attachment can effectively enhance the effect size of the baby face schema. The current results were interpreted according to Bowlby's view of the attachment behavioral system.

Not all "caregivers" are created equal: Liking, caring and facial expression responses to the baby schema as a function of parenthood and testosterone

The baby schema elicits care from potential caregivers. However, much of the research on the baby schema is based on self-report only. To address this issue, we explored the effects of baby schema and child age on facial expressions (EMG) and eye-blink startle, in addition to self-reported liking and caring for 43 men and 48 women (39 parents). Further, basal testosterone was assessed. All groups responded with liking and caring to high baby schema, but only women also responded with more positive facial expressions. Caring and smiling towards infants compared to first graders depended on parenthood and testosterone levels. Basal testosterone levels were negatively associated with overall responsiveness to children in women and fathers, but positively in non-fathers. Whereas the baby schema overall lead to positive affect and caring, the scope of these responses and the processes underlying them depended on gender, parenthood and hormonal status.

Do Infant Faces Maintain the Attention of Adults With High Avoidant Attachment?

We investigated whether adults have attentional bias toward infant faces, whether it is moderated by infant facial expression, and the predictive effect of the adult attachment state on it. One hundred unmarried nulliparous college students [50 men and 50 women; aged 17–24 years (M = 19.70, SD = 1.35)] were recruited. Each completed a self-report questionnaire—the Chinese version of the State Adult Attachment Measure (SAAM), and a dot-probe task with a stimulus presentation duration of 500 ms, which used 192 black-and-white photographs of 64 people (32 infants and 32 adults; each person displayed three expressions: happy, neutral, and sad) as the experimental stimuli. The results showed that, at the duration of 500 ms, individuals' attentional bias toward infant faces disappeared, regardless of the facial expression. However, when the interaction between avoidant attachment state and face was controlled, the attentional bias was significant again, and the avoidant attachment state negatively predicted individuals' attentional bias toward infant faces. This indicates that at the suprathreshold stage, there are individual differences in the attentional bias toward infant faces, and high avoidant attachment will weaken individuals' attentional bias toward infant faces. This study advances previous studies that focused only on individuals' attention to infant faces occurring at the early processing stage of attention. The results provide direction for interventions; specifically, changing the attachment state of avoidant individuals can affect their attention to infants, which may promote the establishment of parent–child relationships.

Individuals with Psychopathic Traits and Poor Attitudes towards Animals Can Recognise Infant Features But Give Them Reduced Attentional Priority

Simple Summary

Certain facial characteristics in companion animals are perceived by humans as being ‘cute’. This includes having large eyes, a round head and a small nose and mouth. These characteristics, which are shared with human infants, trigger care-giving responses in humans. Despite this, however, companion animal abuse occurs. The aim of this research was to better understand cognitive processes of people with pro-social personality traits and positive attitudes towards animals compared to those with anti-social personality traits and negative attitudes towards animals. This was done by assessing participants’ ability to detect cues of cuteness in animal and human infant faces (study 1) and by assessing attention to cuteness cues via an eye-tracking task (study 2). Findings indicate that the ability to detect cuteness cues is widespread, regardless of personality or attitudes. However, individuals with anti-social personality traits and negative attitudes towards animals chose to pay less attention to ‘cute’ stimuli in the eye-tracking task. This proof of concept study is an initial step in determining how individuals ‘at risk’ of committing animal abuse process information on infant features in animals.

Abstract

Infant features are physical traits that are characteristic of human infants and include facial features such as large and low-lying eyes, and a small nose and mouth. Animals possessing high levels of infant features elicit care-giving responses in humans. Despite this, animal cruelty is a common occurrence. The aim of this research was to determine whether the ability to recognise and/or attend to infant features is linked to subclinical psychopathic traits and attitudes towards animals. Using a community sample, participants (n = 387) completed a cuteness forced-choice task. Self-reported psychopathy and attitude towards animals were not related to the participants’ ability to detect cues of cuteness in human infants and animals. In a second study, participants (n = 142) were screened for low versus high primary psychopathy and low versus high animal attitude scores. A Psychopathy-Attitude Composite score was created and a subset of participants (n = 50) from the upper and lower quartiles completed a free-viewing eye-tracking task where ‘Cute’, ‘Neutral, ‘Monetary’ and ‘Control’ images were presented in pairs. Higher levels of psychopathic traits and an anti-animal welfare attitude were associated with decreased attention to ‘Cute’ images in terms of decreased dwell time, mean fixation duration and mean fixation count, measures of voluntary attention. There were a number of interactions between Psychopathy-Attitude Composite classification and attention to each image category in terms of dwell time, first fixation duration, mean fixation duration and fixation count. These findings support the theory that individuals with psychopathic traits recognise facial cues of vulnerability but choose to give them reduced attentional priority. This may have implications for animal welfare.

Mechanisms for the Cognitive Processing of Attractiveness in Adult and Infant Faces: From the Evolutionary Perspective

Research on the cognitive processing of facial attractiveness has mainly focused on adult faces. Recent studies have revealed that the cognitive processing of facial attractiveness in infant faces is not the same as that in adult faces. Therefore, it is necessary to summarize the evidence on the processing of facial attractiveness in each kind of face and compare their underlying mechanisms. In this paper, we first reviewed studies on the cognitive processing of facial attractiveness in adult faces, including attentional and mnemonic processing, and then discussed the underlying mechanisms. Afterward, studies on facial attractiveness in infant faces were reviewed, and the underlying mechanisms were also discussed. Direct comparisons between the two kinds of cognitive processing were subsequently made. The results showed that the mechanisms for the processing of attractiveness in adult faces and infant faces are mainly motivated by the perspectives of mate selection and raising offspring, respectively, in evolutionary psychology. Finally, directions for future research are proposed.