Reactions to children's faces

Group Formation and the Evolution of Human Social Organization

Humans operate in groups that are oftentimes nested in multilayered collectives such as work units within departments and companies, neighborhoods within cities, and regions within nation states. With psychological science mostly focusing on proximate reasons for individuals to join existing groups and how existing groups function, we still poorly understand why groups form ex nihilo, how groups evolve into complex multilayered social structures, and what explains fission-fusion dynamics. Here we address group formation and the evolution of social organization at both the proximate and ultimate level of analysis. Building on models of fitness interdependence and cooperation, we propose that socioecologies can create positive interdependencies among strangers and pave the way for the formation of stable coalitions and groups through reciprocity and reputation-based partner selection. Such groups are marked by in-group bounded, parochial cooperation together with an array of social institutions for managing the commons, allowing groups to scale in size and complexity while avoiding the breakdown of cooperation. Our analysis reveals how distinct group cultures can endogenously emerge from reciprocal cooperation, shows that social identification and group commitment are likely consequences rather than causes of group cooperation, and explains when intergroup relations gravitate toward peaceful coexistence, integration, or conflict.

Development of the Paternal Brain in Humans throughout Pregnancy

Previous studies have demonstrated that paternal caregiving behaviors are reliant on neural pathways similar to those supporting maternal care. Interestingly, a greater variability exists in parental phenotypes in men than in women among individuals and mammalian species. However, less is known about when or how such variability emerges in men. We investigated the longitudinal changes in the neural, hormonal, and psychological bases of expression of paternal caregiving in humans throughout pregnancy and the first 4 months of the postnatal period. We measured oxytocin and testosterone, paternity-related psychological traits, and neural response to infant-interaction videos using fMRI in first-time fathers and childless men at three time points (early to mid-pregnancy, late pregnancy, and postnatal). We found that paternal-specific brain activity in prefrontal areas distinctly develops during middle-to-late pregnancy and is enhanced in the postnatal period. In addition, among fathers, the timing of the development of prefrontal brain activity was associated with specific parenting phenotypes.

The role of oxytocin in modulating self-other distinction in human brain: a pharmacological fMRI study

Self-other distinction is crucial for human interaction. Although with conflicting results, studies have found that oxytocin (OT) sharpens the self-other perceptual boundary. However, little is known about the effect of OT on self-other perception, especially its neural basis. Moreover, it is unclear whether OT influences self-other discrimination when the other is a child or an adult. This double-blind, placebo-controlled study investigated the effect of OT on self-face perception at the behavioral and neural levels. For the stimuli, we morphed participants' faces and child or adult strangers' faces, resulting in 4 conditions. After treatment with either OT or placebo, participants reported whether a stimulus resembled themselves while being scanned using functional magnetic resonance imaging (fMRI). Behavioral results showed that people judged adult-morphed faces better than child-morphed faces. Moreover, fMRI results showed that the OT group exhibited increased activity in visual areas and the inferior frontal gyrus for self-faces. This difference was more pronounced in the adult-face condition. In multivariate fMRI and region of interest analyses, better performance in the OT group indicated that OT increased self-other distinction, especially for adult faces and in the left hemisphere. Our study shows a significant effect of OT on self-referential processes, proving the potential effect of OT on a left hemisphere self-network.

Oxytocin modulates social brain network correlations in resting and task state

The effects of oxytocin (OT) on the social brain can be tracked upon assessing the neural activity in resting and task states, and developing a system-level framework for characterizing the state-based functional relationships of its distinct effect. Here, we contribute to this framework by examining how OT modulates social brain network correlations during resting and task states, using fMRI. First, we investigated network activation, followed by an analysis of the relationships between networks and individual differences. Subsequently, we evaluated the functional connectivity in both states. Finally, the relationship between networks across states was represented by the predictive power of networks in the resting state for task-evoked activities. The differences in the predicted accuracy between the subjects displayed individual variations in this relationship. Our results showed that the activity of the dorsal default mode network in the resting state had the largest predictive power for task-evoked activation of the precuneus network (PN) only in the OT group. The results also demonstrated that OT reduced the individual variation in PN in the prediction process. These findings suggest a distributed but modulatory effect of OT on the association between resting and task-dependent brain networks.

Resemblance Reporting on Children: Sisters Are More Proactive than Brothers

The asymmetric grandparental investment in humans may ultimately be explained by the paternity uncertainty hypothesis. The proximate mechanisms leading to grandparental bias in investment in grandchildren are, however, unclear. In a study of 233 males and females with an opposite sexed sibling, we examined whether comments on resemblance regarding one’s own child, or one’s sibling’s child, changed in frequency after both siblings became parents. We found that comments among siblings on resemblance of children occurred more frequently after both became parents, compared to when only one of the siblings had children, suggesting that resemblance descriptions may become more important after both siblings have children. Furthermore, and in line with the suggestion that mothers may mentally exploit the alloparenting environment by holding a stronger belief about resemblance, brothers reported that their sisters commented on resemblance concerning their own child more often and more intensely. Additionally, sisters corroborated this finding by self-reporting that they were the most proactive during resemblance descriptions of their brothers’ child. Thus, sisters might, through more frequent voicing of stronger opinions on parent–child resemblance than their brothers, influence alloparents’ perception of resemblance to their children and thus influence alloparental investments.

Personalized quantification of facial normality: a machine learning approach

What is a normal face? A fundamental task for the facial reconstructive surgeon is to answer that question as it pertains to any given individual. Accordingly, it would be important to be able to place the facial appearance of a patient with congenital or acquired deformity numerically along their own continuum of normality, and to measure any surgical changes against such a personalized benchmark. This has not previously been possible. We have solved this problem by designing a computerized model that produces realistic, normalized versions of any given facial image, and objectively measures the perceptual distance between the raw and normalized facial image pair. The model is able to faithfully predict human scoring of facial normality. We believe this work represents a paradigm shift in the assessment of the human face, holding great promise for development as an objective tool for surgical planning, patient education, and as a means for clinical outcome measurement.

Development of the paternal brain in expectant fathers during early pregnancy

The human parenting brain network mediates caregiving behaviors. When exposed to the stimuli of their infants, compared with non-parents, both fathers and mothers exhibit distinct patterns of neural activation. As human males, relative to females, do not undergo robust physiological changes during pregnancy, when and how the paternal brain networks begin to form remains unclear. Thus, using functional MRI, we examined brain activation in response to infant-interaction videos in two groups, childless males and first-time expectant fathers during their partners' early pregnancy before remarkable changes in their partners' appearances commenced. Multivoxel pattern analysis revealed that expectant fathers' left anterior insula and inferior frontal gyrus showed incipient changes in response to parenthood during early pregnancy. Furthermore, these changes were associated with several paternal traits, such as a negative image toward parenting. Such external factors might influence the paternal brain's development during early pregnancy.

Sibling Relations in Patchwork Families: Co-residence Is More Influential Than Genetic Relatedness

In "patchwork" families, full siblings, maternal and paternal half-siblings, and non-related children are raised together, and sometimes, genetically related children are separated. As their number is steadily growing, the investigation of the factors that influence within-family relations is becoming more important. Our aim was to explore whether people differentiate between half- and full-siblings in their social relations as implied by the theory of inclusive fitness, and to test whether co-residence or genetic relatedness improves sibling relations to a larger extent. We administered the Sibling Relationship Questionnaire to 196 individuals who were in contact with full-, half-, or step-siblings in their childhood. We built Generalized Linear Mixed Models models to test for the effects of relatedness and co-residence on sibling relations. In general, a higher degree of relatedness was associated with better sibling relations, but only among those who did not live together during childhood. Co-resident siblings' overall pattern of relation quality was not influenced by the actual level of genetic relatedness. In contrast to this, full siblings reported having experienced more conflicts during childhood than half-siblings, possibly resulting from enhanced competition for the same parental resources. The results suggest that inclusive fitness drives siblings' relations even in recent industrial societies. However, among individuals who live together, the effect of relatedness might be obscured by fitness interdependence and the subjective feeling of kinship.

Body odours as a chemosignal in the mother-child relationship: new insights based on an human leucocyte antigen-genotyped family cohort

Mothers are able to identify the body odour (BO) of their own child and prefer this smell above other BOs. It has hence been assumed that the infantile BO functions as a chemosignal promoting targeted parental care. We tested this hypothesis and examined whether children's BOs signal genetic similarity and developmental status to mothers. In addition, we assessed whether BOs facilitate inbreeding avoidance (Westermarck effect). In a cross-sectional design, N = 164 mothers participated with their biological children (N = 226 children, aged 0-18 years) and evaluated BO probes of their own and four other, sex-matched children. Those varied in age and in genetic similarity, which was assessed by human leucocyte antigen profiling. The study showed not only that mothers identified and preferred their own child's BO, but also that genetic similarity and developmental status are transcribed in BOs. Accordingly, maternal preference of their own child's odour changes throughout development. Our data partly supported the Westermarck effect: mothers' preference of pubertal boys' BOs was negatively related to testosterone for the own son, but not for unfamiliar children. This article is part of the Theo Murphy meeting issue 'Olfactory communication in humans'.

Kin recognition and perceived facial similarity

Facial similarity between individuals informs kinship judgments in third-party kin recognition. Indeed, one study found that similarity and kinship judgments encapsulate the same information (Maloney & Dal Martello, 2006). Yet, another study found that this is not the case when comparing adult face pairs of different sex (DeBruine et al., 2009). We replicated these studies to further clarify the role of facial similarity in kin recognition. We recruited 318 raters, who were shown 50 sibling pairs and 50 age- and sex-matched unrelated pairs ranging from 3 to 17 years old. Each rater was randomly assigned to make either kinship judgments (“related” or “unrelated”) or similarity judgments (scale from 0 [not very similar] to 10 [very similar]). The threshold model found that performance in both tasks was equally accurate, with participants detecting child siblings in the kinship task above chance and giving significantly higher similarity ratings to siblings in the similarity task. In both tasks, opposite-sex siblings were perceived to be siblings less often than same-sex siblings, and judgments of unrelated face pairs were not affected by the sex of faces. Conversely, the effect of age difference within pairs of faces differed for the two tasks: a greater age difference decreased all kinship judgments, but only decreased similarity judgments of siblings, not unrelated pairs. In line with DeBruine et al. (2009), these findings suggest that similarity and kinship judgments are highly correlated but not strictly synonymous. The OSF Pre-registration Challenge for this project can be found at osf.io/ps9hy and the data at osf.io/sef9k.

Neural Responses to Infant Emotions and Emotional Self-Awareness in Mothers and Fathers during Pregnancy

Neuroscientific research has largely investigated the neurobiological correlates of maternal and (to a much lesser extent) paternal responsiveness in the post-partum period. In contrast, much less is known about the neural processing of infant emotions during pregnancy. Twenty mothers and 19 fathers were recruited independently during the third trimester of pregnancy. High-density electroencephalography (hdEEG) was recorded while expectant parents passively viewed images representing distressed, ambiguous, happy, and neutral faces of unknown infants. Correlational analyses were performed to detect a link between neural responses to infant facial expressions and emotional self-awareness. In response to infant emotions, mothers and fathers showed similar cerebral activity in regions involved in high-order socio-affective processes. Mothers and fathers also showed different brain activity in premotor regions implicated in high-order motor control, in occipital regions involved in visuo-spatial information processing and visual mental imagery, as well as in inferior parietal regions involved in attention allocation. Low emotional self-awareness negatively correlated with activity in parietal regions subserving empathy in mothers, while it positively correlated with activity in temporal and occipital areas implicated in mentalizing and visual mental imagery in fathers. This study may enlarge knowledge on the neural response to infant emotions during pregnancy.

Exploring the neural basis for paternal protection: an investigation of the neural response to infants in danger

Perceiving potential threat to an infant and responding to it is crucial for offspring survival and parent–child bonding. Using a combination of functional magnetic resonance imaging and multi-informant reports, this longitudinal study explores the neural basis for paternal responses to threat to infants pre-natally (N = 21) and early post-natally (n = 17). Participants viewed videos showing an infant in danger and matched control videos, while instructed to imagine that the infant was their own or someone else’s. Effects were found for infant-threatening vs neutral situations in the amygdala (region-of-interest analyses) and in clusters spanning cortical and subcortical areas (whole-brain analyses). An interaction effect revealed increased activation for own (vs unknown) infants in threatening (vs neutral) situations in bilateral motor areas, possibly indicating preparation for action. Post-natal activation patterns were similar; however, in part of the superior frontal gyrus the distinction between threat to own and unknown infant faded. Fathers showing more protective behavior in daily life recruited part of the frontal pole more when confronted with threat to their own vs an unknown infant. This exploratory study is the first to describe neural mechanisms involved in paternal protection and provides a basis for future work on fathers’ protective parenting.

Medial Cortical Structures Mediate Implicit Trustworthiness Judgments about Kin Faces, but Not Familiar Faces: A Brief Report

Human kin recognition activates substrates of the extended facial processing network, notably the right-hemisphere structures involved in self-face recognition and posterior medial cortical substrates. To understand the mechanisms underlying prosociality toward kin faces in comparison to other familiar faces, we investigated the neural correlates of implicit trustworthiness ratings to faces of actual kin and personal friends, controlling for activation to distracter faces. When controlling for activation associated with unknown faces, trustworthiness ratings of faces of kin, compared to friends, were associated with increased activation in the dorsal anterior cingulate cortex, posterior cingulate, and precuneous. On the other hand, trustworthiness ratings of friend faces, relative to kin faces, were associated with the lateral occipital gyrus and insular cortex. Trustworthiness ratings for unknown faces were only associated with activation in the fusiform gyrus. These findings suggest that we should employ medial cortical substrates known to be part of the self-other network when making implicit social judgements about kin, but not other classes of facial stimuli.

Who Gains More? The Relationship Between Parenthood and Well-Being

Two studies were conducted to explore the effect of parental sex on well-being due to parenthood. Study 1 analyzed the sixth wave of the World Values Survey data. The results indicated that parents were happier than their respective childless peers. However, the effect of motherhood was significantly higher than that of fatherhood. Furthermore, Study 2 analyzed the data from 354 single-child parents in China. The results showed that perceived parent-child facial resemblance moderated the sex difference in well-being. Specifically, in the high parent-child facial resemblance group, both fathers and mothers showed high levels of well-being; however, in the low parent-child facial resemblance group, the well-being level of mothers was higher than fathers. These results supported the renovated pyramid of needs and the hypothesis of paternal uncertainty.

Vasopressin Differentially Affects Handgrip Force of Expectant Fathers in Reaction to Own and Unknown Infant Faces

The underlying mechanisms of paternal responses to infant signals are poorly understood. Vasopressin has previously been proposed to affect these responses. Using a double-blind, placebo-controlled, within-subject design (N = 25 expectant fathers), we examined the effect of vasopressin administration on the use of excessive handgrip force during exposure to infant crying versus matched control sounds, while participants saw morphed images representing their own infant versus an unknown infant. We found that, compared to placebo, AVP administration elicited more excessive force while viewing an unknown infant image compared to viewing the image representing one’s own infant, while the reverse was true under placebo. The results are discussed in light of vasopressin’s role in parenting and parental protection among human fathers.

Weighted Graph Embedding-Based Metric Learning for Kinship Verification

Given a group photograph, it is interesting and useful to judge whether the characters in it share specific kinship relation, such as father-daughter, father-son, mother-daughter, or mother-son. Recently, facial image-based kinship verification has attracted wide attention in computer vision. Some metric learning algorithms have been developed for improving kinship verification. However, most of the existing algorithms ignore fusing multiple feature representations and utilizing kernel techniques. In this paper, we develop a novel weighted graph embedding-based metric learning (WGEML) framework for kinship verification. Inspired by the fact that family members usually show high similarity in facial features like eyes, noses, and mouths, despite their diversity, we jointly learn multiple metrics by constructing an intrinsic graph and two penalty graphs to characterize the intraclass compactness and interclass separability for each feature representation, respectively, so that both the consistency and complementarity among multiple features can be fully exploited. Meanwhile, combination weights are determined through a weighted graph embedding framework. Furthermore, we present a kernelized version of WGEML to tackle nonlinear problems. Experimental results demonstrate both the effectiveness and efficiency of our proposed methods.

If looks could heal: Child health and paternal investment

Data from the first two waves of the Fragile Family and Child Wellbeing study indicate that infants who look like their father at birth are healthier one year later. The reason is such father-child resemblance induces a father to spend more time engaged in positive parenting. An extra day (per month) of time-investment by a typical visiting father enhances child health by just over 10% of a standard deviation. This estimate is not biased by the effect of child health on father-involvement or omitted maternal ability, thereby eliminating endogeneity biases that plague existing studies. The result has implications regarding the role of a father's time in enhancing child health, especially in fragile families.

Attractiveness Modulates Neural Processing of Infant Faces Differently in Males and Females

Consistent attention and proper processing of infant faces by adults are essential for infant survival. Previous behavioral studies showed gender differences in processing infant cues (e.g., crying, laughing or facial attractiveness) and more importantly, the efforts invested in nurturing offspring. The underlying neural mechanisms of processing unknown infant faces provide hints for understanding behavioral differences. This functional magnetic resonance imaging (fMRI) study recruited 32 unmarried adult (16 females and 16 males) participants to view unfamiliar infant faces and rate the attractiveness. Adult faces were also included. Behaviorally, despite that females and males showed no differences in attractiveness ratings of infant faces, a positive correlation was found between female's (but not male's) subjective liking for infants and attractiveness ratings of the infant faces. Functionally, brain activations to infant faces were modulated by attractiveness differently in males and females. Specifically, in female participants, activities in the ventromedial prefrontal cortex (vmPFC) and striatum/Nucleus Accumbens (NAcc) were positively modulated by infant facial attractiveness, and the modulation coefficients of these two regions were positively correlated. In male participants, infant facial attractiveness negatively modulated the activity in the dorsomedial prefrontal cortex (dmPFC). Our findings reveal that different neural mechanisms are involved in the processing of infant faces, which might lead to observed behavioral differences between males and females towards the baby.

Neural Processing of Familiar and Unfamiliar Children's Faces: Effects of Experienced Love Withdrawal, but No Effects of Neutral and Threatening Priming

In the face of a potential threat to his or her child, a parent's caregiving system becomes activated, motivating the parent to protect and care for the child. However, the neural correlates of these responses are not yet well understood. The current study was a pilot study to investigate the processing of subliminally presented threatening primes and their effects on neural responses to familiar and unfamiliar children's faces. In addition, we studied potential moderating effects of empathy and childhood experiences of love-withdrawal. A total of 45 students participated in an fMRI experiment in which they were shown pictures of familiar children (pictures morphed to resemble the participant like an own child would) and unfamiliar children preceded by neutral and threatening primes. Participants completed a modified version of the Children's Report of Parental Behavior Inventory to measure parental love withdrawal, and the Empathic Concern scale of the Interpersonal Reactivity Index to measure affective empathy. Contrary to our expectations, we did not find evidence for subliminal priming effects. However, we did find enhanced activity in the right inferior frontal gyrus (IFG; involved in self-referential processing) and in face processing areas (infero-lateral occipital cortex and fusiform areas) in response to the familiar child, indicating preferential processing of these faces. Effects of familiarity in face processing areas were larger for participants reporting more love withdrawal, suggesting enhanced attention to and processing of these highly attachment relevant stimuli. Unfamiliar faces elicited enhanced activity in bilateral superior temporal gyrus (STG) and other regions associated with theory of mind (ToM), which may indicate more effortful ToM processing of these faces. We discuss the potential difference between a familiarity and a caregiving effect triggered by the morphed faces, and emphasize the need for replication in parents with pictures of their "real" own child.

Language modulates brain activity underlying representation of kinship terms

Kinship terms have been found to be highly diverse across languages. Here we investigated the brain representation of kinship terms in two distinct populations, native Chinese and Caucasian English speakers, with a five-element kinship identification (FEKI) task. The neuroimaging results showed a common extensive frontal and parietal lobe brain activation pattern for different kinship levels for both Chinese and Caucasian English speakers. Furthermore, Chinese speakers had longer reaction times and elicited more fronto-parietal brain networks activation compared to English speakers in level three (e.g., uncle and nephew) and four (e.g., cousin), including an association between the middle frontal gyrus and superior parietal lobe, which might be associated with higher working memory, attention control, and social distance representation load in Chinese kinship system processing. These results contribute to our understanding of the representation of kinship terms in the two languages.

The male advantage in child facial resemblance detection: behavioral and ERP evidence

Males have been suggested to have advantages over females in reactions to child facial resemblance, which reflects the evolutionary pressure on males to solve the adaptive paternal uncertainty problem and to identify biological offspring. However, previous studies showed inconsistent results and the male advantage in child facial resemblance perception, as a kin detection mechanism, is still unclear. Here, we investigated the behavioral and brain mechanisms underlying the self-resembling faces processing and how it interacts with sex and age using event-related potential (ERP) technique. The results showed a stable male advantage in self-resembling child faces processing, such that males have higher detectability to self-resembling child faces than females. For ERP results, males showed smaller N2 and larger late positive component (LPC) amplitudes for self-resembling child faces, which may reflect face-matching and self-referential processing in kin detection, respectively. Further source analysis showed that the N2 component and LPC were originated from the anterior cingulate cortex and medial frontal gyrus, respectively. Our results support the male advantage in self-resembling child detection and further indicate that such distinctions can be found in both early and late processing stages in the brain at different regions.

(Not) bringing up baby: the effects of jealousy on the desire to have and invest in children

The present research uses insights from evolutionary psychology and social cognition to explore the relationship between jealousy-both experimentally activated and chronically accessible-on men's and women's desire to start a family and invest in children. In our first two studies, we found that chronically jealous men and women responded to primed infidelity threat by exhibiting a diminished interest in infants (Study 1) and reporting less happiness upon receiving pregnancy news (Study 2) relative to controls. Study 3 extended these results by examining the effects of jealousy on desired parental investment. Consistent with the proposed theoretical framework, chronically jealous men, but not women, respond to infidelity threat by decreasing their desired level of parental investment relative to controls. Together, these results provide novel empirical support for the hypothesis that jealousy functions to attenuate the reproductive costs associated with partner infidelity.

Sex Differences in the Creation of Fictional Heroes with Particular Emphasis on Female Heroes and Superheroes in Popular Culture: Insights from Evolutionary Psychology

Cultural and psychological perspectives have been used to examine the characteristics of modern fictional heroes, but rarely if ever has an evolutionary approach been applied to this topic, an approach that could be quite enlightening. Evolutionary psychology suggests that sexual selection will have shaped differences in the underlying behavioral tendencies of males and females. Specifically, the higher parental investment of females makes establishing dominance more valuable to males and the helping of family members more valuable for females. If this is true, evolved differences manifesting themselves in the subconscious could influence the characteristics of the fictional heroes created by each sex. Here, I use a preliminary examination of female superheroes from the popular media to help frame an exploration of these predicted sex differences, which is followed by a more systematic approach examining heroes found in recent children's fantasy novels. If there are evolved differences, the female heroes created by men are expected to be more physically powerful and exhibit more displays of physical power than those created by women. In addition, the primary goal of the two types should also differ, with female-generated heroes displaying more concern for family members. Analyzing these characters using evolutionary psychology is compared to previous approaches. If the evolutionary approach proves to be valid, this new method of hero comparisons should be of interest to those studying gender issues and role models for girls.

Visual judgments of kinship: an alternative perspective

Following other researchers, we investigated the premise that visual judgment of kinship might be modelled as a signal-detection task, strictly related to similar facial features. We measured subjects' response times to face-pair stimuli while they performed visual judgments of kinship, similarity, or dissimilarity, and examined some priming effects involved. Our results show that kinship judgment takes longer on average than either similarity or dissimilarity judgment-which is compatible with existing models, yet might also suggest that kinship judgments are of a more complex character. In our priming study we observed selective suppression/enhancement of the efficacy of dissimilarity judgments whenever they followed similarity and kinship judgments. This finding confounds the notion, inherent in previous models, of resemblance cues signalling for kinship, since similarity and dissimilarity cannot be considered just as opposite concepts, and observed priming effects need to be explicitly modelled, including dissimilarity cues. To model kinship judgments across faces that are perceived as dissimilar, a new framework may be required, perhaps accepting the perspective of a task-driven use of the visual cues, modulated by experience and cultural conditioning.

Preference for facial self-resemblance and attractiveness in human mate choice

Empirical studies present considerably consistent data about human mate choice, from which we may infer that it tends to be homogamous for various traits. However, different experiments on facial resemblance led to contradictory results. To obtain additional data about the preference for self-resembling potential mates, male and female composite faces were modified in a manner to resemble subjects. Volunteers were asked to choose a potential partner from three images in different situations: self-resembling faces, non-resembling faces (both with the same degree of other-rated attractiveness), and images which were rated by others as more attractive than the self-resembling faces. Women did not show any preference for similarity; they preferred the most attractive male and female faces. In contrast, men preferred the most attractive images of the opposite sex to self-resembling faces and the self-resembling to non-resembling faces. The self-resemblance of same-sex faces was preferred by neither men nor women. Our results support the hypothesis that both facial similarity (i.e., cues of shared genes) and observer-independent features of attractiveness (i.e., honest signals of genetic quality) play an important role in males' mate choice. The lack of choice for self-resemblance on the female side in this particular study might reflect their more complex decision-making rules that are probably based on other cues beside visual stimuli.

Cues of paternal uncertainty and father to child physical abuse as reported by mothers in Rio de Janeiro, Brazil

OBJECTIVE

Paternity is uncertain, so if paternal feelings evolved to promote fitness, we might expect them to vary in response to variables indicative of paternity probability. We therefore hypothesized that the risk of lapses of paternal affection, including abusive assaults on children, will be exacerbated by cues of non-paternity.

METHODS

Cross-sectional study of 331 Brazilian mothers, interviewed about 1 focal child (age 1-12) residing with her and the putative father. Child physical abuse was assessed using the Conflict Tactic Scales: Parent Child (CTSPC). Two potential cues of (non) paternity were (1) whether the parents co-resided when the child was conceived, and (2) whether third parties allegedly commented on father-child resemblance. Data were analyzed through multiple logistic regressions.

RESULTS

Mothers reported child physical abuse by 15.9% (95% CI 4.6-27.1) of fathers who had not cohabited with them at conception, compared to 5.9% (95% CI 3.1-8.7) of those who had. The odds ratio for abuse by fathers who had not cohabited at conception in relation to those who had-adjusted for income, education, age, sex of child, whether child was first born, household size, time father spent with child, and alcohol abuse and drug use by father-was 4.3 (95% CI 1.4-13.8). Mothers reported abuse of 7.0% (95% CI 4.0-10.0) of children who purportedly resembled their fathers, versus 8.7% (95% CI 0.2-17.1) of those who did not.

CONCLUSION

According to maternal reports, not having co-resided at conception quadrupled the chance of child physical abuse by currently co-residing Brazilian fathers. The reported prevalence of abuse was unrelated to reported allegations of father-child resemblance.

Neural activation to babyfaced men matches activation to babies

Behavioral data supports the commonsense view that babies elicit different responses than adults do. Behavioral research also has supported the babyface overgeneralization hypothesis that the adaptive value of responding appropriately to babies produces a tendency for these responses to be overgeneralized to adults whose facial structure resembles babies. Here we show a neural substrate for responses to babies and babyface overgeneralization in the amygdala and the fusiform face area (FFA). Both regions showed greater percentage BOLD signal change compared with fixation when viewing faces of babies or babyfaced men than maturefaced men. Viewing the first two categories also yielded greater effective connectivity between the two regions. Facial qualities previously shown to elicit strong neural activation could not account for the effects. Babyfaced men were distinguished only by their resemblance to babies. The preparedness to respond to infantile facial qualities generalizes to babyfaced men in perceivers' neural responses just as it does in their behavioral reactions.

Are children's faces really more appealing than those of adults? Testing the baby schema hypothesis beyond infancy

This study examined adults' evaluations of likeability and attractiveness of children's faces from infancy to early childhood. We tested whether Lorenz's baby schema hypothesis (Zeitschrift für Tierpsychologie (1943), Vol. 5, pp. 235-409) is applicable not only to infant faces but also to faces of children at older ages. Adult participants were asked to evaluate children's faces from early infancy to 6 years of age in terms of their likeability and attractiveness, and these judgments were compared with those of adult faces. It was revealed that adults judged faces of younger children as more likeable and attractive than faces of older children, which were in turn judged as more likeable and attractive than adult faces. However, after approximately 4.5 years of age, the baby schema no longer affected adults' judgments of children's facial likeability and attractiveness. These findings suggest that the baby schema affects adults' judgments of not only infant faces but also young children's faces. This influence beyond infancy is likely due to the fact that facial cranial growth is gradual during early childhood and certain crucial infantile facial cues remain readily available during this period. Future studies need to identify these specific cues to better understand why adults generally show positive responses to infantile faces and how such positive responses influence the establishment and maintenance of social relationships between young children and adults.

Examining the Acceptance of and Resistance to Evolutionary Psychology

The field of psychology remains a divided one. Several different sub-disciplines (e.g., developmental, cognitive, behaviorism, social, etc.) form what could be a unified scientific area. However, there is no widely accepted theory of unification. Charles Darwin once theorized that evolutionary theory would change the foundation of psychology; but over the years, evolutionary psychology has been met with hostile resistance from some of the prominent psychologists within the other sub-disciplines. Yet in recent years, all of the divided sub-disciplines of psychology have been slowly implementing evolutionary principles into their literature and research. This slow integration of evolutionary psychology into the other sub-disciplines indicates the possibility of a unified psychology with evolution as its foundation. This paper briefly reviews the literature within each major sub-discipline of psychology to show their implementation of evolutionary psychological theories, indicating the possibility of evolutionary psychology becoming the unifying paradigm upon which the entire field of psychology can be based. A call for action to continue this process is also discussed.

Men do not have a stronger preference than women for self-resemblant child faces

Are men more likely than women to take into account a child's facial resemblance to themselves when making hypothetical parental investment choices? The benefits of self-resemblance in decreasing relatedness uncertainty are larger in men than in women for direct descendants. However, they are identical in men and women for collateral relatives, such as siblings, cousins, nephews, and nieces; these individuals can also be the recipients of parental-like altruism, which comes primarily from women. Published data are contradictory. In the present study, 14 men and 14 women were shown child faces and asked to judge their attractiveness, adoptability, and familiarity. The faces had been digitally manipulated to resemble (at three different resemblance levels, two of which were under recognition threshold) either the experimental participant, an acquaintance, or strangers. We found a significant preference for self-resemblant children in women, but not in men. This was not an artefact of women being better at detecting self-resemblance, given that at the highest resemblance level more men than women recognized themselves. Overall, face preference increased with face familiarity; for self-resemblant faces, this correlation was not mediated by conscious self-recognition. We discuss how the fast-response, multiple-question procedure used in previous experiments may have led to reports of a much larger self-resemblance preference in men than in women.

Psychology of Human Kin Recognition: Heuristic Cues, Erroneous Inferences, and Their Implications

Humans possess explicit, rule-based, and culturally determined systems for identifying kin, but kinship inferences are also influenced implicitly by cue-based mechanisms found commonly across the animal kingdom. These mechanisms are fallible. An evolutionarily informed signal-detection analysis suggests that (a) cue-based kin recognition may sometimes be biased in favor of false-positive errors, resulting in implicit kinship inferences even in the presence of nonkin, and (b) the tendency toward this inferential error may vary predictably in response to specific developmental and contextual circumstances. This analysis has important implications for a wide variety of psychological phenomena (especially in the realms of person perception, interpersonal attraction, and prosocial behavior) and leads to the deduction of many novel hypotheses.