Beauty is in the ease of the beholding: A neurophysiological test of the averageness theory of facial attractiveness

Hundreds of studies have shown that people prefer attractive over unattractive faces. But what is an attractive face, and why is it preferred? Averageness theory claims that faces are perceived as being attractive when their facial configuration approximates the mathematical average facial configuration of the population. Conversely, faces that deviate from this average configuration are perceived as being unattractive. The theory predicts that both attractive and mathematically averaged faces should be processed more fluently than unattractive faces, whereas the averaged faces should be processed marginally more fluently than the attractive faces. We compared neurocognitive and behavioral responses to attractive, unattractive, and averaged human faces to test these predictions. We recorded event-related potentials (ERPs) and reaction times (RTs) from 48 adults while they discriminated between human and chimpanzee faces. The participants categorized averaged and high-attractive faces as being “human” faster than low-attractive faces. The posterior N170 (150–225 ms) face-evoked ERP component was smaller in response to high-attractive and averaged faces than to low-attractive faces. Single-trial electroencephalographic analysis indicated that this reduced ERP response arose from the engagement of fewer neural resources, and not from a change in the temporal consistency of how those resources were engaged. These findings provide novel evidence that faces are perceived as being attractive when they approximate a facial configuration close to the population average, and they suggest that processing fluency underlies preferences for attractive faces.     

Infant's visual preferences for facial traits associated with adult attractiveness judgements: Data from eye-tracking

Human preferences for facial attractiveness appear to emerge at an early stage during infant development. A number of studies have demonstrated that infants display a robust preference for facial attractiveness, preferring to look at physically attractive faces versus less attractive faces as judged by adults. However, to-date, relatively little is known about which traits of the face infants use to base these preferences upon. In contrast, a large number of studies conducted with human adults have identified that preference for attractive faces can be attributed to a number of specific facial traits. The purpose of the experiments here was to measure and assess infant's visual preference via eye-tracker technology for faces manipulated for one of three traits known to effect attractiveness judgments in adult preference tests: symmetry, averageness, and sexually dimorphic traits. Sixty-four infants (28 female and 36 male) aged between 12 and 24 months old each completed a visual paired comparison (VPC) task for one of the three facial dimensions investigated. Data indicated that infants displayed a significant visual preference for facial symmetry analogous to those preferences displayed by adults. Infants also displayed a significant visual preference for feminine versions of faces, in line with some studies of adult preferences. Visual preferences for facial non-averageness, or distinctiveness were also seen, a pattern opposite to that seen in adults. These findings demonstrate that infant's appreciation for facial attractiveness in adult images between the ages of 12 and 24 months of age is based on some, but not all, traits that adults find attractive.     

Attractiveness of facial averageness and symmetry in non-western cultures: in search of biologically based standards of beauty.

Averageness and symmetry are attractive in Western faces and are good candidates for biologically based standards of beauty. A hallmark of such standards is that they are shared across cultures. We examined whether facial averageness and symmetry are attractive in non-Western cultures. Increasing the averageness of individual faces, by warping those faces towards an averaged composite of the same race and sex, increased the attractiveness of both Chinese (experiment 1) and Japanese (experiment 2) faces, for Chinese and Japanese participants, respectively. Decreasing averageness by moving the faces away from an average shape decreased attractiveness. We also manipulated the symmetry of Japanese faces by blending each original face with its mirror image to create perfectly symmetric versions. Japanese raters preferred the perfectly symmetric versions to the original faces (experiment 2). These findings show that preferences for facial averageness and symmetry are not restricted to Western cultures, consistent with the view that they are biologically based. Interestingly, it made little difference whether averageness was manipulated by using own-race or other-race averaged composites and there was no preference for own-race averaged composites over other-race or mixed-race composites (experiment 1). We discuss the implications of these results for understanding what makes average faces attractive. We also discuss some limitations of our studies, and consider other lines of converging evidence that may help determine whether preferences for average and symmetric faces are biologically based.     

Face Perception During Early Infancy

Previous studies of face perception during early infancy are difficult to interpret because of discrepant results and procedural differences. We used a standardized method based on the Teller acuity card procedure to test newborns, 6-week-olds, and 12-week-olds with three pairs of face and nonface stimuli modified from previous studies. Newborns' preferences were influenced both by the visibility of the stimuli and by their resemblance to a human face. There appears to be a mechanism, likely subcortical, predisposing newborns to look toward faces. Changes in preferences at 6 and 12 weeks of age suggest increasing cortical influence over infants' preferences for faces.     

The other-race effect develops during infancy: evidence of perceptual narrowing

Experience plays a crucial role in the development of face processing. In the study reported here, we investigated how faces observed within the visual environment affect the development of the face-processing system during the 1st year of life. We assessed 3-, 6-, and 9-month-old Caucasian infants' ability to discriminate faces within their own racial group and within three other-race groups (African, Middle Eastern, and Chinese). The 3-month-old infants demonstrated recognition in all conditions, the 6-month-old infants were able to recognize Caucasian and Chinese faces only, and the 9-month-old infants' recognition was restricted to own-race faces. The pattern of preferences indicates that the other-race effect is emerging by 6 months of age and is present at 9 months of age. The findings suggest that facial input from the infant's visual environment is crucial for shaping the face-processing system early in infancy, resulting in differential recognition accuracy for faces of different races in adulthood.     

Are average and symmetric faces attractive to infants? Discrimination and looking preferences

Young infants prefer to look at faces that adults find attractive, suggesting a biological basis for some face preferences. However, the basis for infant preferences is not known. Adults find average and symmetric faces attractive. We examined whether 5-8-month-old infants discriminate between different levels of averageness and symmetry in faces, and whether they prefer to look at faces with higher levels of these traits. Each infant saw 24 pairs of female faces. Each pair consisted of two versions of the same face differing either in averageness (12 pairs) or symmetry (12 pairs). Data from the mothers confirmed that adults preferred the more average and more symmetric versions in each pair. The infants were sensitive to differences in both averageness and symmetry, but showed no looking preference for the more average or more symmetric versions. On the contrary, longest looks were significantly longer for the less average versions, and both longest looks and first looks were marginally longer for the less symmetric versions. Mean looking times were also longer for the less average and less symmetric versions, but those differences were not significant. We suggest that the infant looking behaviour may reflect a novelty preference rather than an aesthetic preference.     

Development of preferences for the human body shape in infancy

Two studies investigated the development of infants' visual preferences for the human body shape. In Study 1, infants of 12, 15 and 18 months were tested in a standard preferential looking experiment, in which they were shown paired line drawings of typical and scrambled bodies. Results indicated that the 18-month-olds had a reliable preference for the scrambled body shapes over typical body shapes, while the younger infants did not show differential responding. In Study 2, 12- and 18-month-olds were tested with the same procedure, except that the typical and scrambled body stimuli were photographic images. The results of Study 2 again indicated that only the 18-month-olds had a reliable preference for the scrambled body shapes. This finding contrasts sharply with infants' precocious preferences for human faces, suggesting that infants' learning about human faces and human bodies follow different developmental trajectories.     

Integrating gaze direction and expression in preferences for attractive faces

Few studies have investigated how physical and social facial cues are integrated in the formation of face preferences. Here we show that expression differentially qualifies the strength of attractiveness preferences for faces with direct and averted gaze. For judgments of faces with direct gaze, attractiveness preferences were stronger for smiling faces than for faces with neutral expressions. By contrast, for judgments of faces with averted gaze, attractiveness preferences were stronger for faces with neutral expressions than for smiling faces. Because expressions can differ in meaning depending on whether they are directed toward or away from oneself, it is only by integrating gaze direction, facial expression, and physical attractiveness that one can unambiguously identify the most attractive individuals who are likely to reciprocate one's own social interest.     

Sensitivity to First‐Order Relations of Facial Elements in Infant Rhesus Macaques

Faces are visually attractive to both human and nonhuman primates. Human neonates are thought to have a broad template for faces at birth and prefer face‐like to non‐face‐like stimuli. To better compare developmental trajectories of face processing phylogenetically, here, we investigated preferences for face‐like stimuli in infant rhesus macaques using photographs of real faces. We presented infant macaques aged 15–25 days with human, macaque and abstract faces with both normal and linear arrangements of facial features and measured infants' gaze durations, number of fixations and latency to look to each face using eye‐tracking technology. There was an overall preference for normal over linear facial arrangements for abstract and monkey faces but not human faces. Moreover, infant macaques looked less at monkey faces than at abstract or human faces. These results suggest that species and facial configurations affect face processing in infant macaques, and we discuss potential explanations for these findings. Further, carefully controlled studies are required to ascertain whether infant macaques' face template can be considered as broad as human infants' face template. Copyright © 2013 John Wiley & Sons, Ltd.     

Infants' discrimination of faces by using biological motion cues

We report two experiments in which we used animated averaged faces to examine infants' ability to perceive and discriminate facial motion. The faces were generated by using the motion recorded from the faces of volunteers while they spoke. We tested infants aged 4-8 months to assess their ability to discriminate facial motion sequences (condition 1) and discriminate the faces of individuals (condition 2). Infants were habituated to one sequence with the motion of one actor speaking one phrase. Following habituation, infants were presented with the same sequence together with motion from a different actor (condition 1), or a new sequence from the same actor coupled with a new sequence from a new actor (condition 2). Infants demonstrated a significant preference for the novel actor in both experiments. These findings suggest that infants can not only discriminate complex and subtle biological motion cues but also detect invariants in such displays.     

Dissociating averageness and attractiveness: attractive faces are not always average

Although the averageness hypothesis of facial attractiveness proposes that the attractiveness of faces is mostly a consequence of their averageness, 1 study has shown that caricaturing highly attractive faces makes them mathematically less average but more attractive. Here the authors systematically test the averageness hypothesis in 5 experiments using both rating and visual adaptation paradigms. Visual adaptation has previously been shown to increase both preferences for previously viewed face types (i.e., attractiveness) and their perceived normality (i.e., averageness). The authors used a visual adaptation procedure to test whether facial attractiveness is dependent upon faces' proximity to average (averageness hypothesis) or their location relative to average along an attractiveness dimension in face space (contrast hypothesis). While the typical pattern of change due to visual adaptation was found for judgments of normality, judgments of attractiveness resulted in a very different pattern. The results of these 5 experiments conclusively support the proposal that there are specific nonaverage characteristics that are particularly attractive. The authors discuss important implications for the interpretation of studies using a visual adaptation paradigm to investigate attractiveness.     

Past, current, and future trends in infant face perception research

Our review of infant face perception research had three purposes. First, we briefly attempted to describe a number of themes prevalent in the literature before 1979. Although the themes were broad and difficult to identify clearly, the underlying issues of the time seemed to fit three headings: (a) research that either did or did not support the existence of an innate preference for faces, (b) research that explored infants' general knowledge of faces, particularly their sensitivity to the invariant properties of faces, and (c) how infants acquire information about faces, as demonstrated through studies of facial scanning and feature discrimination. Our second goal was to summarize current trends. Here emphasis was placed on studies concerned with the face as a conveyer of socially-salient information, the neurological basis of face perception, and recent methodological innovations. Our final goal was to provide a sampling of issues and questions that seemed appropriate for investigation during the next decade.     

Adaptation reinforces preferences for correlates of attractive facial cues

It is generally thought that experience with faces recalibrates preferences to match the population average for recently encountered exemplars. Here, however, we demonstrate that viewing faces biases recalibration of preferences towards characteristics that are common to the more attractive faces that were encountered, rather than characteristics of the unbiased population average. Furthermore, this bias in recalibration of preferences was abolished when participants’ attention was directed away from the attractive faces, suggesting it is a consequence of the tendency to look longer and more often at attractive faces than at relatively unattractive faces. These findings suggest a perceptual mechanism that may reinforce directional selection for nonaverage attractive facial characteristics and their correlates, rather than driving stabilizing selection for average traits.     

Attractiveness of own-race, other-race, and mixed-race faces

Averaged face composites, which represent the central tendency of a familiar population of faces, are attractive. If this prototypicality contributes to their appeal, then averaged composites should be more attractive when their component faces come from a familiar, own-race population than when they come from a less familiar, other-race population. We compared the attractiveness of own-race composites, other-race composites, and mixed-race composites (where the component faces were from both races). In experiment 1, Caucasian participants rated own-race composites as more attractive than other-race composites, but only for male faces. However, mixed-race (Caucasian/Japanese) composites were significantly more attractive than own-race composites, particularly for the opposite sex. In experiment 2, Caucasian and Japanese participants living in Australia and Japan, respectively, selected the most attractive face from a continuum with exaggerated Caucasian characteristics at one end and exaggerated Japanese characteristics at the other, with intervening images including a Caucasian averaged composite, a mixed-race averaged composite, and a Japanese averaged composite. The most attractive face was, again, a mixed-race composite, for both Caucasian and Japanese participants. In experiment 3, Caucasian participants rated individual Eurasian faces as significantly more attractive than either Caucasian or Asian faces. Similar results were obtained with composites. Eurasian faces and composites were also rated as healthier than Caucasian or Asian faces and composites, respectively. These results suggest that signs of health may be more important than prototypicality in making average faces attractive.     

Reaching experience increases face preference in 3-month-old infants

The developing infant learns about the physical and the social world by engaging with objects and with people. In the study reported here, we investigated the relationship between infants' interactions with the physical and the social world. Three-month-old infants were trained for 2 weeks and experienced either actively manipulating objects themselves or passively having objects touched to their hands. Following active or passive experiences, spontaneous orienting towards faces and objects was compared between the trained groups and untrained 3- and 5-month-olds. It is known that the onset of reaching behavior increases infants' interest in objects. However, we report that active, self-produced reaching experiences also increase infants' spontaneous orienting towards faces, while passive experiences do not affect orienting behavior. Regression analyses provide evidence for a link between manual engagement and the development of orienting towards faces. Implications of orienting towards faces for the development of triadic interactions, joint attention, and social cognition in general are discussed.     

The role of symmetry in attraction to average faces

Although many studies have demonstrated that average faces tend to be attractive, few studies have examined the extent to which symmetry contributes to the attractiveness of average faces. Such studies are potentially important, however, because average faces are highly symmetric and increasing the symmetry of face images increases their attractiveness. Here we demonstrate that increasing averageness of 2-D face shape independently of symmetry is sufficient to increase attractiveness, indicating that preferences for symmetry cannot solely explain the attractiveness of average faces. Additionally, we show that averageness preferences are significantly weaker when the effects of symmetry are controlled for using computer graphic methods than when the effects of symmetry are not controlled for, suggesting that symmetry contributes to the attractiveness of average faces. Importantly, this latter finding was not explained by the greater perceived similarity between versions offaces that varied in averageness, but not symmetry, than between versions of faces that varied in both averageness and symmetry.     

The validity of composite photographs for assessing masculinity preferences

Among non-human animals, exaggerated male traits may signal immunocompetence and are often attractive to females. This finding has not been reliably replicated in human populations, however, where preferences for feminised male faces are often observed in experiments. Some authors have suggested that certain experimental approaches, and in particular the use of 'composite', or averaged, photographs, may lack ecological validity and elicit misleading responses. This may account for reports of preferences for femininity. To date, however, experiments have varied on numerous, often confounded, methodological dimensions, making the contribution of different factors difficult to assess. To address this, we conducted an experiment to examine the influence of stimulus type on participant responses. Masculinity preferences were measured using both composite photographs and the photographs from which they were composed, while all other methodological variables were held constant. In contrast to predictions by previous authors, composites elicited significantly stronger overall preferences for masculinity, especially when textural information was reduced during the averaging process. The existence of preferences for feminised male faces is unlikely to be explained by the use of composite photographs alone.     

Pattern preferences at birth and their interaction with habituation-induced novelty preferences

Three experiments are described which relate to models of infant visual preferences, and to the ways in which preferences can be modified or created by habituation. In all experiments newborn babies were used as subjects. In Experiments equated 1 and 2 infants were presented with pairs of stimuli that were equated for contour density but which differed in spatial frequency components. The preferences obtained give support to Banks and Salapatek's (1981, Journal of Experimental Child Psychology, 31, 1-45) model of infant preferences which predicts that the maximally preferred stimulus will be that which contains high amplitude spatial frequency components falling within the age group's peak contrast sensitivity. In Experiment 3 an infant-controlled habituation procedure was used. The results obtained suggest that strong natural preferences based on the infants' peak contrast sensitivity cannot be changed by habituating infants either to the preferred or to the nonpreferred member of a stimulus pair. However, where no prior preference exists between two stimuli that are perceptually highly discriminable, very strong novelty preferences are found after habituating newborns to either stimulus. The results suggest that the contrast sensitivity model can be a powerful predictor of preferential looking in newborns, and in addition are further evidence that preferences based on experience can be found from birth.     

The development of emotional face and eye gaze processing

Recent research has demonstrated that infants' attention towards novel objects is affected by an adult's emotional expression and eye gaze toward the object. The current event-related potential (ERP) study investigated how infants at 3, 6, and 9 months of age process fearful compared to neutral faces looking toward objects or averting gaze away from objects. Furthermore, we examined how the processing of novel objects is affected by gaze direction and emotional expression. We hypothesized that an adult's fearful expression should be particularly salient when it is directed toward a referent in the environment. Furthermore, responses to objects should be increased if the face previously expressed fear toward the object. Three-month-olds did not show differential neural responses to fearful vs. neutral faces regardless of gaze direction. Six-month-olds showed an enhanced negative central (Nc) component for fearful relative to neutral faces looking toward objects, but not when eye gaze was averted away from the objects. Furthermore, 6-month-olds showed an enhanced Nc for objects that had been gaze-cued by a fearful compared to a neutral face. Nine-month-olds showed an enhanced Nc for fearful relative to neutral faces in both eye gaze conditions and showed an enhanced Nc for objects that had been gaze-cued by a neutral face. The findings are discussed in the context of social cognitive and brain development.     

Fitting the mind to the world: face adaptation and attractiveness aftereffects

Average faces are attractive, but what is average depends on experience. We examined the effect of brief exposure to consistent facial distortions on what looks normal (average) and what looks attractive. Adaptation to a consistent distortion shifted what looked most normal, and what looked most attractive, toward that distortion. These normality and attractiveness aftereffects occurred when the adapting and test faces differed in orientation by 90° (+45° vs. −45°), suggesting adaptation of high-level neurons whose coding is not strictly retino- topic. Our results suggest that perceptual adaptation can rapidly recalibrate people's preferences to fit the faces they see. The results also suggest that average faces are attractive because of their central location in a distribution of faces (i.e., prototypicality), rather than because of any intrinsic appeal of particular physical characteristics. Recalibration of preferences may have important consequences, given the powerful effects of perceived attractiveness on person perception, mate choice, social interactions, and social outcomes for individuals.