Judgment of gender through facial parts

Sex estimation from biometric face photos for forensic purposes

Sex estimation is an important parameter in cases where individuals need to be identified in forensic cases. Biometric photographs are a form of a passport photo with specific dimensions and features established by the International Civil Aviation Organization, which are read and digitally stored in appropriate devices, are used in travel documents, and are of high quality (at least 600 dpi). This study aims to reveal anthropometric data for estimating sex in Turkish adult population from facial images conforming to biometric photography criteria. Within the scope of this study, biometric facial images of a total of 334 participants, 146 female and 188 male, between the ages of 20 and 79 were used. The photos were taken using a Nikon D5100 and flat front lighting from a distance of 1 m. ImageJ 1.50i software was used to process these images. Statistical analysis was performed using descriptive statistics and discriminant analysis tests. Among the 11 variables on sex estimation, the highest accuracy rate of 78.1% was obtained with the measurement between Gonion points. However, sex estimation could be made with an accuracy of 80.5% by including all age groups and all variables, and when age-specific data were used, it was observed that these accuracy rates increased significantly in all three age groups (84.6%, 89.2%, 85.2%, respectively). Therefore, we are suggesting that using age-specific data generated for estimation in different age groups. Consequently, it has been shown that successful sex estimation can be done by formulas derived from biometric facial images in this study.

Attractiveness Evaluation and Identity of Self-face: The Effect of Sexual Dimorphism

The present study aims to explore the influence of masculine/feminine changes on the attractiveness evaluation of one's own face, and examine the relationship of this attractiveness evaluation and the similarities between masculine/feminine faces and original faces. A picture was taken from each participant and considered as his or her original self-face, and a male or female face with an average attractiveness score was adopted as the original other face. Masculinized and feminized transformations of the original faces (self-face, male other face, and female other face) into 100% masculine and feminine faces were produced with morphing software stepping by 2%. Thirty female participants and 30 male participants were asked to complete three tasks, i.e., to “like” or “not like” the original face judgment of a given face compared to the original face, to choose the most attractive face from a morphed facial clip, and to subjectively evaluate the attractiveness and similarity of morphed faces. The results revealed that the acceptable range of masculine/feminine transformation for self-faces was narrower than that for other faces. Furthermore, the attractiveness ratings for masculinized or femininized self-faces were correlated with the similarity scores of the faces with the original self-faces. These findings suggested that attractiveness enhancement of self-face through masculinity/femininity must be within reasonable extent and take into account the similarity between the modified faces and the original self-face.

An ecological measure of rapid and automatic face-sex categorization

Sex categorization is essential for mate choice and social interactions in many animal species. In humans, sex categorization is readily performed from the face. However, clear neural markers of face-sex categorization, i.e., common responses to widely variable individuals from one sex, have not been identified so far in humans. To isolate a direct signature of rapid and automatic face-sex categorization generalized across a wide range of variable exemplars, we recorded scalp electroencephalogram (EEG) from 32 participants (16 females) while they were exposed to variable natural face images from one sex alternating at a rapid rate of 6 Hz (i.e., 6 images per second). Images from the other sex were inserted every 6th stimulus (i.e., at a 1-Hz rate). A robust categorization response to both sex contrasts emerged at 1 Hz and harmonics in the EEG frequency spectrum over the occipito-temporal cortex of most participants. The response was larger for female faces presented among male faces than the reverse, suggesting that the two sex categories are not equally homogenous. This asymmetrical response pattern disappeared for upside-down faces, ruling out the contribution of low-level physical variability across images. Overall, these observations demonstrate that sex categorization occurs automatically after a single glance at natural face images and can be objectively isolated and quantified in the human brain within a few minutes.

The influence of top-down modulation on the processing of direct gaze

Gaze or eye contact is one of the most important nonverbal social cues, which is fundamental to human social interactions. To achieve real time and dynamic face-to-face communication, our brain needs to process another person's gaze direction rapidly and without explicit instruction. In order to explain the fast and spontaneous processing of direct gaze, the fast-track modulator model was proposed. Here, we review recent developments in gaze processing research in the last decade to extend the fast-track modulator model. In particular, we propose that task demand or top-down modulation could play a more crucial role at gaze processing than formerly assumed. We suggest that under different task demands, top-down modulation can facilitate or interfere with the direct gaze effects for early visual processing. The proposed modification of the model extends the role of task demand and its implication on the direct gaze effect, as well as the need to better control for top-down processing in order to better disentangle the role of top-down and bottom-up processing on the direct gaze effect. This article is categorized under: Cognitive Biology > Evolutionary Roots of Cognition Psychology > Perception and Psychophysics Neuroscience > Cognition.

Discrimination of face gender and expression under dual-task conditions

In order to test whether expression and gender can be attended to simultaneously without a cost in accuracy four experiments were carried out using a dual gender-expression task with male and female faces showing different emotional expressions that were backward masked by emotionally neutral faces. In the dual-facial condition the participants had to report both the gender and the expression of the targets. In two control conditions the participant reported either the gender or the expression of the face and indicated whether a surrounding frame was continuous or discontinuous. In Experiments 1-3, with angry and happy targets, asymmetric interference was observed. Gender discrimination, but no expression discrimination, was impaired in the dual-facial condition compared to the corresponding control. This effect was obtained with a between-subjects design in Experiment 1, with a within-subjects design in Experiment 2, and with androgynous face masks in Experiment 3. In Experiments 4a and 4b different target combinations were tested. No decrement of performance in the dual-facial task was observed for either gender or expression discrimination with fearful-disgusted (Experiment 4a) or fearful-happy faces (Experiment 4b). We conclude that the ability to attend simultaneously to gender and expression cues without a decrement in performance depends on the specific combination of expressions to be differentiated between. Happy and angry expressions are usually directed at the perceiver and command preferential attention. Under conditions of restricted viewing such as those of the present study, discrimination of these expressions is prioritized leading to impaired discrimination of other facial properties such as gender.

Configural Information in Gender Categorisation

The role of configural information in gender categorisation was studied by aligning the top half of one face with the bottom half of another. The two faces had the same or different genders. Experiment l shows that participants were slower and made more errors in categorising the gender in either half of these composite faces when the two faces had a different gender, relative to control conditions where the two faces were nonaligned or had the same gender. This result parallels the composite effect for face recognition (Young et al, 1987 Perception16 747–759) and facial-expression recognition (Calder et al, 2000 Journal of Experimental Psychology: Human Perception and Performance26 527–551). Similarly to responses to face identity and expression, the composite effect on gender discrimination was disrupted by inverting the faces (experiment 2). Both experiments also show that the composite paradigm is sensitive to general contextual interference in gender categorisation.

Facial Structure Predicts Sexual Orientation in Both Men and Women

Biological models have typically framed sexual orientation in terms of effects of variation in fetal androgen signaling on sexual differentiation, although other biological models exist. Despite marked sex differences in facial structure, the relationship between sexual orientation and facial structure is understudied. A total of 52 lesbian women, 134 heterosexual women, 77 gay men, and 127 heterosexual men were recruited at a Canadian campus and various Canadian Pride and sexuality events. We found that facial structure differed depending on sexual orientation; substantial variation in sexual orientation was predicted using facial metrics computed by a facial modelling program from photographs of White faces. At the univariate level, lesbian and heterosexual women differed in 17 facial features (out of 63) and four were unique multivariate predictors in logistic regression. Gay and heterosexual men differed in 11 facial features at the univariate level, of which three were unique multivariate predictors. Some, but not all, of the facial metrics differed between the sexes. Lesbian women had noses that were more turned up (also more turned up in heterosexual men), mouths that were more puckered, smaller foreheads, and marginally more masculine face shapes (also in heterosexual men) than heterosexual women. Gay men had more convex cheeks, shorter noses (also in heterosexual women), and foreheads that were more tilted back relative to heterosexual men. Principal components analysis and discriminant functions analysis generally corroborated these results. The mechanisms underlying variation in craniofacial structure--both related and unrelated to sexual differentiation--may thus be important in understanding the development of sexual orientation.

Aging affects sex categorization of male and female faces in opposite ways

Faces are rich in social information; they easily give away a person's sex, approximate age, feelings, or focus of attention. Past research has mostly focused on investigating the distinct facial signals and perceptual mechanisms that allow us to categorize faces on these individual dimensions. It is less well understood how the different kinds of facial information interact. Here we investigated how the age of a face affects the ease with which young and older adults categorize its sex. Disconfirming everyday intuition, we showed that sex categorization is not generally hampered for older faces. Although categorization of female faces took progressively more time with increasing age, the opposite was found for male faces (Experiment 1). Differential effects of stimulus blurring and inversion for male and female faces of different ages (Experiment 2) strongly suggest one feature as a crucial mediator of the interdependence of age and sex perception - skin texture.

Face features and face configurations both contribute to visual crowding

Crowding refers to the inability to recognize an object in peripheral vision when other objects are presented nearby (Whitney & Levi Trends in Cognitive Sciences, 15, 160-168, 2011). A popular explanation of crowding is that features of the target and flankers are combined inappropriately when they are located within an integration field, thus impairing target recognition (Pelli, Palomares, & Majaj Journal of Vision, 4(12), 12:1136-1169, 2004). However, it remains unclear which features of the target and flankers are combined inappropriately to cause crowding (Levi Vision Research, 48, 635-654, 2008). For example, in a complex stimulus (e.g., a face), to what extent does crowding result from the integration of features at a part-based level or at the level of global processing of the configural appearance? In this study, we used a face categorization task and different types of flankers to examine how much the magnitude of visual crowding depends on the similarity of face parts or of global configurations. We created flankers with face-like features (e.g., the eyes, nose, and mouth) in typical and scrambled configurations to examine the impacts of part appearance and global configuration on the visual crowding of faces. Additionally, we used "electrical socket" flankers that mimicked first-order face configuration but had only schematic features, to examine the extent to which global face geometry impacted crowding. Our results indicated that both face parts and configurations contribute to visual crowding, suggesting that face similarity as realized under crowded conditions includes both aspects of facial appearance.

Female face preference in 4-month-olds: the importance of hairline

At 3-4 months of age, infants respond to gender information in human faces. Specifically, young infants display a visual preference toward female over male faces. In three experiments, using a visual preference task, we investigated the role of hairline information in this bias. In Experiment 1, we presented male and female composite faces with similar hairstyles to 4-month-olds and observed a preference for female faces. In Experiment 2, the faces were presented, but in this instance, without hairline cues, and the preference was eliminated. In Experiment 3, using the same cropping to eliminate hairline cues, but with feminized female faces and masculinized male faces, infants' preference toward female faces was still not in evidence. The findings show that hairline information is important in young infants' preferential orientation toward female faces.

Gender recognition from unconstrained and articulated human body

Gender recognition has many useful applications, ranging from business intelligence to image search and social activity analysis. Traditional research on gender recognition focuses on face images in a constrained environment. This paper proposes a method for gender recognition in articulated human body images acquired from an unconstrained environment in the real world. A systematic study of some critical issues in body-based gender recognition, such as which body parts are informative, how many body parts are needed to combine together, and what representations are good for articulated body-based gender recognition, is also presented. This paper also pursues data fusion schemes and efficient feature dimensionality reduction based on the partial least squares estimation. Extensive experiments are performed on two unconstrained databases which have not been explored before for gender recognition.

A critical role of holistic processing in face gender perception

Whether face gender perception is processed by encoding holistic (whole) or featural (parts) information is a controversial issue. Although neuroimaging studies have identified brain regions related to face gender perception, the temporal dynamics of this process remain under debate. Here, we identified the mechanism and temporal dynamics of face gender perception. We used stereoscopic depth manipulation to create two conditions: the front and behind condition. In the front condition, facial patches were presented stereoscopically in front of the occluder and participants perceived them as disjoint parts (featural cues). In the behind condition, facial patches were presented stereoscopically behind the occluder and were amodally completed and unified in a coherent face (holistic cues). We performed three behavioral experiments and one electroencephalography experiment, and compared the results of the front and behind conditions. We found faster reaction times (RTs) in the behind condition compared with the front, and observed priming effects and aftereffects only in the behind condition. Moreover, the EEG experiment revealed that face gender perception is processed in the relatively late phase of visual recognition (200-285 ms). Our results indicate that holistic information is critical for face gender perception, and that this process occurs with a relatively late latency.

Altering second-order configurations reduces the adaptation effects on early face-sensitive event-related potential components

The spatial distances among the features of a face are commonly referred to as second-order relations, and the coding of these properties is often regarded as a cornerstone in face recognition. Previous studies have provided mixed results regarding whether the N170, a face-sensitive component of the event-related potential, is sensitive to second-order relations. Here we investigated this issue in a gender discrimination paradigm following long-term (5 s) adaptation to normal or vertically stretched male and female faces, considering that the latter manipulation substantially alters the position of the inner facial features. Gender-ambiguous faces were more likely judged to be female following adaptation to a male face and vice versa. This aftereffect was smaller but statistically significant after being adapted to vertically stretched when compared to unstretched adapters. Event-related potential recordings revealed that adaptation effects measured on the amplitude of the N170 show strong modulations by the second-order relations of the adapter: reduced N170 amplitude was observed, however, this reduction was smaller in magnitude after being adapted to stretched when compared to unstretched faces. These findings suggest early face-processing, as reflected in the N170 component, proceeds by extracting the spatial relations of inner facial features.

The role of inner and outer face parts in holistic processing: a developmental study

The effects of inner-outer feature interactions with unfamiliar faces were investigated in 6- and 10-year-old children and adults (20-30 years) to determine their contribution in holistic face vision. Participants completed a two-alternative forced-choice (2AFC) task under two conditions. The congruent condition used whole, inner-only, and outer-only stimuli. The incongruent condition used stimuli combining the inner features from one face with outer features from a novel face, or vice versa. Results yielded strong congruency effects which were moderated by pronounced feature-type asymmetries specific to developmental stage. Adults showed an inner-feature preference during congruent trials, but no asymmetry for incongruent trials. Children showed no asymmetry for congruent trials, but an outer-feature preference for incongruent trials. These findings concur with recent theoretical developments indicating that adults and children are likely to differ in the types of feature-specific information they preferentially encode in face perception, and that holistic effects are moderated differently in adults and children as a function of feature type.

Hands as sex cues: sensitivity measures, male bias measures, and implications for sex perception mechanisms

Sex perceptions, or more particularly, sex discriminations and sex categorisations, are high-value social behaviours. They mediate almost all inter-personal interactions. The two experiments reported here had the aim of exploring some of the basic characteristics of the processes giving rise to sex perceptions. Experiment 1 confirmed that human hands can be used as a cue to an individual's sex even when colour and texture cues are removed and presentations are brief. Experiment 1 also showed that when hands are sexually ambiguous observers tend to classify them as male more often than female. Experiment 2 showed that "male bias" arises not from sensitivity differences but from differences in response biases. Observers are conservative in their judgements of targets as female but liberal in their judgements of targets as male. These data, combined with earlier reports, suggest the existence of a sex-perception space that is cue-invariant.

Photogrammetric analysis of eyebrow and upper eyelid dimensions in South Indians and Malaysian South Indians

BACKGROUND

The eyebrow and eyelid are important sexually dimorphic and ethnic features of the face. In cosmetic surgery, maintenance of these landmarks is important to obtaining satisfactory results.

OBJECTIVES

The authors quantify the dimension and position of the eyebrow and eyelid in South Indians and Malaysian South Indians and assess whether significant differences exist between the sexes and ethnic groups.

METHODS

Evaluation of eyebrow and upper eyelid was performed on standardized photographs of 200 South Indian and 200 Malaysian South Indian subjects, aged 18 to 26 years. We measured eyebrow thickness, apex to lateral limbus distance, apex to lateral canthus distance, interbrow distance, medial end of the eyebrow to medial canthus, lateral end of the eyebrow to lateral canthus, eyebrow height, eyebrow apex inclination, and pretarsal skin height. The measured values were evaluated by an independent t test. We also assessed the prevalence of double lid crease and types of epicanthus and eyebrow apex positions.

RESULTS

A significant difference was found between women in the South Indian and Malaysian South Indian groups for eyebrow apex to lateral limbus distance, medial end to medial canthus, pretarsal skin height, eyebrow height, and eyebrow apex inclination. Male groups showed significant ethnic difference for eyebrow apex to lateral limbus distance. Sexual dimorphism was found for all measurement categories. A double crease fold appeared in 99% of the subjects. Only epicanthus tarsalis (95%) and epicanthus superciliaris (5%) appeared in the subjects. Four types of eyebrow apex position were found.

CONCLUSIONS

Ethnic and sex differences exist for eyebrow and eyelid dimensions in the 2 groups we studied. Knowledge of these trends is significant during surgical planning to obtain ideal outcomes.

The asymmetric distribution of informative face information during gender recognition

Recognition of the gender of a face is important in social interactions. In the current study, the distribution of informative facial information was systematically examined during gender judgment using two methods, Bubbles and Focus windows techniques. Two experiments found that the most informative information was around the eyes, followed by the mouth and nose. Other parts of the face contributed to the gender recognition but were less important. The left side of the face was used more during gender recognition in two experiments. These results show mainly areas around the eyes are used for gender judgment and demonstrate perceptual asymmetry with a normal (non-chimeric) face.

Sex matters: Neural correlates of voice gender perception

The basis for different neural activations in response to male and female voices as well as the question, whether men and women perceive male and female voices differently, has not been thoroughly investigated. Therefore, the aim of the present study was to examine the behavioral and neural correlates of gender-related voice perception in healthy male and female volunteers. fMRI data were collected while 39 participants (19 female) were asked to indicate the gender of 240 voice stimuli. These stimuli included recordings of 3-syllable nouns as well as the same recordings pitch-shifted in 2, 4 and 6 semitone steps in the direction of the other gender. Data analysis revealed a) equal voice discrimination sensitivity in men and women but better performance in the categorization of opposite-sex stimuli at least in men, b) increased responses to increasing gender ambiguity in the mid cingulate cortex and bilateral inferior frontal gyri, and c) stronger activation in a fronto-temporal neural network in response to voices of the opposite sex. Our results indicate a gender specific processing for male and female voices on a behavioral and neuronal level. We suggest that our results reflect higher sensitivity probably due to the evolutionary relevance of voice perception in mate selection.

Categorization in ASD: The Role of Typicality and Development

There is a growing amount of evidence suggesting that individuals with autism spectrum disorders (ASD) differ in the way in which they cognitively process information. A critical aspect of cognitive processing that is receiving more attention in studies of ASD is categorization. The studies presented here examined the effect of typicality on categorization of objects and gender in high-functioning children, adolescents, and adults with ASD and matched controls. The ASD and control groups showed improved categorization throughout the lifespan for typical and somewhat typical object category members and typical gender faces. However, individuals with ASD took more time to categorize atypical object category members and were less accurate in categorizing atypical gender faces from 8-12 years through adulthood. The implications of these results for teaching categories and category labels to individuals with ASD will be discussed.

Motion can amplify the face-inversion effect

The face-inversion effect (FIE) refers to increased response times or error rates for faces that are presented upside-down relative to those seen in a canonical, upright orientation. Here we report one situation in which this FIE can be amplified when observers are shown dynamic facial expressions, rather than static facial expressions. In two experiments observers were asked to assign gender to a random sequence of un-degraded static or moving faces. Each face was seen both upright and inverted. For static images, this task led to little or no effect of inversion. For moving faces, the cost of inversion was a response time increase of approximately 100 ms relative to upright. Motion thus led to a disadvantage in the context of inversion. The fact that such motion could not be ignored in favour of available form cues suggests that dynamic processing may be mandatory. In two control experiments a difference between static and dynamic inversion was not observed for whole-body stimuli or for human-animal decisions. These latter findings suggest that the processing of upside-down movies is not always more difficult for the visual system than the processing of upside-down static images.

Infant preference for individual women's faces extends to girl prototype faces

Three- to 4-month-old infants reared by female caregivers display a spontaneous preference for individual adult women's over men's faces. Here we report that this preference extends to prototype girl over boy faces. The findings suggest transfer of gender-diagnostic facial information from individual adult to prototype child faces.

Monkeys recognize the faces of group mates in photographs

Nonhuman primates possess a highly developed capacity for face recognition, which resembles the human capacity both cognitively and neurologically. Face recognition is typically tested by having subjects compare facial images, whereas there has been virtually no attention to how they connect these images to reality. Can nonhuman primates recognize familiar individuals in photographs? Such facial identification was examined in brown or tufted capuchin monkeys (Cebus apella), a New World primate, by letting subjects categorize facial images of conspecifics as either belonging to the in-group or out-group. After training on an oddity task with four images on a touch screen, subjects correctly identified one in-group member as odd among three out-group members, and vice versa. They generalized this knowledge to both new images of the same individuals and images of juveniles never presented before, thus suggesting facial identification based on real-life experience with the depicted individuals. This ability was unexplained by potential color cues because the same results were obtained with grayscale images. These tests demonstrate that capuchin monkeys, like humans, recognize whom they see in a picture.

Gaze behavior in face comparison: the roles of sex, task, and symmetry

Knowing where people look on a face provides an objective insight into the information entering the visual system and into cognitive processes involved in face perception. In the present study, we recorded eye movements of human participants while they compared two faces presented simultaneously. Observers' viewing behavior and performance was examined in two tasks of parametrically varying difficulty, using two types of face stimuli (sex morphs and identity morphs). The frequency, duration, and temporal sequence of fixations on previously defined areas of interest in the faces were analyzed. As was expected, viewing behavior and performance varied with difficulty. Interestingly, observers compared predominantly the inner halves of the face stimuli-a result inconsistent with the general left-hemiface bias reported for single faces. Furthermore, fixation patterns and performance differed between tasks, independently of stimulus type. Moreover, we found differences in male and female participants' viewing behaviors, but only when the sex of the face stimuli was task relevant.

Effect of partial occlusion on newborns' face preference and recognition

Many studies have shown that newborns prefer (e.g. Goren, Sarty & Wu, 1975; Valenza, Simion, Macchi Cassia & Umiltà, 1996) and recognize (e.g. Bushnell, Say & Mullin, 1989; Pascalis & de Schonen, 1994) faces. However, it is not known whether, at birth, faces are still preferred and recognized when some of their parts are not visible because hindered by other configurations, that is when faces are partly occluded. Also, it is not known whether newborns' preference for an upright over an inverted face and newborns' face recognition are differentially affected depending on the salience of the occluded face features. Seventy-seven newborns (mean age of 43.5 hrs) were tested using the preferential looking (Experiment 1) and the habituation techniques (Experiment 2). Results demonstrated that newborns prefer and recognize occluded faces even if some portions of them are not available, at least when the hindered features are not salient. On the contrary, these abilities are affected by obscuring high salience facial features (i.e. eyes). However, while in the case of face detection, eyes occlusion completely prevented newborns' face detection, in the case of face recognition an analogous stimulus manipulation heavily impaired, but did not totally preclude, newborns' recognition performance. The data collected improve our comprehension of newborns' way of processing and encoding information to detect and recognize faces.

Is medial canthal tilt a powerful cue for facial attractiveness?

PURPOSE

To identify medial canthal tilt as an important cue used by judges in evaluating human female facial attractiveness.

METHODS

An experimental study was conducted with the use of SuperLab Pro, and judges had to make a forced choice between unmodified faces and faces that had their medial canthal tilt accentuated through the use of Adobe Photoshop CS.

RESULTS

Female faces with accentuated medial canthal tilt were preferred 93% of the time over unmodified faces (p < 0.0001).

CONCLUSIONS

Medial canthal tilt appears to be a powerful cue used in judging human female facial attractiveness. Its power may be due to its relation to the neotenic and sexually dimorphic cue of palpebral fissure inclination.

Visual search for orientation of faces by a chimpanzee (Pan troglodytes): face-specific upright superiority and the role of facial configural properties

A previous experiment showed that a chimpanzee performed better in searching for a target human face that differed in orientation from distractors when the target had an upright orientation than when targets had inverted or horizontal orientation [Tomonaga (1999a) Primate Res 15:215-229]. This upright superiority effect was also seen when using chimpanzee faces as targets but not when using photographs of a house. The present study sought to extend these results and explore factors affecting the face-specific upright superiority effect. Upright superiority was shown in a visual search for orientation when caricaturized human faces and dog faces were used as stimuli for the chimpanzee but not when shapes of a hand and chairs were presented. Thus, the configural properties of facial features, which cause an inversion effect in face recognition in humans and chimpanzees, were thought to be a source of the upright superiority effect in the visual search process. To examine this possibility, various stimuli manipulations were introduced in subsequent experiments. The results clearly show that the configuration of facial features plays a critical role in the upright superiority effect, and strongly suggest similarity in face processing in humans and chimpanzees.

How accurately do young children and adults discriminate the gender of natural faces?

The effects of gender-relevant facial features and hairstyles on discrimination of sex of photographed men and women were examined. The stimuli were 36 photographs of natural faces: 9 masculine-males, 9 feminine-males, 9 masculine-females, and 9 feminine-females. Each of the nine faces had one of three hairstyles, hair concealed, short hair, or long hair. 33 children (M age=5:10) and 28 adults were asked to identify the sex of each stimulus. Children had difficulties with cross-gender faces and cross-gender hairstyles, such as a feminine-male face with long hair. Adults' discriminations were accurate except for masculine-female faces, while children's decisions depended both on hairstyle and internal facial features. Children's discriminations might be based both on their perceptual skill in detecting critical visual features and their knowledge of men and women.

Face identification in the near-absence of focal attention

In contrast to artificial geometric shapes, natural scenes and face-gender can be processed even when spatial attention is not fully available. In this study, we investigate whether a finer discrimination, at the level of the individual, is possible in the near-absence of focal attention. Using the paradigm, subjects performed face identification on faces of celebrities and relatively unfamiliar individuals, along with a task that is known to engage spatial attention. We find that face-identification performance is only modestly impaired under dual-task conditions. These results suggest that the visual system is well able to make complex judgments of natural stimuli, even when attention is not fully available.

The role of facial attractiveness and facial masculinity/femininity in sex classification of faces

We tested whether adults (experiment 1) and 4 - 5-year-old children (experiment 2) identify the sex of highly attractive faces faster and more accurately than not very attractive faces in a reaction-time task. We also assessed whether facial masculinity/femininity facilitated identification of sex. Results showed that attractiveness facilitated adults' sex classification of both female and male faces and children's sex classification of female, but not male, faces. Moreover, attractiveness affected the speed and accuracy of sex classification independently of masculinity/femininity. High masculinity in male faces, but not high femininity in female faces, also facilitated sex classification for both adults and children. These findings provide important new data on how the facial cues of attractiveness and masculinity/femininity contribute to the task of sex classification and provide evidence for developmental differences in how adults and children use these cues. Additionally, these findings provide support for Langlois and Roggman's (1990 Psychological Science 1 115 121) averageness theory of attractiveness.

Is face distinctiveness gender based?

Two experiments were carried out to study the role of gender category in evaluations of face distinctiveness. In Experiment 1, participants had to evaluate the distinctiveness and the femininity-masculinity of real or artificial composite faces. The composite faces were created by blending either faces of the same gender (sexed composite faces, approximating the sexed prototypes) or faces of both genders (nonsexed composite faces, approximating the face prototype). The results show that the distinctiveness ratings decreased as the number of blended faces increased. Distinctiveness and gender ratings did not covary for real faces or sexed composite faces, but they did vary for nonsexed composite faces. In Experiment 2, participants were asked to state which of two composite faces, one sexed and one nonsexed, was more distinctive. Sexed composite faces were selected less often. The results are interpreted as indicating that distinctiveness is based on sexed prototypes. Implications for face recognition models are discussed.

Sex differences in face gender recognition in humans

Human faces are ecologically-salient stimuli. Face sex is particularly relevant for human interactions and face gender recognition is an extremely efficient cognitive process that is acquired early during childhood. To measure the minimum information required for correct gender classification, we have used a pixelation filter and reduced frontal pictures (28,672 pixels) of male and female faces to 7168, 1792, 448 and 112 pixels. We then addressed the following questions: Is gender recognition of male and female faces equally efficient? Are male and female subjects equally efficient at recognising face gender? We found a striking difference in categorisation of male and female faces. Categorisation of female faces reduced to 1792 pixels is at chance level whereas categorisation of male faces is above chance even for 112 pixel images. In addition, the same difference in the efficiency of categorisation of male and female faces was detected using a Gaussian noise filter. A clear sex difference in the efficiency of face gender categorisation was detected as well. Female subject were more efficient in recognising female faces. These results indicate that recognition of male and female faces are different cognitive processes and that in general females are more efficient in this cognitive task.

Recognition and sex categorization of adults' and children's faces: examining performance in the absence of sex-stereotyped cues

The ability of children and adults to classify the sex of children's and adults' faces using only the biologically based internal facial structure was investigated. Face images of 7- to 10-year-old children and of adults in their 20s were edited digitally to eliminate hairstyle and clothing cues to sex. Seven-year-olds, nine-year-olds, and adults classified a subset of these faces by sex and were asked, subsequently, to recognize the faces from among the entire set of faces. This recognition task was designed to assess the relationship between categorization and recognition accuracy. Participants categorized the adult faces by sex at levels of accuracy varying from just above chance (7-year-olds) to nearly perfect (adults). All participant groups performed less accurately for children's faces than for adults' faces. The 7-year-olds were unable to classify the children's faces by sex at levels above chance. Finally, the faces of children and adults were equally recognizable--a finding that has theoretical implications for understanding the relationship between categorizing and identifying faces.

Discriminating the sex of faces by 6- and 8-mo.-old infants

The goal of this study was to ascertain at what age infants could discriminate male and female faces using only the internal features of the face. The habituation-dishabituation technique was used to estimate infants' discrimination between male and female faces. Analysis showed that 8-mo.-old infants discriminated female and male faces, whereas 6-mo.-old infants did not, but showed an asymmetry in discrimination. 6-mo.-old infants who were habituated to the female face fixated consistently longer on the novel male face in test trials, so sex discrimination was complete but not observed after habituation to male faces. Data are discussed in relation to the role of experience in face discrimination.

Identification of gender in domestic-cat faces with and without training: perceptual learning of a natural categorization task

Three experiments were conducted to determine whether human observers could identify the gender of 40 domestic cats (20 female, 20 male) depicted in individual color photographs. In experiment 1a, observers performed at chance for photographs depicting whole cats, cat heads (bodies occluded), and cat bodies (heads occluded). Experiment 1b showed that chance performance was also obtained when the photographs were full-face close-ups of the cats. Experiment 2a revealed that even with gender-identification training on 30 (15 female, 15 male) of the 40 face close-ups, observers were unable to generalize their training to reliably identify the gender of the 10 remaining test faces (5 female, 5 male). However, experiment 2b showed that gender-identification training with the 14 most accurately identified faces from experiment 1b (7 female, 7 male) was successful in raising gender identification of the 10 test faces above chance. Experiments 3a and 3b extended this facilitative effect of gender-identification training to a population of animal-care workers. The findings indicate that, with appropriate training, human observers can identify the gender of cat faces at an above-chance level. A perceptual category learning account emphasizing the on-line formation of differentiated male versus female prototypes during training is offered as an explanation of the findings.

The perception of face gender: the role of stimulus structure in recognition and classification

The perception of face gender was examined in the context of extending "face space" models of human face representations to include the perceptual categories defined by male and female faces. We collected data on the recognizability, gender classifiability (reaction time to classify a face as male/female), attractiveness, and masculinity/femininity of individual male and female faces. Factor analyses applied separately to the data for male and female faces yielded the following results. First, for both male and female faces, the recognizability and gender classifiability of faces were independent--a result inconsistent with the hypothesis that both recognizability and gender classifiability depend on a face's "distance" from the subcategory gender prototype. Instead, caricatured aspects of gender (femininity/masculinity ratings) related to the gender classifiability of the faces. Second, facial attractiveness related inversely to face recognizability for male, but not for female, faces--a result that resolves inconsistencies in previous studies. Third, attractiveness and femininity for female faces were nearly equivalent, but attractiveness and masculinity for male faces were not equivalent. Finally, we applied principal component analysis to the pixel-coded face images with the aim of extracting measures related to the gender classifiability and recognizability of individual faces. We incorporated these model-derived measures into the factor analysis with the human rating and performance measures. This combined analysis indicated that face recognizability is related to the distinctiveness of a face with respect to its gender subcategory prototype. Additionally, the gender classifiability of faces related to at least one caricatured aspect of face gender.

An 'other-race effect' for categorizing faces by sex

It is well-known that people recognize faces of their own race more accurately than faces of other races-a phenomenon often referred to as the 'other-race effect'. Using brief presentations of faces, we show a similar effect for the task of discriminating the sex of a face. Specifically, Caucasian observers discriminated male and female Caucasian faces more accurately/efficiently than did Oriental observers, and Oriental observers discriminated male and female Japanese faces more accurately/efficiently than did Caucasian observers. This result indicates that, under suboptimal viewing conditions, the identification of even the most salient of facial characteristics-face sex-is impaired for other-race faces. This finding suggests, also, that the nature and diversity of our experience with faces may affect not only the quality of the face representation for later access by recognition processes, but also the efficiency of a perceptual discrimination process. Intriguingly, too, we found that female observers, for both races tested, were considerably more accurate at the sex classification task than were male observers.