Bernard Tiddeman

Prototyping and transforming facial textures for perception research

Transforming facial images along perceived dimensions (such as age, gender, race, or health) has application in areas as diverse as psychology, medicine, and forensics. We can use prototype images to define the salient features of a particular face classification (for example, European female adult or East-Asian male child). We then use the differences between two prototypes to define an axis of transformation, such as younger to older. By applying these changes to a given input face, we can change its apparent age, race, or gender. Psychological investigations reveal a limitation with existing methods thats particularly apparent when changing the age of faces. We relate the problem to the loss of facial textures (such as stubble and wrinkles) in the prototypes due to the blending process. We review the existing face prototyping and transformation methods and present a new, wavelet-based method for prototyping and transforming facial textures.

Correlated preferences for facial masculinity and ideal or actual partner's masculinity

Studies of womens preferences for male faces have variously reported preferences for masculine faces, preferences for feminine faces and no effect of masculinity–femininity on male facial attractiveness. It has been suggested that these apparently inconsistent findings are, at least partly, due to differences in the methods used to manipulate the masculinity of face images or individual differences in attraction to facial cues associated with youth. Here, however, we show that womens preferences for masculinity manipulated in male faces using techniques similar to the three most widely used methods are positively inter-related. We also show that womens preferences for masculine male faces are positively related to ratings of the masculinity of their actual partner and their ideal partner. Correlations with partner masculinity were independent of real and ideal partner age, which were not associated with facial masculinity preference. Collectively, these findings suggest that variability among studies in their findings for womens masculinity preferences reflects individual differences in attraction to masculinity rather than differences in the methods used to manufacture stimuli, and are important for the interpretation of previous and future studies of facial masculinity.

Menstrual cycle, pregnancy and oral contraceptive use alter attraction to apparent health in faces

Previous studies demonstrating changes in womens face preferences have emphasized increased attraction to cues to possible indirect benefits (e.g. heritable immunity to infection) that coincides with periods of high fertility (e.g. the late follicular phase of the menstrual cycle). By contrast, here we show that when choosing between composite faces with raised or lowered apparent health, womens preferences for faces that are perceived as healthy are (i) stronger during the luteal phase of the menstrual cycle than during the late follicular, fertile phase, (ii) stronger in pregnant women than in non–pregnant women and (iii) stronger in women using oral contraceptives than in women with natural menstrual cycles. Change in preference for male faces was greater for short– than long–term relationships. These findings indicate raised progesterone level is associated with increased attraction to facial cues associated with possible direct benefits (e.g. low risk of infection) and suggest that womens face preferences are influenced by adaptations that compensate for weakened immune system responses during pregnancy and reduce the risk of infection disrupting foetal development.

Symmetry Is Related to Sexual Dimorphism in Faces: Data Across Culture and Species

Background Many animals both display and assess multiple signals. Two prominently studied traits are symmetry and sexual dimorphism, which, for many animals, are proposed cues to heritable fitness benefits. These traits are associated with other potential benefits, such as fertility. In humans, the face has been extensively studied in terms of attractiveness. Faces have the potential to be advertisements of mate quality and both symmetry and sexual dimorphism have been linked to the attractiveness of human face shape. Methodology/Principal Findings Here we show that measurements of symmetry and sexual dimorphism from faces are related in humans, both in Europeans and African hunter-gatherers, and in a non-human primate. Using human judges, symmetry measurements were also related to perceived sexual dimorphism. In all samples, symmetric males had more masculine facial proportions and symmetric females had more feminine facial proportions. Conclusions/Significance Our findings support the claim that sexual dimorphism and symmetry in faces are signals advertising quality by providing evidence that there must be a biological mechanism linking the two traits during development. Such data also suggests that the signalling properties of faces are universal across human populations and are potentially phylogenetically old in primates.

Facial cues of dominance modulate the short-term gaze-cuing effect in human observers

Responding appropriately to gaze cues is essential for fluent social interaction, playing a crucial role in social learning, collaboration, threat assessment and understanding others’ intentions. Previous research has shown that responses to gaze cues can be studied by investigating the gaze-cuing effect (i.e. the tendency for observers to respond more quickly to targets in locations that were cued by others’ gaze than to uncued targets). A recent study demonstrating that macaques demonstrate larger gaze-cuing effects when viewing dominant conspecifics than when viewing subordinate conspecifics suggests that cues of dominance modulate the gaze-cuing effect in at least one primate species. Here, we show a similar effect of facial cues associated with dominance on gaze cuing in human observers: at short viewing times, observers demonstrated a greater cuing effect for gaze cues from masculinized (i.e. dominant) faces than from feminized (i.e. subordinate) faces. Moreover, this effect of facial masculinity on gaze cuing decreased as viewing time was increased, suggesting that the effect is driven by involuntary responses. Our findings suggest that the mechanisms that underpin reflexive gaze cuing evolved to be sensitive to facial cues of others’ dominance, potentially because such differential gaze cuing promoted desirable outcomes from encounters with dominant individuals.

Facial attractiveness judgements reflect learning of parental age characteristics

Mate preferences are shaped by infant experience of parental characteristics in a wide variety of species. Similar processes in humans may lead to physical similarity between parents and mates, yet this possibility has received little attention. The age of parents is one salient physical characteristic that offspring may attend to. The current study used computer–graphic faces to examine how preferences for age in faces were influenced by parental age. We found that women born to ‘old’ parents (over 30) were less impressed by youth, and more attracted to age cues in male faces than women with ‘young’ parents (under 30). For men, preferences for female faces were influenced by their mothers age and not their fathers age, but only for long–term relationships. These data indicate that judgements of facial attractiveness in humans reflect the learning of parental characteristics.

The relationship between shape symmetry and perceived skin condition in male facial attractiveness

Studies have shown that male faces high in symmetry are judged more attractive than faces low in symmetry even in images where visual cues to facial symmetry are reduced. These findings suggest that there are correlates of facial symmetry that influence male facial attractiveness independently of symmetry itself. Apparent healthiness of facial skin is one factor that may influence male facial attractiveness and covary with facial symmetry. Here, using real and composite male faces, we found that males with symmetric faces were perceived as having healthier facial skin than males with relatively asymmetric faces (Study 1), and that facial colour and texture cues were sufficient to maintain an attractiveness–symmetry relationship when the influence of facial shape was minimised (Study 2). These findings suggest that colour and texture cues contribute to the relationship between

Emotional expression modulates perceived gaze direction

Gaze perception is an important social skill, as it portrays information about what another person is attending to. Gaze direction has been shown to affect interpretation of emotional expression. Here the authors investigate whether the emotional facial expression has a reciprocal influence on interpretation of gaze direction. In a forced-choice yes-no task, participants were asked to judge whether three faces expressing different emotions (anger, fear, happiness, and neutral) in different viewing angles were looking at them or not. Happy faces were more likely to be judged as looking at the observer than were angry, fearful, or neutral faces. Angry faces were more often judged as looking at the observer than were fearful and neutral expressions. These findings are discussed on the background of approach and avoidance orientation of emotions and of the self-referential positivity bias.

Three-dimensional geometric morphometrics applied to the study of children with cleft lip and/or palate from the North East of England.

This prospective cross-sectional, case-controlled morphometric study investigated three-dimensional facial morphological variation among and between 8- and 12-year-old children [40 with a unilateral cleft lip and palate (UCLP), 23 with a unilateral cleft lip and alveolus (UCLA), 19 with a bilateral cleft lip and palate (BCLP), and 21 with an isolated cleft palate (ICP)]. Eighty gender- and age-matched individuals comprised the control group. The mean shape of each group was computed using generalized Procrustes analysis (GPA). Differences in shape between group means were assessed using multivariate analysis of variance and permutation tests, and shape differences were visualized for interpretation using warpings of the grand mean shape and transformation grids computed using thin plate splines (TPA). Statistically significant differences between the mean facial shapes and forms (shape plus size) of all groups were found. The greatest difference was in the BCLP group and the second greatest in the UCLP group. The study of asymmetry indicated different degrees and differences in the nature of asymmetry that characterize different cleft lip and palate (CLP) deformities. Principal component analyses (PCA) of form space and of means, plus reflected means, were informative with respect to the differences in facial size and shape and asymmetry between these groups. The results highlight differences in the aetiology of ICP and CLP groups and underline the potential value of statistical shape analysis in assessing the outcomes of CLP treatment.

Towards Realism in Facial Image Transformation: Results of a Wavelet MRF Method

The ability to transform facial images between groups (e.g. from young to old, or from male to female) has applications in psychological research, police investigations, medicine and entertainment. Current techniques suffer either from a lack of realism due to unrealistic or inappropriate textures in the output images, or a lack of statistical validity, e.g. by using only a single example image for training. This paper describes a new method for improving the realism and effectiveness of facial transformations (e.g. ageing, feminising etc.) of individuals. The method aims to transform low resolution image data using the mean differences between the two groups, but converges on more specific texture features at the finer resolutions. We separate high and low resolution information by transforming the image into a wavelet domain. At each point we calculate a mapping from the original set to the target set based on the probability distributions of the input and output wavelet values. These distributions are estimated from the example images, using the assumption that the distribution depends on the values in a local neighbourhood of the point (the Markov Random Field (MRF) assumption). We use a causal neighbourhood that spans multiple coarser scales of the wavelet pyramid. The distributions are estimated by smoothing the histogram of example values. By increasing the smoothing of the histograms at coarser resolutions we are able to maintain perceived identity across the transforms while producing realistic fine-scale textures. We use perceptual testing to validate the new method, and the results show that it can produce more accurate shifts in perceived age and an increase in realism.