What’s in a Smile? Initial results of multilevel principal components analysis of facial shape and image texture

Multilevel principal components analysis (mPCA) has previously been shown to provide a simple and straightforward method of forming point distribution models that can be used in (active) shape models. Here we extend the mPCA approach to model image texture as well as shape. As a test case, we consider a set of (2D frontal) facial images from a group of 80 Finnish subjects (34 male; 46 female) with two different facial expressions (smiling and neutral) per subject. Shape (in terms of landmark points) and image texture are considered separately in this initial analysis. Three-level models are constructed that contain levels for biological sex, “within-subject” variation (i.e., facial expression), and “between-subject” variation (i.e., all other sources of variation). By considering eigenvalues, we find that the order of importance as sources of variation for facial shape is: facial expression (47.5%), between-subject variations (45.1%), and then biological sex (7.4%). By contrast, the order for image texture is: between-subject variations (55.5%), facial expression (37.1%), and then biological sex (7.4%). The major modes for the facial expression level of the mPCA models clearly reflect changes in increased mouth size and increased prominence of cheeks during smiling for both shape and texture. Even subtle effects such as changes to eyes and nose shape during smile are seen clearly. The major mode for the biological sex level of the mPCA models similarly relates clearly to changes between male and female. Model fits yield “scores” for each principal component that show strong clustering for both shape and texture by biological sex and facial expression at appropriate levels of the model. We conclude that mPCA correctly decomposes sources of variation due to biological sex and facial expression (etc.) and that it provides a reliable method of forming models of both shape and image texture

A computerized craniofacial reconstruction method for an unidentified skull based on statistical shape models

Craniofacial reconstruction (CFR) has been widely used to produce the facial appearance of an unidentified skull in the realm of forensic science. Many studies have indicated that the computerized CFR approach is fast, flexible, consistent and objective in comparison to the traditional manual CFR approach. This paper presents a computerized CFR system called CFRTools, which features a CFR method based on a statistical shape model (SSM) of living human head models. Given an unidentified skull, a geometrically-similar template skull is chosen as a template, and a non-registration method is used to improve the accuracy of the construction of dense corresponding vertices through the alignment of the template and the unidentified skull. Generalized Procrustes analysis (GPA) and principal component analysis (PCA) are carried out to construct the skull and face SSMs. The sex of the unidentified skull is then predicted based on skull SSM and centroid size, rather than geometric measurements based on anatomical landmarks. Furthermore, a craniofacial morphological relationship which is learnt from the principal component (PC) scores of the skull and face dataset is used to produce a possible reconstructed face. Finally, multiple possible reconstructed faces for the same skull can further be recreated based on adjusting the PC coefficients. The experimental results show that the average rate of sex classification is 97.14% and the reconstructed face of the unidentified skull can be produced. In addition, experts’ understanding and experience can be harnessed in production of face variations for the same skull, which can further be used as a reference for portraiture creation

Size factor as one of the problems in the sex estimation of skulls: upper Palaeolithic sample from Predmosti (Czech Republic) as an example

In this study we estimate sex and population affinity of Gravettian Předmostí (P) skulls using linear and geometric discriminant analysis (DA), and compare them with results of 2D geometric morphometrics (GM). We used the measurements of P3 and P9 males, P4 and P10 females, as originally estimated by Matiegka (1934), as well as two databases - the recent skull database of Howells and the fossil data of Henke. DA classifies the P skulls as robust and belonging to the “male” region, loosing the sensitivity of inter-population differences influenced by size factor. That is why this approach could not be applied. The geographic inter-population differences according to DA do not define P skull shapes as extreme. The influence of geographic variability could be stronger than the inter-sexual differences. Despite the chronological differences between databases and Gravettian skulls, these differences are a component of regional inter-population variability. According to our results, GM is more successful methodological approach than DA. Our previous sex estimation of P skulls with help of GM is completely in accordance with the classical morphoscopic estimation. However, an appropriate reference database is necessary in both the GM and DA approaches. For the sexing of skull with unknown population affinity, and with absence of appropriate reference database, we suggest to use the application of more subjective visual scoring methods

The Gravettian child mandible from El Castillo Cave (Puente Viesgo, Cantabria, Spain)

Objectives: This article documents an incomplete child's mandible found in H. Obermaier's excavation campaign (in 1912) in El Castillo Cave, Spain. This fossil was assigned to what was then considered a phase of the “Aurignacian-delta”. Materials and Methods: We exhaustively analyzed the original Obermaier documents, with particular attention to those corresponding to the year of the discovery. We extracted a bone sample to radiocarbon date the fossil directly. We also followed established methods to measure, describe and compare the mandible with other human remains. Results: The analysis of Obermaier's documents and new data derived from modern excavations, show that the mandible was discovered in an interior area of the cave. Direct radiocarbon dating yielded a result of 24,720 ± 210 BP and 29,300 – 28,300 cal BP, a date similar to those known for the Gravettian technocomplex both in the El Castillo site and across Europe. The jaw corresponded to a child aged 4–5 years, with modern morphology, but with a certain robustness, especially in the symphyseal region. Comparisons were made with several modern children (Granada, Spitalfields, and Black series) and with immature fossils (European Aurignacian and Gravettian). The few differences between the modern and the fossil children are related to the symphysis and mandibular corpus thickness and height, and to the symphyseal morphology and larger teeth dimensions. Paleoisotopic data for Castillo C correspond with a varied diet. Numerous cutmarks were identified in the midline internal symphyseal region. Discussion and Conclusions: The results agree with those published for other fossils of similar age and chronology (e.g., the mandible of the Lagar Velho child) and show clear differences from the jaws of the young Neanderthals. The interpretation of the original data on the mandible discovery may indicate the destruction of a burial and the displacement, by percolation or by a den, at least of part of the skeleton. The perimortem manipulations in the child's mandible are the first described in the Gravettian world of Western Europe

Sexually dimorphic facial features vary according to level of autistic-like traits in the general population

© 2015 Gilani et al.; licensee BioMed Central. Background: In a recent study, Bejerot et al. observed that several physical features (including faces) of individuals with an autism spectrum disorder (ASD) were more androgynous than those of their typically developed counterparts, suggesting that ASD may be understood as a 'gender defiant' disorder. These findings are difficult to reconcile with the hypermasculinisation account, which proposes that ASD may be an exaggerated form of cognitive and biological masculinity. The current study extended these data by first identifying six facial features that best distinguished males and females from the general population and then examining these features in typically developing groups selected for high and low levels of autistic-like traits. Methods: In study 1, three-dimensional (3D) facial images were collected from 208 young adult males and females recruited from the general population. Twenty-three facial distances were measured from these images and a gender classification and scoring algorithm was employed to identify a set of six facial features that most effectively distinguished male from female faces. In study 2, measurements of these six features were compared for groups of young adults selected for high (n = 46) or low (n = 66) levels of autistic-like traits. Results: For each sex, four of the six sexually dimorphic facial distances significantly differentiated participants with high levels of autistic-like traits from those with low trait levels. All four features were less masculinised for high-trait males compared to low-trait males. Three of four features were less feminised for high-trait females compared to low-trait females. One feature was, however, not consistent with the general pattern of findings and was more feminised among females who reported more autistic-like traits. Based on the four significantly different facial distances for each sex, discriminant function analysis correctly classified 89.7% of the males and 88.9% of the females into their respective high- and low-trait groups. Conclusions: The current data provide support for Bejerot et al.'s androgyny account since males and females with high levels of autistic-like traits generally showed less sex-typical facial features than individuals with low levels of autistic-like traits

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