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"Face (Anatomy)"
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A method for automatic forensic facial reconstruction based on dense statistics of soft tissue thickness
In this paper, we present a method for automated estimation of a human face given a skull remain. Our proposed method is based on three statistical models. A volumetric (tetrahedral) skull model encoding the variations of different skulls, a surface head model encoding the head variations, and a dense statistic of facial soft tissue thickness (FSTT). All data are automatically derived from computed tomography (CT) head scans and optical face scans. In order to obtain a proper dense FSTT statistic, we register a skull model to each skull extracted from a CT scan and determine the FSTT value for each vertex of the skull model towards the associated extracted skin surface. The FSTT values at predefined landmarks from our statistic are well in agreement with data from the literature. To recover a face from a skull remain, we first fit our skull model to the given skull. Next, we generate spheres with radius of the respective FSTT value obtained from our statistic at each vertex of the registered skull. Finally, we fit a head model to the union of all spheres. The proposed automated method enables a probabilistic face-estimation that facilitates forensic recovery even from incomplete skull remains. The FSTT statistic allows the generation of plausible head variants, which can be adjusted intuitively using principal component analysis. We validate our face recovery process using an anonymized head CT scan. The estimation generated from the given skull visually compares well with the skin surface extracted from the CT scan itself.
Journal Article
When Trustworthiness Meets Face: Facial Design for Social Robots
As a technical application in artificial intelligence, a social robot is one of the branches of robotic studies that emphasizes socially communicating and interacting with human beings. Although both robot and behavior research have realized the significance of social robot design for its market success and related emotional benefit to users, the specific design of the eye and mouth shape of a social robot in eliciting trustworthiness has received only limited attention. In order to address this research gap, our study conducted a 2 (eye shape) × 3 (mouth shape) full factorial between-subject experiment. A total of 211 participants were recruited and randomly assigned to the six scenarios in the study. After exposure to the stimuli, perceived trustworthiness and robot attitude were measured accordingly. The results showed that round eyes (vs. narrow eyes) and an upturned-shape mouth or neutral mouth (vs. downturned-shape mouth) for social robots could significantly improve people’s trustworthiness and attitude towards social robots. The effect of eye and mouth shape on robot attitude are all mediated by the perceived trustworthiness. Trustworthy human facial features could be applied to the robot’s face, eliciting a similar trustworthiness perception and attitude. In addition to empirical contributions to HRI, this finding could shed light on the design practice for a trustworthy-looking social robot.
Journal Article
The effects of facial appearance on measures of generalized trust
Research suggests various associations between generalized trust and a wide range of economic, political, and social dimensions. Despite its importance, there is considerable debate about how best to measure generalized trust. One recent solution operationalizes generalized trust as the average of trust ratings across a small set of trust domains and human faces. Here, we investigate whether heterogeneity in facial appearance affects the psychometric properties of these new instruments. In a survey experiment conducted with a sample of U.S. adults (
n
= 5001), we randomly assigned respondents to one of five conditions that varied the features of human and AI-synthesized faces. Irrespective of the condition, respondents rated each face along four trust domains. We find that facial heterogeneity has negligible effects on the measurement validity and measurement equivalence of these new instruments. Small differences are observed on a subset of faces for some psychometric tests. These findings contribute to a growing body of work using faces to measure generalized trust, and demonstrate the utility of using AI-synthesized faces in social science research more broadly.
Journal Article
Gravity's influence on facial shape changes during vertical and horizontal head scanning: Effects of sex, age, and body fat
Recently, CT scans of the head are increasingly being used for a variety of forensic reasons, regardless of the head position in which the scans were taken. The study is aimed at monitoring differences in facial shape in vertical and horizontal positions caused by gravity. The first aim was to analyze variations in facial morphology due to gravity between sexes, looking into which regions are most affected. The second aim was to understand changes in the facial soft tissue position due to gravity with advancing age. The final objective was to investigate how variations in body fat percentage influence facial changes due to gravity.
The study uses 3D facial scans of 132 Czech and Slovak adults (85 females, 47 males), aged 20–72, captured in vertical and horizontal positions. Differences between both facial polygon networks representing the influence of gravity were analyzed by geometric morphometric methods (CPD-DCA, color-coded maps) and the Morphome3cs II software.
Both sexes showed a similar but otherwise intense shift of facial soft tissues in horizontal position. Males exhibited a stronger supero-lateral shift from the upper cheek to parotid-masseteric regions, whereas females showed greater buccal retrusion. Intensities of soft tissue displacement in these areas increase with increasing age. Almost the same trend can be observed when comparing soft tissue displacement with normal and increased body fat percentage.
Positional correction factors should be implemented in craniofacial identification for increased efficiency of facial reconstruction software towards creating realistic approximations.
•3D facial morphology and averages were compared between vertical and horizontal postures using Morphome3cs II software.•Males showed superolateral cheek shift when lying down; females had sunken buccal areas—trend increased with age and body fat•Extensive changes were observed in the lateral facial regions, while positional changes along the midsagittal plane remain minimal or neutral.•Postural differences affect soft tissue positioning, indicating the need to account for body orientation in morphological assessments.
Journal Article
Focal Length Affects Depicted Shape and Perception of Facial Images
Static photographs are currently the most often employed stimuli in research on social perception. The method of photograph acquisition might affect the depicted subject's facial appearance and thus also the impression of such stimuli. An important factor influencing the resulting photograph is focal length, as different focal lengths produce various levels of image distortion. Here we tested whether different focal lengths (50, 85, 105 mm) affect depicted shape and perception of female and male faces. We collected three portrait photographs of 45 (22 females, 23 males) participants under standardized conditions and camera setting varying only in the focal length. Subsequently, the three photographs from each individual were shown on screen in a randomized order using a 3-alternative forced-choice paradigm. The images were judged for attractiveness, dominance, and femininity/masculinity by 369 raters (193 females, 176 males). Facial width-to-height ratio (fWHR) was measured from each photograph and overall facial shape was analysed employing geometric morphometric methods (GMM). Our results showed that photographs taken with 50 mm focal length were rated as significantly less feminine/masculine, attractive, and dominant compared to the images taken with longer focal lengths. Further, shorter focal lengths produced faces with smaller fWHR. Subsequent GMM revealed focal length significantly affected overall facial shape of the photographed subjects. Thus methodology of photograph acquisition, focal length in this case, can significantly affect results of studies using photographic stimuli perhaps due to different levels of perspective distortion that influence shapes and proportions of morphological traits.
Journal Article
Course and Relation of the Facial Vessels—An Anatomical Study
Background and Objectives: Facial vascular anatomy plays a pivotal role in both physiological context and in surgical intervention. While data exist on the individual course of the facial artery and vein, to date, the spatial relationship of the vasculature has been ill studied. The aim of this study was to assess the course of facial arteries, veins and branches one relative to another. Materials and Methods: In a total of 90 halved viscerocrania, the facial vessels were injected with colored latex. Dissection was carried out, the relation of the facial vessels was studied, and the distance at the lower margin of the mandible was measured. Furthermore, branches including the labial and angular vessels were assessed. Results: At the base of the mandible, the facial artery was located anterior to the facial vein in all cases at a mean distance of 6.2 mm (range 0–15 mm), with three cases of both vessels adjacent. An angular vein was present in all cases, while an angular artery was only present in 34.4% of cases. Conclusions: The main trunk of the facial artery and vein yields a rather independent course, with the facial artery always located anterior to the vein, while their branches, especially the labial vessels, demonstrate a closer relationship.
Journal Article
Facial soft tissue thickness differences among different vertical facial patterns
•Vertical divergence affected FSTT values at the level of Stomion, Labiomentale and Pogonion.•FSTT measurements associated with measurements related to the lower face (Lm and Pog).•Moderate to high correlations between mandibular length and ramus length and FSTT values related to the lower face.
In forensic facial approximation, facial soft tissue thickness (FSTT) measurements play a major role. These values are affected by many factors such as ethnicity, age and sex, in addition to measurement errors. We hypothesize that an additional source of error is the lack of consideration of facial type in the assessment of FSTT norms.
The purpose of this study was to: 1- evaluate the presence of significant effects of vertical facial type within the FSTT measurements in adults and 2- assess the correlations between FSTT and hard and soft tissue cephalometric measurements.
The sample consisted of the lateral cephalometric radiographs of 222 adult individuals (87 males; 135 females, 23.49±6.24 years of age) with normal occlusion and balanced profiles. Hard and soft tissue cephalometric measurements were taken, in addition to FSST at 10 facial landmarks. The sample was categorized into 3 vertical pattern groups based on the MP/SN angle: hypodivergent, normodivergent and hyperdivergent. Statistical analyses included MANOVA test and Pearson moment product for associations among variables. Statistically significant effect of vertical divergence on FSTT values was limited to the levels of Stomion, Labiomentale and Pogonion and FSTT measurements were associated with measurements related to the lower face (Lm and Pog) Moderate to high correlations between mandibular length and ramus length and FSTT values related to the lower face (LL, Lm and Pog mainly) emphasize further the important role of the underlying skeleton.
Journal Article
In vivo facial soft tissue depths of a modern adult population from Germany
Forensic facial reconstruction may be the final option available to draw public attention in cases where the identity of an individual cannot be established by standard identification methods. Two fundamental components of all forensic facial reconstruction techniques are cranial morphology and soft tissue depth databases. The purpose of this study was to extend such databases by providing a complete set of accurate facial soft tissue thickness measurements, acquired from a contemporary adult population from Germany. The material for the study consisted of 320 (160 male, 160 female) anonymised multi-slice computerised tomography (MSCT) scans of individuals drawn from a German population. In Amira®, 3D models of the surfaces of the skull and the facial skin were semi-automatically segmented using calculated thresholds and surface extraction algorithms. Facial soft tissue depth was measured at 10 midline and 28 bilateral anatomical landmarks. The analysis of facial soft tissue thickness versus BMI, sex and age indicated that, at a number of the landmarks, facial soft tissue depth is significantly (
p
< 0.05) influenced by all three biometric variables. Facial soft tissue thickness increased with increasing BMI. The differences between males and females were statistically significant (
p
< 0.05) for almost all anatomical landmarks with the exception of a few in the region of the nasal root and orbitals. Asymmetry was noted at over half of the bilateral landmarks. The differences between the results from this sample and those obtained from comparable databases contradict the hypothesis that population specificity significantly influences facial soft tissue thickness.
Journal Article