Prototype Face Research Articles

The Role of Familiarity for Representations in Norm-Based Face Space.

According to the norm-based version of the multidimensional face space model (nMDFS, Valentine, 1991), any given face and its corresponding anti-face (which deviates from the norm in exactly opposite direction as the original face) should be equidistant to a hypothetical prototype face (norm), such that by definition face and anti-face should bear the same level of perceived typicality. However, it has been argued that familiarity affects perceived typicality and that representations of familiar faces are qualitatively different (e.g., more robust and image-independent) from those for unfamiliar faces. Here we investigated the role of face familiarity for rated typicality, using two frequently used operationalisations of typicality (deviation-based: DEV), and distinctiveness (face in the crowd: FITC) for faces of celebrities and their corresponding anti-faces. We further assessed attractiveness, likeability and trustworthiness ratings of the stimuli, which are potentially related to typicality. For unfamiliar faces and their corresponding anti-faces, in line with the predictions of the nMDFS, our results demonstrate comparable levels of perceived typicality (DEV). In contrast, familiar faces were perceived much less typical than their anti-faces. Furthermore, familiar faces were rated higher than their anti-faces in distinctiveness, attractiveness, likability and trustworthiness. These findings suggest that familiarity strongly affects the distribution of facial representations in norm-based face space. Overall, our study suggests (1) that familiarity needs to be considered in studies of mental representations of faces, and (2) that familiarity, general distance-to-norm and more specific vector directions in face space make different and interactive contributions to different types of facial evaluations.

First Impressions of Strangers Rely on Generalization of Behavioral Traits Associated with previously Seen Facial Features

Information drawn from faces at the very first encounter can be essential in guiding current and subsequent behavior. These decisions also rely on expectations about what are the characteristic features of those who can be trusted or not. After novel experiences these expectations will be revised, and the facial prototypes stored in the memory will be updated. The aim of the recent experiment was to test whether behavioral information about individuals will be transferred to composite facial images. We created composite faces of individual images which were previously presented with either positive or negative behavioral descriptions. We found that the composite made from faces shown with traits referring to high social desirability, was rated as significantly more trustworthy. We propose that exposure to faces and acquisition of socially relevant information shape facial prototypes, ensuring that the evaluation of unknown individuals reflects expectations based on real-life experiences. We further propose that this process is mediated by the generalization of behavior information and facial features, rather than the detection of visual similarity.

3D face reconstruction via landmark depth estimation and shape deformation

Since a human face could be represented by a few landmarks with less redundant information, and calculated by a linear combination of a small number of prototypical faces, we propose a two-step 3D face reconstruction approach including landmark depth estimation and shape deformation. The proposed approach allows us to reconstruct a realistic 3D face from a 2D frontal face image. First, we apply a coupled dictionary learning method based on sparse representation to explore the underlying mappings between pair of 2D and 3D training landmarks. In the method, a weighted l1 norm sparsity function is introduced to better pursuit the l0 norm sparsity. Then, the depth of the landmarks could be estimated. Second, we propose a novel shape deformation method to reconstruct the 3D face by combining a small number of most relevant deformed faces which are obtained by the estimated landmarks. The sparsity regulation is also introduced to find the relevant faces in the second step. The proposed approach could explore the distributions of 2D and 3D faces and the underlying mappings between them well, because human faces are represented by low-dimensional landmarks, and their distributions are described by sparse representations. Moreover, it is much more flexible since we can make any change in any step. Extensive experiments are conducted on BJUT_3D database, and the results validate the effectiveness of the proposed approach.

Adults with autism spectrum disorder show evidence of figural aftereffects with male and female faces

The norm-based coding model of face perception posits that face perception involves an implicit comparison of observed faces to a representation of an average face (prototype) that is shaped by experience. Using some methods, observers with autism spectrum disorder (ASD) have shown atypical face perception, but other methods suggest preserved face perception. Here, we used a figural aftereffects paradigm to test whether adults with ASD showed evidence of norm-based coding of faces, and whether they encode separate prototypes for male and female faces, as typical observers do. Following prolonged exposure to distorted faces that differ from their stored prototype, neurotypical adults show aftereffects: their prototype shifts in the direction of the adapting face. We measured aftereffects following adaptation to one distorted gender. There were no significant group differences in the size or direction of the aftereffects; both groups showed sex-selective aftereffects after adapting to expanded female faces but showed aftereffects for both sexes after adapting to contracted face of either sex, demonstrating that adults with and without ASD show evidence of partially dissociable male and female face prototypes. This is the first study to examine sex-selective prototypes using figural aftereffects in adults with ASD and replicates the findings of previous studies examining aftereffects in adults with ASD. The results contrast with studies reporting diminished adaptation in children with ASD.

English

Biometrics is an automated method of recognizing a person based on a physiological or behavioral appearance. Biometric detection technology relies upon the physical appearance of an individual, such as fingerprints, voiceprint, prototype of the iris of the eye and facial prototype, in identifying an individual, offering positive identification that is difficult to counterfeit. Instances of physiological biometric traits include height, weight, body odour, the aspect of the hand, the prototype of veins, retina or iris, the face and the prototypes on the skin of thumbs or fingers (fingerprints). Instances of behavioral biometrics are voice prototypes, signature and keystroke sequences and gait (the body movement while walking). Biometric identifiers are the distinctive, measurable appearances used to label and describe individuals [1]. Currently, passwords, Personal Identification cards are used for personal detection. However, cards can be stolen, and passwords and numbers can be guessed or forgotten. To solve these problems, biometric verification technology, which identifies people by their unique biological information, is attracting attention [2]. Biometrics is mostly used for authentication purposes to ensure proper safety.

The effect of context on responses to racially ambiguous faces: changes in perception and evaluation.

Reactions to individuals who possess features associated with multiple racial groups may be particularly susceptible to external contextual influences, leading to meaningfully different racial perceptions and judgments in different situations. In the present study, we found that an extrinsic race-label cue not only changed evaluative associations activated by a racially ambiguous face, but also changed quickly occurring neural responses sensitive to racial perception. Behaviorally, prototypical Black faces and racially ambiguous faces labeled as Black activated more negative implicit associations than prototypical White faces and racially ambiguous faces labeled as White. Neurally, prototypical faces and racially ambiguous faces cued with the same race elicited similar responses. Specifically, prototypical Black and racially ambiguous faces labeled as Black elicited larger P200s but smaller N200s than prototypical White and racially ambiguous faces labeled as White. These results show that racial perception can be changed by an external cue and this, in turn, influences subsequent evaluative reactions.

Constructing faces from memory: the impact of image likeness and prototypical representations

Purpose – Research suggests that memory for unfamiliar faces is pictorial in nature, with recognition negatively affected by changes to image-specific information such as head pose, lighting and facial expression. Further, within-person variation causes some images to resemble a subject more than others. Here, the purpose of this paper is to explore the impact of target-image choice on face construction using a modern evolving type of composite system, EvoFIT. Design/methodology/approach – Participants saw an unfamiliar target identity and then created a single composite of it the following day with EvoFIT by repeatedly selecting from arrays of faces with “breeding”, to “evolve” a face. Targets were images that had been previously categorised as low, medium or high likeness, or a face prototype comprising averaged photographs of the same individual. Findings – Identification of composites of low likeness targets was inferior but increased as a significant linear trend from low to medium to high likeness. Also, identification scores decreased when targets changed by pose and expression, but not by lighting. Similarly, composite identification from prototypes was more accurate than those from low likeness targets, providing some support that image averages generally produce more robust memory traces. Practical implications – The results emphasise the potential importance of matching a target's pose and expression at face construction; also, for obtaining image-specific information for construction of facial-composite images, a result that would appear to be useful to developers and researchers of composite software. Originality/value – This current project is the first of its kind to formally explore the potential impact of pictorial properties of a target face on identifiability of faces created from memory. The design followed forensic practices as far as is practicable, to allow good generalisation of results.

The self prefers itself? Self-referential versus parental standards in face attractiveness.

Preference for phenotypic similarity in assortative mating may be influenced by either a preference for self-similarity or parent-similarity. The aim of the current study was to assess whether people’s preference in face attractiveness is influenced by resemblance to the opposite sex parent’s face (parental phenotype) or their own face (self-based phenotype or “self-imprinting”). We used computerized image manipulations of facial photographs of participants, their mothers and fathers. The original photographs were combined with 78% of the participants’ opposite sex prototype face (i.e., male and female prototypes made from equal contributions of a hundred faces), creating morphs where the contribution from the familiar faces went unnoticed. Female and male participants ranked these images together with the opposite-sex prototype different familiar morphs. Each participant did the same for the morphs generated with other same-sex participants’ faces and of their parents. We found that the female participants preferred the self-based morphs to the prototype faces. Male participants showed a general tendency towards self-referential standard. Parental face morphs were ranked low in attractiveness, which may be accounted for by the age difference of the faces blended into the self-based versus parental face morphs, since we used present-time photographs of both the participants and their parents.

Is preference for ovulatory female's faces associated with men's testosterone levels?

Women's ovulation is perceivable with different senses. Already subtle face shape differences are enough to trigger men's preference for the ovulatory female. The aim of the present study is to investigate if men's testosterone level can be linked to their preference for the ovulatory female. Thirty-nine heterosexual participants were shown face pairs of which one of them was transformed to the shape of a prototype face of a woman in her luteal cycle phase and the other was transformed to the shape of a prototype face of an ovulatory woman. Participants were asked to choose the face which they perceived as being more attractive (attractiveness task), or the woman with whom they would have better chances to get a date (dating task). In both tasks, the ovulatory female was chosen more often. Testosterone was not predictive for the chosen face; regardless of testosterone level men preferred the ovulatory woman. However testosterone predicted how confident the men were with their choice. Men with lower testosterone levels were more confident with their choice than men with higher testosterone levels.

Category-specific face prototypes are emerging, but not yet mature, in 5-year-old children

Adults’ expertise in face recognition has been attributed to norm-based coding. Moreover, adults possess separable norms for a variety of face categories (e.g., race, sex, age) that appear to enhance recognition by reducing redundancy in the information shared by faces and ensuring that only relevant dimensions are used to encode faces from a given category. Although 5-year-old children process own-race faces using norm-based coding, little is known about the organization and refinement of their face space. The current study investigated whether 5-year-olds rely on category-specific norms and whether experience facilitates the development of dissociable face prototypes. In Experiment 1, we examined whether Chinese 5-year-olds show race-contingent opposing aftereffects and the extent to which aftereffects transfer across face race among Caucasian and Chinese 5-year-olds. Both participant races showed partial transfer of aftereffects across face race; however, there was no evidence for race-contingent opposing aftereffects. To examine whether experience facilitates the development of category-specific prototypes, we investigated whether race-contingent aftereffects are present among Caucasian 5-year-olds with abundant exposure to Chinese faces (Experiment 2) and then tested separate groups of 5-year-olds with two other categories with which they have considerable experience: sex (male/female faces) and age (adult/child faces) (Experiment 3). Across all three categories, 5-year-olds showed no category-contingent opposing aftereffects. These results demonstrate that 5years of age is a stage characterized by minimal separation in the norms and associated coding dimensions used for faces from different categories and suggest that refinement of the mechanisms that underlie expert face processing occurs throughout childhood.

Respiratory source control using surgical masks with nanofiber media.

Background: Potentially infected individuals (‘source’) are sometimes encouraged to use face masks to reduce exposure of their infectious aerosols to others (‘receiver’). To improve compliance with Respiratory Source Control via face mask and therefore reduce receiver exposure, a mask should be comfortable and effective. We tested a novel face mask designed to improve breathability and filtration using nanofiber filtration.Methods: Using radiolabeled test aerosols and a calibrated exposure chamber simulating source to receiver interaction, facepiece function was measured with a life-like ventilated manikin model. Measurements included mask airflow resistance (pressure difference during breathing), filtration, (mask capture of exhaled radiolabeled test aerosols), and exposure (the transfer of ‘infectious’ aerosols from the ‘source’ to a ‘receiver’). Polydisperse aerosols were measured at the source with a mass median aerodynamic diameter of 0.95 µm. Approximately 90% of the particles were <2.0 µm. Tested facepieces included nanofiber prototype surgical masks, conventional surgical masks, and for comparison, an N95-class filtering facepiece respirator (commonly known as an ‘N95 respirator’). Airflow through and around conventional surgical face mask and nanofiber prototype face mask was visualized using Schlieren optical imaging.Results: Airflow resistance [ΔP, cmH2O] across sealed surgical masks (means: 0.1865 and 0.1791 cmH2O) approached that of the N95 (mean: 0.2664 cmH2O). The airflow resistance across the nanofiber face mask whether sealed or not sealed (0.0504 and 0.0311 cmH2O) was significantly reduced in comparison. In addition, ‘infected’ source airflow filtration and receiver exposure levels for nanofiber face masks placed on the source were comparable to that achieved with N95 placed on the source; 98.98% versus 82.68% and 0.0194 versus 0.0557, respectively. Compared to deflection within and around the conventional face masks, Schlieren optical imaging demonstrated enhanced airflow through the nanofiber mask.Conclusions: Substituting nanofiber for conventional filter media significantly reduced face mask airflow resistance directing more airflow through the face mask resulting in enhanced filtration. Respiratory source control efficacy similar to that achieved through the use of an N95 respirator worn by the source and decreased airflow resistance using nanofiber masks may improve compliance and reduce receiver exposure.

Neanderthal Paintings? Production of Prototypical Human (Homo Sapiens) Faces Shows Systematic Distortions

People's sketches of human faces seem to be systematically distorted: the eye position is always higher than in reality. This bias was experimentally analyzed by a series of experiments varying drawing conditions. Participants either drew prototypical faces from memory (studies 1 and 2: free reconstruction; study 3: cued reconstruction) or directly copied average faces (study 4). Participants consistently showed this positioning bias, which is even in accord with facial depictions published in influential research articles by famous face researchers (study 5). We discuss plausible explanations for this reliable and stable bias, which is coincidentally similar to the morphology of Neanderthals.

Archetypal-imaging and mirror-gazing.

Mirrors have been studied by cognitive psychology in order to understand self-recognition, self-identity, and self-consciousness. Moreover, the relevance of mirrors in spirituality, magic and arts may also suggest that mirrors can be symbols of unconscious contents. Carl G. Jung investigated mirrors in relation to the unconscious, particularly in Psychology and Alchemy. However, the relationship between the conscious behavior in front of a mirror and the unconscious meaning of mirrors has not been clarified. Recently, empirical research found that gazing at one’s own face in the mirror for a few minutes, at a low illumination level, produces the perception of bodily dysmorphic illusions of strange-faces. Healthy observers usually describe huge distortions of their own faces, monstrous beings, prototypical faces, faces of relatives and deceased, and faces of animals. In the psychiatric population, some schizophrenics show a dramatic increase of strange-face illusions. They can also describe the perception of multiple-others that fill the mirror surface surrounding their strange-face. Schizophrenics are usually convinced that strange-face illusions are truly real and identify themselves with strange-face illusions, diversely from healthy individuals who never identify with them. On the contrary, most patients with major depression do not perceive strange-face illusions, or they perceive very faint changes of their immobile faces in the mirror, like death statues. Strange-face illusions may be the psychodynamic projection of the subject’s unconscious archetypal contents into the mirror image. Therefore, strange-face illusions might provide both an ecological setting and an experimental technique for “imaging of the unconscious”. Future researches have been proposed.

The role of temporal context in norm-based encoding of faces

Research shows that the human brain encodes faces in terms of how they relate to a prototypical face, a phenomenon referred to as norm-based encoding. The goal of this study was to examine the effect of short-term exposure on the development of the norm, independently of global, long-term exposure. We achieved this by varying the sequence of presentation of the stimuli while keeping global exposure constant. We found that a systematic manipulation of the average face in a set of 10 preceding trials can shift this norm toward that average. However, there was no effect of order or recency among these trials; thus, there was no evidence that the last faces mattered more than the first. This suggests that the position of the face norm is modified by information that is integrated across multiple recent faces.

Heterogeneous Face Recognition Using Kernel Prototype Similarities

Heterogeneous face recognition (HFR) involves matching two face images from alternate imaging modalities, such as an infrared image to a photograph or a sketch to a photograph. Accurate HFR systems are of great value in various applications (e.g., forensics and surveillance), where the gallery databases are populated with photographs (e.g., mug shot or passport photographs) but the probe images are often limited to some alternate modality. A generic HFR framework is proposed in which both probe and gallery images are represented in terms of nonlinear similarities to a collection of prototype face images. The prototype subjects (i.e., the training set) have an image in each modality (probe and gallery), and the similarity of an image is measured against the prototype images from the corresponding modality. The accuracy of this nonlinear prototype representation is improved by projecting the features into a linear discriminant subspace. Random sampling is introduced into the HFR framework to better handle challenges arising from the small sample size problem. The merits of the proposed approach, called prototype random subspace (P-RS), are demonstrated on four different heterogeneous scenarios: 1) near infrared (NIR) to photograph, 2) thermal to photograph, 3) viewed sketch to photograph, and 4) forensic sketch to photograph.

The influence of averageness on children’s judgments of facial attractiveness

We examined developmental changes in the influence of averageness on judgments of facial attractiveness by showing adults and children pairs of individual faces in which one face was transformed 50% toward its group average, whereas the other face was transformed 50% away from that average. In one comparison, adults and 5-year-olds rated the more average faces as more attractive whether the faces were of adult females, 5-year-old boys, or 5-year-old girls. The influence of averageness, however, was weaker in 5-year-olds than in adults. In another comparison, a new group of adults and 9-year-olds rated the more average faces as more attractive for male and female faces of adults, 9-year-olds, and 5-year-olds. The influence of averageness was again weaker for children than for adults, although the strength of 9-year-olds’ preference was greater than that of 5-year-olds. Developmental changes may reflect the refinement of an average face prototype as children are exposed to more faces, increased sensitivity as visual perception develops, and/or the greater salience of attractiveness after puberty.

The neural correlates of the face attractiveness aftereffect: A functional near-infrared spectroscopy (fNIRS) study

Extensive behavioral evidence shows that our internal representation of faces, or face prototype, can be dynamically updated by immediate experience. This is illustrated by the robust attractiveness aftereffect phenomenon whereby originally unattractive faces become attractive after we are exposed to a set of unattractive faces. Although behavioral evidence suggests this effect to have a strong neural basis, limited neuroimaging evidence exists. Here we used functional near-infrared spectroscopy methodology (fNIRS) to bridge this gap. During the pre-adaptation trials, participants judged the attractiveness of three sets of faces: normal/undistorted faces, compressed faces (the internal features and distances between them were compressed), and expanded faces (the internal features and distances between them were stretched). Then, participants were shown extremely compressed faces for 5min as adaptation stimuli, after which participants judged the same three sets of faces in post-adaptation trials. Behaviorally, after the adaptation trials, participants rated the compressed faces more attractive whereas they judged the other two sets of faces as less attractive, replicating the robust adaptation effect. fNIRS results showed that short-term exposure to compressed faces led to significant decreases in neural activity to all face types, but in a more extended network of cortical regions in the frontal and occipital cortexes for undistorted faces. Taken together, these findings suggest that the face attractiveness aftereffect mainly reflects changes in the neural representation of the face prototype in response to recent exposures to new face exemplars.

Implicit face prototype learning from geometric information

There is evidence that humans implicitly learn an average or prototype of previously studied faces, as the unseen face prototype is falsely recognized as having been learned (Solso & McCarthy, 1981). Here we investigated the extent and nature of face prototype formation where observers’ memory was tested after they studied synthetic faces defined purely in geometric terms in a multidimensional face space. We found a strong prototype effect: The basic results showed that the unseen prototype averaged from the studied faces was falsely identified as learned at a rate of 86.3%, whereas individual studied faces were identified correctly 66.3% of the time and the distractors were incorrectly identified as having been learned only 32.4% of the time. This prototype learning lasted at least 1week. Face prototype learning occurred even when the studied faces were further from the unseen prototype than the median variation in the population. Prototype memory formation was evident in addition to memory formation of studied face exemplars as demonstrated in our models. Additional studies showed that the prototype effect can be generalized across viewpoints, and head shape and internal features separately contribute to prototype formation. Thus, implicit face prototype extraction in a multidimensional space is a very general aspect of geometric face learning.

Extracting Prototypical Facial Images from Exemplars

A computer graphic method for extracting a natural image of an individual's facial prototype, or average appearance, from a number of different images of that individual is presented. The process improves upon previous photographic and computational techniques. Synthesis of a person's average expression and pose from a sample of images is derived in an automatic and quantitative way. Possible uses of composite faces produced in this manner in psychological investigations of facial qualities (eg attractiveness) and in applied areas such as telecommunication are pointed out.

Preschooler’s faces in spontaneous emotional contexts—how well do they match adult facial expression prototypes?

Prototypical facial expressions of emotion, also known as universal facial expressions, are the underpinnings of most research concerning recognition of emotions in both adults and children. Data on natural occurrences of these prototypes in natural emotional contexts are rare and difficult to obtain in adults. By recording naturalistic observations targeted at emotional contexts in day-to-day kindergarten activities, we investigated the spontaneous facial behavior of 3-year-old children in order to explore associations between context and facial activity and verify the degree of matching between the well-known adult prototypes and facial configurations actually produced by children. When taken individually, most facial actions matched those that comprise the respective emotion prototypical face, but full facial configurations with all characteristic facial actions were scarce but for joy.