The role of skin texture and facial shape in representations of age and identity

The 2024 Richardson Lecture: Prosopagnosia - A Classic Neurologic Deficit Meets the Modern Era

Acquired prosopagnosia is a rare disorder, but it serves as a model for impairments in expert-level visual processing. This review discusses five key observations made over the past 30 years. First, there are variants, an apperceptive type linked to damage to the inferior occipitotemporal cortex and an amnestic type associated with anterior temporal lesions, both either right or bilateral. Second, these variants are clustered in syndromes with other perceptual deficits, the apperceptive type with field defects, dyschromatopsia and topographagnosia, and the amnestic type with topographagnosia and the auditory disorders of phonagnosia and acquired amusia. Third, extensive testing often shows additional problems with recognizing exemplars of other objects, especially when degrees of expertise are taken into account. Fourth, the prosopagnosic impairment does not affect all facial information. For example, the perception of expression and lip-reading likely depends on other neural substrates than those for processing facial identity. Last, face perception in prosopagnosia is not immutable but can improve with extensive training, though as yet this does not represent a cure for the condition. Continuing work with neural networks and animal models will enhance our understanding of this intriguing condition and what it tells us about how our brains process vision.

Face shape and motion are perceptually separable: Support for a revised model of face processing

A recent model of face processing proposes that face shape and motion are processed in parallel brain pathways. Although tested in neuroimaging, the assumptions of this theory remain relatively untested through controlled psychophysical studies until now. Recruiting undergraduate students over the age of 18, we test this hypothesis using a tight control of stimulus factors, through computerized three-dimensional face models and calibration of dimensional discriminability, and of decisional factors, through a model-based analysis using general recognition theory (GRT). Theoretical links between neural and perceptual forms of independence within GRT allowed us to derive the a priori hypotheses that perceptual separability of shape and motion should hold, while other forms of independence defined within GRT might fail. We found evidence to support both of those predictions.

The role of facial skin tone and texture in the perception of age

Age and gender perception from looking at people's faces, without any cultural or conventional cues, is primarily based on two independent components: a) the shape or facial structure, and b) surface reflectance (skin tone and texture, STT). This study examined the relative contribution of facial STT to the perception of age. A total of 204 subjects participated in four experiments presenting artificial 3D realistic faces of different age versions under two key experimental conditions: with and without STT. Two experiments involved a discrimination-age task, and other two involved a direct age-estimation task. The faces for the last experiment were generated from the photographs of real people. The results were quite consistent throughout the experiments. Data suggest that the contribution of the STT information leads to roughly 25-33 % of accuracy in age perception. Interestingly, a differential pattern emerges in relation to facial age: the relative contribution of skin information increases sharply with advancing age, to the point that age judgments of the older faces (60 years old) without STT information fall to the chance level. This pattern suggests that facial skin tone and texture are the main sources of information for estimating the age of people past their maturity as those are the principal visual signs of aging beyond the anatomical changes of facial structure.

A narrow band of image dimensions is critical for face recognition

A key challenge in human and computer face recognition is to differentiate information that is diagnostic for identity from other sources of image variation. Here, we used a combined computational and behavioural approach to reveal critical image dimensions for face recognition. Behavioural data were collected using a sorting and matching task with unfamiliar faces and a recognition task with familiar faces. Principal components analysis was used to reveal the dimensions across which the shape and texture of faces in these tasks varied. We then asked which image dimensions were able to predict behavioural performance across these tasks. We found that the ability to predict behavioural responses in the unfamiliar face tasks increased when the early PCA dimensions (i.e. those accounting for most variance) of shape and texture were removed from the analysis. Image similarity also predicted the output of a computer model of face recognition, but again only when the early image dimensions were removed from the analysis. Finally, we found that recognition of familiar faces increased when the early image dimensions were removed, decreased when intermediate dimensions were removed, but then returned to baseline recognition when only later dimensions were removed. Together, these findings suggest that early image dimensions reflect ambient changes, such as changes in viewpoint or lighting, that do not contribute to face recognition. However, there is a narrow band of image dimensions for shape and texture that are critical for the recognition of identity in humans and computer models of face recognition.

Treatment of acne in the aesthetic patient: A round table update

BACKGROUND

The popularity of social media appears to be increasing the acceptance of cosmetic treatments, prompting more consumers to seek cosmetic treatments. As the estimated prevalence of acne vulgaris among adult women may be as high as 54%, acne is commonly observed among patients presenting for cosmetic treatments. Concomitant treatment of acne in the aesthetic patient population will improve overall clinical outcomes.

AIMS

The goal of this work was to deliver a high-quality ethical and evidence-based educational program to physicians and adjunctive health care providers to advance patient care.

METHODS

This paper is based on a webcam presentation with roundtable discussion by several notable experts in their field.

RESULTS

A range of topical medications, injectable products, chemical peels, and energy-based devices are available for treating acne vulgaris. In most instances, these are compatible with rejuvenation procedures in the aesthetic patient.

CONCLUSION

The growth of social media is raising awareness of aesthetic procedures and appears to be increasing the number of patients seeking aesthetic treatment. Educating patients about the importance of treating acne vulgaris can improve overall treatment outcomes. In most instances, the presence of acne is not a barrier to aesthetic care.

Corneal reflections and skin contrast yield better memory of human and virtual faces

Virtual faces have been found to be rated less human-like and remembered worse than photographic images of humans. What it is in virtual faces that yields reduced memory has so far remained unclear. The current study investigated face memory in the context of virtual agent faces and human faces, real and manipulated, considering two factors of predicted influence, i.e., corneal reflections and skin contrast. Corneal reflections referred to the bright points in each eye that occur when the ambient light reflects from the surface of the cornea. Skin contrast referred to the degree to which skin surface is rough versus smooth. We conducted two memory experiments, one with high-quality virtual agent faces (Experiment 1) and the other with the photographs of human faces that were manipulated (Experiment 2). Experiment 1 showed better memory for virtual faces with increased corneal reflections and skin contrast (rougher rather than smoother skin). Experiment 2 replicated these findings, showing that removing the corneal reflections and smoothening the skin reduced memory recognition of manipulated faces, with a stronger effect exerted by the eyes than the skin. This study highlights specific features of the eyes and skin that can help explain memory discrepancies between real and virtual faces and in turn elucidates the factors that play a role in the cognitive processing of faces.

Smiling makes you look older, even when you wear a mask: the effect of face masks on age perception

The widespread use of face masks in the era of the Covid-19 pandemic has promoted research on their effect on the perception and recognition of faces. There is growing evidence that masks hinder the recognition of identity and expression, as well as the interpretation of speech from facial cues. It is less clear whether and in what manner masks affect the perception of age from facial cues. Recent research has emphasized the role of the upper region of the face, a part not covered by a mask, in the evaluation of age. For example, smile-related wrinkles in the region of the eyes make smiling faces appear older than neutral faces of the same individuals (the aging effect of smiling, AES). In two experiments, we tested the effect of face masks on age evaluations of neutral and smiling faces in a range of different age groups from 20 to 80 years. The results showed that smiling faces were perceived as older than neutral faces even when individuals were wearing a face mask—and there was no effect of masks on bias in age evaluations. Additional analyses showed reduced accuracy in age evaluations for smiling compared to neutral faces and for masked compared to unmasked faces. The results converge on previous studies emphasizing the importance of the upper region of the face in evaluations of age.

Improving Face-Based Age Estimation With Attention-Based Dynamic Patch Fusion

With the increasing popularity of convolutional neural networks (CNNs), recent works on face-based age estimation employ these networks as the backbone. However, state-of-the-art CNN-based methods treat each facial region equally, thus entirely ignoring the importance of some facial patches that may contain rich age-specific information. In this paper, we propose a face-based age estimation framework, called Attention-based Dynamic Patch Fusion (ADPF). In ADPF, two separate CNNs are implemented, namely the AttentionNet and the FusionNet. The AttentionNet dynamically locates and ranks age-specific patches by employing a novel Ranking-guided Multi-Head Hybrid Attention (RMHHA) mechanism. The FusionNet uses the discovered patches along with the facial image to predict the age of the subject. Since the proposed RMHHA mechanism ranks the discovered patches based on their importance, the length of the learning path of each patch in the FusionNet is proportional to the amount of information it carries (the longer, the more important). ADPF also introduces a novel diversity loss to guide the training of the AttentionNet and reduce the overlap among patches so that the diverse and important patches are discovered. Through extensive experiments, we show that our proposed framework outperforms state-of-the-art methods on several age estimation benchmark datasets.

Face processing in the temporal lobe

Face perception is a socially important but complex process with many stages and many facets. There is substantial evidence from many sources that it involves a large extent of the temporal lobe, from the ventral occipitotemporal cortex and superior temporal sulci to anterior temporal regions. While early human neuroimaging work suggested a core face network consisting of the occipital face area, fusiform face area, and posterior superior temporal sulcus, studies in both humans and monkeys show a system of face patches stretching from posterior to anterior in both the superior temporal sulcus and inferotemporal cortex. Sophisticated techniques such as fMRI adaptation have shown that these face-activated regions show responses that have many of the attributes of human face processing. Lesions of some of these regions in humans lead to variants of prosopagnosia, the inability to recognize the identity of a face. Lesion, imaging, and electrophysiologic data all suggest that there is a segregation between identity and expression processing, though some suggest this may be better characterized as a distinction between static and dynamic facial information.

Whole-object effects in visual word processing: Parallels with and differences from face recognition

Visual words and faces differ in their structural properties, but both are objects of high expertise. Holistic processing is said to characterize expert face recognition, but the extent to which whole-word processes contribute to word recognition is unclear, particularly as word recognition is thought to proceed by a component-based process. We review the evidence for experimental effects in word recognition that parallel those used to support holistic face processing, namely inversion effects, the part-whole task, and composite effects, as well as the status of whole-word processing in pure alexia and developmental dyslexia, contrasts between familiar and unfamiliar languages, and the differences between handwriting and typeset font. The observations support some parallels in whole-object influences between face and visual word recognition, but do not necessarily imply similar expert mechanisms. It remains to be determined whether and how the relative balance between part-based and whole-object processing differs for visual words and faces.

Colour matters more than shape for chimpanzees' recognition of developmental face changes

Social primates must recognise developmental stages of other conspecifics in order to behave appropriately. Infant faces have peculiar morphological characteristics-relatively large eyes, a small nose, and small mouth-known as baby schema. In addition, the infant faces of many primate species have unique skin coloration. However, it is unclear which features serve as critical cues for chimpanzees to recognise developmental changes in their faces. The present study aimed to investigate the relative contributions of facial shape and colour to age categorisation in chimpanzees. We used a symbolic matching-to-sample task in which chimpanzees were trained to discriminate between adult and infant faces. Then, we tested how their age category judgments transferred to a series of morphed faces which systematically differed in facial shape and colour. Statistical image quantification analysis revealed significant differences both in shape and colour between adult and infant faces. However, we found that facial coloration contributed to age categorisation in chimpanzees more than facial shape. Our results showed that chimpanzees use unique infantile facial coloration as a salient cue when discriminating between adult and infant faces. The display of their developmental stages through facial colour may help chimpanzees to induce appropriate behaviour from other individuals.

Expert Consensus on Injection Technique and Area-Specific Recommendations for the Hyaluronic Acid Dermal Filler VYC-12L to Treat Fine Cutaneous Lines

Background

VYC-12L is a hyaluronic acid (HA) injectable gel designed to treat fine cutaneous lines and improve skin quality attributes such as hydration and elasticity.

Objective

Expert consensus was sought on VYC-12L injection technique and primary treatment target areas.

Methods

A multinational group of aesthetic medicine clinicians (n = 128) attended product training and each identified ~10 patients for VYC-12L. After treating their first and last patients, the clinicians completed a survey on preferred injection methodology/technique, including injection angle, volume, and spacing. An expert panel (n = 12) discussed survey results and their clinical experiences to obtain consensus on VYC-12L technique and appropriate treatment areas.

Results

Recommendations included micro-depot injections of VYC-12L into the deep dermis with a 32G ½ inch needle inserted at <45º to the skin, spaced 0.5‒1.0 cm apart, with 0.01‒0.05 mL volume per injection (full-face total volume: ~2 mL). Recommended primary treatment areas were the malar, perioral, neck, and décolletage regions. Injection techniques for different treatment areas/demographic characteristics were similar, with some variability in treatment approach. Patient selection criteria, pre- and post-treatment guidelines, and managing patient expectations are important components of treatment.

Conclusion

These consensus recommendations may assist clinicians in optimizing the treatment of fine lines with VYC-12L.

Difference between the biologic and chronologic age as an individualized indicator for the skincare intensity selection: skin cell profile and age difference studies

Background

The present research addresses the issue of skin aging and corresponding skin treatment individualization. Particular research question was on the development of a simplified criterion supporting patient-specific decisions about the necessity and intensity of skin treatment. Basing on published results and a wide pool of our own experimental data, a hypothesis is formulated that a difference between biologic and chronologic age can be used as a powerful indicator of skin aging.

Methods

In the present paper, we report the results of studies with 80 volunteers between 15 and 65 years of age linking skin cell profile parameters to biologic and chronologic age. Biologic age was calculated using the empirical expressions based on the forced vital lung capacity, systolic blood pressure, urea concentration, and blood cholesterol level. Epidermis and derma cellular structures were studied using skin biopsy samples taken from the gluteal region.

Results

The present study supports the conclusion that biologic and chronologic age difference is changing in the progress of life. Our studies are showing that time point when calculated biologic age becomes equal to the chronologic one reflecting the onset of specific changes in the age dependencies of experimentally measured skin cell profile parameters. Thus, it is feasible that a difference between chronologic and individually assessed biologic age indeed reflects the process of skin aging.

Conclusions

With all reservations to the relatively small number of study participants, it seems feasible that a difference between biologic and chronologic age can be used as an indicator of skin aging. Additional research linking blood immune profile and skin topography to the difference of biologic and chronologic age (reported in the following paper) provides further support for the formulated hypotheses. So, a difference between calculated biologic age and chronologic age can be used as an individualized criterion supporting decisions on skin treatment strategies. Further research involving larger numbers of participants aimed at optimizing the expressions for calculating biologic age could lead to reliable and easily available express criterion supporting the decision for the individualized skin treatment.

VYC-12 Injectable Gel Is Safe And Effective For Improvement Of Facial Skin Topography: A Prospective Study

Objective

Evaluate safety and effectiveness of VYC-12 (Juvéderm Volite; an injectable crosslinked hyaluronic acid gel designed to improve skin quality attributes such as surface smoothness and hydration) for facial intradermal injection.

Materials and methods

In a prospective, single-arm study, subjects with moderate/severe cheek skin roughness per Allergan Skin Roughness Scale (ASRS) received VYC-12 in the cheeks and forehead, and/or neck, with touch-up treatment to correct asymmetry 30 days later and optional repeat treatment 9 months after last treatment. The primary effectiveness measure was ASRS responder rate (percentage of cheeks with ≥1-point improvement from baseline) at month 1. Skin hydration was instrument-assessed.

Results

Of 131 subjects treated, 31 (23.7%) received touch-up treatment. ASRS responder rate was 96.2% at month 1, 76.3% at month 4, 34.9% at month 6, and 87.1% after repeat treatment. Responder rate in cheeks with severe baseline roughness was 93.8%, 83.1%, and 52.3% at months 1, 4, and 6, respectively. Skin hydration improved significantly (P<0.01) from baseline at all timepoints through month 9. Injection site responses were as expected. All treatment-related adverse events were mild/moderate.

Conclusion

VYC-12 safely and effectively improved skin smoothness up to 6 months and hydration lasting 9 months.

Improvements in satisfaction with skin after treatment of facial fine lines with VYC-12 injectable gel: Patient-reported outcomes from a prospective study

BACKGROUND

VYC-12, a hyaluronic acid injectable gel, is designed to treat fine lines and provides improvements in other skin quality attributes. A prospective study demonstrated the safety and effectiveness of VYC-12 for the improvement of fine lines as measured by changes in skin texture.

AIMS

To evaluate patient-reported outcomes in subjects treated intradermally with VYC-12 in the cheeks, forehead, and neck (optional) in the prospective study.

METHODS

Subjects received an initial treatment of VYC-12 (N = 131), with a touch-up treatment, if deemed necessary, offered 30 days later, and optional repeat treatment 9 months after initial or touch-up treatment. Subjects completed the FACE-Q Satisfaction With Skin scale and assessed willingness to recommend treatment to a friend at baseline, months 1, 4, 6, and 9, and month 1 after repeat treatment. Subjects also evaluated their return to normal daily social activities.

RESULTS

Satisfaction with skin improved from baseline in 90.8% of subjects at month 1, 88.4% at month 4, 83.6% at month 6, 76.4% at month 9, and 91.9% at month 1 after repeat treatment (P < .001, all time points). At least 94% of subjects returned to normal daily social activities one day after treatment (initial, touch-up, or repeat). More than 80% of subjects said they would recommend treatment to a friend at all time points through month 9 (97% at month 1 after repeat treatment).

CONCLUSION

Treatment with VYC-12 significantly improved satisfaction with skin in the majority of subjects, with most subjects returning to normal activities 1 day after treatment.

The Visual Word Booster: A Spatial Layout of Words Descriptor Exploiting Contour Cues

Although researchers have made efforts to use the spatial information of visual words to obtain better image representations, none of the studies take contour cues into account. Meanwhile, it has been shown that contour cues are important to the perception of imagery in the literature. Inspired by these studies, we propose to use the Spatial Layout of Words (SLoW) to boost visual word based image descriptors by exploiting contour cues. Essentially, the SLoW descriptor utilises contours and incorporates different types of commonly used visual words, including hand-crafted basic contour elements (referred to as "contons"), textons and Scale-Invariant Feature Transform (SIFT) words, deep convolutional words and a special type of words: LBP (Local Binary Pattern) codes. Moreover, SLoW features are combined with Spatial Pyramid Matching (SPM) or Vector of Locally Aggregated Descriptors (VLAD) features. The SLoW descriptor and its combined versions are tested in different tasks. Our results show that they are superior to, or at least comparable to, their counterparts examined in this study. In particular, the joint use of the SLoW descriptor boosts the performance of the SPM and VLAD descriptors. We attribute these results to the fact that contour cues are important to human visual perception and, the SLoW descriptor captures not only local image characteristics but also the global spatial layout of these characteristics in a more perceptually consistent way than its counterparts.

Facial Contrast Is a Cross-Cultural Cue for Perceiving Age

Age is a fundamental social dimension and a youthful appearance is of importance for many individuals, perhaps because it is a relevant predictor of aspects of health, facial attractiveness and general well-being. We recently showed that facial contrast-the color and luminance difference between facial features and the surrounding skin-is age-related and a cue to age perception of Caucasian women. Specifically, aspects of facial contrast decrease with age in Caucasian women, and Caucasian female faces with higher contrast look younger (Porcheron et al., 2013). Here we investigated faces of other ethnic groups and raters of other cultures to see whether facial contrast is a cross-cultural youth-related attribute. Using large sets of full face color photographs of Chinese, Latin American and black South African women aged 20-80, we measured the luminance and color contrast between the facial features (the eyes, the lips, and the brows) and the surrounding skin. Most aspects of facial contrast that were previously found to decrease with age in Caucasian women were also found to decrease with age in the other ethnic groups. Though the overall pattern of changes with age was common to all women, there were also some differences between the groups. In a separate study, individual faces of the 4 ethnic groups were perceived younger by French and Chinese participants when the aspects of facial contrast that vary with age in the majority of faces were artificially increased, but older when they were artificially decreased. Altogether these findings indicate that facial contrast is a cross-cultural cue to youthfulness. Because cosmetics were shown to enhance facial contrast, this work provides some support for the notion that a universal function of cosmetics is to make female faces look younger.

An Own-Age Bias in Recognizing Faces with Horizontal Information

Horizontal information, as a result of a selective filtering process, is essential in younger adults’ (YA) ability to recognize human faces. Obermeyer et al. (2012) recently reported impaired recognition of faces with horizontal information in older adults (OA) suggesting age-variant processing. Two yet unconsidered factors (stimulus age and exposure duration) that may have influenced previous results, were investigated in this study. Forty-seven YA (18–35 years) and 49 OA (62–83 years) were tested in a 2 × 2 × 2 × 2 mixed design with the between-subjects factors age group (YA vs. OA) and stimulus age (young faces vs. older faces) and the within-subjects factors filter [filtered (HF) faces vs. unfiltered faces (UF)] and exposure duration (0.8 s vs. 8 s). Subjects were presented morph videos between pairs of faces: a starting face gradually merged into either the previously encoded target face or a control face. As expected, results showed an increase in recognition sensitivity (d′) with longer exposure duration in YA with both younger and older HF faces. OA, however, were unable to recognize filtered young faces not even with increased exposure duration. Furthermore, only elderly participants showed more accurate recognition with faces of their own age relative to other-age faces (own-age bias, OAB). For YA no OAB was observed. Filtered face recognition was significantly correlated with unfiltered recognition in YA but not in OA. It is concluded, that processing of horizontal information changes at a higher age. Presenting filtered or unfiltered faces both targets convergent face-specific processing only in YA but not in OA.

Smiling makes you look older

People smile in social interactions to convey different types of nonverbal communication. However, smiling can potentially change the way a person is perceived along different facial dimensions, including perceived age. It is commonly assumed that smiling faces are perceived as younger than faces carrying a neutral expression. In the series of experiments reported here, I describe an unintuitive and robust effect in the opposite direction. Across different experimental conditions and stimulus sets, smiling faces were consistently perceived as older compared to neutral face photos of the same persons. I suggest that this effect is due to observer failure to ignore smile-associated wrinkles, mainly along the region of the eyes. These findings point to a misconception regarding the relationship between facial smile and perceived age and shed new light on the processes underlying human age perception.

Recognizing and identifying people: A neuropsychological review

Recognizing people is a classic example of a cognitive function that involves multiple processing stages and parallel routes of information. Neuropsychological data have provided important evidence for models of this process, particularly from case reports; however, the quality and extent of the data varies widely between studies. In this review we first discuss the requirements and logical basis of the types of neuropsychological evidence to support conclusions about the modules in this process. We then survey the adequacy of the current body of reports to address two key issues. First is the question of which cognitive operation generates a sense of familiarity: the current debate revolves around whether familiarity arises in modality-specific recognition units or later amodal processes. Key evidence on this point comes from the search for dissociations between familiarity for faces, voices and names. The second question is whether lesions can differentially affect the abilities to link diverse sources of person information (e.g., face, voice, name, biographic data). Dissociations of these linkages may favor a 'distributed-only' model of the organization of semantic knowledge, whereas a 'person-hub' model would predict uniform impairments of all linkages. While we conclude that there is reasonable evidence for dissociations in name, voice and face familiarity in regards to the first question, the evidence for or against dissociated linkages between information stores in regards to the second question is tenuous at best. We identify deficiencies in the current literature that should motivate and inform the design of future studies.

Interactions between the perception of age and ethnicity in faces: an event-related potential study

Face perception models propose that different facial attributes are processed by anatomically distinct neural pathways that partially overlap. Whether these attributes interact functionally is an open question. Our goal was to determine if there are interactions between age and ethnicity processing and, if so, at what temporal epoch these interactions are evident. We monitored event-related potentials on electroencephalography while subjects categorized faces by age or ethnicity in two conditions: a baseline in which the other of these two properties not being categorized was held constant and an interference condition in which it also varied, as modelled after the Garner interference paradigm. We found that, when participants were categorizing faces by age, variations in ethnicity increased the amplitude of the right face-selective N170 component. When subjects were categorizing faces by ethnicity, variations in age did not alter the N170. We concluded that there is an asymmetric pattern of influence between age and ethnicity on early face-specific stages of visual processing, which has parallels with behavioural evidence of asymmetric interactions between identity and expression processing of faces.

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.

Global Shape Information Increases but Color Information Decreases the Composite Face Effect

The separation of visual shape and surface information may be useful for understanding holistic face perception—that is, the perception of a face as a single unit (Jiang, Blanz, & Rossion, 2011, Visual Cognition, 19, 1003–1034). A widely used measure of holistic face perception is the composite face effect (CFE), in which identical top face halves appear different when aligned with bottom face halves from different identities. In the present study the influences of global face shape (ie contour of the face) and color information on the CFE are investigated, with the hypothesis that global face shape supports but color impairs holistic face perception as measured in this paradigm. In experiment 1 the CFE is significantly increased when face stimuli possess natural global shape information than when cropped to a generic (ie oval) global shape; this effect is not found when the stimuli are presented inverted. In experiment 2 the CFE is significantly decreased when face stimuli are presented with color information than when presented in grayscale. These findings indicate that grayscale stimuli maintaining natural global face shape information provide the most adept measure of holistic face perception in the behavioral composite face paradigm. More generally, they show that reducing different types of information diagnostic for individual face perception can have opposite effects on the CFE, illustrating the functional dissociation between shape and surface information in face perception.

Adding years to your life (or at least looking like it): a simple normalization underlies adaptation to facial age

Adaptation has been widely used to probe how experience shapes the visual encoding of faces, but the pattern of perceptual changes produced by adaptation and the neural mechanisms these imply remain poorly characterized. We explored how adaptation alters the perceived age of faces, a fundamental facial attribute which can uniquely and reliably be scaled by observers. This allowed us to measure how adaptation to one age level affected the full continuum of perceived ages. Participants guessed the ages of faces ranging from 18-89, before or after adapting to a different set of faces composed of younger, older, or middle-aged adults. Adapting to young or old faces induced opposite linear shifts in perceived age that were independent of the model's age. Specifically, after adapting to younger or older faces, faces of all ages appeared 2 to 3 years older or younger, respectively. In contrast, middle-aged adaptors induced no aftereffects. This pattern suggests that adaptation leads to a simple and uniform renormalization of age perception, and is consistent with a norm-based neural code for the mechanisms mediating the perception of facial age.

Erasing the face after-effect

Perceptual after-effects decay over time at a rate that depends on several factors, such as the duration of adaptation and the duration of the test stimuli. Whether this decay is accelerated by exposure to other faces after adaptation is not known. Our goal was to determine if the appearance of other faces during a delay period after adaptation affected the face identity after-effect. In the first experiment we investigated whether, in the perception of ambiguous stimuli created by morphing between two faces, the repulsive after-effects from adaptation to one face were reduced by brief presentation of the second face in a delay period. We found no effect; however, this may have been confounded by a small attractive after-effect from the interference face. In the second experiment, the interference stimuli were faces unrelated to those used as adaptation stimuli, and we examined after-effects at three different delay periods. This showed a decline in after-effects as the time since adaptation increased, and an enhancement of this decline by the presentation of intervening faces. An exponential model estimated that the intervening faces caused an 85% reduction in the time constant of the after-effect decay. In conclusion, we confirm that face after-effects decline rapidly after adaptation and that exposure to other faces hastens the re-setting of the system.

The visual representations of words and style in text: an adaptation study

While the nature of face representations in the human perceptual system has been extensively studied using adaptation, there has been little investigation using this technique of the neural basis of another parallel class of high-level objects, words. We used the perceptual-bias technique to determine if aftereffects could be generated for either the word content or stylistic properties of textual stimuli, and if these aftereffects showed invariance for the non-adapted dimension. In a first experiment, we examined adaptation for word versus handwriting style. In a second experiment we contrasted adaptation for words with adaptation for computer font. The third experiment performed a similar study of aftereffects for words and case. In all three experiments we consistently found adaptation for words, which were not diminished by changing the style between the adapting and probe stimuli: hence word aftereffects are invariant for handwriting, font and case. Aftereffects were negligible for style. Additional analyses showed that discriminative ability was better for word than for style content. These results confirm that the neural representations of words can be probed with the adaptation technique and suggest that adaptation accesses word representations at an abstract level, where the identity of a word is invariant for stylistic properties.