Investigating the Influence of Biological Sex on the Behavioral and Neural Basis of Face Recognition

Gyral crowns contribute to the cortical infrastructure of human face processing

Neuroanatomical features across spatial scales contribute to functional specialization and individual differences in behavior across species. Among species with gyrencephalic brains, gyral crown height, which measures a key aspect of the morphology of cortical folding, may represent an anatomical characteristic that importantly shapes neural function. Nevertheless, little is known about the relationship between functional selectivity and gyral crowns-especially in clinical populations. Here, we investigated this relationship and found that the size and gyral crown height of the middle, but not posterior, face-selective region on the fusiform gyrus (FG) was smaller in individuals with developmental prosopagnosia (DPs; N = 22, 68% female, aged 25-62) compared to neurotypical controls (NTs; N = 25, 60% females, aged 21-55), and this difference was related to face perception. Additional analyses replicated the relationship between gyral crowns and face selectivity in 1,053 NTs (55% females, aged 22-36). These results inform theoretical models of face processing while also providing a novel neuroanatomical feature contributing to the cortical infrastructure supporting face processing.

Significance Statement

Understanding how brain structure supports specialized brain functions is a central goal of neuroscience. Here, we identified a role of gyral crown height-an understudied cortical feature-in shaping the cortical infrastructure underlying face processing. By examining face-selective regions of the fusiform gyrus in both neurotypical individuals and those with developmental prosopagnosia, we demonstrate that reduced gyral crown height is associated with diminished face-selective region surface area and impaired face recognition ability. Furthermore, this structural-functional relationship extends to a large neurotypical sample of over 1,000 individuals, highlighting a generalizable link between cortical anatomy and functional specialization. These findings introduce a new neuroanatomical factor to theoretical models of face perception, which could extend to additional neurodevelopmental disorders and other cognitive tasks.

Investigating the stability of individual differences in face recognition behavior

Individual differences in face recognition abilities are characterized as heritable and resilient to change. However, this work is largely based on inter-individual differences, tends to include participants with extreme behavior (e.g., prosopagnosia, super-recognizers), and does not accommodate patterns of bias in intra-individual recognition behavior. Here, we investigated the continuity and stability of intra-individual differences in face recognition behavior among emerging adults using two tasks of unfamiliar face recognition that differ in the gender of the faces to be recognized. Although the estimate of stability is high (0.71) across the sample, there are instabilities in the behavior of many individual participants. For example, approximately 16.7% of the sample exhibited a discrepancy between tasks that was larger than 1 SD. Also, stability was more characteristic of extreme behavior. This is a bit surprising given the potential for close generalization of performance across these two tasks (identical structure and similar stimuli). Inter-individual differences in participant characteristics (i.e., gender, age, social skills) do not explain this variability. These findings are difficult to accommodate into current models of individual differences in face recognition behavior.

Challenges of face identification with varied mask coverage in the post COVID-19 era

Introduction

Recent studies have shown that wearing masks can influence face recognition abilities. During the COVID-19 pandemic, people became increasingly familiar with seeing masked faces, leading to a reduced familiarity with fully uncovered faces. With Taiwan now transitioning to a post-COVID-19 phase and the removal of mask mandates, this study investigates how varying levels of mask coverage affect face identification accuracy and response times.

Methods

We examined three levels of mask coverage-full coverage (FC), coverage up to the middle of the nose bridge (MB), and coverage up to the bottom of the nose bridge (BB)-to determine their effects on identification performance. A computer-based simulation was conducted with 100 university students (50 men and 50 women), where participants completed 30 trials (5 trials for each mask coverage level across two target sexes). Each trial presented a masked target face corresponding to one of the three coverage levels, alongside four full-face images. Participants were instructed to choose the image that best matched the masked target face, with an option to select "None" if no match was found.

Results

The findings indicate that faces with FC were identified both faster and more accurately, while those with MB coverage were the most challenging and time-consuming to recognize, particularly for female targets. The performance with BB coverage was intermediate between the other two levels.

Conclusion

This study highlights a notable shift in face identification processes in the aftermath of the pandemic, with FC now leading to quicker and more accurate recognitions, suggesting a significant adaptability in human perceptual mechanisms. These results emphasize the importance of further research into face recognition as we continue to adapt to the pandemic's lasting effects on social interactions and identity verification.

Own-gender bias in facial feature recognition yields sex differences in holistic face processing

INTRODUCTION

Female observers in their luteal cycle phase exhibit a bias towards a detail-oriented rather than global visuospatial processing style that is well-documented across cognitive domains such as pattern recognition, navigation, and object location memory. Holistic face processing involves an integration of global patterns and local parts into a cohesive percept and might thus be susceptible to the influence of sex and cycle-related processing styles. This study aims to investigate potential sex differences in the part-whole effect as a measure a of holistic face processing and explores possible relationships with sex hormone levels.

METHODS

147 participants (74 male, 51 luteal, 22 non-luteal) performed a part-whole face recognition task while being controlled for cycle phase and sex hormone status. Eye tracking was used for fixation control and recording of fixation patterns.

RESULTS

We found significant sex differences in the part-whole effect between male and luteal phase female participants. In particular, this sex difference was based on luteal phase participants exhibiting higher face part recognition accuracy than male participants. This advantage was exclusively observed for stimulus faces of women. Exploratory analyses further suggest a similar advantage of luteal compared to non-luteal participants, but no significant difference between non-luteal and male participants. Furthermore, testosterone emerged as a possible mediator for the observed sex differences.

CONCLUSION

Our results suggest a possible modulation of face encoding and/or recognition by sex and hormone status. Moreover, the established own-gender bias in face recognition, that is, female advantage in recognition of faces of the same gender might be based on more accurate representations of face-parts.

The neuropsychological evaluation of face identity recognition

Facial identity recognition (FIR) is arguably the ultimate form of recognition for the adult human brain. Even if the term prosopagnosia is reserved for exceptionally rare brain-damaged cases with a category-specific abrupt loss of FIR at adulthood, subjective and objective impairments or difficulties of FIR are common in the neuropsychological population. Here we provide a critical overview of the evaluation of FIR both for clinicians and researchers in neuropsychology. FIR impairments occur following many causes that should be identified objectively by both general and specific, behavioral and neural examinations. We refute the commonly used dissociation between perceptual and memory deficits/tests for FIR, since even a task involving the discrimination of unfamiliar face images presented side-by-side relies on cortical memories of faces in the right-lateralized ventral occipito-temporal cortex. Another frequently encountered confusion is between specific deficits of the FIR function and a more general impairment of semantic memory (of people), the latter being most often encountered following anterior temporal lobe damage. Many computerized tests aimed at evaluating FIR have appeared over the last two decades, as reviewed here. However, despite undeniable strengths, they often suffer from ecological limitations, difficulties of instruction, as well as a lack of consideration for processing speed and qualitative information. Taking into account these issues, a recently developed behavioral test with natural images manipulating face familiarity, stimulus inversion, and correct response times as a key variable appears promising. The measurement of electroencephalographic (EEG) activity in the frequency domain from fast periodic visual stimulation also appears as a particularly promising tool to complete and enhance the neuropsychological assessment of FIR.

Sex differences in development of functional connections in the face processing network

BACKGROUND AND PURPOSE

Understanding sex differences in typical development of the face processing network is important for elucidating disruptions during atypical development in sex-linked developmental disorders like autism spectrum disorder. Based on prior sex difference studies in other cognitive domains, this study examined whether females show increased integration of core and extended face regions with age for face viewing, while males would show increased segregation.

METHODS

This study used a cross-sectional design with typically developing children and adults (n = 133) and a functional MRI face localizer task. Psychophysiological interaction (PPI) analysis examined functional connectivity between canonical and extended face processing network regions with age, with greater segregation indexed by decreased core-extended region connectivity with age and greater integration indexed by increased core-extended region connectivity with age.

RESULTS

PPI analysis confirmed increased segregation for males-right fusiform face area (FFA) coupling to right inferior frontal gyrus (IFG) opercular when viewing faces and left amygdala when viewing objects decreased with age. Females showed increased integration with age (increased coupling of the right FFA to right IFG opercular region and right occipital face area [OFA] to right IFG orbital when viewing faces and objects, respectively) and increased segregation (decreased coupling with age of the right OFA with IFG opercular region when viewing faces).

CONCLUSIONS

Development of core and extended face processing network connectivity follows sexually dimorphic paths. These differential changes mostly occur across childhood and adolescence, with males experiencing segregation and females both segregation and integration changes in connectivity.

The Privileged Status of Peer Faces: Subordinate-level Neural Representations of Faces in Emerging Adults

Faces can be represented at a variety of different subordinate levels (e.g., race) that can become "privileged" for visual recognition in perceivers and is reflected as patterns of biases (e.g., own-race bias). The mechanisms encoding privileged status are likely varied, making it difficult to predict how neural systems represent subordinate-level biases in face processing. Here, we investigate the neural basis of subordinate-level representations of human faces in the ventral visual pathway, by leveraging recent behavioral findings indicating the privileged nature of peer faces in identity recognition for adolescents and emerging adults (i.e., ages 18-25 years). We tested 166 emerging adults in a face recognition paradigm and a subset of 31 of these participants in two fMRI task paradigms. We showed that emerging adults exhibit a peer bias in face recognition behavior, which indicates a privileged status for a subordinate-level category of faces that is not predicted based on experience alone. This privileged status of peer faces is supported by multiple neural mechanisms within the ventral visual pathway, including enhanced neural magnitude and neural size in the neural size in the fusiform area (FFA1), which is a critical part of the face-processing network that fundamentally supports the representations of subordinate-level categories of faces. These findings demonstrate organizational principles that the human ventral visual pathway uses to privilege relevant social information in face representations, which is essential for navigating human social interactions. It will be important to understand whether similar mechanisms support representations of other subordinate-level categories like race and gender.

Functionally and structurally distinct fusiform face area(s) in over 1000 participants

The fusiform face area (FFA) is a widely studied region causally involved in face perception. Even though cognitive neuroscientists have been studying the FFA for over two decades, answers to foundational questions regarding the function, architecture, and connectivity of the FFA from a large (N>1000) group of participants are still lacking. To fill this gap in knowledge, we quantified these multimodal features of fusiform face-selective regions in 1053 participants in the Human Connectome Project. After manually defining over 4,000 fusiform face-selective regions, we report five main findings. First, 68.76% of hemispheres have two cortically separate regions (pFus-faces/FFA-1 and mFus-faces/FFA-2). Second, in 26.69% of hemispheres, pFus-faces/FFA-1 and mFus-faces/FFA-2 are spatially contiguous, yet are distinct based on functional, architectural, and connectivity metrics. Third, pFus-faces/FFA-1 is more face-selective than mFus-faces/FFA-2, and the two regions have distinct functional connectivity fingerprints. Fourth, pFus-faces/FFA-1 is cortically thinner and more heavily myelinated than mFus-faces/FFA-2. Fifth, face-selective patterns and functional connectivity fingerprints of each region are more similar in monozygotic than dizygotic twins and more so than architectural gradients. As we share our areal definitions with the field, future studies can explore how structural and functional features of these regions will inform theories regarding how visual categories are represented in the brain.

The rise and fall of face recognition awareness across the life span

A core component of metacognition is cognitive awareness, insight into how one's cognitive abilities compare with others. Previous studies of cognitive awareness have focused on basic aspects of perception, memory, and learning. Further, studies of the awareness of one's social-cognitive abilities have been limited to examining awareness of others' thinking (i.e., theory of mind). The current study characterizes awareness of one's own social-cognitive abilities, specifically face recognition awareness, and examines its change across the life span. We used a large, web-based sample (N = 4,143) with a broad age range (ages 10-70), administering well-validated measures of objective (Cambridge Face Memory Test 3) and self-reported (Cambridge Face Memory Questionnaire) face recognition. We found a robust overall association between objective and self-reported face recognition (r = .42 in females, r = .36 in males). While we found that face recognition ability peaked in the early- to mid-30s, face recognition awareness peaked in the early- to mid-20s, was relatively stable throughout the 20s-40s, and declined in the 50s-60s. Relative subjective versus objective face recognition bias measures demonstrated that 10- to 18- and 51- to 70-year-olds overestimated their self-reported face recognition abilities in comparison with 19- to 50-year-olds. Finally, compared with males, females had greater face recognition awareness and a bias to relatively underestimate their face recognition abilities. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Recognition of Masked Faces in the Era of the Pandemic: No Improvement Despite Extensive Natural Exposure

Face masks, which became prevalent across the globe during the COVID-19 pandemic, have had a negative impact on face recognition despite the availability of critical information from uncovered face parts, especially the eyes. An outstanding question is whether face-mask effects would be attenuated following extended natural exposure. This question also pertains, more generally, to face-recognition training protocols. We used the Cambridge Face Memory Test in a cross-sectional study ( N = 1,732 adults) at six different time points over a 20-month period, alongside a 12-month longitudinal study ( N = 208). The results of the experiments revealed persistent deficits in recognition of masked faces and no sign of improvement across time points. Additional experiments verified that the amount of individual experience with masked faces was not correlated with the mask effect. These findings provide compelling evidence that the face-processing system does not easily adapt to visual changes in face stimuli, even following prolonged real-life exposure.

Investigation of Brain Activation Patterns Related to the Feminization or Masculinization of Body and Face Images across Genders

Previous studies demonstrated sex-related differences in several areas of the human brain, including patterns of brain activation in males and females when observing their own bodies and faces (versus other bodies/faces or morphed versions of themselves), but a complex paradigm touching multiple aspects of embodied self-identity is still lacking. We enrolled 24 healthy individuals (12 M, 12 F) in 3 different fMRI experiments: the vision of prototypical body silhouettes, the vision of static images of the face of the participants morphed with prototypical male and female faces, the vision of short videos showing the dynamic transformation of the morphing. We found differential sexual activations in areas linked to self-identity and to the ability to attribute mental states: In Experiment 1, the male group activated more the bilateral thalamus when looking at sex congruent body images, while the female group activated more the middle and inferior temporal gyrus. In Experiment 2, the male group activated more the supplementary motor area when looking at their faces; the female group activated more the dorsomedial prefrontal cortex (dmPFC). In Experiment 3, the female group activated more the dmPFC when observing either the feminization or the masculinization of their face. The defeminization produced more activations in females in the left superior parietal lobule and middle occipital gyrus. The performance of all classifiers built using single ROIs exceeded chance level, reaching an area under the ROC curves > 0.85 in some cases (notably, for Experiment 2 using the V1 ROI). The results of the fMRI tasks showed good agreement with previously published studies, even if our sample size was small. Therefore, our functional MRI protocol showed significantly different patterns of activation in males and females, but further research is needed both to investigate the gender-related differences in activation when observing a morphing of their face/body, and to validate our paradigm using a larger sample.

Introducing the female Cambridge face memory test - long form (F-CFMT+)

The Cambridge Face Memory Test (CFMT) is one of the most used assessments of face recognition abilities in the science of face processing. The original task, using White male faces, has been empirically evaluated for psychometric properties (Duchaine & Nakayama, 2006), while the longer and more difficult version (CFMT+; Russell et al., 2009) has not. Critically, no version exists using female faces. Here, we present the Female Cambridge Face Memory Test - Long Form (F-CFMT+) and evaluate the psychometric properties of this task in comparison to the Male Cambridge Face Memory Test - Long Form (M-CFMT+). We tested typically developing emerging adults (18 to 25 years old) in both Cambridge face recognition tasks, an old-new face recognition task, and a car recognition task. Results indicate that the F-CFMT+ is a valid, internally consistent measure of unfamiliar face recognition that can be used alone or in tandem with the M-CFMT+ to assess recognition abilities for young adult White faces. When used together, performance on the F-CFMT+ and M-CFMT+ can be directly compared, adding to the ability to understand face recognition abilities for different kinds of faces. The two tasks have high convergent validity and relatively good divergent validity with car recognition in the same task paradigm. The F-CFMT+ will be useful to researchers interested in evaluating a broad range of questions about face recognition abilities in both typically developing individuals and those with atypical social information processing abilities.

The development of race effects in face processing from childhood through adulthood: Neural and behavioral evidence

Most adults are better at recognizing recently encountered faces of their own race, relative to faces of other races. In adults, this race effect in face recognition is associated with differential neural representations of own- and other-race faces in the fusiform face area (FFA), a high-level visual region involved in face recognition. Previous research has linked these differential face representations in adults to viewers' implicit racial associations. However, despite the fact that the FFA undergoes a gradual development which continues well into adulthood, little is known about the developmental time-course of the race effect in FFA responses. Also unclear is how this race effect might relate to the development of face recognition or implicit associations with own- or other-races during childhood and adolescence. To examine the developmental trajectory of these race effects, in a cross-sectional study of European American (EA) children (ages 7-11), adolescents (ages 12-16) and adults (ages 18-35), we evaluated responses to adult African American (AA) and EA face stimuli, using functional magnetic resonance imaging and separate behavioral measures outside the scanner. We found that FFA responses to AA and EA faces differentiated during development from childhood into adulthood; meanwhile, the magnitudes of race effects increased in behavioral measures of face-recognition and implicit racial associations. These three race effects were positively correlated, even after controlling for age. These findings suggest that social and perceptual experiences shape a protracted development of the race effect in face processing that continues well into adulthood.

Emotion sensitivity and self-reported symptoms of generalized anxiety disorder across the lifespan: A population-based sample approach

BACKGROUND

Individuals with generalized anxiety disorder (GAD) symptoms show deficits in emotion processing, but results of prior studies have been conflicting, and little is known about developmental trajectories of emotion processing over time. We examined the association between GAD symptoms and sensitivity to recognizing emotional facial expressions (emotion sensitivity: ES) for three emotions (happiness, anger, fear) in a large, diverse, population-based sample. We hypothesized that higher anxiety scores would be associated with poorer performance, and expected that ES performance and anxiety scores would decline across the lifespan.

METHOD

Participants were 7,176 responders to a web-based ES study (age range = 10-96 years old).

RESULTS

Higher GAD-7 scores were associated with poorer ES performance for all emotion categories (happiness, anger, fear). The relationship between GAD-7 and ES scores remained significant after controlling for the effects of age and sex, and there was no significant interaction, indicating that the relationship does not change across age. Age significantly predicted ES and GAD-7 scores across emotions, with older ages showing lower ES scores and lower anxiety.

CONCLUSIONS

In the largest study of its kind, GAD symptoms were associated with impaired ES performance across three emotion types. Future research should explore the connection between anxiety symptoms, cognitive processing, and social processing to better characterize the mechanisms of how GAD is linked with both social and non-social information processing. Future work may also look at if ES is related over time to changes in anxiety, making it a promising target for intervention.

Object, spatial and social recognition testing in a single test paradigm

Animals have the ability to process information about an object or a conspecific's physical features and location, and alter its behavior when such information is updated. In the laboratory, the object, spatial and social recognition are often studied in separate tasks, making them unsuitable to study the potential dissociations and interactions among various types of recognition memories. The present study introduced a single paradigm to detect the object and spatial recognition, and social recognition of a familiar and novel conspecific. Specifically, male and female Sprague-Dawley adult (>75 days old) or preadolescent (25-28 days old) rats were tested with two objects and one social partner in an open-field arena for four 10-min sessions with a 20-min inter-session interval. After the first sample session, a new object replaced one of the sampled objects in the second session, and the location of one of the old objects was changed in the third session. Finally, a new social partner was introduced in the fourth session and replaced the familiar one. Exploration time with each stimulus was recorded and measures for the three recognitions were calculated based on the discrimination ratio. Overall results show that adult and preadolescent male and female rats spent more time exploring the social partner than the objects, showing a clear preference for social stimulus over nonsocial one. They also did not differ in their abilities to discriminate a new object, a new location and a new social partner from a familiar one, and to recognize a familiar conspecific. Acute administration of MK-801 (a NMDA receptor antagonist, 0.025 and 0.10 mg/kg, i.p.) after the sample session dose-dependently reduced the total time spent on exploring the social partner and objects in the adult rats, and had a significantly larger effect in the females than in the males. MK-801 also dose-dependently increased motor activity. However, it did not alter the object, spatial and social recognitions. These findings indicate that the new triple recognition paradigm is capable of recording the object, spatial location and social recognition together and revealing potential sex and age differences. This paradigm is also useful for the study of object and social exploration concurrently and can be used to evaluate cognition-altering drugs in various stages of recognition memories.