The importance of skin color and facial structure in perceiving and remembering others: An electrophysiological study

Neural timing of the other-race effect across the lifespan: A review

Face race influences the way we process faces, so that faces of a different ethnic group are processed for identity less efficiently than faces of one's ethnic group - a phenomenon known as the Other-Race Effect (ORE). Although widely replicated, the ORE is still poorly characterized in terms of its development and the underlying mechanisms. In the last two decades, the Event-Related Potential (ERP) technique has brought insight into the mechanisms underlying the ORE and has demonstrated potential to clarify its development. Here, we review the ERP evidence for a differential neural processing of own-race and other-race faces throughout the lifespan. In infants, race-related processing differences emerged at the N290 and P400 (structural encoding) stages. In children, race affected the P100 (early processing, attention) perceptual stage and was implicitly encoded at the N400 (semantic processing) stage. In adults, processing difficulties for other-race faces emerged at the N170 (structural encoding), P200 (configuration processing) and N250 (accessing individual representations) perceptual stages. Early in processing, race was implicitly encoded from other-race faces (N100, P200 attentional biases) and in-depth processing preferentially applied to own-race faces (N200 attentional bias). Encoding appeared less efficient (Dm effects) and retrieval less recollection-based (old/new effects) for other-race faces. Evidence admits the contribution of perceptual, attentional, and motivational processes to the development and functioning of the ORE, offering no conclusive support for perceptual or socio-cognitive accounts. Cross-racial and non-cross-racial studies provided convergent evidence. Future research would need to include less represented ethnic populations and the developmental population.

Understanding racial bias through electroencephalography

Research on racial bias in social and cognitive psychology has focused on automatic cognitive processes such as categorisation or stereotyping. Neuroimaging has revealed differences in the neural circuit when processing social information about one's own or another's ethnicity. This review investigates the influence of racial bias on human behaviour by reviewing studies that examined changes in neural circuitry (i.e. ERP responses) during automatic and controlled processes elicited by specific tasks. This systematic analysis of specific ERP components across different studies provides a greater understanding of how social contexts are perceived and become associated with specific stereotypes and behavioural predictions. Therefore, investigating these related cognitive and neurobiological functions can further our understanding of how racial bias affects our cognition more generally and guide more effective programs and policies aimed at its mitigation.

The role of task demands in racial face encoding

People more accurately remember faces of their own racial group compared to faces of other racial groups; this phenomenon is called the other-race effect. To date, numerous researchers have devoted themselves to exploring the reasons for this other-race effect, and they have posited several theoretical explanations. One integrated explanation is the categorization-individuation model, which addresses two primary ways (categorization and individuation) of racial face processing and emphasizes the emergence of these two ways during the encoding stage. Learning-recognition and racial categorization tasks are two classical tasks used to explore racial face processing. Event-related potentials can facilitate investigation of the encoding differences of own- and other-race faces under these two typical task demands. Unfortunately, to date, results have been mixed. In the current study, we investigated whether categorization and individuation differ for own- and other-race faces during the encoding stage by using racial categorization and learning-recognition tasks. We found that task demands not only influence the encoding of racial faces, but also have a more profound effect in the encoding stage of recognition tasks for other-race faces. More specifically, own-race faces demonstrate deeper structural encoding than other-race faces, with less attentional involvement. Moreover, recognitions tasks might ask for more individual-level encoding, requiring more attentional resources in the early stage that may be maintained until relatively late stages. Our results provide some evidence concerning task selection for future racial face studies and establish a groundwork for a unified interpretation of racial face encoding.

Race and early face-sensitive event-related potentials in children and adults

Studies examining children's face perception have revealed developmental changes in early and face-sensitive event-related potential (ERP) components. Children also tend to show racial biases in their face perception and evaluation of others. The current study examined how early face-sensitive ERPs are influenced by face race in children and adults. A second objective examined face recognition proficiency and implicit racial bias in relation to ERP responses to own- and other-race faces. Electroencephalographic responses were recorded while Caucasian children and adults viewed Caucasian and East Asian faces. Participants also completed recognition tasks and an IAT with Caucasian and East Asian faces. Other-race faces elicited larger P100 amplitudes than own-race faces. Furthermore, adults with better other-race recognition proficiency showed larger P100 amplitude responses to other-race faces compared with adults with worse other-race recognition proficiency. In addition, larger implicit biases favoring own-race individuals were associated with larger P100 to N170 peak-to-peak amplitudes for other-race faces in adults. In contrast, larger implicit biases favoring own-race individuals were associated with smaller P100 to N170 peak-to-peak amplitudes for both own- and other-race faces in 8- to 10-year-olds. There was also an age-related decrease in P100 to N170 peak-to-peak amplitudes for own-race faces among 5- to 10-year-olds with better own-race recognition proficiency. The age-related decrease in N170 latency for other-race faces was also more pronounced in 5- to 10-year-olds with better other-race recognition proficiency. Thus, recognition proficiency and implicit racial bias are associated with early ERP responses in adults and children, but in different ways.

Racial Ingroup Bias and Efficiency Consideration Influence Distributive Decisions: A Dynamic Analysis of Time Domain and Time Frequency

Although previous studies have demonstrated that identity had effect on justice norms and behavioral decisions, the neural mechanism of that effect remains unclear. In this study, the subjects made their distributive decisions on the trade-off between equity and efficiency among Chinese and foreign children and their scalp potentials were recorded. Behavioral results showed that efficiency consideration played an important part in the distribution task. Meanwhile, participants gave preferential treatment to same-race children. Relative to the distribution within ingroup children, the distribution involving outgroup children induced higher N170 amplitude. The distribution involving outgroup children also elicited weakened P300 amplitude and enhanced delta response than the distribution within ingroup children when subjects are facing the conflict between equality and efficiency. In other words, ingroup bias affected the neural process of the trade-off between equality and efficiency. The combination of time-domain and time-frequency analyses provided spatiotemporal and spectral results for a better understanding of racial ingroup favoritism on distributive justice.

Explicit Categorization Goals Affect Attention-Related Processing of Race and Gender During Person Construal

Faces are categorized by gender and race very quickly, seemingly without regard to perceivers' goals or motivations, suggesting an automaticity to these judgments that has downstream consequences for evaluations, stereotypes, and social interactions. The current study investigated the extent to which early neurocognitive processes involved in the categorization of faces vary when participants' tasks goals were to categorize faces by race or by gender. In contrast to previous findings, task-related differences were found, such that differentiation in the P2 event-related potential (ERP) according to perceived gender was facilitated by having an explicit task goal of categorizing faces by gender; however, the P2 was sensitive to race regardless of task goals. Use of principal components analysis (PCA) revealed two underlying components that comprised the P2 and that were differentially sensitive to the gender and race of the faces, depending on participants' top-down task goals. Results suggest that top-down task demands facilitate discrimination of faces along the attended dimension within less than 200 ms, but that the effect of top-down task demands may not be evident when examining early ERP components that reflect more than one distinct underlying process.

Social categorization modulates own-age bias in face recognition and ERP correlates of face processing

The aim of the present study was to further understanding of how social categorization influences face recognition. According to the categorization-individuation model, face recognition can either be biased toward categorization or individuation. We hypothesized that the face recognition bias associated with a social category (e.g., the own-age bias) would be larger when faces were initially categorized according to that category. To examine this hypothesis, young adults (N = 63) completed a face recognition task after either making age or sex judgments while encoding child and adult faces. Young adults showed the own-age and own-sex biases in face recognition. Consistent with our hypothesis, the magnitude of the own-age bias in face recognition was larger when individuals made age, rather than sex, judgments at encoding. To probe the mechanisms underlying this effect, we examined ERP responses to child and adult faces across the social categorization conditions. Neither the P1 nor the N170 ERP components were modulated by the social categorization task or the social category membership of the face. However, the P2, which is associated with second-order configural processing, was larger to adult faces than child faces only in the age categorization condition. The N250, which is associated with individuation, was larger (i.e., more negative) to adult than child faces and during age categorization than sex categorization. These results are interpreted within the context of the categorization-individuation model and current research on biases in face recognition.

MicroRNA-24 alleviates isoflurane-induced neurotoxicity in rat hippocampus via attenuation of oxidative stress

Several miRNAs have been recently suggested as potential therapeutic targets for anesthesia-related diseases. This study was carried out to explore the biological roles of miR-24 in isoflurane-treated rat hippocampal neurons. Isoflurane was used to induce neurotoxicity in a rat model. Gain- and loss-of-function of miR-24 was performed, and the size and Ca²⁺ permeability of mitochondria, as well as cell proliferation and apoptosis, and levels of oxidative-stress-related factors were measured both in vivo and in vitro. Dual luciferase reporter gene assays were used to identify the target relationship between miR-24 and p27^kip1. In this study, isoflurane treatment decreased miR-24 expression, after which, levels of neuron apoptosis and oxidative-stress-related factors were elevated and neuron viability was reduced. Over-expression of miR-24 inhibited oxidative damage and neuronal apoptosis in hippocampal tissues, and suppressed the size and Ca²⁺ permeability of mitochondria of hippocampal neurons. miR-24 enhanced the viability of rat hippocampal neurons by targeting p27^kip1. To conclude, this study demonstrated that miR-24 attenuates isoflurane-induced neurotoxicity in rat hippocampus via its antioxidative properties and inhibiting p27^kip1 expression.

Attention and Working Memory Biases to Black and Asian Faces During Intergroup Contexts

Categorizing and individual as a racial ingroup or outgroup member results in processing and memory differences. However, despite processing differences for racial ingroups and outgroups, very little is known about processing of racial ingroup and outgroup members during intergroup contexts. Thus, the present research investigated attention and memory differences for racial ingroup and outgroup members during competition for attention (i.e., intergroup contexts). In experiment 1, event-related potentials (ERPs) were obtained while participants completed a working memory task that presented 4 faces (2 Black, 2 White) at once then, following a short delay, were probed to indicate the spatial location of one of the faces. Participants showed better location memory for Black than White faces. During encoding, ERP results revealed differences based on the race of the face in P300 amplitudes, such that there was greater motivated processing when attending to Black faces. At probe, the N170 indicated enhanced early processing of Black faces and greater LPCs were associated with better recollection of Black face location. In a follow-up study using the same task, we examined attention and working memory biases for Asian and White faces in Caucasian and Asian participants. Results for both Caucasian and Asian participants indicated better working memory for Asian relative to White faces. Together, results indicate that during intergroup contexts, racial minority faces capture attention, resulting in better memory for those faces. The study underscores that examining racial biases with single stimuli paradigms obscures important aspects of attention and memory biases during intergroup contexts.

Using trial-level data and multilevel modeling to investigate within-task change in event-related potentials

EEG data, and specifically the ERP, provide psychologists with the power to examine quickly occurring cognitive processes at the native temporal resolution at which they occur. Despite the advantages conferred by ERPs to examine processes at different points in time, ERP researchers commonly ignore the trial-to-trial temporal dimension by collapsing across trials of similar types (i.e., the signal averaging approach) because of constraints imposed by repeated measures ANOVA. Here, we present the advantages of using multilevel modeling (MLM) to examine trial-level data to investigate change in neurocognitive processes across the course of an experiment. Two examples are presented to illustrate the usefulness of this technique. The first demonstrates decreasing differentiation in N170 amplitude to faces of different races across the course of a race categorization task. The second demonstrates attenuation of the ERN as participants commit more errors within a task designed to measure implicit racial bias. Although the examples presented here are within the realm of social psychology, the use of MLM to analyze trial-level EEG data has the potential to contribute to a number of different theoretical domains within psychology.

Fair Play: A Study of Scientific Workforce Trainers' Experience Playing an Educational Video Game about Racial Bias

Explicit racial bias has decreased in the United States, but racial stereotypes still exist and conspire in multiple ways to perpetuate the underparticipation of Blacks in science careers. Capitalizing on the potential effectiveness of role-playing video games to promote the type of active learning required to increase awareness of and reduce subtle racial bias, we developed the video game Fair Play, in which players take on the role of Jamal, a Black male graduate student in science, who experiences discrimination in his PhD program. We describe a mixed-methods evaluation of the experience of scientific workforce trainers who played Fair Play at the National Institutes of Health Division of Training Workforce Development and Diversity program directors' meeting in 2013 (n = 47; 76% female, n = 34; 53% nonwhite, n = 26). The evaluation findings suggest that Fair Play can promote perspective taking and increase bias literacy, which are steps toward reducing racial bias and affording Blacks equal opportunities to excel in science.

The Effects of Face Inversion and Face Race on the P100 ERP

Research about the neural basis of face recognition has investigated the timing and anatomical substrates of different stages of face processing. Scalp-recorded ERP studies of face processing have focused on the N170, an ERP with a peak latency of ∼170 msec that has long been associated with the initial structural encoding of faces. However, several studies have reported earlier ERP differences related to faces, suggesting that face-specific processes might occur before N170. Here, we examined the influence of face inversion and face race on the timing of face-sensitive scalp-recorded ERPs by examining neural responses to upright and inverted line-drawn and luminance-matched white and black faces in a sample of white participants. We found that the P100 ERP evoked by inverted faces was significantly larger than that evoked by upright faces. Although this inversion effect was statistically significant at 100 msec, the inverted-upright ERP difference peaked at 138 msec, suggesting that it might represent an activity in neural sources that overlap with P100. Inverse modeling of the inversion effect difference waveform suggested possible neural sources in pericalcarine extrastriate visual cortex and lateral occipito-temporal cortex. We also found that the inversion effect difference wave was larger for white faces. These results are consistent with behavioral evidence that individuals process the faces of their own races more configurally than faces of other races. Taken together, the inversion and race effects observed in the current study suggest that configuration influences face processing by at least 100 msec.

Detecting gender before you know it: How implementation intentions control early gender categorization

Gender categorization is highly automatic. Studies measuring ERPs during the presentation of male and female faces in a categorization task showed that this categorization is extremely quick (around 130ms, indicated by the N170). We tested whether this automatic process can be controlled by goal intentions and implementation intentions. First, we replicated the N170 modulation on gender-incongruent faces as reported in previous research. This effect was only observed in a task in which faces had to be categorized according to gender, but not in a task that required responding to a visual feature added to the face stimuli (the color of a dot) while gender was irrelevant. Second, it turned out that the N170 modulation on gender-incongruent faces was altered if a goal intention was set that aimed at controlling a gender bias. We interpret this finding as an indicator of nonconscious goal pursuit. The N170 modulation was completely absent when this goal intention was furnished with an implementation intention. In contrast, intentions did not alter brain activity at a later time window (P300), which is associated with more complex and rather conscious processes. In line with previous research, the P300 was modulated by gender incongruency even if individuals were strongly involved in another task, demonstrating the automaticity of gender detection. We interpret our findings as evidence that automatic gender categorization that occurs at a very early processing stage can be effectively controlled by intentions.

We are more selfish than we think: The endowment effect and reward processing within the human medial-frontal cortex

Perceived ownership has been shown to impact a variety of cognitive processes: attention, memory, and--more recently--reward processing. In the present experiment we examined whether or not perceived ownership would interact with the construct of value-the relative worth of an object. Participants completed a simple gambling game in which they gambled either for themselves or for another while electroencephalographic data were recorded. In a key manipulation, gambles for oneself or for another were for either small or large rewards. We tested the hypothesis that value affects the neural response to self-gamble outcomes, but not other-gamble outcomes. Our experimental data revealed that while participants learned the correct response option for both self and other gambles, the reward positivity evoked by wins was impacted by value only when gambling for oneself. Importantly, our findings provide additional evidence for a self-ownership bias in cognitive processing and further demonstrate the insensitivity of the medial-frontal reward system to gambles for another.

The neuroscience of prejudice and stereotyping

Despite global increases in diversity, social prejudices continue to fuel intergroup conflict, disparities and discrimination. Moreover, as norms have become more egalitarian, prejudices seem to have 'gone underground', operating covertly and often unconsciously, such that they are difficult to detect and control. Neuroscientists have recently begun to probe the neural basis of prejudice and stereotyping in an effort to identify the processes through which these biases form, influence behaviour and are regulated. This research aims to elucidate basic mechanisms of the social brain while advancing our understanding of intergroup bias in social behaviour.

The role of featural processing in other-race face classification advantage: an ERP study

The current study investigated the time course of the other-race advantage (ORCA) in the subordinate classification of faces and isolated eyes by race. A significant ORCA was found on RTs to both full faces and isolated eyes and faces were classified faster and more accurate than eyes. The ERP data showed that for both stimuli the categorization processes follow basic level classification of physiognomic stimuli, which is not influenced by the stimulus race. The most conspicuous difference between own-race and other-race stimuli as well as between faces and isolated eyes was found in the modulation of the P3 component. The overall pattern of these modulations suggests that the classification of own-race faces is delayed. Since the amplitude of the P3 is sensitive primarily to the perceptual demands of a task, these data suggest that the delay of the own-race classification is caused by an own-race specific process that precedes or interferes with the subordinate classification.

Knowledge is power: how conceptual knowledge transforms visual cognition

In this review, we synthesize the existing literature demonstrating the dynamic interplay between conceptual knowledge and visual perceptual processing. We consider two theoretical frameworks that demonstrate interactions between processes and brain areas traditionally considered perceptual or conceptual. Specifically, we discuss categorical perception, in which visual objects are represented according to category membership, and highlight studies showing that category knowledge can penetrate early stages of visual analysis. We next discuss the embodied account of conceptual knowledge, which holds that concepts are instantiated in the same neural regions required for specific types of perception and action, and discuss the limitations of this framework. We additionally consider studies showing that gaining abstract semantic knowledge about objects and faces leads to behavioral and electrophysiological changes that are indicative of more efficient stimulus processing. Finally, we consider the role that perceiver goals and motivation may play in shaping the interaction between conceptual and perceptual processing. We hope to demonstrate how pervasive such interactions between motivation, conceptual knowledge, and perceptual processing are in our understanding of the visual environment, and to demonstrate the need for future research aimed at understanding how such interactions arise in the brain.

Do neural correlates of face expertise vary with task demands? Event-related potential correlates of own- and other-race face inversion

We are typically more accurate at remembering own- than other-race faces. This “own-race bias” has been suggested to result from enhanced expertise with and more efficient perceptual processing of own-race than other-race faces. In line with this idea, the N170, an event-related potential correlate of face perception, has been repeatedly found to be larger for other-race faces. Other studies, however, found no difference in N170 amplitude for faces from diverse ethnic groups. The present study tested whether these seemingly incongruent findings can be explained by varying task demands. European participants were presented with upright and inverted European and Asian faces (as well as European and Asian houses), and asked to either indicate the ethnicity or the orientation of the stimuli. Larger N170s for other-race faces were observed in the ethnicity but not in the orientation task, suggesting that the necessity to process facial category information is a minimum prerequisite for the occurrence of the effect. In addition, N170 inversion effects, with larger amplitudes for inverted relative to upright stimuli, were more pronounced for own- relative to other-race faces in both tasks. Overall, the present findings suggest that the occurrence of ethnicity effects in N170 for upright faces depends on the amount of facial detail required for the task at hand. At the same time, the larger inversion effects for own- than other-race faces occur independent of task and may reflect the fine-tuning of perceptual processing to faces of maximum expertise.

The influence of flankers on race categorization of faces

Context affects multiple cognitive and perceptual processes. In the present study, we asked how the context of a set of faces would affect the perception of a target face's race in two distinct tasks. In Experiments 1 and 2, participants categorized target faces according to perceived racial category (Black or White). In Experiment 1, the target face was presented alone or with Black or White flanker faces. The orientation of flanker faces was also manipulated to investigate how face inversion effect would interact with the influences of flanker faces on the target face. The results showed that participants were more likely to categorize the target face as White when it was surrounded by inverted White faces (an assimilation effect). Experiment 2 further examined how different aspects of the visual context would affect the perception of the target face by manipulating flanker faces' shape and pigmentation, as well as their orientation. The results showed that flanker faces' shape and pigmentation affected the perception of the target face differently. While shape elicited a contrast effect, pigmentation appeared to be assimilative. These novel findings suggest that the perceived race of a face is modulated by the appearance of other faces and their distinct shape and pigmentation properties. However, the contrast and assimilation effects elicited by flanker faces' shape and pigmentation may be specific to race categorization, since the same stimuli used in a delayed matching task (Experiment 3) revealed that flanker pigmentation induced a contrast effect on the perception of target pigmentation.

Electrophysiological correlates of processing own- and other-race faces

Most adults have more experience in identifying faces of their own race than in identifying faces from another race, and thus may be considered as own-race face experts. This effect was investigated by recording and analyzing ERPs as well as induced gamma oscillations. The race modulation occurred post the stage of structural processing revealed by N170. Larger P2 component and induced gamma activity for own-race than other-race faces could be associated with more elaborate processing on the basis of configural computation due to more experience that we have for own-race faces.

Structural face encoding: How task affects the N170's sensitivity to race

The N170 event-related potential (ERP) component differentiates faces from non-faces, but studies aimed at investigating whether the processing indexed by this component is also sensitive to racial differences among faces have garnered conflicting results. Here, we explore how task affects the influence of race on the N170 among White participants. N170s were larger to ingroup White faces than outgroup Black faces, but only for those required to attend to race, suggesting that attention to race can result in deeper levels of processing for ingroup members. Conversely, N170s were larger to Black faces than White faces for participants who attended to the unique identity of the faces, suggesting that attention to identity can result in preferential recruitment of cognitive resources for outgroup members. Taken together, these findings suggest that race can differentially impact face processing at early stages of encoding, but differences in processing are contingent upon one's goal state.

Relative influences of lightness and facial morphology on perceived race

In a recent study (Brooks and Gwinn, 2010 Perception 39 1142-1145), the lightness contrast illusion was employed to study the influences of skin tone and facial morphology on race perception. The findings were rather counterintuitive: they suggested that skin tone does not play a major role in racial categorisation. To investigate this further, we used a parametric paradigm including five lightness levels, five morphing levels, and two face orientations. In accordance with Brooks and Gwinn, we found that race categorisation of African-American and Caucasian faces by Caucasian participants relied mainly on morphological cues. However, the relative influence of lightness increased when morphological information was ambiguous and when the faces were upside down. Overall, the results point to a flexible multicue-based mechanism underlying race perception.