Electrophysiological correlates of processing own- and other-race faces

Decoding the Temporal Structures and Interactions of Multiple Face Dimensions Using Optically Pumped Magnetometer Magnetoencephalography (OPM-MEG)

Humans possess a remarkable ability to rapidly access diverse information from others' faces with just a brief glance, which is crucial for intricate social interactions. While previous studies using event-related potentials/fields have explored various face dimensions during this process, the interplay between these dimensions remains unclear. Here, by applying multivariate decoding analysis to neural signals recorded with optically pumped magnetometer magnetoencephalography, we systematically investigated the temporal interactions between invariant and variable aspects of face stimuli, including race, gender, age, and expression. First, our analysis revealed unique temporal structures for each face dimension with high test-retest reliability. Notably, expression and race exhibited a dominant and stably maintained temporal structure according to temporal generalization analysis. Further exploration into the mutual interactions among face dimensions uncovered age effects on gender and race, as well as expression effects on race, during the early stage (∼200-300 ms postface presentation). Additionally, we observed a relatively late effect of race on gender representation, peaking ∼350 ms after the stimulus onset. Taken together, our findings provide novel insights into the neural dynamics underlying the multidimensional aspects of face perception and illuminate the promising future of utilizing OPM-MEG for exploring higher-level human cognition.

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.

Do perceptual expertise and implicit racial bias predict early face-sensitive ERP responses?

Studies examining the visual perception of face race have revealed mixed findings regarding the presence or direction of effects on early face-sensitive event-related potential (ERP) components. Few studies have examined how early ERP components are influenced by individual differences in bottom-up and top-down processes involved in face perception, and how such factors might interact to influence early face-sensitive ERP components has yet to be investigated. Thus, the current study examined whether P100, N170, and P200 responses can be predicted by individual differences in own- and other-race face recognition, implicit racial bias, and their interaction. Race effects were observed in the P100, N170, and P200 responses. Other-race face recognition, implicit racial biases, and their interaction explained a significant amount of unique variability in N170 responses when viewing other-race faces. Responses to own-race faces were minimally influenced with only implicit racial bias predicting a significant amount of unique variability in N170 latency when viewing own-race faces. Face recognition, implicit racial bias, or their interaction did not predict P100 responses. The current findings suggest that face recognition abilities and its interaction with implicit racial bias modulate the early stages of other-race face processing.

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.

Prejudice drives exogenous attention to outgroups

Exogenous attention allows the automatic detection of relevant stimuli and the reorientation of our current focus of attention towards them. Faces from an ethnic outgroup tend to capture exogenous attention to a greater extent than faces from an ethnic ingroup. We explored whether prejudice toward the outgroup, rather than lack of familiarity, is driving this effect. Participants (N = 76) performed a digit categorization task while distractor faces were presented. Faces belonged to (i) a prejudiced outgroup, (ii) a non-prejudiced outgroup and (iii) their ingroup. Half of the faces were previously habituated in order to increase their familiarity. Reaction times, accuracy and event-related potentials (ERPs) were recorded to index exogenous attention to distractor faces. Additionally, different indexes of explicit and implicit prejudice were measured, the latter being significantly greater towards prejudiced outgroup. N170 amplitude was greater to prejudiced outgroup-regardless of their habituation status-than to both non-prejudiced outgroup and ingroup faces and was associated with implicit prejudice measures. No effects were observed at the behavioral level. Our results show that implicit prejudice, rather than familiarity, is under the observed attention-related N170 effects and that this ERP component may be more sensitive to prejudice than behavioral measures under certain circumstances.

Are We Sensitive to Different Types of Safety Signs? Evidence from ERPs

Purpose

Safety signs are widely used to deliver safety-related information. There are many different types of safety signs. Although previous studies have paid attention to the design and effectiveness of safety signs, little attention has been devoted to investigating how people process the information conveyed by different types of safety signs. Accordingly, the current study is intended to explore the neural mechanisms underlying people’s perception of different types of safety signs.

Methods

Three types of safety signs (prohibition, mandatory and warning signs) were used in the study. We employed questionnaire and event-related potentials (ERPs) experiment with an implicit paradigm to probe how people perceive these three types of safety signs.

Results

Behaviorally, warning signs induced a higher level of perceived hazard than prohibition signs and mandatory signs, and prohibition signs induced a higher level of perceived hazard than mandatory signs. At the brain level, prohibition signs and warning signs led to reduced P2 amplitudes compared to mandatory signs. In addition, warning signs elicited larger N2 and N4 amplitudes than prohibition signs and mandatory signs, and prohibition signs elicited larger N2 and N4 amplitudes than mandatory signs, coinciding with the behavioral results.

Conclusion

Different types of safety signs led to significant differences in individuals’ hazard perception. Based on the neural results, we suggest that the processing of safety signs consists of two stages: the rapid detection of hazard information (indicated by P2) and the conscious integration of hazard information in working memory (indicated by N2 and N4).

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.

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.

Theory of Mind Impairments in Youth at Clinical High Risk of Psychosis

OBJECTIVE

The normal maturational processes of theory of mind (ToM) capacity are ongoing during adolescence and even early adulthood. However, research has shown that ToM ability also declines among adults suffering from prodromal psychotic experiences. The goal of this study was to investigate the characteristics of ToM performance in youth with clinical high risk (CHR) of psychosis.

METHODS

The Reading Mind in Eyes Task (RMET), including own-race and other-race eyes, was administered to 40 CHR youth; 42 age-, gender-, and education-matched healthy controls (HCs); and 62 adult patients with schizophrenia (SZ). Nine-month follow-up data were collected from 31 CHR subjects, of whom 7 (22.6%) had made the transition to psychosis.

RESULTS

CHR youth showed significant impairment in RMET performance compared to HC youth but performed better than did SZ patients. Moreover, they were significantly slower than were HC youth in responding to the RMET, with a response time similar to that of SZ patients. In particular, they had significantly poorer accuracy in interpreting positive and neutral eye expressions compared to the HC group, but not in interpreting negative eye expressions. Preliminary follow-up data showed a trend toward significance (p = 0.079) for RMET performance between those who transitioned to psychosis and those who did not.

CONCLUSIONS

Our findings illustrate that deficits in ToM capacity, specifically the ability to interpret people's mental state from eye expressions, occur early on in prodromal psychosis in youth. Early interventions for CHR youth focusing on ToM enhancement may halt progress toward psychosis.

Brain Signals of Face Processing as Revealed by Event-Related Potentials

We analyze the functional significance of different event-related potentials (ERPs) as electrophysiological indices of face perception and face recognition, according to cognitive and neurofunctional models of face processing. Initially, the processing of faces seems to be supported by early extrastriate occipital cortices and revealed by modulations of the occipital P1. This early response is thought to reflect the detection of certain primary structural aspects indicating the presence grosso modo of a face within the visual field. The posterior-temporal N170 is more sensitive to the detection of faces as complex-structured stimuli and, therefore, to the presence of its distinctive organizational characteristics prior to within-category identification. In turn, the relatively late and probably more rostrally generated N250r and N400-like responses might respectively indicate processes of access and retrieval of face-related information, which is stored in long-term memory (LTM). New methods of analysis of electrophysiological and neuroanatomical data, namely, dynamic causal modeling, single-trial and time-frequency analyses, are highly recommended to advance in the knowledge of those brain mechanisms concerning face processing.

Human sex differences in emotional processing of own-race and other-race faces

There is evidence that women and men show differences in the perception of affective facial expressions. However, none of the previous studies directly investigated sex differences in emotional processing of own-race and other-race faces. The current study addressed this issue using high time resolution event-related potential techniques. In total, data from 25 participants (13 women and 12 men) were analyzed. It was found that women showed increased N170 amplitudes to negative White faces compared with negative Chinese faces over the right hemisphere electrodes. This result suggests that women show enhanced sensitivity to other-race faces showing negative emotions (fear or disgust), which may contribute toward evolution. However, the current data showed that men had increased N170 amplitudes to happy Chinese versus happy White faces over the left hemisphere electrodes, indicating that men show enhanced sensitivity to own-race faces showing positive emotions (happiness). In this respect, men might use past pleasant emotional experiences to boost recognition of own-race faces.

Configural processing advantage for Mongoloid than Caucasian faces during the structure coding stage

Configural processing is considered to be the hallmark of face expertise, which has been widely investigated by face global inversion (inversion effect) and local inversion (Thatcher effect). Using a passive detection task in which face stimuli are task-irrelevant, both the face inversion effect and the Thatcher effect on race perception of faces were investigated. We found that although the N170 inversion effect (enhanced and delayed N 170 for inverted than upright condition) was similar across races of faces, Chinese participants showed a larger N 170 Thatcher effect (enhanced N 170 to Thatcherized faces than normal faces) for Mongoloid faces. The present data indicates the perceptual advantage of configural changes for in-group than out-group faces.

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.