Racial salience modulated the face race lightness illusion: A comparative study of Caucasians and Asians.

Previous research has demonstrated the existence of the face race lightness (FRL) illusion. It indicates that Black faces tend to appear darker than White faces, even when their luminance values are objectively adjusted to be the same. However, the debate over the exclusive influence of face-race categories on the FRL illusion continues, with the impact of racial groups on the illusion remaining relatively unexplored. To address these gaps, we conducted studies to investigate whether the FRL illusion varies in terms of racial salience and racial groups. We manipulated the racial salience by altering the orientation of the faces. A total of 64 Caucasians (Study 1) and 63 Asians (Study 2) were recruited. Participants were shown pairs of faces in rapid succession and were asked to report which face appeared lighter or darker. In each trial, the two faces belonged to the same race category: Black, Black-White ambiguous, or White. The luminance of the first face remained consistent across trials while the luminance of the second face varied and was adjusted across eight levels (- 20, - 12, - 8, - 4, + 4, + 8, + 12, + 20). Our findings reveal that the FRL illusion is largely dependent on the salience of face-race information. When faces were presented upright, the FRL illusion was prominent; however, it disappeared when faces were inverted. Remarkably, the FRL illusion was observed not only in Caucasians but also in Asians. Therefore, our results suggest that the FRL illusion primarily stems from race salience rather than participants' racial groups.

Rigid facial motion at study facilitates the holistic processing of own-race faces during the structural encoding stage.

Holistic processing is a fundamental element of face-recognition studies. Some behavioral studies have investigated the impact of rigid facial motion on holistic face processing, yet it is still unclear how rigid motion affects the time course of holistic face processing for different face races. The current study investigated this issue, using the composite face effect (CFE) as a direct measure of holistic processing. Participants were asked to match the identity of the top half of a static composite face with the study face during the test stage, where the study face was either static or rigidly-moving. ERP results showed that rigidly-moving study faces elicited a larger CFE relative to static study faces in the N170 component when recognizing own-race faces. The amplitude of P1, N170 and P2 components indicated that rigid motion facilitated holistic face processing, with differences observed between the hemispheres over time. Specifically, the CFE was only observed after exposure to rigidly-moving faces in the P1 and P2 components of the right hemisphere. Additionally, a greater CFE was observed following exposure to rigidly-moving faces compared to static faces, particularly in the N170 component of the left hemisphere. This study suggests that holistic processing is a fundamental aspect of face perception that applies to both static and moving faces, not just static ones. Furthermore, rigid facial motion improves holistic processing of own-race faces during the structural encoding stage. These findings provide evidence of distinct neural mechanisms underlying the holistic processing of static and moving faces.

Event-related potential correlates of implicit processing of own- and other-race faces in children.

Human adults typically experience difficulties in recognizing and discriminating individual faces belonging to racial groups other than their own. The origin of this "other-race" effect is set in infancy, but the understanding of its developmental course is fragmented. We aimed to access the mechanisms of the other-race effect in childhood by unraveling the neural time course of own- and other-race face processing during a masked priming paradigm. White 6- and 7-year-old children (N = 19) categorized fully visible Asian (other-race) or White (own-race) target faces according to gender. Target faces were preceded by masked same-identity or different-identity prime faces, matching the target for race and gender. We showed an early priming effect on the N100 component, with larger amplitude to different-face pairs than to same-face pairs, and a later race effect on the N200 component, with larger amplitude to own-race face pairs than to other-race face pairs. Critically, race did not interact with priming at any processing stage (P100, N100, P200, N200, or P300). Our results suggest that race could have a temporally limited impact on face processing and that the implicit and unconscious identity processing of own- and other-race faces could be similar in 6- and 7-year-olds, depicting an immature other-race effect during childhood.

Face motion form at learning influences the time course of face spatial frequency processing during test.

Studies that use static faces suggest that facial processing follows a coarse-to-fine sequence; i.e., holistic precedes featural processing, due to low and high spatial frequencies (LSF, HSF) transmitting holistic/global and featural/local information respectively. Although recent studies have focused on the role of facial movement in holistic facial processing, it is unclear whether moving faces have the same processing mechanism as static ones, especially in the time course of processing. The current study uses the event-related potential technique to investigate this issue by manipulating the facial format at study and face spatial frequency during the test. ERP results showed that the P1 amplitude was increased by LSF faces relative to HSF ones, using both moving and static study faces, with the former larger than the latter. The N170 amplitude was more sensitive to HSF than LSF faces when only static study faces were used, while the P2 amplitude was more sensitive to LSF faces regardless of the facial study format. The above results were not modulated by the race of the faces. These results favor the view that regardless of face race, moving study faces promote holistic processing during the earliest stage of face recognition. Furthermore, holistic processing is observed to be the same for both static and moving study faces at a later stage associated with more in-depth processing. It is evident that facial motion should be factored into further studies of face recognition, given the distinctions between holistic and featural processing for moving and static study faces.

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.

Multidimensional Face Representation in a Deep Convolutional Neural Network Reveals the Mechanism Underlying AI Racism.

The increasingly popular application of AI runs the risk of amplifying social bias, such as classifying non-white faces as animals. Recent research has largely attributed this bias to the training data implemented. However, the underlying mechanism is poorly understood; therefore, strategies to rectify the bias are unresolved. Here, we examined a typical deep convolutional neural network (DCNN), VGG-Face, which was trained with a face dataset consisting of more white faces than black and Asian faces. The transfer learning result showed significantly better performance in identifying white faces, similar to the well-known social bias in humans, the other-race effect (ORE). To test whether the effect resulted from the imbalance of face images, we retrained the VGG-Face with a dataset containing more Asian faces, and found a reverse ORE that the newly-trained VGG-Face preferred Asian faces over white faces in identification accuracy. Additionally, when the number of Asian faces and white faces were matched in the dataset, the DCNN did not show any bias. To further examine how imbalanced image input led to the ORE, we performed a representational similarity analysis on VGG-Face's activation. We found that when the dataset contained more white faces, the representation of white faces was more distinct, indexed by smaller in-group similarity and larger representational Euclidean distance. That is, white faces were scattered more sparsely in the representational face space of the VGG-Face than the other faces. Importantly, the distinctiveness of faces was positively correlated with identification accuracy, which explained the ORE observed in the VGG-Face. In summary, our study revealed the mechanism underlying the ORE in DCNNs, which provides a novel approach to studying AI ethics. In addition, the face multidimensional representation theory discovered in humans was also applicable to DCNNs, advocating for future studies to apply more cognitive theories to understand DCNNs' behavior.

Infant Eye Gaze While Viewing Dynamic Faces.

Research using eye tracking methods has revealed that when viewing faces, between 6 to 10 months of age, infants begin to shift visual attention from the eye region to the mouth region. Moreover, this shift varies with stimulus characteristics and infants' experience with faces and languages. The current study examined the eye movements of a racially diverse sample of 98 infants between 7.5 and 10.5 months of age as they viewed movies of White and Asian American women reciting a nursery rhyme (the auditory component of the movies was replaced with music to eliminate the influence of the speech on infants' looking behavior). Using an analytic approach inspired by the multiverse analysis approach, several measures from infants' eye gaze were examined to identify patterns that were robust across different analyses. Although in general infants preferred the lower regions of the faces, i.e., the region containing the mouth, this preference depended on the stimulus characteristics and was stronger for infants whose typical experience included faces of more races and for infants who were exposed to multiple languages. These results show how we can leverage the richness of eye tracking data with infants to add to our understanding of the factors that influence infants' visual exploration of faces.

Perceptual integration and the composite face effect.

The composite face paradigm is widely used to investigate holistic perception of faces. In the paradigm, parts from different faces (usually the top and bottom halves) are recombined. The principal criterion for holistic perception is that responses involving the component parts of composites in which the parts are aligned into a face-like configuration are disrupted compared with the same parts in a misaligned (not face-like) format. This is often taken as evidence that seeing a whole face in the aligned condition interferes with perceiving its separate parts, but the extent to which the effect is perceptually driven remains unclear. We used salient perceptual categories of gender (male or female) and race (Asian or Caucasian appearance) to create composite stimuli from parts of faces that varied orthogonally on these characteristics. In Experiment 1, participants categorised the gender of the parts of aligned composite and misaligned images created from parts with the same (congruent) or different (incongruent) gender and the same (congruent) or different (incongruent) race. In Experiment 2, the same stimuli were used but the task changed to categorising race. In both experiments, there was a strong influence of the task-relevant manipulation on the composite effect, with slower responses to aligned stimuli with incongruent gender in Experiment 1 and incongruent race in Experiment 2. In contrast, the task-irrelevant variable (race in Experiment 1, gender in Experiment 2) did not exert much influence on the composite effect in either experiment. These findings show that although holistic integration of salient visual properties makes a strong contribution to the composite face effect, it clearly also involves targeted processing of an attended visual characteristic.