Perception of global facial geometry is modulated through experience

Familiarity Facilitates Detection of Angry Expressions

Personal familiarity facilitates rapid and optimized detection of faces. In this study, we investigated whether familiarity associated with faces can also facilitate the detection of facial expressions. Models of face processing propose that face identity and face expression detection are mediated by distinct pathways. We used a visual search paradigm to assess if facial expressions of emotion (anger and happiness) were detected more rapidly when produced by familiar as compared to unfamiliar faces. We found that participants detected an angry expression 11% more accurately and 135 ms faster when produced by familiar as compared to unfamiliar faces while happy expressions were detected with equivalent accuracies and at equivalent speeds for familiar and unfamiliar faces. These results suggest that detectors in the visual system dedicated to processing features of angry expressions are optimized for familiar faces.

Psychophysical profiles in super-recognizers

Facial identity matching ability varies widely, ranging from prosopagnosic individuals (who exhibit profound impairments in face cognition/processing) to so-called super-recognizers (SRs), possessing exceptional capacities. Yet, despite the often consequential nature of face matching decisions—such as identity verification in security critical settings—ability assessments tendentially rely on simple performance metrics on a handful of heterogeneously related subprocesses, or in some cases only a single measured subprocess. Unfortunately, methodologies of this ilk leave contributions of stimulus information to observed variations in ability largely un(der)specified. Moreover, they are inadequate for addressing the qualitative or quantitative nature of differences between SRs’ abilities and those of the general population. Here, therefore, we sought to investigate individual differences—among SRs identified using a novel conservative diagnostic framework, and neurotypical controls—by systematically varying retinal availability, bandwidth, and orientation of faces’ spatial frequency content in two face matching experiments. Psychophysical evaluations of these parameters’ contributions to ability reveal that SRs more consistently exploit the same spatial frequency information, rather than suggesting qualitatively different profiles between control observers and SRs. These findings stress the importance of optimizing procedures for SR identification, for example by including measures quantifying the consistency of individuals’ behavior.

Decisional space determines saccadic reaction times in healthy observers and acquired prosopagnosia

Determining the familiarity and identity of a face have been considered as independent processes. Covert face recognition in cases of acquired prosopagnosia, as well as rapid detection of familiarity have been taken to support this view. We tested P.S. a well-described case of acquired prosopagnosia, and two healthy controls (her sister and daughter) in two saccadic reaction time (SRT) experiments. Stimuli depicted their family members and well-matched unfamiliar distractors in the context of binary gender, or familiarity decisions. Observers' minimum SRTs were estimated with Bayesian approaches. For gender decisions, P.S. and her daughter achieved sufficient performance, but displayed different SRT distributions. For familiarity decisions, her daughter exhibited above chance level performance and minimum SRTs corresponding to those reported previously in healthy observers, while P.S. performed at chance. These findings extend previous observations, indicating that decisional space determines performance in both the intact and impaired face processing system.

A regional composite-face effect for species-specific recognition: Upper and lower halves play different roles in holistic processing of monkey faces

Using a composite-face paradigm, we examined the holistic processing induced by Asian faces, Caucasian faces, and monkey faces with human Asian participants in two experiments. In Experiment 1, participants were asked to judge whether the upper halves of two faces successively presented were the same or different. A composite-face effect was found for Asian faces and Caucasian faces, but not for monkey faces. In Experiment 2, participants were asked to judge whether the lower halves of the two faces successively presented were the same or different. A composite-face effect was found for monkey faces as well as for Asian faces and Caucasian faces. Collectively, these results reveal that own-species (i.e., own-race and other-race) faces engage holistic processing in both upper and lower halves of the face, but other-species (i.e., monkey) faces engage holistic processing only when participants are asked to match the lower halves of the face. The findings are discussed in the context of a region-based holistic processing account for the species-specific effect in face recognition.

Social Saliency of the Cue Slows Attention Shifts

Eye gaze is a powerful cue that indicates where another person's attention is directed in the environment. Seeing another person's eye gaze shift spontaneously and reflexively elicits a shift of one's own attention to the same region in space. Here, we investigated whether reallocation of attention in the direction of eye gaze is modulated by personal familiarity with faces. On the one hand, the eye gaze of a close friend should be more effective in redirecting our attention as compared to the eye gaze of a stranger. On the other hand, the social relevance of a familiar face might itself hold attention and, thereby, slow lateral shifts of attention. To distinguish between these possibilities, we measured the efficacy of the eye gaze of personally familiar and unfamiliar faces as directional attention cues using adapted versions of the Posner paradigm with saccadic and manual responses. We found that attention shifts were slower when elicited by a perceived change in the eye gaze of a familiar individual as compared to attention shifts elicited by unfamiliar faces at short latencies (100 ms). We also measured simple detection of change in direction of gaze in personally familiar and unfamiliar faces to test whether slower attention shifts were due to slower detection. Participants detected changes in eye gaze faster for familiar faces than for unfamiliar faces. Our results suggest that personally familiar faces briefly hold attention due to their social relevance, thereby slowing shifts of attention, even though the direction of eye movements are detected faster in familiar faces.

The Role of Familiarity for Representations in Norm-Based Face Space

According to the norm-based version of the multidimensional face space model (nMDFS, Valentine, 1991), any given face and its corresponding anti-face (which deviates from the norm in exactly opposite direction as the original face) should be equidistant to a hypothetical prototype face (norm), such that by definition face and anti-face should bear the same level of perceived typicality. However, it has been argued that familiarity affects perceived typicality and that representations of familiar faces are qualitatively different (e.g., more robust and image-independent) from those for unfamiliar faces. Here we investigated the role of face familiarity for rated typicality, using two frequently used operationalisations of typicality (deviation-based: DEV), and distinctiveness (face in the crowd: FITC) for faces of celebrities and their corresponding anti-faces. We further assessed attractiveness, likeability and trustworthiness ratings of the stimuli, which are potentially related to typicality. For unfamiliar faces and their corresponding anti-faces, in line with the predictions of the nMDFS, our results demonstrate comparable levels of perceived typicality (DEV). In contrast, familiar faces were perceived much less typical than their anti-faces. Furthermore, familiar faces were rated higher than their anti-faces in distinctiveness, attractiveness, likability and trustworthiness. These findings suggest that familiarity strongly affects the distribution of facial representations in norm-based face space. Overall, our study suggests (1) that familiarity needs to be considered in studies of mental representations of faces, and (2) that familiarity, general distance-to-norm and more specific vector directions in face space make different and interactive contributions to different types of facial evaluations.

Real-life experience with personally familiar faces enhances discrimination based on global information

Despite the agreement that experience with faces leads to more efficient processing, the underlying mechanisms remain largely unknown. Building on empirical evidence from unfamiliar face processing in healthy populations and neuropsychological patients, the present experiment tested the hypothesis that personal familiarity is associated with superior discrimination when identity information is derived based on global, as opposed to local facial information. Diagnosticity and availability of local and global information was manipulated through varied physical similarity and spatial resolution of morph faces created from personally familiar or unfamiliar faces. We found that discrimination of subtle changes between highly similar morph faces was unaffected by familiarity. Contrariwise, relatively more pronounced physical (i.e., identity) differences were more efficiently discriminated for personally familiar faces, indicating more efficient processing of global, as opposed to local facial information through real-life experience.

Upright or inverted, entire or exploded: right-hemispheric superiority in face recognition withstands multiple spatial manipulations

Background. The ability to identify faces has been interpreted as a cerebral specialization based on the evolutionary importance of these social stimuli, and a number of studies have shown that this function is mainly lateralized in the right hemisphere. The aim of this study was to assess the right-hemispheric specialization in face recognition in unfamiliar circumstances.

Methods. Using a divided visual field paradigm, we investigated hemispheric asymmetries in the matching of two subsequent faces, using two types of transformation hindering identity recognition, namely upside-down rotation and spatial “explosion” (female and male faces were fractured into parts so that their mutual spatial relations were left intact), as well as their combination.

Results. We confirmed the right-hemispheric superiority in face processing. Moreover, we found a decrease of the identity recognition for more extreme “levels of explosion” and for faces presented upside-down (either as sample or target stimuli) than for faces presented upright, as well as an advantage in the matching of female compared to male faces.

Discussion. We conclude that the right-hemispheric superiority for face processing is not an epiphenomenon of our expertise, because we are not often exposed to inverted and “exploded” faces, but rather a robust hemispheric lateralization. We speculate that these results could be attributable to the prevalence of right-handedness in humans and/or to early biases in social interactions.

Familiar Face Detection in 180 ms

The visual system is tuned for rapid detection of faces, with the fastest choice saccade to a face at 100 ms. Familiar faces have a more robust representation than do unfamiliar faces, and are detected faster in the absence of awareness and with reduced attentional resources. Faces of family and close friends become familiar over a protracted period involving learning the unique visual appearance, including a view-invariant representation, as well as person knowledge. We investigated the effect of personal familiarity on the earliest stages of face processing by using a saccadic-choice task to measure how fast familiar face detection can happen. Subjects made correct and reliable saccades to familiar faces when unfamiliar faces were distractors at 180 ms--very rapid saccades that are 30 to 70 ms earlier than the earliest evoked potential modulated by familiarity. By contrast, accuracy of saccades to unfamiliar faces with familiar faces as distractors did not exceed chance. Saccades to faces with object distractors were even faster (110 to 120 ms) and equivalent for familiar and unfamiliar faces, indicating that familiarity does not affect ultra-rapid saccades. We propose that detectors of diagnostic facial features for familiar faces develop in visual cortices through learning and allow rapid detection that precedes explicit recognition of identity.

Differential Processing of Vertical Interfeature Relations Due to Real-Life Experience with Personally Familiar Faces

Identification of personally familiar faces is possibly the most complex and likewise efficient task achieved by the human visual system, yet to date the mechanisms underlying this extreme proficiency remain largely unknown. Building on empirical evidence from unfamiliar face processing in healthy populations and neuropsychological patients, the present work aimed to determine the type of information processed differently due to repeated, real-life experience with faces. A modulatory effect of familiarity was observed for processing of vertical interfeature distances, which have been suggested to rely on holistic processing skills. Contrariwise, no such effect was found for processing of information that can be discriminated locally (ie featural cues, interocular distances). The results indicate that familiarity-related advantages in face processing may arise from more efficient, or increased, holistic processing.