From eye to face: The impact of face outline, feature number, and feature saliency on the early neural response to faces

Effects of Inversion and Fixation Location on the Processing of Face and House Stimuli - A Mass Univariate Analysis

Most Event Related Potential studies investigating the time course of visual processing have focused mainly on the N170 component. Stimulus orientation affects the N170 amplitude for faces but not for objects, a finding interpreted as reflecting holistic/configural processing for faces and featural processing for objects. Furthermore, while recent studies suggest where on the face people fixate impacts the N170, fixation location effects have not been investigated in objects. A data-driven mass univariate analysis (all time points and electrodes) was used to investigate the time course of inversion and fixation location effects on the neural processing of faces and houses. Strong and widespread orientation effects were found for both faces and houses, from 100-350ms post-stimulus onset, including P1 and N170 components, and later, a finding arguing against a lack of holistic processing for houses. While no clear fixation effect was found for houses, fixation location strongly impacted face processing early, reflecting retinotopic mapping around the C2 and P1 components, and during the N170-P2 interval. Face inversion effects were also largest for nasion fixation around 120ms. The results support the view that facial feature integration (1) depends on which feature is being fixated and where the other features are situated in the visual field, (2) occurs maximally during the P1-N170 interval when fixation is on the nasion and (3) continues past 200ms, suggesting the N170 peak, where weak effects were found, might be an inflexion point between processes rather than the end of a feature integration into a whole process.

Effects of expectation on face perception and its association with expertise

Perceptual decisions are derived from the combination of priors and sensorial input. While priors are broadly understood to reflect experience/expertise developed over one's lifetime, the role of perceptual expertise at the individual level has seldom been directly explored. Here, we manipulate probabilistic information associated with a high and low expertise category (faces and cars respectively), while assessing individual level of expertise with each category. 67 participants learned the probabilistic association between a color cue and each target category (face/car) in a behavioural categorization task. Neural activity (EEG) was then recorded in a similar paradigm in the same participants featuring the previously learned contingencies without the explicit task. Behaviourally, perception of the higher expertise category (faces) was modulated by expectation. Specifically, we observed facilitatory and interference effects when targets were correctly or incorrectly expected, which were also associated with independently measured individual levels of face expertise. Multivariate pattern analysis of the EEG signal revealed clear effects of expectation from 100 ms post stimulus, with significant decoding of the neural response to expected vs. not stimuli, when viewing identical images. Latency of peak decoding when participants saw faces was directly associated with individual level facilitation effects in the behavioural task. The current results not only provide time sensitive evidence of expectation effects on early perception but highlight the role of higher-level expertise on forming priors.

High familiar faces have both eye recognition and holistic processing advantages

People recognize familiar faces better than unfamiliar faces. However, it remains unknown whether familiarity affects part-based and/or holistic processing. Wang et al., Frontiers in Psychology, 6, 559 (2015), Vision Research, 157, 89-96 (2019) found both enhanced part-based and holistic processing in eye relative to mouth regions (i.e., in a region-selective manner) for own-race and own-species faces, i.e., faces with more experience. Here, we examined the role of face familiarity in eyes (part-based, region-selective) and holistic processing. Face familiarity was tested at three levels: high-familiar (faces of students from the same department and the same class who attended almost all courses together), low-familiar (faces of students from the same department but different classes who attended some courses together), and unfamiliar (faces of schoolmates from different departments who seldom attended the same courses). Using the old/new task in Experiment 1, we found that participants recognized eyes of high-familiar faces better than low-familiar and unfamiliar ones, while similar performance was observed for mouths, indicating a region-selective, eyes familiarity effect. Using the "Perceptual field" paradigm in Experiment 2, we observed a stronger inversion effect for high-familiar faces, a weaker inversion effect for low-familiar faces, but a non-significant inversion effect for unfamiliar faces, indicating that face familiarity plays a role in holistic processing. Taken together, our results suggest that familiarity, like other experience-based variables (e.g., race and species), can improve both eye processing and holistic processing.

Looking at the upper facial half enlarges the range of holistic face processing

Previous studies suggested that upper and lower facial halves might be involved in the human holistic face processing differently. In this study, we replicated and extended the finding above. In Experiment 1, we used the standard composite-face task to measure holistic face processing when participants made judgements on the upper and lower facial halves separately. Results showed that the composite-face effect was stronger for the upper facial half compared to the lower half. In Experiment 2, we investigated how facial information was integrated when participants focused on different features, using the perceptual field paradigm. Results showed that: (1) more "peripheral faces" were chosen when participants fixated at the eyes than when they fixated at the mouth; (2) less "peripheral faces" were chosen for inverted faces regardless of the fixated features. Findings from both experiments together indicate that more peripheral facial information were integrated when participants focused on the upper facial half, highlighting the significance of focusing on the upper facial half in face processing.

From Gaze Perception to Social Cognition: The Shared-Attention System

When two people look at the same object in the environment and are aware of each other's attentional state, they find themselves in a shared-attention episode. This can occur through intentional or incidental signaling and, in either case, causes an exchange of information between the two parties about the environment and each other's mental states. In this article, we give an overview of what is known about the building blocks of shared attention (gaze perception and joint attention) and focus on bringing to bear new findings on the initiation of shared attention that complement knowledge about gaze following and incorporate new insights from research into the sense of agency. We also present a neurocognitive model, incorporating first-, second-, and third-order social cognitive processes (the shared-attention system, or SAS), building on previous models and approaches. The SAS model aims to encompass perceptual, cognitive, and affective processes that contribute to and follow on from the establishment of shared attention. These processes include fundamental components of social cognition such as reward, affective evaluation, agency, empathy, and theory of mind.