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

Two faces of holistic face processing: Facilitation and interference underlying part-whole and composite effects

Holistic processing, a strong tendency to process multiple features together, is regarded as a hallmark of face perception. Holistic effects can be revealed by several tasks, including the part-whole task, standard composite task, and complete composite task. Although holistic effects are readily observed using these tasks, the lack of correlations among these effects and the mixed findings across these tasks when examining the effects among various populations or manipulations pose questions about how these effects should be understood. We distinguished facilitation and interference effects within the holistic effects in the complete composite task and found that the holistic effect in the part-whole task appeared to be correlated with facilitation but not interference in the complete composite task, whereas the holistic effect in the standard composite task was correlated with interference but not facilitation in the complete composite task. These findings suggest that clarifying the roles of facilitation and interference is critical for understanding holistic face processing.

Facilitation and interference are asymmetric in holistic face processing

A hallmark of face specificity is holistic processing. It is typically measured by paradigms such as the part-whole and composite tasks. However, these tasks show little evidence for common variance, so a comprehensive account of holistic processing remains elusive. One aspect that varies between tasks is whether they measure facilitation or interference from holistic processing. In this study, we examined facilitation and interference in a single paradigm to determine the way in which they manifest during a face perception task. Using congruent and incongruent trials in the complete composite face task, we found that these two aspects are asymmetrically influenced by the location and cueing probabilities of the target facial half, suggesting that they may operate somewhat independently. We argue that distinguishing facilitation and interference has the potential to disentangle mixed findings from different popular paradigms measuring holistic processing in one unified framework.

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.

Robust holistic face processing in early childhood during the COVID-19 pandemic

The timing of the developmental emergence of holistic face processing and its sensitivity to experience in early childhood are somewhat controversial topics. To investigate holistic face perception in early childhood, we used an online testing platform and administered a two-alternative forced-choice task to 4-, 5-, and 6-year-old children. The children saw pairs of composite faces and needed to decide whether the faces were the same or different. To determine whether experience with masked faces may have negatively affected holistic processing, we also administered a parental questionnaire to assess the children's exposure to masked faces during the COVID-19 pandemic. We found that all three age groups performed holistic face processing when the faces were upright (Experiment 1) but not when the faces were inverted (Experiment 2), that response accuracy increased with age, and that response accuracy was not related to degree of exposure to masked faces. These results indicate that holistic face processing is relatively robust in early childhood and that short-term exposure to partially visible faces does not negatively affect young children's holistic face perception.

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.

Holistic face processing is influenced by non-conscious visual information

Holistic face processing has been widely implicated in conscious face perception. Yet, little is known about whether holistic face processing occurs when faces are processed unconsciously. The present study used the composite face task and continuous flash suppression (CFS) to inspect whether the processing of target facial information (the top half of a face) is influenced by irrelevant information (the bottom half) that is presented unconsciously. Results of multiple experiments showed that the composite effect was observed in both monocular and CFS conditions, providing the first evidence that the processing of top facial halves is influenced by the aligned bottom halves no matter whether they are presented consciously or unconsciously. However, much of the composite effect for faces without masking was disrupted when bottom facial parts were rendered with CFS. These results suggest that holistic face processing can occur unconsciously, but also highlight the significance of holistic processing of consciously presented faces.

Different measures of holistic face processing tap into distinct but partially overlapping mechanisms

Holistic processing, which includes the integration of facial features and analysis of their relations to one another, is a hallmark of what makes faces 'special'. Various experimental paradigms purport to measure holistic processing but these have often produced inconsistent results. This has led researchers to question the nature and structure of the mechanism(s) underlying holistic processing. Using an individual differences approach, researchers have examined relations between various measures of holistic processing in an attempt to resolve these questions. In keeping with this, we examined relationships between four commonly used measures of holistic face processing in a large group of participants (N = 223): (1) The Face Inversion Effect, (2) the Part Whole Effect (PWE), (3) the Composite Face Effect, and (4) the Configural Featural Detection Task (CFDT). Several novel methodological and analytical elements were introduced, including the use of factor analysis and the inclusion of control conditions to confirm the face specificity of all of the effects measured. The four indexes of holistic processing derived from each measure loaded onto two factors, one encompassing the PWE and the CFDT, and one encompassing the CE. The 16 conditions tested across the four tasks loaded onto four factors, each factor corresponding to a different measure. These results, together with those of other studies, suggest that holistic processing is a multifaceted construct and that different measures tap into distinct but partially overlapping elements of it.

Development of Holistic Face Processing From Childhood and Adolescence to Young Adulthood in Chinese Individuals

Previous studies have indicated that holistic face processing is important for the development of face perception. The purpose of this study was to verify the development trajectory of holistic processing, from older childhood to young adulthood, using the complete composite paradigm. Participants from three different age groups (children, adolescents, young adults) were recruited for this study. The results showed that all groups demonstrated the composite effect with similar magnitude. Furthermore, face processing performance improved with age. These results, together with previous results, imply it is a race-general phenomenon that holistic face processing is similar among older children, adolescents, and young adults.