The development of processing second-order spatial relations of faces in Chinese preschoolers

Second-order relational information processing is the perception of the relative distance between facial features. Previous studies ignored the effect of different spatial manipulations on second-order sensitivity in face processing, and little is known about its developmental trajectory in East Asian populations, who have stronger holistic face processing than Western populations. We addressed these gaps in the literature through an experiment with four groups of Chinese preschool children (aged 3-6 years; n = 157) and a group of adults (n = 25). The participants were presented with face pairs displaying features with various spatial distance manipulations (Change 1: changes in the spacing between eyes; Change 2: nose-mouth spacing changes; Change 3: a combination of Changes 1 and 2) using a simultaneous two-alternative forced-choice task. Second-order sensitivity was already present in 3-year-old children across all manipulations and became more pronounced in 4-year-old children. Second-order sensitivity to the spatial distance between the eyes (i.e., Changes 1 and 3) among 4-year-olds was higher than that of 3-year-olds and was similar to that of adults, suggesting a key increase of this sensitivity from 3 to 4 years of age. Regarding the Change 2 condition, preschoolers aged 5 and 6 years had higher sensitivity than 3-year-olds; however, all preschoolers' sensitivity was inferior to that of adults. These findings show that the development of Chinese preschoolers' sensitivity for detecting spatial relations between the eyes might be faster than that for detecting nose-mouth spacing, supporting the importance of eyes in face 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.

Configural properties of face portraits change between childhood and adulthood

Adult observers are sensitive to the configuration of facial features within a face, able to distinguish between relative differences in feature spacing, and detecting deviations from typical facial appearance. How does the representation of the typical configuration of facial features develop? While there is a great deal of work describing children’s developing abilities to detect differences in feature spacing across face images, there is substantially less work examining what children think constitutes a typical arrangement of facial features. In the current study, we investigated this issue using a production task in which adults and 5- to 10-year-old children created a face “portrait” by arranging the eyes, nose, and mouth of a standard face within an empty outline. Using this simple task, we found differences in face configuration across age groups, such that children of all ages made far larger errors than adult participants, expanding facial features outward from the center of the face more than adults. These results were not affected by face inversion, potentially implying a domain-general rather than face-specific process. We also found that children of all ages endorsed the correct configuration as a best likeness in a perceptual task. We discuss these results in terms of ongoing debate regarding the extent to which configural processing is a meaningful component of face recognition and the conclusions we can draw from production paradigms as compared to purely perceptual tasks.

Eye Placement Bias Is Remarkably Robust

When drawing faces, people show a systematic bias of placing the eyes higher up the head than they are placed in reality. This study investigated the development of this phenomenon while removing the potential confound of drawing ability. Participants (N = 124) in three age groups (3-5 yo, 10-11 yo, and adults) reconstructed two foam faces: one from observation and one from memory. The high eye placement bias was remarkably robust with mean eye placement in every condition significantly higher than the original faces. The same bias was not shown for mouth placement. Eye placement was highest for the youngest participants and for the memory conditions. The results suggest that an eye placement bias is not caused by the motor skill demands required for drawing and lend evidence to the suggestion that an eye placement bias is caused by perceptual and decision-making processes.

Developmental Commonalities between Object and Face Recognition in Adolescence

In the visual perception literature, the recognition of faces has often been contrasted with that of non-face objects, in terms of differences with regard to the role of parts, part relations and holistic processing. However, recent evidence from developmental studies has begun to blur this sharp distinction. We review evidence for a protracted development of object recognition that is reminiscent of the well-documented slow maturation observed for faces. The prolonged development manifests itself in a retarded processing of metric part relations as opposed to that of individual parts and offers surprising parallels to developmental accounts of face recognition, even though the interpretation of the data is less clear with regard to holistic processing. We conclude that such results might indicate functional commonalities between the mechanisms underlying the recognition of faces and non-face objects, which are modulated by different task requirements in the two stimulus domains.

Selectivity of Face Perception to Horizontal Information over Lifespan (from 6 to 74 Year Old)

Face recognition in young human adults preferentially relies on the processing of horizontally-oriented visual information. We addressed whether the horizontal tuning of face perception is modulated by the extensive experience humans acquire with faces over the lifespan, or whether it reflects an invariable processing bias for this visual category. We tested 296 subjects aged from 6 to 74 years in a face matching task. Stimuli were upright and inverted faces filtered to preserve information in the horizontal or vertical orientation, or both (HV) ranges. The reliance on face-specific processing was inferred based on the face inversion effect (FIE). FIE size increased linearly until young adulthood in the horizontal but not the vertical orientation range of face information. These findings indicate that the protracted specialization of the face processing system relies on the extensive experience humans acquire at encoding the horizontal information conveyed by upright faces.

The sensitivity to replacement and displacement of the eyes region in early adolescence, young and later adulthood

Recent evidence suggests a rather gradual developmental trajectory for processing vertical relational face information, lasting well into late adolescence (de Heering and Schlitz, 2008). Results from another recent study (Tanaka et al., 2014) indicate that children and young adolescents use a smaller spatial integration field for faces than do adults, which particularly affects assessment of long-range vertical relations. Here we studied sensitivity to replacement of eyes and eyebrows (F), variation of inter-eye distance (H), and eye height (V) in young adolescents (11-12 years), young (21-25 years), and middle-age adults (51-62 years). In order to provide a baseline for potential age effects the sensitivity to all three types of face manipulations was calibrated to equal levels for the young adults group. Both the young adolescents and the middle-age adults showed substantially lower sensitivity compared to young adults, but only the young adolescents had selective impairment for V relational changes. Their inversion effects were at similar levels for all types of face manipulations, while in both adult groups the inversion effects for V were considerably stronger than for H or F changes. These results suggest that young adolescents use a limited spatial integration field for faces, and have not reached a mature state in processing vertical configural cues. The H-V asymmetry of inversion effects found for both adult groups indicates that adults integrate across the whole face when they view upright stimuli. However, the notably lower sensitivity of middle-age adults for all types of face manipulations, which was accompanied by a strong general "same" bias, suggests early age-related decline in attending cues for facial difference.