Naiqi G. Xiao

Development of face scanning for own- and other-race faces in infancy

The present study investigated whether infants visually scan own- and other-race faces differently as well as how these differences in face scanning develop with age. A multi-method approach was used to analyze the eye-tracking data of 6- and 9-month-old Caucasian infants scanning dynamically displayed own- and other-race faces. We found that 6-month-olds showed differential fixation, fixating significantly more on the left eye and mouth of own-race faces, but more on the nose of other-race faces. Infants at 9 months of age fixated more on the eyes of own-race faces, but more on the mouth of other-race faces. A scan path analysis revealed that infants shifted their attention between the eyes of the own-race faces significantly more frequently than for other-race faces. Overall, younger and older infants responded differentially to own- versus other-race faces not only in the absolute amount of time spent fixating specific features, but also on their fixation shifts between features.

Rigid facial motion influences featural, but not holistic, face processing

We report three experiments in which we investigated the effect of rigid facial motion on face processing. Specifically, we used the face composite effect to examine whether rigid facial motion influences primarily featural or holistic processing of faces. In Experiments 1-3, participants were first familiarized with dynamic displays in which a target face turned from one side to another; then at test, participants judged whether the top half of a composite face (the top half of the target/foil face aligned or misaligned with the bottom half of a foil face) belonged to the target face. We compared performance in the dynamic condition to various static control conditions in Experiments 1-3, which differed from each other in terms of the display order of the multiple static images or the inter-stimulus interval (ISI) between the images. We found that the size of the face composite effect in the dynamic condition was significantly smaller than that in the static conditions. In other words, the dynamic face display influenced participants to process the target faces in a part-based manner and consequently their recognition of the upper portion of the composite face at test became less interfered with by the aligned lower part of the foil face. The findings from the present experiments provide the strongest evidence to date to suggest that the rigid facial motion mainly influences facial featural, but not holistic, processing.

Asian infants show preference for own-race but not other-race female faces: the role of infant caregiving arrangements

Previous studies have reported that 3- to 4-month-olds show a visual preference for faces of the same gender as their primary caregiver (e.g., Quinn et al., 2002). In addition, this gender preference has been observed for own-race faces, but not for other-race faces (Quinn et al., 2008). However, most of the studies of face gender preference have focused on infants at 3–4 months. Development of gender preference in later infancy is still unclear. Moreover, all of these studies were conducted with Caucasian infants from Western countries. It is thus unknown whether a gender preference that is limited to own-race faces can be generalized to infants from other racial groups and different cultures with distinct caregiving practices. The current study investigated the face gender preferences of Asian infants presented with male versus female face pairs from Asian and Caucasian races at 3, 6, and 9 months and the role of caregiving arrangements in eliciting those preferences. The results showed an own-race female face preference in 3- and 6-month-olds, but not in 9-month-olds. Moreover, the downturn in the female face preference correlated with the cumulative male face experience obtained in caregiving practices. In contrast, no gender preference or correlation between gender preference and face experience was found for other-race Caucasian faces at any age. The data indicate that the face gender preference is not specifically rooted in Western cultural caregiving practices. In addition, the race dependency of the effect previously observed for Caucasian infants reared by Caucasian caregivers looking at Caucasian but not Asian faces extends to Asian infants reared by Asian caregivers looking at Asian but not Caucasian faces. The findings also provide additional support for an experiential basis for the gender preference, and in particular suggest that cumulative male face experience plays a role in inducing a downturn in the preference in older infants.

Eye tracking reveals a crucial role for facial motion in recognition of faces by infants.

Current knowledge about face processing in infancy comes largely from studies using static face stimuli, but faces that infants see in the real world are mostly moving ones. To bridge this gap, 3-, 6-, and 9-month-old Asian infants (N = 118) were familiarized with either moving or static Asian female faces, and then their face recognition was tested with static face images. Eye-tracking methodology was used to record eye movements during the familiarization and test phases. The results showed a developmental change in eye movement patterns, but only for the moving faces. In addition, the more infants shifted their fixations across facial regions, the better their face recognition was, but only for the moving faces. The results suggest that facial movement influences the way faces are encoded from early in development.

Elastic Facial Movement Influences Part-Based but Not Holistic Processing

Face processing has been studied for decades. However, most of the empirical investigations have been conducted using static face images as stimuli. Little is known about whether static face processing findings can be generalized to real-world contexts in which faces are constantly moving. The present study investigated the nature of face processing (holistic vs. part-based) in elastic moving faces. Specifically, we focused on whether elastic moving faces, as compared with static ones, can facilitate holistic or part-based face processing. Using the composite paradigm, we asked participants to remember either an elastic moving face (i.e., a face that blinks and chews) or a static face, and then tested with a static composite face. The composite effect was (a) significantly smaller in the dynamic condition than in the static condition, (b) consistently found with different face encoding times (Experiments 1-3), and (c) present for the recognition of both upper and lower face parts (Experiment 4). These results suggest that elastic facial motion facilitates part-based processing rather than holistic processing. Thus, whereas previous work with static faces has emphasized an important role for holistic processing, the current work highlights an important role for featural processing with moving faces.

An adult face bias in infants that is modulated by face race

The visual preferences of infants for adult versus infant faces were investigated. Caucasian 3.5- and 6-month-olds were presented with Caucasian adult vs. infant face pairs and Asian adult vs. infant face pairs, in both upright and inverted orientations. Both age groups showed a visual preference for upright adult over infant faces when the faces were Caucasian, but not when they were Asian. The preference is unlikely to have arisen because of low-level perceptual features because: (1) no preference was observed for the inverted stimuli, (2) no differences were observed in adult similarity ratings of the upright infant–adult face pairs from the two races, and (3) no differences between the infant and adult faces were observed across races in an image-based analysis of salience. The findings are discussed in terms of the social attributes of faces that are learned from experience and what this implies for developmental accounts of a recognition advantage for adult faces in particular and models of face processing more generally.

Visual scanning and recognition of Chinese, Caucasian, and racially ambiguous faces: contributions from bottom-up facial physiognomic information and top-down knowledge of racial categories.

Recent studies have shown that participants use different eye movement strategies when scanning own- and other-race faces. However, it is unclear (1) whether this effect is related to face recognition performance, and (2) to what extent this effect is influenced by top-down or bottom-up facial information. In the present study, Chinese participants performed a face recognition task with Chinese, Caucasian, and racially ambiguous faces. For the racially ambiguous faces, we led participants to believe that they were viewing either own-race Chinese faces or other-race Caucasian faces. Results showed that (1) Chinese participants scanned the nose of the true Chinese faces more than that of the true Caucasian faces, whereas they scanned the eyes of the Caucasian faces more than those of the Chinese faces; (2) they scanned the eyes, nose, and mouth equally for the ambiguous faces in the Chinese condition compared with those in the Caucasian condition; (3) when recognizing the true Chinese target faces, but not the true target Caucasian faces, the greater the fixation proportion on the nose, the faster the participants correctly recognized these faces. The same was true when racially ambiguous face stimuli were thought to be Chinese faces. These results provide the first evidence to show that (1) visual scanning patterns of faces are related to own-race face recognition response time, and (2) it is bottom-up facial physiognomic information that mainly contributes to face scanning. However, top-down knowledge of racial categories can influence the relationship between face scanning patterns and recognition response time.

A New “Fat Face” Illusion

We report a novel fat face illusion that when two identical images of the same face are aligned vertically, the face at the bottom appears ‘fatter’. This illusion emerged when the faces were shown upright, but not inverted, with the size of the illusion being 4%. When the faces were presented upside down, the illusion did not emerge. Also, when upright clocks were shown in the same vertically aligned fashion, we did not observe the illusion, indicating that the fat illusion does not generalize to every category of canonically upright objects with similar geometric shape as a face.

Facial Movements Facilitate Part-Based, Not Holistic, Processing in Children, Adolescents, and Adults.

Although most of the faces we encounter daily are moving ones, much of what we know about face processing and its development is based on studies using static faces that emphasize holistic processing as the hallmark of mature face processing. Here the authors examined the effects of facial movements on face processing developmentally in children (8-year-olds), adolescents (12-year-olds), and adults (20-year-olds). In particular, the composite face effect was used to measure the influence of facial movements on part-based versus holistic processing after participants had viewed either a moving or static face in a within-subject design. Experiment 1 examined elastic facial movement (i.e., blinking and chewing). The results showed that children, adolescents, and adults exhibited a significantly smaller composite effect after viewing a moving face than after viewing a static face. This result indicates that elastic facial movement facilitates part-based face processing from at least 8 years of age onward. Experiment 2 examined rigid facial movement (i.e., head turning) and revealed that it too facilitates part-based face processing in children, adolescents, and adults. The results taken together suggest that contrary to the prevailing view, facial movements facilitate part-based, not holistic, face processing in children, adolescents, and adults. The findings call for revision in the conventional way of thinking about what constitutes the developmental trajectory toward mature face processing and also point to the importance of using more naturalistic moving face stimuli to study face processing and its development.