Paul C Quinn. Encyclopedia of Perception. Editor: E Bruce Goldstein. 2010. Sage Publication.
Faces as perceptual stimuli pack a double punch in terms of being (1) the most extensively experienced class of stimuli that a human observer will encounter over the course of a lifetime, and (2) unique in the sense of conveying a wealth of information (e.g., emotion, gender, race, trustworthiness) that is absent in other objects, even those objects in which we are expert in recognizing. Investigators interested in the development of face perception have been examining the nature of the face representation that infants bring to the task of learning about faces and how that representation changes as a function of differential experience with mother versus stranger, male versus female, same- versus other-race, same- versus other-species, attractive versus unattractive, and positive versus negative emotion. This entry describes newborn face perception abilities in the first year of life and beyond infancy.
Newborn Face Perception Abilities
Newborn infants, just a few minutes from birth, will track with their eyes a schematic visual stimulus resembling a face more than they will track a stimulus that has the external shape of the head but has the internal features of the face scrambled. This result supports the idea that newborn infants enter the world with an internal representation of a face, although some have suggested that the information in the representation may be relatively coarse, consisting of three high-contrast blobs in the correct relative locations for the eyes and the mouth, framed in the contour of a head shape. The coarseness of the representation has actually led to the notion that the newborn representation is not necessarily specialized for faces, but that it reflects a preference for more general perceptual properties (such as symmetry, top heaviness, and congruence) that may also be present in nonface objects. However, the possibility that the initial face representation may be more elaborate is suggested by the finding that newborn infants will imitate facial gestures (such as mouth opening and tongue protrusion) that they see an adult modeling. Whether derived from specialized or more general processes, the newborn representation is believed to equip infants with a mechanism that biases visual attention to the face information present in a visual display. This mechanism may be viewed as adaptive in terms of allowing infants to attend to and recognize members of their own species and also specific people, such as the primary caregiver.
Development of Face Perception in the First Year
If infants have an initial representation of a face as a set of features in a particular arrangement, then the question arises as to how sensitivity develops to the individual features versus sensitivity to the structural whole that incorporates the spatial relations among the features. In addition, for structural processing, there is the question of how infants come to process first-order relations (i.e., categorical spatial relations—the eyes above the nose) and second-order relations (i.e., metric spatial relations—the distance between the eyes and the nose). The expertise that adults have for processing faces is believed to be associated with sensitivity to second-order relations. Initial sensitivity to both first- and second-order relations is present in infancy, although full development of sensitivity to second-order relations to adultlike levels may follow a protracted course lasting even into adolescence.
There is also a growing literature on how infants come to process social attributes of faces during their first year (e.g., identity, emotion, gender, race, attractiveness). This literature initially focused on the question of mother-stranger differentiation with its implications for the development of attachment. For example, past studies have examined how soon after birth infants display a preference for mother over stranger, how much exposure to the mother’s face is needed to elicit a preference, what perceptual cues mediate the preference, and whether the preference can be manifest in other modalities besides vision. This research collectively suggests that the preference for mother over stranger is manifest in the late third trimester in the auditory domain and shortly after birth in the visual and olfactory domains. The visual preference is facilitated by increased exposure to the mother’s face and voice in the first few hours and days after birth. The preference also relies increasingly on the internal features of the mother’s face during the first months of life.
A related line of inquiry has investigated issues related to how infants process emotion information from faces. Studies have examined the roles of static versus dynamic cues in the extraction of emotion information from faces and how multimodal information from face and voice may contribute to infants’ developing understanding of emotion. Other research has considered whether infants (1) extract emotion information more robustly when familiar individuals present that information, (2) recognize emotional expressions as members of a common category (e.g., happiness), and (3) display spontaneous looking preferences for some facial depictions of emotions over others. Taken together, the studies suggest that infants may process emotion information more efficiently from dynamic and familiar faces, and that multimodal information may contribute to infants’ developing understanding of the “meaning” of emotion by lessening the likelihood that attention will be focused on modality-specific cues (e.g., toothiness in the visual input). In addition, infants can categorize emotional expressions across variation in the intensity of the emotion and the individuals depicting the emotion, and also display differential responsiveness to classes of emotion through spontaneous preference (e.g., fearful faces are preferred to happy ones).
Recent investigations have focused on how infants respond to gender and race information in faces. These studies have produced evidence consistent with the observation of familiarity preference in the face identification literature. In particular, by three months of age, infants prefer the gender of the primary caregiver and same- to other-race faces, with both preferences driven by differential experience. Experience also affects infants’ face recognition memory. Specifically, three-month-olds reared by a female caregiver and presented with a series of female faces preferred a novel over familiar female face; however, when presented with male faces, there was no differential preference for a novel over familiar male face. In addition, although three-month-old Caucasian infants exposed predominantly to Caucasian faces performed as well on a recognition memory task involving either own- or other-race faces, nine-month-old Caucasian infants demonstrated recognition memory only for Caucasian faces. The recognition advantage for same-race faces and its time course of development has also been observed for human infants viewing same- versus other-species of faces (humans versus monkeys). All of the results suggest that experience with faces in the first half-year of life narrows infants’ face representation from a general to a specific one that is tuned to the attributes of frequently encountered face categories.
Another social dimension of faces that infants respond to is physical attractiveness. In particular, infants will spend more time looking at attractive faces (as judged by adults) when these are shown paired with less attractive human faces. Infant preference for attractive faces has been observed for a range of human faces, including Caucasian and African American adult female faces, adult male faces, and infant faces. The attractiveness effect can be demonstrated even in newborn infants: It is orientation dependent, occurring for upright but not inverted faces, and it is driven by the internal features of faces.
A question of interest is whether the attractiveness preference in infants is dependent on perceptual learning mechanisms or whether it reflects the face representation that newborn infants bring to the learning situation for faces. The learning account of the attractiveness effect is couched in terms of an averaging process known as prototype formation: When several faces are averaged, adults perceive the resulting face as more attractive than any of the individual faces. By this learning account, infant preference for attractive faces may reflect a preference for faces similar to a composite of the faces seen since birth. This account can apply even to the results obtained with the newborn infants, given that those infants were two to three days old at testing, and would likely have experienced a multitude of faces even during that short time frame. In contrast, by a nativist account, newborn infants could enter the world with a face representation, and attractive faces are preferred because they more closely match this representation. This representation could still be in the form of a prototype, except that it would have been formed through evolutionary mechanisms. Consistent with the nativist account, young infants have also been found to prefer attractive over unattractive nonhuman animal faces for which they had no previous experience (i.e., cats, tigers).
The finding that the attractiveness preference in infants extends beyond conspecifics also suggests that it is not reflective of an adaptation to mate choice, as some have suggested, but may point toward the operation of more general mechanisms that process a family of preferred perceptual features that includes, but may not be limited to, particular features, such as large eyes, and the complex geometric attributes that characterize the spatial relations among the features, such as their location (e.g., height) and arrangement (e.g., symmetry) within the whole. Thus, just as the perception of some social attributes of faces (i.e., identity, emotion, gender, and race) seems to be driven by experience, the perception of other social attributes of faces (i.e., attractiveness) may be determined by the initial settings of our perceptual systems.
Development of Face Perception beyond Infancy
Beyond infancy, the development of face perception seems both constrained by experiences occurring during infancy for the processing of some kinds of information and characterized by flexibility with regard to the processing of other kinds of information. For example, the absence of visual input in early infancy as a result of congenital cataracts adversely affects sensitivity to second-order, but not first-order relational information. Also, with respect to species, the ability to individuate human faces is maintained in later development, whereas the ability to individuate monkey faces, while comparable to individuating human faces before nine months of age, is now absent in adulthood. In addition, children who have suffered a history of physical abuse perceive anger in emotionally ambiguous faces more often than children who have not been abused. By contrast, although face processing seems to tune into gender and race during infancy, there is flexibility thereafter. In the case of gender, same-sex preferences and recognition advantages emerge in childhood, and there is dissociation of preference and recognition in adulthood (i.e., preference for opposite-sex faces and superior recognition for same-sex faces). Similarly, for race, Korean adults adopted by French families during childhood (ages three-nine years) display a recognition deficit for Korean faces relative to their ability to recognize European faces. Evidence such as this indicates that experience contributes to the development of face perception beyond the first year of life.