Lisa S. Scott

A Domain-General Theory of the Development of Perceptual Discrimination

In this article, we posit a domain-general principle that may account for the improvement that is observed in several aspects of perceptual development over the first years of life. Development during this time frame is characterized by a process of perceptual narrowing, whereby the discrimination of perceptual information is broadly tuned at first and then declines to more selective levels with experience. This process appears to cut across both the visual and auditory modalities and may reflect the development of a common neural architecture.

A Reevaluation of the Electrophysiological Correlates of Expert Object Processing

Subordinate-level object processing is regarded as a hallmark of perceptual expertise. However, the relative contribution of subordinate- and basic-level category experience in the acquisition of perceptual expertise has not been clearly delineated. In this study, participants learned to classify wading birds and owls at either the basic (e.g., wading bird, owl) or the subordinate (e.g., egret, snowy owl) level. After 6 days of training, behavioral results showed that subordinate-level but not basic-level training improved subordinate discrimination of trained exemplars, novel exemplars, and exemplars from novel species. Event-related potentials indicated that both basic- and subordinate-level training enhanced the early N170 component, but only subordinate-level training amplified the later N250 component. These results are consistent with models positing separate basic and subordinate learning mechanisms, and, contrary to perspectives attempting to explain visual expertise solely in terms of subordinate-level processing, suggest that expertise enhances neural responses of both basic and subordinate processing.

The Origin of Biases in Face Perception

Experience with certain types of faces during the first year of development defines which types of faces are more efficiently recognized later in life. In work described here, we found that infants who learned to recognize six monkey faces individually (i.e., each face was individually labeled) over a 3-month period maintained the ability to discriminate monkey faces. However, infants who learned these same six faces categorically (i.e., all faces were labeled “monkey”) or were simply exposed to these faces (i.e., faces were not labeled) showed a decline in the ability to discriminate monkey faces. These results suggest that experience individuating faces from 6 to 9 months of age, via labeling, critically shapes the perceptual representation that is responsible for later recognition and discrimination of faces.

Featural and configural face processing in adults and infants : A behavioral and electrophysiological investigation

We sought to elucidate the behavioral and electrophysiological correlates of face processing, in adults and infants, by manipulating either the featural or configural information within the face. Two different experiments are reported. In these experiments, event-related potentials (ERPs) were recorded from the scalp while adult, 8-month-old, and 4-month-old participants completed configural-change and featural-change face tasks. The infants also completed a behavioral visual paired-comparison task with featural and configural face changes. ERP results reveal hemispheric differences in processing featural but not configural changes for the N170 in adults. Furthermore, featural and configural changes are processed differently within the right and left hemispheres. The right hemisphere N170 is significantly greater for configural compared to featural changes. The left hemisphere N170, however, exhibits the opposite effect. Infant data suggest that similar to adults, 8-month-old, but not 4-month-old participants, exhibit similar hemispheric differences between featural and configural changes for the P400 component. Behavioral results suggest increased sensitivity to both featural and configural face changes in 8-month-olds compared to 4-month-olds.

The role of category learning in the acquisition and retention of perceptual expertise: A behavioral and neurophysiological study

This study examined the neural mechanisms underlying perceptual categorization and expertise. Participants were either exposed to or learned to classify three categories of cars (sedans, SUVs, antiques) at either the basic or subordinate level. Event-Related Potentials (ERPs) as well as accuracy and reaction time were recorded before, immediately after, and 1-week after training. Behavioral results showed that only subordinate-level training led to better discrimination of trained cars, and this ability was retained a week after training. ERPs showed an equivalent increase in the N170 across all three training conditions whereas the N250 was only enhanced in response to subordinate-level training. The behavioral and electrophysiological results distinguish category learning at the subordinate level from category learning occurring at the basic level or from simple exposure. Together with data from previous investigations, the current results suggest that subordinate-level training, but not basic-level or exposure training, leads to expert-like improvements in categorization accuracy. These improvements are mirrored by changes in the N250 rather than the N170 component, and these effects persist at least a week after training, so are conceivably related to long-term learning processes supporting perceptual expertise.

Connecting developmental trajectories: Biases in face processing from infancy to adulthood

The nature of the developmental trajectory of face recognition abilities from infancy through adulthood is multifaceted and currently not well understood. We argue that the understanding of this trajectory can be greatly informed by taking a more functionalist approach in which the influence of age-appropriate developmental tasks and goals are considered. To build this argument, we provide a focused review of developmental change across several important biases within face processing (species, race, age, and gender biases) from infancy through adulthood. We show that no existing theoretical framework can simultaneously and parsimoniously explain these very different trajectories and relative degrees of plasticity. We offer several examples of infant- and adolescent-specific developmental tasks that we predict have an essential influence on the content and description of information that individuals need to extract from faces at these very different developmental stages. Finally, we suggest that this approach may provide a unique opportunity to study the role of early experience in (i.e., age of acquisition effects) and the quality and range of experiences that are critical for shaping behaviors through the course of development, from infancy to adulthood.

The N250 brain potential to personally familiar and newly learned faces and objects

Studies employing event-related potentials have shown that when participants are monitoring for a novel target face, the presentation of their own face elicits an enhanced negative brain potential in posterior channels approximately 250 ms after stimulus onset. Here, we investigate whether the own face N250 effect generalizes to other highly familiar objects, specifically, images of the participant’s own dog and own car. In our experiments, participants were asked to monitor for a pre-experimentally unfamiliar target face (Joe), a target dog (Experiment 1: Joe’s Dog) or a target car (Experiment 2: Joe’s Car). The target face and object stimuli were presented with non-target foils that included novel face and object stimuli, the participant’s own face, their own dog (Experiment 1), and their own car (Experiment 2). The consistent findings across the two experiments were the following: (1) the N250 potential differentiated the target faces and objects from the non-target face and object foils and (2) despite being non-targets, the own face and own objects produced an N250 response that was equal in magnitude to the target faces and objects by the end of the experiment. Thus, as indicated by its response to personally familiar and recently familiarized faces and objects, the N250 component is a sensitive index of individuated representations in visual memory.

The own-species face bias: A review of developmental and comparative data

Face recognition is characterized in part by biases resulting in enhanced perception and memory for individuals within frequently encountered groups and impaired recognition for individuals within uncommonly encountered groups. These biases are found across multiple categories and levels, including species, race, age, and gender (Scherf & Scott, 2012). At the highest level of categorization, human adults and nonhuman primates exhibit improved recognition (Dufour, Pascalis, & Petit, 2006; Pascalis & Bachevalier, 1998) and discrimination abilities (Pascalis, de Haan, & Nelson, 2002) for individuals within their own species, reflecting what has been called an “own-species” or “species-specific” bias in face processing. The own-species bias is a model system for delineating the role of experience and the developmental trajectory of face-processing biases, for further understanding the malleability of face biases in adults, and for examining and comparing face-processing abilities across species. Here, we will review findings from studies investigating the perception of other-species faces during development, into adulthood and across species.

Mechanisms underlying the emergence of object representations during infancy

The effects of individual versus category training, using behavioral indices of stimulus discrimination and neural ERPs indices of holistic processing, were examined in infants. Following pretraining assessments at 6 months, infants were sent home with training books of objects for 3 months. One group of infants was trained with six different strollers labeled individually, and another group was trained with the same six strollers labeled at the category level (i.e., “stroller”). Infants returned for posttraining assessments at 9 months. Discrimination of objects was facilitated for infants trained with the individually labeled strollers but was unchanged after training at the category level. Relative to pretraining and to category-level training, individual-level training resulted in increased holistic processing of strollers recorded over occipital brain regions. These results suggest that labeling nonface objects individually, in infancy, facilitates discrimination and leads to the emergence of holistic neural representations not present with category-level labeling.

Behavioral and electrophysiological evidence of species-specific face processing.

Several recent reports suggest that the behavioral and cortical specificity of face processing may be influenced by experience. To test this hypothesis, behavioral and electrophysiological data were recorded from adults in response to human and monkey faces differing in familiarity and orientation. An analysis of event-related potential and behavioral data revealed differentiation across species, familiarity, and orientation. Behavioral measures were correlated with amplitude and latency measures for each factor of interest. These analyses revealed that accuracy was positively related to the amplitude of the vertex positive potential in the human face task but not in the monkey face task. These findings suggest that previous experience with different categories of faces modulates the link between behavioral and electrophysiological measures of face processing.