The development of visual categorization based on high-level cues.

This study investigated the development of rapid visual object categorization. N = 20 adults (Experiment 1), N = 21 five to six-year-old children (Experiment 2), and N = 140 four-, seven-, and eleven-month-old infants (Experiment 3; all predominantly White, 81 females, data collected in 2013-2020) participated in a fast periodic visual stimulation electroencephalographic task. Similar categorization of animal and furniture stimuli emerged in children and adults, with responses much reduced by phase-scrambling (R2 = .34-.73). Categorization was observed from 4 months, but only at 11 months, high-level cues enhanced performance (R2 = .11). Thus, first signs of rapid categorization were evident from 4 months, but similar categorization patterns as in adults were recorded only from 11 months on.

Neural discrimination of facial cues associated with trustworthiness in adults and 6-month-old infants as revealed by fast periodic visual stimulation.

Adults and children easily distinguish between fine-grained variations in trustworthiness intensity based on facial appearance, but the developmental origins of this fundamental social skill are still debated. Using a fast periodic visual stimulation (FPVS) oddball paradigm coupled with electroencephalographic (EEG) recording, we investigated neural discrimination of morphed faces that adults perceive as low- and high-trustworthy in a sample of 6-month-old infants (N = 29; 56% male; Mage = 196.8 days; all White) and young adults (N = 21; 40% male; Mage = 24.61 years; all White) recruited in Italy. Stimulus sequences were presented at 6 Hz with deviant faces interleaved every fifth stimulus (i.e., 1.2 Hz); oddball category (high/low trustworthiness) was varied within subjects. FPVS responses were analyzed at both frequencies of interest and their harmonics as a function of deviant type (high- vs. low-trustworthy) over occipital and occipitolateral electrode clusters. For both infants and adults, the baseline response did not differ between trustworthiness conditions. Significant responses were centered on the right parietal electrodes in infants, and on the occipital and left occipitotemporal clusters in adults. Oddball responses were significant for both infants and adults, with cross-age differences in the topographical localization of the response on the scalp. Overall, results suggest that, by the age of 6 months, infants discriminate between faces that adults rate as high and low in trustworthiness, extending prior evidence of early sensitivity to this face dimension in humans. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Infants' fast neural categorization of artificial objects: The impact of stimulus and task characteristics.

This study explores how 7-month-old infants categorize graphical images varying in basic perceptual features by using a fast periodic visual stimulation (FPVS) task. Most participants were Caucasian and their parents had a higher education, but the family's socioeconomic background was mixed. Experiment 1 (N = 23) tested brain responses to configurational versus scrambled image sequences and found an oddball effect for both conditions, with configurational information leading to stronger neural responses. Experiment 2 explored the role of category learning for later FPVS performance: Group A (control; n = 22) participated in the FPVS categorization task only. Group B (fam; n = 21) was first familiarized with standard exemplars. Group C (fam + contrast; n = 29) was presented an additional exemplar of the contrasting category before the FPVS task. Electroencephalogram analyses revealed a decrease in Nc amplitude (measuring attention) throughout the familiarization phase. Long looking at the out-of-category exemplar in Group C indicated infants' visual interest. Brain responses in the subsequently presented FPVS were strong but did not differ between groups. This highlights the ability of the infant brain to organize perceptual input very rapidly without requiring familiarization but also points to the need for further studies exploring brain processes associated with infants' category learning and categorization at the brain level. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Frequency tagging with infants: The visual oddball paradigm.

Combining frequency tagging with electroencephalography (EEG) provides excellent opportunities for developmental research and is increasingly employed as a powerful tool in cognitive neuroscience within the last decade. In particular, the visual oddball paradigm has been employed to elucidate face and object categorization and intermodal influences on visual perception. Still, EEG research with infants poses special challenges that require consideration and adaptations of analyses. These challenges include limits to attentional capacity, variation in looking times, and presence of artefacts in the EEG signal. Moreover, potential differences between age-groups must be carefully evaluated. This manuscript evaluates challenges theoretically and empirically by (1) a systematic review of frequency tagging studies employing the oddball paradigm and (2) combining and re-analyzing data from seven-month-old infants (N = 124, 59 females) collected in a categorization task with artifical, unfamiliar stimuli. Specifically, different criteria for sequence retention and selection of harmonics, the influence of bins considered for baseline correction and the relation between fast periodic visual stimulation (FPVS) responses and looking time are analyzed. Overall, evidence indicates that analysis decisions should be tailored based on age-group to optimally capture the observed signal. Recommendations for infant frequency tagging studies are developed to aid researchers in selecting appropriate stimulation and analysis strategies in future work.

Superior neural individuation of mother's than stranger's faces by five months of age.

Human adults are better at recognizing different views of a given face as belonging to the same person when that person is familiar rather than unfamiliar. To clarify the developmental origin of this well-established phenomenon, one group of five-month-olds (N = 22) was presented with pictures of four different unfamiliar female faces at a fixed rate (6 Hz, 166 msec stimulus onset asynchrony), interrupted every 5th stimulus (1.2 Hz) by either their mother's face (mother oddball condition) or, in different stimulation sequences, a stranger's face (stranger oddball condition). In another group of five-month-olds (N = 17), stimulation sequences were reversed such that their mothers' or a given stranger's face were repeated at 6 Hz and interrupted every 5 stimuli by pictures of different female faces (mother standard, stranger standard conditions, respectively). Twelve variable images of each identity served as stimulus material. Besides clear frequency-tagged EEG responses at the 6 Hz stimulation rate over the medial occipital region in all conditions, significant activity at 1.2 Hz and harmonics (2.4 Hz, etc.) was observed in this region, reflecting selective responses to facial identity across changes of views. This effect was strongest when the mother's face was immediately repeated at every stimulation cycle (mother standard). Overall, these observations point to an early developmental advantage of identifying a familiar face presented from different views during immediate stimulus repetition.

Audio-visual priming in 7-month-old infants: An ERP study.

The current study investigates categorical priming across modalities in 7-month-old infants using electroencephalographic (EEG) measures. In two experiments, infants were presented with sounds as primes, followed by images of human figures and furniture items as targets. In experiment 1 (N = 20), images were preceded by infant-directed (ID) or adult-directed (AD) speech to explore effects of intermodal categorical mismatches. Furniture targets (mismatching category) elicited an increased amplitude of the Negative central (Nc) component compared to human targets (matching category), p < .01, indicating increased attention. Results did not vary with manner of speaking (ID or AD). Experiment 2 (N = 17) explored whether a categorical mismatch between prime and target would elicit increased positive slow wave (PSW) amplitudes for human targets, indicating increased memory effort. Here, bicycle ringtones and ID speech served as primes. Again, furniture targets elicited an increased Nc regardless of prime category, p < .05, and a categorical change from human speech to furniture target images elicited an increased PSW, p < .05. No PSW effect was found for human targets following bicycle ringtones, however. The experiments reported here suggest that auditory primes may increase infant attention and memory updating particularly for non-social, categorically mismatching stimuli.

Rapid Categorization of Human and Ape Faces in 9-Month-Old Infants Revealed by Fast Periodic Visual Stimulation.

This study investigates categorization of human and ape faces in 9-month-olds using a Fast Periodic Visual Stimulation (FPVS) paradigm while measuring EEG. Categorization responses are elicited only if infants discriminate between different categories and generalize across exemplars within each category. In study 1, human or ape faces were presented as standard and deviant stimuli in upright and inverted trials. Upright ape faces presented among humans elicited strong categorization responses, whereas responses for upright human faces and for inverted ape faces were smaller. Deviant inverted human faces did not elicit categorization. Data were best explained by a model with main effects of species and orientation. However, variance of low-level image characteristics was higher for the ape than the human category. Variance was matched to replicate this finding in an independent sample (study 2). Both human and ape faces elicited categorization in upright and inverted conditions, but upright ape faces elicited the strongest responses. Again, data were best explained by a model of two main effects. These experiments demonstrate that 9-month-olds rapidly categorize faces, and unfamiliar faces presented among human faces elicit increased categorization responses. This likely reflects habituation for the familiar standard category, and stronger release for the unfamiliar category deviants.

How do 9-month-old infants categorize human and ape faces? A rapid repetition ERP study.

The current study investigates how infants categorize human compared to ape faces. Nine-month-old infants were presented with priming stimuli related to human (N = 24) or ape (N = 25) face targets on different levels of categorization. Event-related potentials were recorded during a passive-looking rapid repetition paradigm. In a within-subjects design, priming effects of the same faces, different faces from the same basic-level category, different faces from the other basic-level category (human/ape faces), and house fronts were examined. Human and ape faces were first categorized on a superordinate level ("faces"), as indicated by enhanced P1 amplitude and reduced P1 latency for faces primed by any faces. Then, human and ape faces were categorized on a basic level. N290 amplitude and latency were larger for human and monkey targets primed by human faces. Neither human nor ape faces were categorized on the individual level.

The neural correlates of processing newborn and adult faces in 3-year-old children.

The current study examines the processing of upright and inverted faces in 3-year-old children (n = 35). Event-related potentials (ERPs) were recorded during a passive looking paradigm including adult and newborn face stimuli. We observed three face-sensitive components, the P1, the N170 and the P400. Inverted faces elicited shorter P1 latency and larger P400 amplitude. P1 and N170 amplitudes were larger for adult faces. To examine the role of experience in the development of face processing, the processing of adult and newborn faces was compared for children with a younger sibling (n = 23) and children without a younger sibling (n = 12). Age of sibling at test correlated negatively with P1 amplitude for adult and newborn faces. This may indicate more efficient processing of different face ages in children with a younger sibling and potentially reflects a more flexible face representation.

Three-month-olds' brain responses to upright and inverted faces and cars.

We examined the processing of upright and inverted faces and cars in 3-month-old infants applying an event-related-potentials paradigm. The current study is the first to contrast human faces with an object category, cars, in a within-subjects design with infants. N290 amplitude was larger for inverted than upright faces, whereas no inversion effect was observed for cars. Moreover, N290 latency was enhanced for inverted faces and cars. This indicates that neural processing may already be partly face-specific in young infants.

The early development of face processing--what makes faces special?

In the present article we review behavioral and neurophysiological studies on face processing in adults and in early development. From the existing empirical and theoretical literature we derive three aspects that distinguish face processing from the processing of other visual object categories. Each of these aspects is discussed from a developmental perspective. First, faces are recognized and represented at the individual level rather than at the basic level. Second, humans typically acquire extensive expertise in individuating faces from early on in development. And third, more than other objects, faces are processed holistically. There is a quantitative difference in the amount of visual experience for faces and other object categories in that the amount of expertise typically acquired for faces is greater than that for other object categories. In addition, we discuss possible qualitative differences in experience for faces and objects. For instance, there is evidence for a sensitive period in infancy for building up a holistic face representation and for perceptual narrowing for faces of one's own species and race. We conclude our literature review with questions for future research, for instance, regarding the exact relationship between behavioral and neuronal markers of face processing across development.