Visual stimulus structure, visual system neural activity, and visual behavior in young human infants.

In visual perception and information processing, a cascade of associations is hypothesized to flow from the structure of the visual stimulus to neural activity along the retinogeniculostriate visual system to behavior and action. Do visual perception and information processing adhere to this cascade near the beginning of life? To date, this three-stage hypothetical cascade has not been comprehensively tested in infants. In two related experiments, we attempted to expose this cascade in 6-month-old infants. Specifically, we presented infants with two levels of visual stimulus intensity, we measured electrical activity at the infant cortex, and we assessed infants' preferential looking behavior. Chromatic saturation provided a convenient stimulus dimension to test the cascade because greater saturation is known to excite increased activity in the primate visual system and is generally hypothesized to stimulate visual preference. Experiment 1 revealed that infants prefer (look longer) at the more saturated of two colors otherwise matched in hue and brightness. Experiment 2 showed increased aggregate neural cortical excitation in infants (and adults) to the more saturated of the same pair of colors. Thus, experiments 1 and 2 taken together confirm a cascade: Visual stimulation of relatively greater intensity evokes relatively greater levels of bioelectrical cortical activity which in turn is associated with relatively greater visual attention. As this cascade obtains near the beginning of life, it helps to account for early visual preferences and visual information processing.

Contrasting Electroencephalography-Derived Entropy and Neural Oscillations With Highly Skilled Meditators.

Meditation is an umbrella term for a number of mental training practices designed to improve the monitoring and regulation of attention and emotion. Some forms of meditation are now being used for clinical intervention. To accompany the increased clinical interest in meditation, research investigating the neural basis of these practices is needed. A central hypothesis of contemplative neuroscience is that meditative states, which are unique on a phenomenological level, differ on a neurophysiological level. To identify the electrophysiological correlates of meditation practice, the electrical brain activity of highly skilled meditators engaging in one of six meditation styles (shamatha, vipassana, zazen, dzogchen, tonglen, and visualization) was recorded. A mind-wandering task served as a control. Lempel-Ziv complexity showed differences in nonlinear brain dynamics (entropy) during meditation compared with mind wandering, suggesting that meditation, regardless of practice, affects neural complexity. In contrast, there were no differences in power spectra at six different frequency bands, likely due to the fact that participants engaged in different meditation practices. Finally, exploratory analyses suggest neurological differences among meditation practices. These findings highlight the importance of studying the electroencephalography (EEG) correlates of different meditative practices.

Integration of thought and action continued: Scale errors and categorization in toddlers.

To further explore the effect of weighted arms on toddler's performance in problem solving (Arterberry et al., 2018, Infancy, 23(2), 173), the present study explored scale errors and categorization, two instances where infants appear to show more advanced knowledge than toddlers. Experiment 1 (N = 67) used a novel task for inducing scale errors among 24- to 29-month-olds. Results replicated rates of scale errors found in previous research that used different tasks. Experiment 2 used sequential touching (N = 31) and sorting measures (N = 23) to test categorization in 24-month-old children. In both measures, children showed categorization at the basic level when there was high contrast between the exemplars, but not at a basic level with low contrast or a subordinate level. In Experiments 1 and 2, half the participants were tested while wearing weighted wristbands. Weighting the arms did not affect error rates, in contrast to previous research showing that weights improved performance in search tasks. The findings are discussed in light of children's difficulty in integrating perception, cognition, and action.

Children's Memory for Temporal Information: The Roles of Temporal Language and Executive Function.

The ability to recall the temporal order of events develops much more slowly than the ability to recall facts about events. To explore what processes facilitate memory for temporal information, we tested 3- to 6-year-old children (N = 40) for immediate memory of the temporal order of events from a storybook, using a visual timeline task and a yes/no recognition task. In addition, children completed tasks assessing their understanding of before and after and the executive functions of inhibition using the Day/Night Stroop task and cognitive shifting using the Dimensional Change Card Sort (DCCS) task. Older children (Mage = 69.25 months) outperformed younger children (Mage = 52.35 months) on all measures; however, the only significant predictor of memory for the temporal ordering of events was cognitive shifting. The findings suggest that the difficulty in memory for temporal information is related to development of a general cognitive ability, as indexed by the DCCS, rather than specific temporal abilities.

Categorization of two-dimensional and three-dimensional stimuli by 18-month-old infants.

In two experiments, 18-month-old infants' categorization of 3D replicas and 2D photographs of the same animals and vehicles were compared to explore infants' flexibility in categorization across different object representations. Using a sequential touching procedure, infants completed one superordinate and two basic-level categorization tasks with 3D replicas, 2D cut out photographs, or 2D images on photo cubes ("2D cubes"). For superordinate sets, 3D replicas elicited longer mean run lengths than 2D cut outs, and 3D replicas elicited equivalent mean run lengths as 2D cubes. For basic-level sets, infants categorized high-contrast animal sets when presented with 3D replicas, but they failed to categorize any of the 2D photograph sets. Categorization processes appear to differ for 3D and 2D stimuli, and infants' discovery of object properties over time while manipulating objects may facilitate categorization, as least at the superordinate level. These findings are discussed in the context of infants' representation abilities and the integration of perception and action.

Differentiated brain activity in response to faces of "own" versus "unfamiliar" babies in primipara mothers: an electrophysiological study.

Experiences with one's own infant attune the parent nervous system to infant stimuli. To explore the effects of motherhood on brain activity patterns, electroencephalogram (EEG) was recorded while primipara mothers of 3- and 6-month-olds viewed images of faces of their own child and an unfamiliar but appearance-matched child. Mothers of 3- and 6-month-olds showed equivalent early-wave (N/P1 "visual" and N170 "face-sensitive") responses to own and unfamiliar baby faces but differentiating late-wave (N/P600 "familiar/ novel") activity to own versus unfamiliar infant faces. Based on 3 months experience with their own infant's face, mothers' brain patterns give evidence of distinctive late-wave (recognition) sensitivity.

Brain dynamics in young infants' recognition of faces: EEG oscillatory activity in response to mother and stranger.

The brain electrical responses of 3-month-old infants were compared between images of familiar and unfamiliar faces. Infants were shown images of their mothers and of appearance-matched female strangers for 500 ms per trial while their electroencephalography was recorded. Electroencephalographic signals were segmented from stimulus onset through 1200 ms, and segments were analyzed in the time-frequency domain with a continuous wavelet transform. Differentiated responses were apparent in three time windows: 370-480, 610-690, and 830-960 ms. Across response windows, event-related synchronization or desynchronization was observed in beta or gamma frequency bands at the left frontal, midline central, bilateral temporal, and right parietal sites. In conclusion, these findings provide the first evidence of organized brain activity underlying familiar face recognition in very young infants and are discussed in relation to comparable patterns that have been observed in adults.

Categorization of real and replica objects by 14- and 18-month-old infants.

In studies of infant categorization (especially sequential touching), replicas of real objects are often utilized on the assumption that infants treat replicas as they do reals. Do infants categorize replicas of objects in the same way as they categorize real objects? This question was addressed in a sequential touching task, where 14- and 18-month-olds were presented with four sets of objects: real telephones and hairbrushes, real lemons and pears, replica telephones and hairbrushes, and replica lemons and pears. On the whole, mean run length, number of contacts, and appropriate actions did not differ between real and replica objects. Moreover, mean run length was significantly greater than chance for telephones and hairbrushes, but not for lemons and pears; both ages categorized the former sets but not the latter. Infants of this age appear to treat replicas as equivalent to reals, and replicas are appropriate stimuli to use in the sequential touching procedure to address questions of infants' categorization.

Object perception in 5-month-old infants of clinically depressed and nondepressed mothers.

Five-month-old infants of clinically depressed and nondepressed mothers were familiarized to a wholly novel object and afterward tested for their discrimination of the same object presented in the familiar and in a novel perspective. Infants in both groups were adequately familiarized, but infants of clinically depressed mothers failed to discriminate between novel and familiar views of the object, whereas infants of nondepressed mothers successfully discriminated. The difference in discrimination between infants of depressed and nondepressed mothers is discussed in light of infants' differential object processing and maternal sociodemographics, mind-mindedness, depression, stress, and interaction styles that may moderate opportunities for infants to learn about their world or influence the development of their perceptuocognitive capacities.

Assessing categorization performance at the individual level: a comparison of Monte Carlo simulation and probability estimate model procedures.

Two analytical procedures for identifying young children as categorizers, the Monte Carlo Simulation and the Probability Estimate Model, were compared. Using a sequential touching method, children aged 12, 18, 24, and 30 months were given seven object sets representing different levels of categorical classification. From their touching performance, the probability that children were categorizing was then determined independently using Monte Carlo Simulation and the Probability Estimate Model. The two analytical procedures resulted in different percentages of children being classified as categorizers. Results using the Monte Carlo Simulation were more consistent with group-level analyses than results using the Probability Estimate Model. These findings recommend using the Monte Carlo Simulation for determining individual categorizer classification.

Young infants' eye movements over "natural" scenes and "experimental" scenes.

Eye movements of 30 4-month-olds were tracked as infants viewed animals and vehicles in "natural" scenes and, for comparison, in homogeneous "experimental" scenes. Infants showed equivalent looking time preferences for natural and experimental scenes overall, but fixated natural scenes and objects in natural scenes more than experimental scenes and objects in experimental scenes and shifted fixations between objects and contexts more in natural than in experimental scenes. The findings show how infants treat objects and contexts in natural scenes and suggest that they treat more commonly used experimental scenes differently.

Perception of object-context relations: eye-movement analyses in infants and adults.

Twenty-eight 4-month-olds' and twenty-two 20-year-olds' attention to object-context relations was investigated using a common eye-movement paradigm. Infants and adults scanned both objects and contexts. Infants showed equivalent preferences for animals and vehicles and for congruent and incongruent object-context relations overall, more fixations of objects in congruent object-context relations, more fixations of contexts in incongruent object-context relations, more fixations of objects than contexts in vehicle scenes, and more fixation shifts in incongruent than congruent vehicle scenes. Adults showed more fixations of congruent than incongruent scenes, vehicles than animals, and objects than contexts; equal fixations of animals and their contexts but more fixations of vehicles than their contexts; and more shifts of fixation when inspecting animals in context than vehicles in context. These findings for location, number, and order of eye movements indicate that object-context relations play a dynamic role in the development and allocation of attention.

Discrimination of facial expression by 5-month-old infants of nondepressed and clinically depressed mothers.

Five-month-old infants of nondepressed and clinically depressed mothers were habituated to either a face with a neutral expression or the same face with a smile. Infants of nondepressed mothers subsequently discriminated between neutral and smiling facial expressions, whereas infants of clinically depressed mothers failed to make the same discrimination.

The development of object categorization in young children: hierarchical inclusiveness, age, perceptual attribute, and group versus individual analyses.

Multiple levels of category inclusiveness in 4 object domains (animals, vehicles, fruit, and furniture) were examined using a sequential touching procedure and assessed in both individual and group analyses in eighty 12-, 18-, 24-, and 30-month-olds. The roles of stimulus discriminability and child motor development, fatigue, and actions were also investigated. More inclusive levels of categorization systematically emerged before less inclusive levels, and a consistent advantage for categorizing high versus low perceptual contrasts was found. Group and individual analyses generally converged, but individual analyses added information about child categorization over group analyses. The development of object categorization in young children is discussed in light of efficiency of processing and similarity-differentiation theories.

Infant object categorization transcends diverse object-context relations.

Infants' categorization of objects in different object-context relations was investigated. The experiment used a multiple-exemplar habituation-categorization procedure where 92 6-month olds formed categories of animals and vehicles embedded in congruent, incongruent, and homogeneous object-context relations. Across diverse object-context relations, infants habituated to multiple exemplars within a category and categorized novel members of both animal and vehicle categories. Infants showed a slight advantage for categorizing animals. Infant object categorization appears to be robust to diversity in object-context relations.

Mechanisms of Visual Object Recognition in Infancy: Five-Month-Olds Generalize Beyond the Interpolation of Familiar Views.

This work examined predictions of the interpolation of familiar views (IFV) account of object recognition performance in 5-month-olds. Infants were familiarized to an object either from a single viewpoint or from multiple viewpoints varying in rotation around a single axis. Object recognition was then tested in both conditions with the same object rotated around a novel axis. Infants in the multiple-views condition recognized the object, whereas infants in the single-view condition provided no evidence for recognition. Under the same 2 familiarization conditions, infants in a 2nd experiment treated as novel an object that differed in only 1 component from the familiar object. Infants' object recognition is enhanced by experience with multiple views, even when that experience is around an orthogonal axis of rotation, and infants are sensitive to even subtle shape differences between components of similar objects. In general, infants' performance does not accord with the predictions of the IFV model of object recognition. These findings motivate the extension of future research and theory beyond the limits of strictly interpolative mechanisms.

Infant perceptual and conceptual categorization: the roles of static and dynamic stimulus attributes.

Infants' categorization of animals and vehicles based on static vs. dynamic attributes of stimuli was investigated in five experiments (N=158) using a categorization habituation-of-looking paradigm. In Experiment 1, 6-month-olds categorized static color images of animals and vehicles, and in Experiment 2, 6-month-olds categorized dynamic point-light displays showing only motions of the same animals and vehicles. In Experiments 3, 4, and 5, 6- and 9-month-olds were tested in an habituation-transfer paradigm: half of the infants at each age were habituated to static images and tested with dynamic point-light displays, and the other half were habituated to dynamic point-light displays and tested with static images. Six-month-olds did not transfer. Only 9-month-olds who were habituated to dynamic displays showed evidence of category transfer to static images. Together the findings show that 6-month-olds categorize animals and vehicles based on static and dynamic information, and 9-month-olds can transfer dynamic category information to static images. Transfer, static vs. dynamic information, and age effects in infant categorization are discussed.