Indexing Early Visual Memory Durability in Infancy.

The goal was to examine the scope and development of early visual memory durability. We investigated individual- and age-related differences across three unique tasks in 6- to 12-month-olds (Mage  = 8.87, N = 49) by examining the effect of increased delay on memory performance. Results suggest longer-term memory processes are quantifiable by 8 months using a modified Change Detection paradigm and spatial-attention cueing processes are quantifiable by 10 months using a modified Delayed Response paradigm, utilizing 500-1,250 ms delays. Performance improved from 6 to 12 months and longer delays impaired performance. We found no evidence for success on the Delayed Match Retrieval task at any age. These outcomes help inform our understanding of infant visual memory durability and its emergence throughout early development.

Orientation Effects in the Development of Linear Object Tracking in Early Infancy.

Infants' oculomotor tracking develops rapidly but is poorer when there are horizontal and vertical movement components. Additionally, persistence of objects moving through occlusion emerges at 4 months but initially is absent for objects moving obliquely. In two experiments, we recorded eye movements of thirty-two 4-month-old and thirty-two 6-month-old infants (mainly Caucasian-White) tracking horizontal, vertical, and oblique trajectories. Infants tracked oblique trajectories less accurately, but 6-month olds tracked more accurately such that they tracked oblique trajectories as accurately as 4-month olds tracked horizontal and vertical trajectories. Similar results emerged when the object was temporarily occluded. Thus, 4-month olds' tracking of oblique trajectories may be insufficient to support object persistence, whereas 6-month olds may track sufficiently accurately to perceive object persistence for all trajectory orientations.

Infants' learning of non-adjacent regularities from visual sequences.

Tracking adjacent (AD) and non-adjacent (NAD) dependencies in a sequence of elements is critical for the development of many complex abilities, such as language acquisition and social interaction. While learning of AD in infancy is a domain-general ability that is functioning across different domains, infants' processing of NAD has been reported only for speech sequences. Here, we tested 9- to 12- and 13- to 15-month-olds' ability to extract AxB grammars in visual sequences of unfamiliar elements. Infants were habituated to a series of 3-visual arrays following an AxB grammar in which the first element (A) predicted the third element (B), while intervening X elements changed continuously. Following habituation, infants were tested with 3-item arrays in which initial and final positions were switched (novel) or kept consistent with the habituation phase (familiar). Older infants successfully recognized the familiar AxB grammar at test, whereas the younger group showed some sensitivity to extract to NAD, albeit in a less robust form. This finding provides the first evidence that the ability to track NAD is a domain-general ability that is present also in the visual domain and that the sensitivity to such dependencies is related to developmental changes, as demonstrated in the auditory domain.

Infants' identification of gender in biological motion displays.

Infants' knowledge of social categories, including gender-typed characteristics, is a vital aspect of social cognitive development. In the current study, we examined 9- to 12-month-old infants' understanding of the categories "male" and "female" by testing for gender matching in voices or faces with biological motion depicted in point light displays (PLDs). Infants did not show voice-PLD gender matching spontaneously (Experiment 1) or after "training" with gender-matching voice-PLD pairs (Experiment 2). In Experiment 3, however, infants were trained with gender-matching face-PLD pairs and we found that patterns of visual attention to top regions of PLD stimuli during training predicted gender matching of female faces and PLDs. Prior to the end of the first postnatal year, therefore, infants may begin to identify gender in human walk motions, and perhaps form social categories from biological motion.

Rule learning transfer across linguistic and visual modalities in 7-month-old infants.

Rule learning (RL) refers to infants' ability to extract high-order, repetition-based rules from a sequence of elements and to generalize them to new items. RL has been demonstrated in both the auditory and the visual modality, but no studies have investigated infants' transfer of learning across these two modalities, a process that is fundamental for the development of many complex cognitive skills. Using a visual habituation procedure within a cross-modal RL task, we tested 7-month-old infants' transfer of learning both from speech to vision (auditory-visual-AV-condition) and from vision to speech (visual-auditory-VA-condition). Results showed a transfer of learning in the AV condition, but only for those infants who were able to efficiently extract the rule during the learning (habituation) phase. In contrast, in the VA condition infants provided no evidence of RL. Overall, this study indicates that 7-month-old infants can transfers high-order rules across modalities with an advantage for transferring from speech to vision, and that this ability is constrained by infants' individual differences in the way they process the to-be-learned rules.

Electrophysiological signatures of visual statistical learning in 3-month-old infants at familial and low risk for autism spectrum disorder.

Visual statistical learning (VSL) refers to the ability to extract associations and conditional probabilities within the visual environment. It may serve as a precursor to cognitive and social communication development. Quantifying VSL in infants at familial risk (FR) for Autism Spectrum Disorder (ASD) provides opportunities to understand how genetic predisposition can influence early learning processes which may, in turn, lay a foundation for cognitive and social communication delays. We examined electroencephalography (EEG) signatures of VSL in 3-month-old infants, examining whether EEG correlates of VSL differentiated FR from low-risk (LR) infants. In an exploratory analysis, we then examined whether EEG correlates of VSL at 3 months relate to cognitive function and ASD symptoms at 18 months. Infants were exposed to a continuous stream of looming shape pairs with varying probability that the shapes would occur in sequence (high probability-deterministic condition; low probability-probabilistic condition). EEG was time-locked to shapes based on their transitional probabilities. EEG analysis examined group-level characteristics underlying specific components, including the late frontal positivity (LFP) and N700 responses. FR infants demonstrated increased LFP and N700 response to the probabilistic condition, whereas LR infants demonstrated increased LFP and N700 response to the deterministic condition. LFP at 3 months predicted 18-month visual reception skills and not ASD symptoms. Our findings thus provide evidence for distinct VSL processes in FR and LR infants as early as 3 months. Atypical pattern learning in FR infants may lay a foundation for later delays in higher level, nonverbal cognitive skills, and predict ASD symptoms well before an ASD diagnosis is made.

Intermodal emotion matching at 15 months, but not 9 or 21 months, predicts early childhood emotion understanding: A longitudinal investigation.

Emotion understanding is a crucial skill for early social development, yet little is known regarding longitudinal development of this skill from infancy to early childhood. To address this issue, the present longitudinal study followed 40 participants from 9 to 30 months. Intermodal emotion matching was assessed using eye tracking at 9, 15, and 21 months, and emotion understanding was measured using the Affective Knowledge Test at 30 months of age. A novelty preference on the emotion matching task at 15 months (but not at 9 or 21 months) significantly predicted emotion understanding performance at 30 months. However, linear and quadratic trajectories for emotion matching development across 9- to 21-months did not predict later emotion understanding. No gender differences were observed in emotion matching or emotion understanding. These results hold implications for better understanding how infant emotion matching may relate to later emotion understanding, and the role that infant emotion perception may play in early emotional development.

Automated Study Challenges the Existence of a Foundational Statistical-Learning Ability in Newborn Chicks.

What mechanisms underlie learning in newborn brains? Recently, researchers reported that newborn chicks use unsupervised statistical learning to encode the transitional probabilities (TPs) of shapes in a sequence, suggesting that TP-based statistical learning can be present in newborn brains. Using a preregistered design, we attempted to reproduce this finding with an automated method that eliminated experimenter bias and allowed more than 250 times more data to be collected per chick. With precise measurements of each chick's behavior, we were able to perform individual-level analyses and substantially reduce measurement error for the group-level analyses. We found no evidence that newborn chicks encode the TPs between sequentially presented shapes. None of the chicks showed evidence for this ability. Conversely, we obtained strong evidence that newborn chicks encode the shapes of individual objects, showing that this automated method can produce robust results. These findings challenge the claim that TP-based statistical learning is present in newborn brains.

Real-world scene perception in infants: What factors guide attention allocation?

The foci of visual attention were modeled as a function of perceptual salience, adult fixation locations, and attentional control mechanisms (measured in separate tasks) in infants (N = 45, 3- to 15-month-olds) as they viewed static real-world scenes. After controlling for the center bias, the results showed that low-level perceptual salience predicts where infants look. In addition, high-level factors also played a role: Infants fixated parts of the scenes frequently fixated by adults and this effect was stronger for older than younger infants. In line with this finding, infant fixation durations were longer on regions more frequently fixated by adults, implying longer time taken to process the available information. Fixation durations decreased with age, and this decline interacted with orienting skills such that fixation durations decreased faster with age for infants with high orienting skills, relative to infants with low orienting skills. There was a further interaction between fixation durations and selective attention abilities: Infants with low selective attention skills showed a decrease in fixation durations with age, whereas infants with higher selective attention skills showed a slight increase in fixation durations with age. These findings imply that infants' visual processing of static real-world stimuli develops in accord with attentional control.

Early contributions to infants' mental rotation abilities.

Some cognitive abilities exhibit reliable gender differences, with females outperforming males in specific aspects of verbal ability, and males showing an advantage on certain spatial tasks. Among these cognitive gender differences, differences in mental rotation are the most robust, and appear to be present even in infants. A large body of animal research suggests that gonadal hormones, particularly testosterone, during early development could contribute to this gender difference in mental rotation. Also, substantial evidence supports an influence of socialization on mental rotation performance. The present study investigated the relationship of two types of factors, early postnatal testosterone exposure and parental attitudes about gender, to mental rotation performance in 61 healthy infants (29 males, 32 females). We measured salivary testosterone at two time points: 1-2.5 months of age and 5-6 months of age. Infants' mental rotation performance and parents' attitudes about gender were assessed at 5-6 months of age. As predicted, testosterone concentrations were significantly higher in boys than girls in early infancy (d = 0.54), and boys performed significantly better than girls on mental rotation (d = 0.64). A significant positive correlation between testosterone at age 1-2.5 months and mental rotation was found only in boys (r = 0.50, p = .01). A significant negative correlation between parents' gender-stereotypical attitudes and mental rotation performance was found only in girls (r = -.57, p = .002). These findings suggest that the early postnatal testosterone surge (also known as "mini-puberty") may have organizational influences on mental rotation performance in boys, and that parents may influence their daughters' mental rotation abilities beginning very early in life.

Selective attention to the mouth is associated with expressive language skills in monolingual and bilingual infants.

Infants increasingly attend to the mouths of others during the latter half of the first postnatal year, and individual differences in selective attention to talking mouths during infancy predict verbal skills during toddlerhood. There is some evidence suggesting that trajectories in mouth-looking vary by early language environment, in particular monolingual or bilingual language exposure, which may have differential consequences in developing sensitivity to the communicative and social affordances of the face. Here, we evaluated whether 6- to 12-month-olds' mouth-looking is related to skills associated with concurrent social communicative development-including early language functioning and emotion discriminability. We found that attention to the mouth of a talking face increased with age but that mouth-looking was more strongly associated with concurrent expressive language skills than chronological age for both monolingual and bilingual infants. Mouth-looking was not related to emotion discrimination. These data suggest that selective attention to a talking mouth may be one important mechanism by which infants learn language regardless of home language environment.

Family expressiveness relates to happy emotion matching among 9-month-old infants.

Perceiving and understanding the emotions of those around us is an imperative skill to develop early in life. An infant's family environment provides most of their emotional exemplars in early development. However, the relation between the early development of emotion perception and family expressiveness remains understudied. To investigate this potential link to early emotion perception development, we examined 38 infants at 9 months of age. We assessed infants' ability to match emotions across facial and vocal modalities using an intermodal matching paradigm for angry-neutral, happy-neutral, and sad-neutral pairings. We also attained family expressiveness information via parent report. Our results indicate a significant positive relation between emotion matching and family expressiveness specific to the happy-neutral condition. However, we found no evidence for emotion matching for the infants as a group in any of the three conditions. These results suggest that family expressiveness does relate to emotion matching for the earliest developing emotional category among 9-month-old infants and that emotion matching with multiple emotions at this age is a challenging task.

Infant perception of sex differences in biological motion displays.

We examined mechanisms underlying infants' ability to categorize human biological motion stimuli from sex-typed walk motions, focusing on how visual attention to dynamic information in point-light displays (PLDs) contributes to infants' social category formation. We tested for categorization of PLDs produced by women and men by habituating infants to a series of female or male walk motions and then recording posthabituation preferences for new PLDs from the familiar or novel category (Experiment 1). We also tested for intrinsic preferences for female or male walk motions (Experiment 2). We found that infant boys were better able to categorize PLDs than were girls and that male PLDs were preferred overall. Neither of these effects was found to change with development across the observed age range (∼4-18 months). We conclude that infants' categorization of walk motions in PLDs is constrained by intrinsic preferences for higher motion speeds and higher spans of motion and, relatedly, by differences in walk motions produced by men and women.

Gazepath: An eye-tracking analysis tool that accounts for individual differences and data quality.

Eye-trackers are a popular tool for studying cognitive, emotional, and attentional processes in different populations (e.g., clinical and typically developing) and participants of all ages, ranging from infants to the elderly. This broad range of processes and populations implies that there are many inter- and intra-individual differences that need to be taken into account when analyzing eye-tracking data. Standard parsing algorithms supplied by the eye-tracker manufacturers are typically optimized for adults and do not account for these individual differences. This paper presents gazepath, an easy-to-use R-package that comes with a graphical user interface (GUI) implemented in Shiny (RStudio Inc 2015). The gazepath R-package combines solutions from the adult and infant literature to provide an eye-tracking parsing method that accounts for individual differences and differences in data quality. We illustrate the usefulness of gazepath with three examples of different data sets. The first example shows how gazepath performs on free-viewing data of infants and adults, compared to standard EyeLink parsing. We show that gazepath controls for spurious correlations between fixation durations and data quality in infant data. The second example shows that gazepath performs well in high-quality reading data of adults. The third and last example shows that gazepath can also be used on noisy infant data collected with a Tobii eye-tracker and low (60 Hz) sampling rate.

Young infants' visual fixation patterns in addition and subtraction tasks support an object tracking account.

Investigating infants' numerical ability is crucial to identifying the developmental origins of numeracy. Wynn (1992) claimed that 5-month-old infants understand addition and subtraction as indicated by longer looking at outcomes that violate numerical operations (i.e., 1+1=1 and 2-1=2). However, Wynn's claim was contentious, with others suggesting that her results might reflect a familiarity preference for the initial array or that they could be explained in terms of object tracking. To cast light on this controversy, Wynn's conditions were replicated with conventional looking time supplemented with eye-tracker data. In the incorrect outcome of 2 in a subtraction event (2-1=2), infants looked selectively at the incorrectly present object, a finding that is not predicted by an initial array preference account or a symbolic numerical account but that is consistent with a perceptual object tracking account. It appears that young infants can track at least one object over occlusion, and this may form the precursor of numerical ability.

Limits of Object Persistence: Young Infants Perceive Continuity of Vertical and Horizontal Trajectories, But Not 45-Degree Oblique Trajectories.

Previous research indicated that 4-month-old infants perceive continuity of objects moving on horizontal trajectories but appear to have difficulty processing occlusion events involving oblique trajectories. However, because perception of continuity of vertical trajectories has not been tested, it is uncertain whether this indicates a specific deficit for oblique trajectories or a specific advantage for horizontal trajectories. We evaluated the contribution of trajectory orientation and the form of occlusion in three experiments with one hundred and forty-four 4-month-olds. Infants perceived continuity of horizontal and vertical trajectories under all conditions presented. However, they did not perceive continuity of an oblique (45°) trajectory under any condition. Thus, 4-month-olds appear unable to process continuity of a 45° trajectory. In a fourth experiment with forty-eight 6- and 8-month-old infants, we demonstrated that by 6 months, infants' difficulty with oblique trajectories is overcome. We suggest that young infants' difficulty with markedly oblique trajectories likely relates to immature eye movement control.

Electrophysiological evidence of heterogeneity in visual statistical learning in young children with ASD.

Statistical learning is characterized by detection of regularities in one's environment without an awareness or intention to learn, and it may play a critical role in language and social behavior. Accordingly, in this study we investigated the electrophysiological correlates of visual statistical learning in young children with autism spectrum disorder (ASD) using an event-related potential shape learning paradigm, and we examined the relation between visual statistical learning and cognitive function. Compared to typically developing (TD) controls, the ASD group as a whole showed reduced evidence of learning as defined by N1 (early visual discrimination) and P300 (attention to novelty) components. Upon further analysis, in the ASD group there was a positive correlation between N1 amplitude difference and non-verbal IQ, and a positive correlation between P300 amplitude difference and adaptive social function. Children with ASD and a high non-verbal IQ and high adaptive social function demonstrated a distinctive pattern of learning. This is the first study to identify electrophysiological markers of visual statistical learning in children with ASD. Through this work we have demonstrated heterogeneity in statistical learning in ASD that maps onto non-verbal cognition and adaptive social function.

Infants' statistical learning: 2- and 5-month-olds' segmentation of continuous visual sequences.

Past research suggests that infants have powerful statistical learning abilities; however, studies of infants' visual statistical learning offer differing accounts of the developmental trajectory of and constraints on this learning. To elucidate this issue, the current study tested the hypothesis that young infants' segmentation of visual sequences depends on redundant statistical cues to segmentation. A sample of 20 2-month-olds and 20 5-month-olds observed a continuous sequence of looming shapes in which unit boundaries were defined by both transitional probability and co-occurrence frequency. Following habituation, only 5-month-olds showed evidence of statistically segmenting the sequence, looking longer to a statistically improbable shape pair than to a probable pair. These results reaffirm the power of statistical learning in infants as young as 5 months but also suggest considerable development of statistical segmentation ability between 2 and 5 months of age. Moreover, the results do not support the idea that infants' ability to segment visual sequences based on transitional probabilities and/or co-occurrence frequencies is functional at the onset of visual experience, as has been suggested previously. Rather, this type of statistical segmentation appears to be constrained by the developmental state of the learner. Factors contributing to the development of statistical segmentation ability during early infancy, including memory and attention, are discussed.

Detecting 'infant-directedness' in face and voice.

Five- and 3-month-old infants' perception of infant-directed (ID) faces and the role of speech in perceiving faces were examined. Infants' eye movements were recorded as they viewed a series of two side-by-side talking faces, one infant-directed and one adult-directed (AD), while listening to ID speech, AD speech, or in silence. Infants showed consistently greater dwell time on ID faces vs. AD faces, and this ID face preference was consistent across all three sound conditions. ID speech resulted in higher looking overall, but it did not increase looking at the ID face per se. Together, these findings demonstrate that infants' preferences for ID speech extend to ID faces.

Visual search and attention to faces during early infancy.

Newborn babies look preferentially at faces and face-like displays, yet over the course of their first year much changes about both the way infants process visual stimuli and how they allocate their attention to the social world. Despite this initial preference for faces in restricted contexts, the amount that infants look at faces increases considerably during the first year. Is this development related to changes in attentional orienting abilities? We explored this possibility by showing 3-, 6-, and 9-month-olds engaging animated and live-action videos of social stimuli and also measuring their visual search performance with both moving and static search displays. Replicating previous findings, looking at faces increased with age; in addition, the amount of looking at faces was strongly related to the youngest infants' performance in visual search. These results suggest that infants' attentional abilities may be an important factor in facilitating their social attention early in development.