This study examined infants' sensitivity to a speaker's verbal accuracy and whether the reliability of the speaker had an effect on their selective trust. Forty-nine 18-month-old infants were exposed to a speaker who either accurately or inaccurately labeled familiar objects. Subsequently, the speaker administered a series of tasks in which infants had an opportunity to: learn a novel word, imitate the speaker's “irrational” actions, and help the speaker obtain an out-of-reach object. In contrast to infants in the accurate (reliable) condition, those in the inaccurate (unreliable) condition performed more poorly on a word-learning task and were less likely to imitate. All infants demonstrated high rates of instrumental helping behavior. These results are the first to demonstrate that infants as young as 18 months of age cannot only detect a speaker's verbal inaccuracy but also use this information to attenuate their word recognition and learning of novel actions.

Evidence suggests that children and adults diagnosed with autism spectrum disorders (ASD) exhibit difficulties with postural control. Retrospective video studies of infants later diagnosed with ASD indicate that infants who eventually receive an ASD diagnosis exhibit delays in postural development. This study investigates early posture development prospectively and longitudinally in 22 infants at heightened biological risk for ASD (HR) and 18 infants with no such risk (Low Risk; LR). Four HR infants received an autism diagnosis (AD infants) at 36 months. Infants were videotaped at home at 6, 9, 12, and 14 months during everyday activities and play. All infant postures were coded and classified as to whether or not they were infant-initiated. Relative to LR infants, HR infants were slower to develop skill in sitting and standing postures. AD infants exhibited substantial delays in the emergence of more advanced postures and initiated fewer posture changes. Because posture advances create opportunities for infants to interact with objects and people in new and progressively more sophisticated ways, postural delays may have cascading effects on opportunities for infant exploration and learning. These effects may be greater for infants with ASD, for whom posture delays are more significant.

Emotion regulation strategies and variation in their presentation were explored toward understanding infants' responses during reunion with mother (Re) following baseline mother–infant interaction (Bl) and differential treatment (DT) episodes. Correlation analyses revealed cohesion among distress and mother-directed touch and proximity-seeking during DT and Re, mother-directed gaze during DT, and resistance during Re. The association between mother-directed gaze during DT and distress during Re suggests that visual inattention during DT serves as a regulatory strategy. Overall, these linkages yield expanded understanding of jealousy protest as a constellation of responses that endures beyond the eliciting condition and includes regulatory behaviors. Cross-context comparisons revealed that distress was lower during Re than during DT, but not as low as Bl, suggesting that DT poses challenge to interactive repair. Inquiry into individual variation revealed that distress during Re was augmented in laterborn males and with risk influences of dysregulated fear, and maternal insensitivity and hostility. Conversely, maternal depression was associated with less distress; later judgment as insecure, especially insecure-avoidance, was associated with less mother-directed behaviors. These findings suggest that dysregulation following DT is indicated by both resistance and passivity. In sum, the results highlight emotion regulation as a powerful framework for addressing recovery following DT.

Language learners rapidly acquire extensive semantic knowledge, but the development of this knowledge is difficult to study, in part because it is difficult to assess young children's lexical semantic representations. In our studies, we solved this problem by investigating lexical semantic knowledge in 24-month-olds using the Head-turn Preference Procedure. In Experiment 1, looking times to a repeating spoken word stimulus (e.g., kitty-kitty-kitty) were shorter for trials preceded by a semantically related word (e.g., dog-dog-dog) than trials preceded by an unrelated word (e.g., juice-juice-juice). Experiment 2 yielded similar results using a method in which pairs of words were presented on the same trial. The studies provide evidence that young children activate of lexical semantic knowledge, and critically, that they do so in the absence of visual referents or sentence contexts. Auditory lexical priming is a promising technique for studying the development and structure of semantic knowledge in young children.

Recent work has shown that young children can use fine phonetic detail during the recognition of isolated and sentence-final words from early in lexical development. The present study investigates 24-month-olds' word recognition in sentence-medial position in two experiments using an Intermodal Preferential Looking paradigm. In Experiment 1, French toddlers detect word-final voicing mispronunciations (e.g., buz [byz] for bus [bys] “bus”), and they compensate for native voicing assimilations (e.g., buz devant toi [buzdəvɑ̃twa] “bus in front of you”) in the middle of sentences. Similarly, English toddlers detect word-final voicing mispronunciations (e.g., sheeb for sheep) in Experiment 2, but they do not compensate for illicit voicing assimilations (e.g., sheeb there). Thus, French and English 24-month-olds can take into account fine phonetic detail even if words are presented in the middle of sentences, and French toddlers show language-specific compensation abilities for pronunciation variation caused by native voicing assimilation.

While the specificity of infants' early lexical representations has been studied extensively, researchers have only recently begun to investigate how words are organized in the developing lexicon and what mental representations are activated during processing of a word. Integrating these two lines of research, the current study asks how specific the phonological match between a perceived word and its stored form has to be in order to lead to (cascaded) lexical activation of related words during infant lexical processing. We presented German 24-month-olds with a cross-modal semantic priming task where the prime word was either correctly or incorrectly pronounced. Results indicate that correct pronunciations and mispronunciations both elicit similar semantic priming effects, suggesting that the infant word recognition system is flexible enough to handle deviations from the correct form. This might be an important prerequisite to children's ability to cope with imperfect input and to recognize words under more challenging circumstances.

Recent research suggests that 12-month-old infants use shape to individuate the number of objects present in a scene. This study addressed the question of whether infants would also rely on shape when shape is only a temporary attribute of an object. Specifically, we investigated whether infants realize that shape changes reliably indicate identity changes only in the case of rigid objects, but not in the case of deformable plastic objects. Twelve-month-old infants observed how either a rigid or a plastic object was placed in a box. When searching the box, they retrieved either an object with the same (no-switch event) or with a different shape (switch event). Infants correctly inferred two distinct objects in the switch event in the case of rigid objects, but not in the case of plastic objects. A control experiment confirmed that this result was not due to a lack of salience of the shape transformation. Thus, infants' re-searching behavior indicated that they viewed shape as being diagnostic in the individuation process of rigid objects only.

We followed the nondistressed vocalization dynamics of 30 mother–infant dyads observed in a naturalistic setting using multiple time points between 3 and 11 months to identify subtle relationships between age, sex and maternal behavior ending by 1 year of age with diverging trajectories of nondistressed vocalization. We observed no mean differences between boys and girls in frequency or duration of nondistressed vocalizations at any one time period. However, while these parameters were essentially static for boys, girls showed a quadratic developmental curve, declining in frequency and duration between 6 and 8 months and climbing above their early starting point by 9–11 months. Mothers of boys showed a linear decrease in the duration of their speech over the 9 months of our study. In contrast, mothers of girls showed quadratic patterns of ultimately increasing vocalization frequency and duration, over the months 3–11 of development. Finally, boys' and girls' vocalization contingent to maternal speech revealed no differences. Mothers of boys, however, did not change significantly over time, while mothers of girls showed an increase in contingent responsiveness from 3–5 months to 9–11 months and from 6–8 months to 9–11 months. A similar pattern was followed for object-related maternal vocal responses.

Although it is well accepted that parents greatly impact infant development, it is less clear which factors impact change in quantity and quality of parenting across infancy. This longitudinal study (N = 120 families) investigated how infant temperament and marital adjustment related to trajectories of mother and father involvement and sensitivity across infancy using multilevel models. Parental involvement (caregiving and play), infant temperament (surgency, negative affectivity, regulation), and marital adjustment were assessed from questionnaires when the infant was 3, 5, 7, 12, 14, and 20 months of age; parental sensitivity was coded from two episodes of the Still-Face Paradigm in early infancy (3, 5, and 7 months). On average, mothers showed higher levels of caregiving, play, and sensitivity than fathers. Mother caregiving, play, and sensitivity increased over time. Father caregiving and play also increased over time, whereas sensitivity did not change with age. Happier marriages were related to increased play for both mothers and fathers. Infant surgency was also significantly related to caregiving, play, and sensitivity trajectories for mothers but not fathers. Findings are discussed in relation to parenting roles and family dynamics.

In a prospective longitudinal study of a representative community sample (N = 264), mothers' references to infants' mental states were coded during a topic-sharing task in the home at 6 months. Joint attention behaviour was assessed in the laboratory at 12 months. Individual joint attention skills (gaze following, gaze alternating, and declarative pointing) were significantly inter-correlated, with a single factor accounting for 68% of the variance. Mothers' references to infants' mental states at 6 months predicted infants' joint attention at 12 months. The association was not explained by sociodemographic characteristics of the family, the mother's mental state, or by the quantity or acoustic properties of her speech. However, variability in pitch of maternal speech was an independent predictor of the infants' later joint attention skills. Taken together, these findings suggest that mothers' infant-directed speech fosters infants' attentive participation in topic-sharing interactions, which in turn provide an important arena in which joint attention skills develop over the first year of life.

Research has demonstrated that infants recognize emotional expressions of adults in the first half year of life. We extended this research to a new domain, infant perception of the expressions of other infants. In an intermodal matching procedure, 3.5- and 5-month-old infants heard a series of infant vocal expressions (positive and negative affect) along with side-by-side dynamic videos in which one infant conveyed positive facial affect and another infant conveyed negative facial affect. Results demonstrated that 5-month-olds matched the vocal expressions with the affectively congruent facial expressions, whereas 3.5-month-olds showed no evidence of matching. These findings indicate that by 5 months of age, infants detect, discriminate, and match the facial and vocal affective displays of other infants. Further, because the facial and vocal expressions were portrayed by different infants and shared no face–voice synchrony, temporal, or intensity patterning, matching was likely based on detection of a more general affective valence common to the face and voice.

The study evaluated the association between maternal disrupted communication and the reactivity and regulation of the psychobiology of the stress response in infancy. Mothers and infants were recruited via the National Health Service from the 20% most economically impoverished data zones in a suburban region of Scotland. Mothers (N = 63; M age = 25.9) and their 4-month-old infants (35 boys, 28 girls) were videotaped interacting for 8 min, including a still-face procedure as a stress inducer and a 5-min coded recovery period. Saliva samples were collected from the dyads prior to, during, and after the still-face procedure and later assayed for cortisol. Level of disruption in maternal communication with the infant was coded from the 5-min videotaped interaction during the recovery period which followed the still-face procedure. Severely disrupted maternal communication was associated with lower levels of maternal cortisol and a greater divergence between mothers' and infants' cortisol levels. Results point to low maternal cortisol as a possible mechanism contributing to the mother's difficulty in sensitively attuning to her infant's cues, which in turn has implications for the infant's reactivity to and recovery from a mild stressor in early infancy.

Recent evidence suggests that infants can generate expectations about future events from a sample of probabilistic data. However, little is known about the conditions that support the development of this ability. Three experiments tested the prediction that 8- and 12-month-olds respond to base rates as well as perceptual cues when they generate expectations from a sample of probabilistic data. Results revealed that 12-month-olds were sensitive to the statistical and perceptual properties of the evidence depending on the distribution of high-to-low base rate items in the sample. Specifically, 12-month-olds focused on perceptual features of the evidence when a sample was large and more skewed (e.g., 6:1), whereas they attended to statistical properties when the sample was smaller and less skewed (e.g., 4:1). In contrast, eight-month-olds always focused on the perceptual features of the evidence. Neither group generated expectations from a small, less skewed sample (e.g., 2:1). These results suggest that the ability to generate expectations about future events is mediated by specific features of the available evidence and undergoes significant change during the first year of life.

Several studies have shown that at 7 months of age, infants display an attentional bias toward fearful facial expressions. In this study, we analyzed visual attention and heart rate data from a cross-sectional study with 5-, 7-, 9-, and 11-month-old infants (Experiment 1) and visual attention from a longitudinal study with 5- and 7-month-old infants (Experiment 2) to examine the emergence and stability of the attentional bias to fearful facial expressions. In both experiments, the attentional bias to fearful faces appeared to emerge between 5 and 7 months of age: 5-month-olds did not show a difference in disengaging attention from fearful and nonfearful faces, whereas 7- and 9-month-old infants had a lower probability of disengaging attention from fearful than nonfearful faces. Across the age groups, heart rate (HR) data (Experiment 1) showed a more pronounced and longer-lasting HR deceleration to fearful than nonfearful expressions. The results are discussed in relation to the development of the perception and experience of fear and the interaction between emotional and attentional processes.

Recent work has suggested the value of electroencephalographic (EEG) measures in the study of infants' processing of human action. Studies in this area have investigated desynchronization of the sensorimotor mu rhythm during action execution and action observation in infancy. Untested but critical to theory is whether the mu rhythm shows a differential response to actions which share similar goals but have different motor requirements or sensory outcomes. By varying the invisible property of object weight, we controlled for the abstract goal (reach, grasp, and lift the object), while allowing other aspects of the action to vary. The mu response during 14-month-old infants' own executed actions showed a differential hemispheric response between acting on heavier and lighter objects. EEG responses also showed sensitivity to “expected object weight” when infants simply observed an experimenter reach for objects that the infants' prior experience indicated were heavier vs. lighter. Crucially, this neural reactivity was predictive—during the observation of the other reaching toward the object, before lifting occurred. This suggests that infants' own self-experience with a particular object's weight influences their processing of others' actions on the object, with implications for developmental social-cognitive neuroscience.

Why infants prefer to look at and use information provided by some informants over others was examined in four experiments. In each experiment, 52 12-month-old infants participated. In Experiment 1, a familiar expert and a familiar nonexpert and in Experiment 2, a novel expert and a novel nonexpert presented an ambiguous object and provided positive information. In both experiments, the infants preferred to look at the expert and regulated their behavior more in accordance with positive information provided by the expert, regardless of she was novel or more familiar. In Experiment 3, a familiar expert and a familiar nonexpert and in Experiment 4, a novel expert and a novel nonexpert presented an ambiguous object and provided negative information. In both experiments, the infants looked more at the expert and regulated their behavior more in accordance with negative information provided by the expert, regardless of she was novel or more familiar. The results support an expertise perspective of infant behavior in social-referencing situations.

This study investigated prosodic and structural characteristics of infant-directed speech to hearing-impaired infants as they gain hearing experience with a cochlear implant over a 12-month period of time. Mothers were recorded during a play interaction with their HI infants (N = 27, mean age 18.4 months) at 3, 6, and 12 months postimplantation. Two separate control groups of mothers with age-matched normal-hearing infants (NH-AM) (N = 21, mean age 18.1 months) and hearing experience-matched normal-hearing infants (NH-EM) (N = 24, mean age 3.1 months) were recorded at three testing sessions. Mothers produced less exaggerated pitch characteristics, a larger number of syllables per utterance, and faster speaking rate when interacting with NH-AM as compared to HI infants. Mothers also produced more syllables and demonstrated a trend suggesting faster speaking rate in speech to NH-EM relative to HI infants. Age-related modifications included decreased pitch standard deviation and increased number of syllables in speech to NH-AM infants and increased number of syllables in speech to HI and NH-EM infants across the 12-month period. These results suggest that mothers are sensitive to the hearing status of their infants and modify characteristics of infant-directed speech over time.

We examined the relation between 6- and 7-month-old infants' (N = 60) manual activity with objects during free play and their perception of the features of dynamic, multimodal events. Infants were habituated to a single event in which a hand reached for and manipulated a colorful, multifeatured object, and a sound was heard (e.g., a hand squeezed a purple round object, causing a whistling sound) and then their response to events that involved a change in the appearance of the object, the action, or the sound was assessed. Infants responded least to changes in the appearance of the objects, and their sensitivity to this feature was related to their manual activity with objects during free play. Infants' responding to changes in the sound or action was unrelated to motor activity, suggesting that at this age motor achievements related to object exploration are associated with infants' perception of some, but not all, object features.

This study explores the relationship between tonal synchrony and maternal-infant social engagement based on free-play recordings of 15 mothers and their 3-month-old infants in a laboratory setting. Moment-by-moment analyses on a microlevel were used to study social engagement and vocal interaction. We analysed and categorized 854 vocalization periods (mother-only vocalizations, tonal interaction periods, nontonal interaction periods, and mutual silence). Tonal synchrony was analysed in terms of harmonic and pentatonic series based on pitch frequency analyses. Social engagement was microanalyzed in terms of matched and mismatched engagement states. ANOVA-repeated measures revealed, most importantly, a significant relationship between TIPs and social interaction repair, which indicates the importance of tonal synchrony in the flow of social engagement in mother–infant dyads. Other significant relationships were found between (a) nTIPs/mismatch–mismatch, and, (b) MOV/affect loss. As mentioned in the discussion, the findings are suggestive for clinical applications (e.g., music therapy) and warrant further research.

Evidence for approximate number system (ANS) representations in infancy is robust but has typically only been found when infants are presented with arrays of four or more elements. In addition, several studies have found that infants fail to discriminate between small numbers when continuous variables such as surface area and contour length are controlled. These findings suggest that under some circumstances, infants fail to recruit either the ANS or object file representations for small sets. Here, we used a numerical change detection paradigm to assess 6-month-old infants' ability to represent small values. In Experiment 1, infants were tested with 1 versus 3, 1 versus 2, and 2 versus 3 dots. Infants successfully discriminated 1 versus 3 and 1 versus 2, but failed with 2 versus 3. In Experiment 2, we tested whether infants could compare small and large values with a 2 versus 4 condition. Across both experiments, infants' performance exhibited ratio dependence, the hallmark of the ANS. Our results indicate that infants can attend to the purely numerical attributes of small sets and that the numerical change detection paradigm accesses ANS representations in infancy regardless of set size.

The ability to effectively regulate emotions is a critical component of early socio-emotional development. This longitudinal study examined the developmental trajectories of emotion regulation in a sample of 3-, 5-, and 7-month-olds during an interaction with mothers and fathers. Infants' negative affect and use of behavioral strategies, including distraction, self-soothing, and high intensity motor behaviors were rated during the still-face episode of the Still-Face Paradigm. Longitudinal mixed-effects models were tested to determine whether strategies were followed by an increase or decrease in negative affect. Results from mother-infant and father-infant dyads indicated that focusing attention away from the unresponsive parent and engaging in self-soothing behaviors were associated with a subsequent decline in negative affect and the strength of these temporal associations were stable across infancy. In contrast, high-intensity motor behaviors were followed by an increase in negative affect and this effect declined over time. No significant effects were found for the behavioral strategy of looking at the parent. Results underscore the importance of considering infant age and the social partner when studying the effectiveness of emotion regulatory strategies in early infancy.

Memory based on a one-time experience is an important element of its definition as “episodic.” Infants' memories for one-time experiences over long delays are largely unexplored. Using elicited imitation, we tested 20- and 16-month-olds' (Experiment 1) and 13-month-olds' (Experiment 2) memories as a function of number of experiences and delay. Over 1 month, 20- and 16-month-olds remembered individual actions of one-time events; 20-month-olds also remembered temporal order; with verbal reminders, 16-month-olds did as well. Over 3 months, recall depended on multiple experiences. Thirteen-month-olds' required multiple experiences, even over 1 month. The findings speak to the gradual emergence of an important element of episodic memory, namely the ability to preserve memories of one-time experiences over long periods of time.

Adults typically use an exaggerated, distinctive speaking style when addressing infants. However, the effects of infant-directed (ID) speech on infants' learning are not yet well understood. This research investigates how ID speech affects how infants perform a key function in language acquisition, associating the sounds of words with their meanings. Seventeen-month-old infants were presented with two label-object pairs in a habituation-based word learning task. In Experiment 1, the labels were produced in adult-directed (AD) speech. In Experiment 2, the labels were produced in ID prosody; they had higher pitch, greater pitch variation, and longer durations than the AD labels. We found that infants failed to learn the labels in AD speech, but succeeded in learning the same labels when they were produced in ID speech. Experiment 3 investigated the role of variability in learning from ID speech. When the labels were presented in ID prosody with no variation across tokens, infants failed to learn them. Our findings indicate that ID prosody can affect how readily infants map sounds to meanings and that the variability in prosody that is characteristic of ID speech may play a key role in its effect on learning new words.

Currently, about 10% of infants have a weight for length greater than the 95th percentile for their age and sex, which puts them at risk for obesity as they grow. In a pilot obesity prevention study, primiparous mothers and their newborn infants were randomly assigned to a control group or a Soothe/Sleep intervention. Previously, it has been demonstrated that this intervention contributed to lower weight-for-length percentiles at 1 year; the aim of the present study was to examine infant behavior diary data collected during the intervention. Markov modeling was used to characterize infants' patterns of behavioral transitions at ages 3 and 16 weeks. Results showed that heavier mothers were more likely to follow their infants' fussing/crying episodes with a feeding. The intervention increased infants' likelihood of transitioning from a fussing/crying state to an awake/calm state. A shorter latency to feed in response to fussing/crying was associated with a higher subsequent weight status. This study provides preliminary evidence that infants' transitions out of fussing/crying are characterized by inter-individual differences, are modifiable, and are linked to weight outcomes, suggesting that they may be promising targets for early behavioral obesity interventions, and highlighting the methodology used in this study as an appropriate and innovative tool to assess the impact of such interventions.

For several decades, many authors have claimed the existence, early in life, of a tight link between perceptual and productive systems in speech. However, the question whether this link is acquired or is already present at birth remains open. This study aimed at investigating this question by employing the paradigm of neonatal facial imitation. We compared imitative responses of newborn infants presented either visual-only, audiovisual congruent, or audiovisual incongruent models. Our results revealed that the newborns imitated significantly more quickly the movements of the model's mouth when this model was audiovisual congruent rather than visual-only. Moreover, when observing an audiovisual incongruent model, the newborns did not produce imitative behavior. These findings, by highlighting the influence of speech perception on newborns' imitative responses, suggest that the neural architecture for perception–production is already in place at birth. The implications of these results are discussed in terms of a link between language and neonatal imitation, which could represent a precursor of more mature forms of vocal imitation and speech development in general.

Non-verbal referential communication is impaired in children with autism spectrum disorders (ASD). However, the development of difficulties with referential communication in the younger siblings of children with ASD (High-Risk Siblings)—and the degree to which early referential communication predicts later autism symptomatology—is not clear. We modeled the early developmental trajectories of three types of referential communication: responding to joint attention (RJA), initiating joint attention (IJA), and initiating behavioral requests (IBR) across 8, 10, 12, 15, and 18 months of age in High-Risk Siblings (n = 40) and the infant siblings of children without ASD (Low-Risk Siblings; n = 21). Hierarchical linear modeling indicated that High-Risk Siblings exhibited lower levels of baseline RJA and IJA and a lower rate of linear change in IBR than Low-Risk Siblings. When the 10 High-Risk Siblings who received an ASD diagnosis were excluded from analyses, group differences in the development of referential communication remained significant only for RJA. Baseline levels of IJA were associated with later ASD symptomatology among High-Risk Siblings, suggesting that individual differences in referential communication development at 8 months may index early manifestations of ASD.

Previous research has shown that caregiver protective behavior may exacerbate toddler distress in specific contexts. This study sought to extend this work to examine associations between these variables and toddler cortisol reactivity. Ninety-three 24-month-old toddlers were observed across six novel contexts designed to elicit distress. Toddlers were asked to give saliva samples at the beginning and end of the laboratory procedure. Toddler sadness, toddler fear and caregiver protective behavior were coded. Results indicate that caregiver protective behavior accounted for the association between toddler sadness and cortisol reactivity where higher levels of protective behavior were associated with higher cortisol reactivity. This study showed that caregiver protective behavior, which functions to prevent a child from interacting with a novel stimulus, is an important mechanism to consider when understanding toddler stress responses during novel contexts.

Newborn infants preferentially orient to familiar over unfamiliar speech sounds. They are also better at remembering unfamiliar speech sounds for short periods of time if learning and retention occur after a feed than before. It is unknown whether short-term memory for speech is enhanced when the sound is familiar (versus unfamiliar) and, if so, whether the effect is further enhanced by feeding. We used a two-factorial design and randomized infants to one of four groups: prefeed-unfamiliar, prefeed-familiar, postfeed-unfamiliar, and postfeed-familiar. Memory for either familiar or unfamiliar speech (the infant's mother saying “baby” versus a female stranger saying “beagle”) was assessed using head turning to sound in an habituation–recovery paradigm and a retention delay of 85 sec either before or after a typical milk feed. Memory for the familiar speech–voice was enhanced relative to the unfamiliar speech–voice, expressed by significantly less head turning toward the habituated sound stimulus when it was re-presented after the delay. Memory for familiar or unfamiliar speech was not significantly enhanced from pre- to postfeeding, nor was there a significant interaction. This is the first demonstration in newborns that familiarity enhances short-term memory for speech–voice sound.

The aim of this study was to examine the combined influences of infants' attention and use of social cues in the prediction of their language outcomes. This longitudinal study measured infants' visual attention on a distractibility task (11 months), joint attention (14 months), and language outcomes (word–object association, 14 months; MBCDI vocabulary size and multi-word productions at 18 months of age). Path analyses were conducted for two different language outcomes. The analysis for vocabulary revealed unique direct prediction from infants' visual attention on a distractibility task (i.e., maintaining attention to a target event in the presence of competing events) and joint attention (i.e., more frequent response to tester's bids for attention) for larger vocabulary size at outcome; this model accounted for 48% of variance in vocabulary, after controlling for baseline communication status (assessed at 11 months). The analysis for multi-word productions yielded direct effects for infants' distractibility, but not joint attention; this model accounted for 45% of variance in multi-word productions, again after controlling for baseline communication status. Indirect effects were not significant in either model. Results are discussed in light of the unique predictive role of attentional factors and social/attention cues for emerging language.

We investigated the development of the other-race effect “ORE” in a longitudinal sample of 3-, 6-, and 9-month-old Caucasian infants. Previous research using cross-sectional samples has shown an unstable ORE at 3 months, an increase at 6 months and full development at 9 months. In Experiment 1, we tested whether 9-month-olds showed the ORE with Caucasian and African faces. As expected, the 9-month-olds discriminated faces within their own ethnicity (Caucasian) but not within the unfamiliar ethnicity (African). In months. In Experiment 2, we longitudinally tested infants at 3, 6, and 9 months by presenting either the Caucasian or the African faces used in Experiment 1. In contrast to previous cross-sectional studies and Experiment 1, we found that infants discriminated between all stimuli. Hence, we did not find the ORE in this longitudinal study even at 9 months. We assume that the infants in our longitudinal study showed no ORE because of previous repetitive exposure to African faces at 3 and 6 months. We argue that only a few presentations of faces from other ethnic categories sufficiently slow the development of the ORE.

The study of dyadic interaction plays a major role in infancy research. To advance conceptually informed measurement of dyadic interaction and integration across studies, we examined factor structure of individual parents' and infants' measures and dyadic measures from face-to-face interactions in two samples of 6-month-old infants and their parents: mothers from a demographically heterogeneous sample (N = 164), and mothers and fathers (N = 156) from a Caucasian middle-class sample. Results suggested that a) individual and dyadic measures, and parents' and infants' behaviors contribute independent information, b) measures of both valence and process are needed, c) there are context-general and context-specific qualities, and d) structure of dyadic interaction is more similar among mother–infant dyads from independent samples than between mother–infant and father–infant dyads within the same sample. Future research should use multiple measures incorporating valence, temporal processes, contextual influences, and behaviors of individual partners along with dyadic measures to adequately assess the quality of dyadic interaction.

This study examines the relationship between various basic mental processing abilities in infancy. Two groups of 7-month-olds received the same delayed-response task to assess visuo-spatial working memory, but two different habituation–dishabituation tasks to assess processing speed and recognition memory. The single-stimulus group (N = 32) was familiarized with only one abstract stimulus, whereas the categorization group (N = 32) received varying exemplars of the same kind. In the categorization group, infants high on working memory showed stronger habituation and dishabituation responses than infants scoring low in working memory. No corresponding relations were found for the single-stimulus group. This suggests that working memory performance is systematically linked to other basic mental skills in 7-month-olds, but that corresponding relations may not get evident in any kind of habituation–dishabituation procedure. Implications for understanding the complex interplay of basic mental abilities in infancy will be discussed.

This study examines face-scanning behaviors of infants at 6, 9, and 12 months as they watched videos of a woman describing an object in front of her. The videos were created to vary information in the mouth (speaking vs. smiling) and the eyes (gazing into the camera vs. cueing the infant with head turn or gaze direction to an object being described). Infants tended to divide their attention between the eyes and the mouth, looking less at the eyes with age and more at the mouth than the eyes at 9 and 12 months. Attention to the mouth was greater on speaking trials than on smiling trials at all three ages, and this difference increased between 6 and 9 months. Despite consistent results within subjects, there was considerable variation between subjects. This raises the question of whether a developmental “norm” of face scanning in infancy ought to be pursued. Rather, these data add to emerging evidence suggesting that individual differences in face scanning might reliably predict aspects of later development.

The goal of this study was to examine developmental change in visual attention to dynamic visual and audiovisual stimuli in 3-, 6-, and 9-month-old infants. Infant look duration was measured during exposure to dynamic geometric patterns and Sesame Street video clips under three different stimulus modality conditions: unimodal visual, synchronous audiovisual, and asynchronous audiovisual. Infants looked longer toward Sesame Street stimuli than geometric patterns, and infants also looked longer during multimodal audiovisual (synchronous and asynchronous) presentations than during unimodal visual presentations. There was a three-way interaction of age, stimulus type, and stimulus modality. Significant differences were found within and between age groups related to stimulus modality (visual or audiovisual) while viewing Sesame Street clips. No significant interaction was found between age and stimulus type while infants viewed dynamic geometric patterns. These findings indicate that patterns of developmental change in infant attention vary based on stimulus complexity and modality of presentation.

We investigated the effects of distraction on attention and task performance during toddlerhood. Thirty toddlers (24- to 26-month-olds) completed different tasks (2 of each: categorization, problem solving, memory, free play) in one of two conditions: No Distraction or Distraction. The results revealed that the distractor had varying effects on performance scores depending on the task: The problem solving and memory tasks were more susceptible to distraction. In addition, the two conditions showed different patterns of attention over time. Toddlers in the No Distraction condition were more attentive, and their attention remained consistently high across the session. Toddlers in the Distraction condition increased their attention to the task and decreased their attention to the distractor in the second half of the session. This study demonstrates how the presence of distraction influences toddlers’ performance on individual cognitive tasks and contributes to our understanding of distractibility and endogenous attention during toddlerhood. This work also has implications for how environmental noise, such as background television, may influence cognitive development.

It has long been thought that the prefrontal cortex, as the seat of most higher brain functions, is functionally silent during most of infancy. This review highlights recent work concerned with the precise mapping (localization) of brain activation in human infants, providing evidence that prefrontal cortex exhibits functional activation much earlier than previously thought. A systematic evaluation of the activation patterns in these neuroimaging studies mainly based on functional near-infrared spectroscopy reveals that prefrontal cortex function can be broadly divided into two distinct anatomical clusters with different functional properties. One cluster of activations falls within the region of the medial prefrontal cortex and is mainly involved in affective processes; another cluster is located in lateral aspects of the prefrontal cortex and shows sensitivity to cognitive processes such as memory and attention. This distinction is in line with adult data and evolutionary models and may represent a developmentally continuous organization principle of prefrontal cortex function. All in all, this review is aimed at providing a synthesis of new findings that are emerging from the use of neuroimaging techniques with infants as well as at encouraging further theory-driven research to understand the developmental origins of prefrontal cortex function.

Three-dimensional (3D) object completion, the ability to perceive the backs of objects seen from a single viewpoint, emerges at around 6 months of age. Yet, only relatively simple 3D objects have been used in assessing its development. This study examined infants’ 3D object completion when presented with more complex stimuli. Infants (N = 48) were habituated to an “L”-shaped object shown from a limited viewpoint; then they were tested with volumetrically complete (solid) and incomplete (hollow) versions of the object. Four-month-olds and 6-month-old girls had no preference for either display. Six-month-old boys and both sexes at 9.5 months of age showed a novelty preference for the incomplete object. A control group (N = 48), only shown the test displays, had no spontaneous preference. Perceptual completion of complex 3D objects requires infants to integrate multiple, local object features and thus may tax their nascent attentional skills. Infants might use mental rotation to supplement performance, giving an advantage to young boys. Examining the development of perceptual completion of more complex 3D objects reveals distinct mechanisms for the acquisition and refinement of 3D object completion in infancy.

Young children begin helping others with simple instrumental problems from soon after their first birthdays. In previous observations of this phenomenon, both naturalistic and experimental, children’s parents were in the room and could potentially have influenced their behavior. In the two current studies, we gave 24-month-old children the opportunity to help an unfamiliar adult obtain an out-of-reach object when the parent (or a friendly female adult) (i) was present but passive, (ii) was present and highlighted the problem for the child, (iii) was present and actively encouraged the child to help, (iv) was present and ordered the child to help, or (v) was absent from the room. The children helped at relatively high levels and equally under all these treatment conditions. There was also no differential effect of treatment condition on children’s helping in a subsequent test phase in which no parent was present, and children had to disengage from a fun activity to help. Young children’s helping behavior is not potentiated or facilitated by parental behavior in the immediate situation, suggesting that it is spontaneous and intrinsically motivated.

This study explored variation in affective and behavioral components of infants’ jealousy protests during an eliciting condition in which mother and an experimenter directed differential attention exclusively toward a rival. Variation was examined in relation to child temperamental emotionality, maternal interaction style, and attachment security. At 45 weeks, intensity of infants’distress and durations of mother- and stranger-directed behavioral responses, including gaze, touch, and proximity-seeking, were observed in the eliciting condition. We also assessed infants’positive emotionality (PE) and negative emotionality (NE) and maternal interaction styles of sensitivity and engagement. At 54 weeks, attachment security was measured in the Strange Situation Procedure. Findings revealed that distress differed with temperamental emotionality and maternal interaction style. Specifically, distress was greater in infants with lower PE and having mothers who displayed less sensitivity and engagement. Analyses on behavioral responses toward the experimenter revealed linkages with maternal interaction style. Specifically, experimenter-directed gaze and touch were greater among infants of mothers who demonstrated less sensitivity and engagement. Behavioral responses toward mother were found associated with quality of attachment. Specifically, mother-directed proximity and touch were highest among infants later judged insecure resistant and lowest among those later judged insecure/avoidant; with infants later judged secure displaying moderate durations of mother-directed proximal contact.

Infants’ sensitivity to the vitality or tension envelope within dyadic social exchanges was investigated by examining their responses following normal and interrupted games of peek-a-boo embedded in a Still-Face Task. Infants 5–6 months old engaged in two modified Still-Face Tasks with their mothers. In one task, the initial interaction ended with a sequence of normal peek-a-boos that included tension build-up, peak, and release. In the other task, the initial interaction was followed by a sequence of peek-a-boos that ended with an interrupted peek-a-boo in which the build-up was followed directly by the still face. Infants showed the still-face effect with their attention and smiling when the still face followed the normal peek-a-boo sequence, but only with smiling when the still face followed the sequence with the interrupted peek-a-boo. Infants’ social bidding to their mothers in the still-face phase was greater following the interrupted peek-a-boo sequence. When social exchanges are interrupted before the closure of the vitality envelope, infants respond with more attention vigilance and social bidding, demonstrating their awareness of the structure of social exchanges.

Relations between maternal sensitivity and physiological reactivity to infant crying were examined using measures of heart rate (HR) and respiratory sinus arrhythmia (RSA) in 49 mothers of second-born infants. Using the Ainsworth Sensitivity Scale, an independent assessment of maternal sensitivity was made during maternal free play and bathing of their infants. Physiological reactivity was measured while mothers listened to three blocks of infant cry sounds in a standard cry paradigm. Mothers scoring high on sensitivity were compared to less sensitive mothers on both their physiological reactivity to the presented crying sounds and their physiological mean-level differences. Significant interaction effects were found for both HR and RSA. Highly sensitive mothers showed a larger increase in HR and stronger RSA withdrawal in response to the first block of cry sounds compared to less sensitive mothers. Main effects showed that highly sensitive mothers had lower mean overall HR, and higher mean RSA levels across all three blocks of crying sounds compared to less sensitive mothers. RSA withdrawal and accompanying HR increases are discussed from a polyvagal perspective as indicative of a better capability in responding to infant signals of negative affect.

The present experiment examined whether 9-month-old infants’ mental rotation ability was related to their crawling ability. Forty-eight 9-month-old infants were tested; half of them crawled for 7.1 weeks on average. Infants were habituated to a video of a simplified Shepard–Metzler object rotating back and forth through a 240° angle around the longitudinal axis of the object. Infants were tested with videos of the same object rotating through the previously unseen 120° angle and with the mirror image of that display. The results showed that the crawlers looked significantly longer at the mirror object than at the familiar object. The results support the interpretation that crawling experience is associated with 9-month-old infants’ mental rotation ability.