Humans adopt non-linguistic signals, from smoke signals to Morse code, to communicate. This communicative flexibility emerges early: embedding novel sine-wave tones in a social, communicative exchange permits 6-month-olds to imbue them with communicative status, and to use them in subsequent learning. Here, to specify the mechanism(s) that undergird this capacity, we introduced infants to a novel signal—sine-wave tone sequences—in brief videotaped vignettes with non-human agents, systematically manipulating the socio-communicative cues in each vignette. Next, we asked whether infants interpreted new tone sequences as communicative in a fundamental cognitive task: object categorization. Infants successfully interpreted tones as communicative if they were produced in dialogues with one agent speaking (Study 1) or both agents producing tones (Study 2), or in monologues involving only a single agent (Study 3). What was essential was cross-modal temporal synchrony between an agent’s movements and the tones: when this synchrony was disrupted (Study 4), infants failed in the subsequent task. This synchrony, we propose, licensed an inference that the tones, generated by an agent, were candidate communicative signals. Infants’ early capacity to use synchrony to identify new communicative signals and recruit them in subsequent learning has implications for theory and for interventions to support infants facing communicative challenges.

Importance The association between online activities and youth suicide is an important issue for parents, clinicians, and policy makers. However, most information exploring potential associations is drawn from survey data and mainly focuses on risk related to overall screen time. Objective To evaluate the association between a variety of online risk factors and youth suicide-related behavior using real-world online activity data. Design, Setting, and Participants A matched case-control study was conducted from July 27, 2019, to May 26, 2020, with the sample drawn from more than 2600 US schools participating in an online safety monitoring program via the Bark online safety tool. For 227 youths having a severe suicide/self-harm alert requiring notification of school administrators, cases were matched 1:5 to 1135 controls on location, the amount of follow-up time, and general volume of online activity. Exposures Eight potential online risk factors (cyberbullying, violence, drug-related, hate speech, profanity, sexual content, depression, and low-severity self-harm) through assessment of text, image, and video data. Main Outcomes and Measures Severe suicide/self-harm alert requiring notification of school administrators; severe suicide alerts are statements by youths indicating imminent or recent suicide attempts and/or self-harm. Results The 1362 participants had a mean (SD) age of 13.3 (2.41) years; 699 (51.3%) were male. All 8 online risk factors studied exhibited differences between case and control populations and were significantly associated with subsequent severe suicide/self-harm alerts when examining total direct and indirect pathways. These associations ranged from an adjusted odds ratio (aOR) of 1.17 (95% CI, 1.09-1.26) for drug-related content to an aOR of 1.82 (95% CI, 1.63-2.03) for depression-related content. When considering the total number of different types of online risk factors among the 8 measured, there was an exponentially larger risk of severe suicide/self-harm alerts; youths with 5 or more of the 8 risk factors present in their online activity had a more than 70-fold increased odds of subsequently having a severe suicide/self-harm alert (aOR, 78.64; 95% CI, 34.39-179.84). Conclusions and Relevance The findings of this study suggest that many discrete types of risk factors are identifiable from online data and associated with subsequent youth suicide-related behavior. Although each risk factor carries a specific association with suicide-related behavior, the greatest risk is evident for youths demonstrating multiple types of online risk factors.

To use a symbol, children must understand that the symbol stands for something in the world. This development has often been investigated in the model-room task (DeLoache, 1987, 2000) in which children use a scale model to try to find a toy that is hidden in the room that the model represents. To succeed, children must acquire dual representation: they must put aside their understanding of the model as an object and focus more on what the model represents (Hartstein & Berthier, 2017). Here we suggest that forgetting irrelevant details or misleading information may be an important part of acquiring and maintaining dual representation. Based on prior research showing that forgetting can promote insight in children and adults (e.g., Sio & Ormerod, 2009; Vlach et al., 2014) and that a small sample of 3-year-olds could improve on the model-room task with a delay (Marzolf & DeLoache, 1994), we hypothesized that taking a break during the model-room task would facilitate forgetting and hence symbolic insight. Eighty-eight 3-year-olds performed 8 trials of the model-room task. Half of the children received a 24-hour delay after trial 4 and half performed the 8 trials consecutively. Children who received a 24-hour delay had better symbolic performance on the last 4 trials compared to children whose testing sessions occurred consecutively on one day, even when statistically controlling for the effects of learning over trials and memory on children’s performance. This study provides strong initial evidence that a delay can promote symbolic insight in 3-year-old children.

Psychological scientists have become increasingly concerned with issues related to methodology and replicability, and infancy researchers in particular face specific challenges related to replicability: For example, high-powered studies are difficult to conduct, testing conditions vary across labs, and different labs have access to different infant populations. Addressing these concerns, we report on a large-scale, multisite study aimed at (a) assessing the overall replicability of a single theoretically important phenomenon and (b) examining methodological, cultural, and developmental moderators. We focus on infants’ preference for infant-directed speech (IDS) over adult-directed speech (ADS). Stimuli of mothers speaking to their infants and to an adult in North American English were created using seminaturalistic laboratory-based audio recordings. Infants’ relative preference for IDS and ADS was assessed across 67 laboratories in North America, Europe, Australia, and Asia using the three common methods for measuring infants’ discrimination (head-turn preference, central fixation, and eye tracking). The overall meta-analytic effect size (Cohen’s d) was 0.35, 95% confidence interval = [0.29, 0.42], which was reliably above zero but smaller than the meta-analytic mean computed from previous literature (0.67). The IDS preference was significantly stronger in older children, in those children for whom the stimuli matched their native language and dialect, and in data from labs using the head-turn preference procedure. Together, these findings replicate the IDS preference but suggest that its magnitude is modulated by development, native-language experience, and testing procedure.

Speakers can make inferences about the meaning of new words appearing in an utterance based on the lexical semantics of other words that co-occur with them. Previous work has revealed that infants at 19 and 24 months of age can recruit the semantic selectional restrictions of known verbs (e.g., eating) to deduce that a noun appearing in the subject position maps onto an animate referent. We asked whether this ability to capitalize on the semantics of familiar words to identify the referent of a novel noun in subject position extends to adjectives, which also denote properties, and which also have animacy constraints (e.g., hungry). We found that unlike in the previous studies with verbs, neither 24- nor 36-month-olds could successfully recruit known adjectival semantics in an online task to home in on an animate nominal referent. However, 36-month-olds were successful in a more interactive, forced-choice version of the task without such strict time limitations. We discuss multiple non-mutually-exclusive hypotheses for this pattern of results, focusing on the role of the morphosyntactic cues, the (lack of) perceptual cues for the target property in context of the utterance, truth conditions, and cross-linguistic implications. These possibilities raise fundamental questions about the infant's developing lexicon and the linguistic and conceptual mechanisms at play in the process of word learning.

Abstracting the structure or 'rules' underlying observed patterns is central to mature cognition, yet research with infants suggests this far-reaching capacity is initially restricted to certain stimuli. Infants successfully abstract rules from auditory sequences (e.g., language), but fail when the same rules are presented as visual sequences (e.g., shapes). We propose that this apparent gap between rule learning in the auditory and visual modalities reflects the distinct requirements of the perceptual systems that interface with cognition: The auditory system efficiently extracts patterns from sequences structured in time, but the visual system best extracts patterns from sequences structured in space. Here, we provide the first evidence for this proposal with adults in an abstract rule learning task. We then reveal strong developmental continuity: infants as young as 3 months of age also successfully learn abstract rules in the visual modality when sequences are structured in space. This provides the earliest evidence to date of abstract rule learning in any modality.

Everyone agrees that infants possess general mechanisms for learning about the world, but the existence and operation of more specialized mechanisms is controversial. One mechanism – rule learning – has been proposed as potentially specific to speech, based on findings that 7-month-olds can learn abstract repetition rules from spoken syllables (e.g., ABB patterns: wo-fe-fe, ga-tu-tu...) but not from closely matched stimuli, such as tones. Subsequent work has shown that learning of abstract patterns is not simply specific to speech. However, we still lack a parsimonious explanation to tie together the diverse, messy, and occasionally contradictory findings in that literature. We took two routes to creating a new profile of rule learning: meta-analysis of 20 prior reports on infants’ learning of abstract repetition rules (including 1,318 infants in 63 experiments total), and an experiment on learning of such rules from a natural, non-speech communicative signal. These complementary approaches revealed that infants were most likely to learn abstract patterns from meaningful stimuli. We argue that the ability to detect and generalize simple patterns supports learning across domains in infancy but chiefly when the signal is meaningfully relevant to infants’ experience with sounds, objects, language, and people.

We assessed 24-month-old infants' lexical processing efficiency for both novel and familiar words. Prior work documented that 19-month-olds successfully identify referents of familiar words (e.g., The dog is so little) as well as novel words whose meanings were informed only by the surrounding sentence (e.g., The vep is crying), but that the speed with which they identify the referents of novel words lagged far behind that for familiar words. Here we take a developmental approach, extending this work to 24-month-olds. By comparing the performance of 19- and 24-month-olds directly, we document that during this period of rapid vocabulary growth, infants make significant processing gains for both familiar and novel words. We also offer the first evidence to date that, at both 19- and 24-months, the number of verbs infants know predicts their ability to use known verbs to learn novel nouns. These results reveal that 24-month-olds can efficiently learn novel words just by listening to the conversations around them.

Language exerts a powerful influence on our concepts. We review evidence documenting the developmental origins of a precocious link between language and object categories in very young infants. This collection of studies documents a cascading process in which early links between language and cognition provide the foundation for later, more precise ones. We propose that, early in life, language promotes categorization at least in part through its status as a social, communicative signal. But over the first year, infants home in on the referential power of language and, by their second year, begin teasing apart distinct kinds of names (e.g. nouns, adjectives) and their relation to distinct kinds of concepts (e.g. object categories, properties). To complement this proposal, we also relate this evidence to several alternative accounts of language's effect on categorization, appealing to similarity (‘labels-as-features’), familiarity (‘auditory overshadowing’), and communicative biases (‘natural pedagogy’).

Infants' experiences are defined by the presence of concurrent streams of perceptual information in social environments. Touch from caregivers is an especially pervasive feature of early development. Using three lab experiments and a corpus of naturalistic caregiver-infant interactions, we examined the relevance of touch in supporting infants' learning of structure in an altogether different modality: audition. In each experiment, infants listened to sequences of sine-wave tones following the same abstract pattern (e.g., ABA or ABB) while receiving time-locked touch sequences from an experimenter that provided either informative or uninformative cues to the pattern (e.g., knee-elbow-knee or knee-elbow-elbow). Results showed that intersensorily redundant touch supported infants' learning of tone patterns, but learning varied depending on the typicality of touch sequences in infants' lives. These findings suggest that infants track touch sequences from moment to moment and in aggregate from their caregivers, and use the intersensory redundancy provided by touch to discover patterns in their environment.

The mechanisms underlying the discovery of abstract rules like those found in natural language may be evolutionarily tuned to speech, according to previous research. When infants hear speech sounds, they can learn rules that govern their combination, but when they hear non-speech sounds such as sine-wave tones, they fail to do so. Here we show that infants' rule learning is not tied to speech per se, but is instead enhanced more broadly by communicative signals. In two experiments, infants succeeded in learning and generalizing rules from tones that were introduced as if they could be used to communicate. In two control experiments, infants failed to learn the very same rules when familiarized to tones outside of a communicative exchange. These results reveal that infants' attention to social agents and communication catalyzes a fundamental achievement of human learning.

The power of human language rests upon its intricate links to human cognition. By 3 months of age, listening to language supports infants' ability to form object categories, a building block of cognition. Moreover, infants display a systematic shift between 3 and 4 months - a shift from familiarity to novelty preferences - in their expression of this link between language and core cognitive processes. Here, we capitalize on this tightly-timed developmental shift in fullterm infants to assess (a) whether it also appears in preterm infants and (b) whether it reflects infants' maturational status or the duration of their postnatal experience. Healthy late preterm infants (N = 22) participated in an object categorization task while listening to language. Their performance, coupled with that of fullterm infants, reveals that this developmental shift is evident in preterm infants and unfolds on the same maturational timetable as in their fullterm counterparts.

Over the first year, infants tune into the signals of their native language and begin to link them to meaning. Here, we ask whether infants, like adults, can also infer the communicative function of otherwise arbitrary signals (here, tone sequences) and link these to meaning as well. We examined 6-month-olds' object categorization in the context of sine-wave tones, a signal that fails to support categorization at any point during their first year. However, before the categorization task, we exposed infants to tones in one of two vignettes. In one, the tones were produced by an actor in a rich communicative exchange; in the other, infants heard the very same tones, but these were uncoupled from the actors' activity. Infants exposed to the communicative vignette successfully formed object categories in the subsequent test; those exposed to the non-communicative vignette failed, performing identically to infants with no prior exposure to this novel signal. This reveals in 6-month-old infants a remarkable flexibility in identifying which signals in the ambient environment are communicative and in linking these signals to core cognitive capacities including categorization.