The role of the gut microbiome in infant development has gained increasing interest in recent years. Most research on this topic has focused on the first three to four years of life because this is a critical period for developing gut-brain connections. Prior studies have identified associations between the composition and diversity of the gut microbiome in infancy and markers of temperament, including negative affect. However, the specific microbes affected, and the directionality of these associations have differed between studies, likely due to differences in the developmental period of focus and assessment approaches. In the current preregistered study, we examined connections between the gut microbiome, assessed at two time points in infancy (2 weeks and 18 months), and negative affect measured at 30 months of age in a longitudinal study of infants and their caregivers. We found that infants with higher gut microbiome diversity at 2 weeks showed more observed negative affect during a study visit at 30 months. We also found evidence for associations between specific genera of bacteria in infancy and negative affect. These results suggest associations between specific features of the gut microbiome and child behavior may differ based on timing of gut microbiome measurement.

Most scientists are aware that developmental databases derive primarily from Western, middle-class samples, but fewer are cognizant that developmental theories can be similarly biased. There is urgency in revising developmental theories, both scientifically (embracing diversity is essential to the study of human psychology) and applied (it is damaging to apply WEIRD standards/methods/theories to evaluate development in the multitude of non-WEIRD contexts).

We evaluate the extent to which two prominent developmental theories are inclusive. We find that Shared Intentionality Theory is based on a WEIRD bias in the foundational databases: the core constructs lack culturally diverse data, undermining claims that this theory explains human-general social cognition. In Attachment Theory, we illuminate the lack of inclusivity in the core assumptions and resulting claims of the meaning and measure of the attachment system: this theory excludes cultural diversity in social-emotional constructs focused on communal orientations (e.g., interdependence, attachment networks) found in many people of the Global South, and neglects culture-specific adaptive behavior patterns.

Acknowledging the lack of inclusivity at the level of theory is necessary. We urge researchers to take a more WILD approach: obtain Worldwide samples, study development In situ, focus on Local cultural practices and ethnotheories, and consider development as Diverse. Being WILD entails attending to inclusivity during the entire research process, from framing the research questions to interpreting the data (e.g., respecting all adaptive behaviors in development). Five Steps for Increasing Inclusivity can be used as a practical guide to decenter psychological theories from their current WEIRD mindset.

This study investigated how infants deal with cross-talker variability in the perception of native lexical tones, paying specific attention to developmental changes and the role of task demands. Using the habituation-based visual fixation procedures, we tested Cantonese-learning infants of different age groups on their ability to discriminate Cantonese Tone 1 (high level) and Tone 3 (mid level) produced by either multiple talkers or a single talker. Results demonstrated that the 12-month-old and 24-month-old groups showed reliable discrimination across talkers, whereas the 18-month-old group did not (Experiment 1), despite their ability to discriminate the same contrast when the talker was held constant (Experiment 2). In a task that included a novel object as a referent to the sound, the 18-month-olds discriminated the contrast across talkers from Tone 1 to Tone 3 (Experiment 3). These results revealed a U-shaped developmental path and perceptual asymmetry in native lexical tone discrimination across talkers.

Difficulties in empathy are frequent among children with autism spectrum disorder (ASD), and often considered a core feature of autism. Reduced empathy during the second year of life has been shown to predict subsequent ASD diagnosis. However, links between empathy in the first year and ASD have not yet been investigated. Moreover, prior work focused on empathy for others’ distress but not for others’ joy. To address these gaps, this prospective longitudinal study followed 60 infants (33% girls), 39 at high genetic risk of ASD (siblings of children with ASD) and a matching control group. Infants’ empathic responses to others’ distress and happiness were assessed at ages 6, 9, and 12 months, using simulations by the mother/experimenter and videos of crying and laughing infants. Diagnosis was determined between 18 and 36 months. Infants later diagnosed with ASD showed a reduced empathic response toward a person simulating distress, but not toward a video of a crying peer, and not in response to others’ joy (either in simulation or video). Overall, reduced empathic concern during the first year of life appears to be an early prodromal marker of subsequent ASD. Implications for theory, research, and practice are discussed.

Exposure to maternal depressive symptoms (MDS) may have a pertinent role in shaping children’s emotional development. However, little is known about how these processes emerge in the early postpartum period. The current study examined the direct and interactive associations between MDS and cry-processing cognitions in the prediction of infant negative emotionality and affective concern. Participants were 130 mother-child dyads (50% female) assessed at three time points. During the second trimester of pregnancy, expectant mothers completed a procedure to assess responses to video clips of distressed infants and reported about MDS. Mothers also reported about MDS at 1- and 3-months postpartum. At age 3 months, infants’ negative emotionality and affective concern responses were observed and rated. We found no direct associations between MDS and both measures of infant emotional reactivity. However, MDS interacted with cry-processing cognitions to predict affective concern and negative emotionality. Overall, MDS were related to increased affective concern and decreased negative emotionality when mothers held cognitions that were more focused on their own emotions in the face of the infant’s cry rather than the infant’s emotional state and needs. Clinical implications for early screening and intervention are discussed.

The 10th International Yakult Symposium was held in Milan, Italy, on 13–14 October 2022. Two keynote lectures covered the crewed journey to space and its implications for the human microbiome, and how current regulatory systems can be adapted and updated to ensure the safety of microorganisms used as probiotics or food processing ingredients. The remaining lectures were split into sections entitled “Chances” and “Challenges.” The “Chances” section explored opportunities for the science of probiotics and fermented foods to contribute to diverse areas of health such as irritable bowel syndrome, major depression, Parkinson’s disease, immune dysfunction, infant colic, intensive care, respiratory infections, and promoting healthy longevity. The “Challenges” section included selecting appropriate clinical trial participants and methodologies to minimise heterogeneity in responses, how to view probiotics in the context of One Health, adapting regulatory frameworks, and understanding how substances of bacterial origin can cross the blood–brain barrier. The symposium provided evidence from cutting-edge research that gut eubiosis is vital for human health and, like space, the microbiota deserves further exploration of its vast potential.

Inadequate protein intake and lack of micronutrients may affect neurodevelopment in infants. This randomised controlled trial was conducted to measure the effect of two milk–cereal mixes with modest and high amounts of protein and enriched with multiple micronutrients, given between 6 and 12 months, on cognitive, language, motor and behavioural scores at 12 and 24 months of age, compared with no-supplementation. The two supplements were also compared with each other. The study was conducted in urban Delhi, India, and the infants were randomised in a 1:1:1 ratio to the three study groups. At 12 and 24 months of age, 1134 and 1214 children were available, respectively. At 12 months of age, compared with no-supplement group, an increase in the motor scores (mean difference, MD 1·52, 95 % CI: 0·28, 2·75) and a decrease in the infant temperament scores (MD − 2·76, 95 % CI: −4·23, −1·29) in the modest-protein group was observed. Those in the high-protein group had lower socio-emotional scores (MD − 1·40, 95 % CI: −2·43, −0·37) and higher scores on Infant Temperament Scale (MD 2·05, 95 % CI: 0·62, 3·48) when compared with modest-protein group. At 24 months, no significant differences in any of the neurodevelopment scores between the three study groups was found. In conclusion, supplementation with modest amount of protein and multiple micronutrients may lead to short-term small improvements in motor function and infant temperament. There appears no advantage of supplementing with high protein, rather negative effects on infant behaviour were observed

Pre-diagnostic deficits in social motivation are hypothesized to contribute to autism spectrum disorder (ASD), a heritable neurodevelopmental condition. We evaluated psychometric properties of a social motivation index (SMI) using parent-report item-level data from 597 participants in a prospective cohort of infant siblings at high and low familial risk for ASD. We tested whether lower SMI scores at 6, 12, and 24 months were associated with a 24-month ASD diagnosis and whether social motivation’s course differed relative to familial ASD liability. The SMI displayed good internal consistency and temporal stability. Children diagnosed with ASD displayed lower mean SMI T-scores at all ages and a decrease in mean T-scores across age. Lower group-level 6-month scores corresponded with higher familial ASD liability. Among high-risk infants, strong decline in SMI T-scores was associated with 10-fold odds of diagnosis. Infant social motivation is quantifiable by parental report, differentiates children with versus without later ASD by age 6 months, and tracks with familial ASD liability, consistent with a diagnostic and susceptibility marker of ASD. Early decrements and decline in social motivation indicate increased likelihood of ASD, highlighting social motivation’s importance to risk assessment and clarification of the ontogeny of ASD.

Exposure to early-life adversity (ELA) and iron deficiency early in life are known risk factors for suboptimal brain and socioemotional development. Iron deficiency may arise from and co-occur with ELA, which could negatively affect development. In the present study, we investigated whether ELA is associated with iron deficiency in infants receiving no iron supplementation. This study is a secondary analysis of extant data collected in the 1990s; participants were healthy infants from working-class communities in Santiago, Chile (N = 534, 45.5% female). We measured stressful life events, maternal depression, and low home support for child development during infancy and assessed iron status when the infant was 12 months old. Slightly more than half of the infants were iron-deficient (51%), and 25.8% were iron-deficient anemic at 12 months. Results indicated that ELA was associated with lower iron levels and iron deficiency at 12 months. The findings are consistent with animal and human prenatal models of stress and iron status and provide evidence of the association between postnatal ELA and iron status in humans. The findings also highlight a nutritional pathway by which ELA may impact development and present a nutritionally-focused avenue for future research on ELA and psychopathology.