Does Neonatal Imitation Exist? Insights From a Meta-Analysis of 336 Effect Sizes

Neonatal imitation is a cornerstone in many theoretical accounts of human development and social behavior, yet its existence has been debated for the past 40 years. To examine possible explanations for the inconsistent findings in this body of research, we conducted a multilevel meta-analysis synthesizing 336 effect sizes from 33 independent samples of human newborns, reported in 26 articles. The meta-analysis found significant evidence for neonatal imitation (d = 0.68, 95% CI = [0.39, 0.96], p < .001) but substantial heterogeneity between study estimates. This heterogeneity was not explained by any of 13 methodological moderators identified by previous reviews, but it was associated with researcher affiliation, test of moderators (QM) (15) = 57.09, p < .001. There are at least two possible explanations for these results: (a) Neonatal imitation exists and its detection varies as a function of uncaptured methodological factors common to a limited set of studies, and (2) neonatal imitation does not exist and the overall positive result is an artifact of high researcher degrees of freedom.

Associations between technoference, quality of parent-infant interactions, and infants' vocabulary development

"Technoference" describes the distraction from interpersonal activities that can occur due to use of mobile screen devices. Focusing on parent-infant interactions, our study investigated the associations between potential sources of "technoference" and parental responsiveness, scaffolding and directiveness toward their infant, and coordinated joint attention (CJA). Previous research demonstrates that each of these dimensions is related to early language development. Potential sources of "technoference" employed in our study included the amount of time the parent spends on their mobile device per hour when with their infant; the number of audible notifications the parent receives per hour, the number of times per hour they check their device; and parents' score on the Distraction In Social Relations and Use of Parent Technology (DISRUPT) scale. We investigated associations between our measures of parental "technoference" and infants' language development, and whether parental responsiveness, scaffolding, directiveness or parent-infant CJA mediate associations between "technoference" and language. Frequency of audible notifications negatively predicted infant vocabulary, and this relationship was fully mediated by parental directiveness.

Peek-a-who? Exploring the dynamics of early communication with an interactive partner swap paradigm and state space grid visualization

Effective caregiver-infant communication occurs when interactive partners successfully coordinate multiple modalities (e.g., body movements, affect, eye gaze). The complex interplay of multiple modalities during caregiver-infant interactions is difficult to capture, which has made a comprehensive, evidence-based understanding of caregiver-infant communication difficult to achieve. We present a novel methodological approach to address this challenge by combining an Interactive Partner Swap (IPS) paradigm with a longitudinal design, detailed multimodal coding, and data visualization via state space grids (SSGs). We demonstrate the utility of our approach by presenting three sets of SSGs which reveal both dyadic flexibility and stability in caregiver-infant peek-a-boo interactions across three levels: micro (moment-to-moment), meso (interactive context), and macro (infant development). By using SSGs to explore the patterns that hold and others that differ systematically across interactive partner and infant development, our novel approach promises to offer critical first steps to creating a more detailed understanding of the dynamics of early multimodal communication.

Individual differences in neonatal "imitation" fail to predict early social cognitive behaviour

The influential hypothesis that humans imitate from birth - and that this capacity is foundational to social cognition - is currently being challenged from several angles. Most prominently, the largest and most comprehensive longitudinal study of neonatal imitation to date failed to find evidence that neonates copied any of nine actions at any of four time points (Oostenbroek et al., [2016] Current Biology, 26, 1334-1338). The authors of an alternative and statistically liberal post-hoc analysis of these same data (Meltzoff et al., [2017] Developmental Science, 21, e12609), however, concluded that the infants actually did imitate one of the nine actions: tongue protrusion. In line with the original intentions of this longitudinal study, we here report on whether individual differences in neonatal "imitation" predict later-developing social cognitive behaviours. We measured a variety of social cognitive behaviours in a subset of the original sample of infants (N = 71) during the first 18 months: object-directed imitation, joint attention, synchronous imitation and mirror self-recognition. Results show that, even using the liberal operationalization, individual scores for neonatal "imitation" of tongue protrusion failed to predict any of the later-developing social cognitive behaviours. The average Spearman correlation was close to zero, mean r_s  = 0.027, 95% CI [-0.020, 0.075], with all Bonferroni adjusted p values > .999. These results run counter to Meltzoff et al.'s rebuttal, and to the existence of a "like me" mechanism in neonates that is foundational to human social cognition.

Mothers are sensitive to men's beards as a potential cue of paternal investment

Mating strategy theories assert that women's preferences for androgen dependent traits in men are stronger when the costs of reduced paternal investment are lowest. Past research has shown that preferences for facial masculinity are stronger among nulliparous and non-pregnant women than pregnant or parous women. In two studies, we examine patterns in women's preferences for men's facial hair - likely the most visually conspicuous and sexually dimorphic of men's secondary sexual traits - when evaluating men's masculinity, dominance, age, fathering, and attractiveness. Two studies were conducted among heterosexual pregnant women, mothers, non-contractive and contraceptive users. Study 1 used a between-subjects sample (N = 2103) and found that mothers had significantly higher preferences for beards when judging fathering than all other women. Pregnant women and mothers also judged beards as more masculine and older, but less attractive, than non-contractive and contraceptive users. Parous women judged beards higher for age, masculinity and fathering, but lower for attractiveness, than nulliparous women. Irrespective of reproductive status, beards were judged as looking more dominant than clean-shaven faces. Study 2 used a within-subjects design (N = 53) among women surveyed during pregnancy and three months post-partum. Judgments of parenting skills were higher for bearded stimuli during pregnancy among women having their first baby, whereas among parous women parenting skills judgments for bearded stimuli were higher post-partum. Our results suggest that mothers are sensitive to beardedness as a masculine secondary sexual characteristic that may denote parental investment, providing evidence that women's mate preferences could reflect sexual selection for direct benefits.