An ethological analysis of human infant crying: answering Tinbergen's four questions

Age and parous-experience dependent changes in emotional contagion for positive infant sounds

Introduction

Emotional contagion is achieved by inferring and emotionally resonating with other persons' feelings. It is unclear whether age-related changes in emotional contagion for infant sounds are modulated by the experience of childbirth or childcare. This study aims to evaluate changes in inference and emotional resonance for positive and negative infant sounds (laughter and crying) among women, based on age and parous experience.

Methods

A total of 241 women (60 young nulliparous, 60 young parous, 60 old nulliparous, and 61 old parous) completed a web-based questionnaire. After listening to three types of infant sounds (laughter, cooing, and crying), participants responded with their valence for hearing infant sounds and estimated infant valence on an 11-point Likert scale.

Results

The analysis for emotional resonance revealed that the correlation coefficient between self and estimated infant valences was greater in young parous and old nulliparous women than in young nulliparous women, in laughter and cooing sounds. However, correlation coefficients for crying did not differ among any of the four groups.

Conclusion

The degree of emotional resonance for infant valence increased depending on age and parous-experience for positive infant sounds.

Preventing and Treating Colic: An Update

Infantile colic (IC) is c is a self-limiting functional gastrointestinal disorder (FGID) with a favorable natural history. Worldwide, IC has a significant impact on many newborns and their families. Although not an indication of an illness, its symptoms are wide and generic and may indicate a potentially serious underlying issue in a tiny percentage of newborns who may require a medical evaluation. The pathogenesis appears to be multifactorial implying a complex relationship between the infant and the environment. One of the most studied theories attributes a key role to the gut microbiota in the pathogenesis of IC. A variety of approaches have been suggested for the clinical management of IC, and several randomized controlled trials have been reported in the literature. Probiotics can change the host's microbiota and positively impact health. They may be able to restore balance and create a better intestinal microbiota landscape since there is mounting evidence that the gut microbial environment of colicky newborns differs from that of healthy infants. In this review, we revise the most commonly studied probiotics and mixtures to treat and prevent IC and the most recent recommendations.

Infant cries convey both stable and dynamic information about age and identity

What information is encoded in the cries of human babies? While it is widely recognized that cries can encode distress levels, whether cries reliably encode the cause of crying remains disputed. Here, we collected 39201 cries from 24 babies recorded in their homes longitudinally, from 15 days to 3.5 months of age, a database we share publicly for reuse. Based on the parental action that stopped the crying, which matched the parental evaluation of cry cause in 75% of cases, each cry was classified as caused by discomfort, hunger, or isolation. Our analyses show that baby cries provide reliable information about age and identity. Baby voices become more tonal and less shrill with age, while individual acoustic signatures drift throughout the first months of life. In contrast, neither machine learning algorithms nor trained adult listeners can reliably recognize the causes of crying.

Therapists' oxytocin response mediates the association between patients' negative emotions and psychotherapy outcomes

BACKGROUND

Existing literature suggests that patients' experiences of emotions, especially negative emotions, predict outcomes in psychotherapies for major depressive disorder. However, the specific mechanisms underlying this effect remain unclear. Based on studies pointing to the role of oxytocin (OT) in attachment relationships, we proposed and tested a mediation model where the therapists' hormonal responses, as represented by increases in their OT levels, mediates the association between negative emotions and symptomatic change.

METHOD

OT saliva samples (pre- and post-session, N = 435) were collected on a fixed schedule over 16 sessions from the therapists of 62 patients receiving psychotherapy for major depression. The Hamilton Rating Scale for Depression was administered to the patients before the sessions, and the patients reported their in-session emotions after the sessions.

RESULTS

The findings support the proposed within-person mediation model: (a) higher levels of negative emotions in patients predicted greater increases in therapist OT levels pre- to post-session throughout treatment; (b) greater OT levels in therapists, in turn, predicted reduction in patients' depressive symptoms on the subsequent assessment; and (c) the therapists' OT levels significantly mediated the association between patients' negative emotions and reduction in their depressive symptoms.

LIMITATIONS

This design precluded establishing a time sequence between patients' negative emotions and therapists' OT; thus, causality could not be inferred.

CONCLUSION

These findings point to a possible biological mechanism underlying the effects of patients' experiences of negative emotions on treatment outcomes. The findings suggest that therapists' OT responses could potentially serve as a biomarker of an effective therapeutic processes.

Sows' Responses to Piglets in Distress: An Experimental Investigation in a Natural Setting

Domestic pigs (Sus scrofa) possess complex socio-cognitive skills, and sows show high inter-individual variability in maternal behaviour. To evaluate how females-reared under natural conditions-react to the isolation calls of their own piglets or those of other females, we conducted observations and experimental trials. In January-February 2021, we conducted all-occurrences sampling on affiliation, aggression, and lactation (daily, 7:30-16:30 h) on six lactating and four non-lactating females at the ethical farm Parva Domus (Turin, Italy). The trials (30 s each, n = 37/sow) consisted of briefly catching and restraining a piglet. We recorded the sow response (none/reactive/proactive movement towards the piglet; self-directed anxiety behaviours such as body shaking) before and during the trial and under control conditions. Increased levels of anxiety behaviour in sows were accompanied by an increased frequency of responses. Less aggressive sows and lactating sows showed the highest frequencies of response. Finally, the isolation calls' maximum intensity had an influence on the type of response observed, with higher proactive response frequencies following lower intensity isolation calls. Our results suggest that being under lactation could play a key role in increasing sow response levels and that specific acoustic features may influence the response.

A Scientometric Review of Infant Cry and Caregiver Responsiveness: Literature Trends and Research Gaps over 60 Years of Developmental Study

Infant cry is an adaptive signal of distress that elicits timely and mostly appropriate caring behaviors. Caregivers are typically able to decode the meaning of the cry and respond appropriately, but maladaptive caregiver responses are common and, in the worst cases, can lead to harmful events. To tackle the importance of studying cry patterns and caregivers' responses, this review aims to identify key documents and thematic trends in the literature as well as existing research gaps. To do so, we conducted a scientometric review of 723 documents downloaded from Scopus and performed a document co-citation analysis. The most impactful publication was authored by Barr in 1990, which describes typical developmental patterns of infant cry. Six major research thematic clusters emerged from the analysis of the literature. Clusters were renamed "Neonatal Pain Analyzer" (average year of publication = 2002), "Abusive Head Trauma" (average year of publication = 2007), "Oxytocin" (average year of publication = 2009), "Antecedents of Maternal Sensitivity" (average year of publication = 2010), "Neurobiology of Parental Responses" (average year of publication = 2011), and "Hormonal Changes & Cry Responsiveness" (average year of publication = 2016). Research clusters are discussed on the basis of a qualitative inspection of the manuscripts. Current trends in research focus on the neurobiology of caregiver responses and the identification of factors promoting maternal sensitivity. Recent studies have also developed evidence-based strategies for calming crying babies and preventing caregivers' maladaptive responses. From the clusters, two topics conspicuously call for future research: fathers' responsiveness to infant cry and the impact of caregiver relationship quality on cry responsiveness.

Functional near-infrared spectroscopy is a useful tool for multi-perspective psychobiological study of neurophysiological correlates of parenting behaviour

The quality of the relationship between caregiver and child has long-term effects on the cognitive and socio-emotional development of children. A process involved in human parenting is the bio-behavioural synchrony that occurs between the partners in the relationship during interaction. Through interaction, bio-behavioural synchronicity allows the adaptation of the physiological systems of the parent to those of the child and promotes the positive development and modelling of the child's social brain. The role of bio-behavioural synchrony in building social bonds could be investigated using functional near-infrared spectroscopy (fNIRS). In this paper we have (a) highlighted the importance of the quality of the caregiver-child relationship for the child's cognitive and socio-emotional development, as well as the relevance of infantile stimuli in the activation of parenting behaviour; (b) discussed the tools used in the study of the neurophysiological substrates of the parental response; (c) proposed fNIRS as a particularly suitable tool for the study of parental responses; and (d) underlined the need for a multi-systemic psychobiological approach to understand the mechanisms that regulate caregiver-child interactions and their bio-behavioural synchrony. We propose to adopt a multi-system psychobiological approach to the study of parental behaviour and social interaction.

A self-training automatic infant-cry detector

Infant cry is one of the first distinctive and informative life signals observed after birth. Neonatologists and automatic assistive systems can analyse infant cry to early-detect pathologies. These analyses extensively use reference expert-curated databases containing annotated infant-cry audio samples. However, these databases are not publicly accessible because of their sensitive data. Moreover, the recorded data can under-represent specific phenomena or the operational conditions required by other medical teams. Additionally, building these databases requires significant investments that few hospitals can afford. This paper describes an open-source workflow for infant-cry detection, which identifies audio segments containing high-quality infant-cry samples with no other overlapping audio events (e.g. machine noise or adult speech). It requires minimal training because it trains an LSTM-with-self-attention model on infant-cry samples automatically detected from the recorded audio through cluster analysis and HMM classification. The audio signal processing uses energy and intonation acoustic features from 100-ms segments to improve spectral robustness to noise. The workflow annotates the input audio with intervals containing infant-cry samples suited for populating a database for neonatological and early diagnosis studies. On 16 min of hospital phone-audio recordings, it reached sufficient infant-cry detection accuracy in 3 neonatal care environments (nursery—69%, sub-intensive—82%, intensive—77%) involving 20 infants subject to heterogeneous cry stimuli, and had substantial agreement with an expert’s annotation. Our workflow is a cost-effective solution, particularly suited for a sub-intensive care environment, scalable to monitor from one to many infants. It allows a hospital to build and populate an extensive high-quality infant-cry database with a minimal investment.

Vocal complexity in Antillean manatees (Trichechus manatus manatus)

Vocal complexity can be expressed through variations in repertoire size, structure, and individual manatee repertoires. Here we aimed to assess the complexity of the vocal behaviour of Antillean manatees living in captivity (i.e., artificial pools) and in reintroduction enclosures (i.e., natural enclosures placed in an estuarine area). Specifically, we evaluated: (i) the structure of vocalisations to assess whether they had variants; (ii) the variation in call production (rate and pattern) between groups with different configurations; (iii) whether individuality occurred in vocalisation structure. We found four categories of vocalisations, of which two had different variants. Not all study groups produced all call categories and variants. Older and younger males in the reintroduction enclosures had the highest call rates compared to captive females and captive males. The vocal and behavioural patterns differed between groups. Squeak call structure differed between individuals. Such vocal complexity may aid manatees in adapting to their dynamic social and structural environment, facilitating communication.

Turn-taking skills in mammals: A systematic review into development and acquisition

How human language evolved remains one of the most intriguing questions in science, and different approaches have been used to tackle this question. A recent hypothesis, the Interaction Engine Hypothesis, postulates that language was made possible through the special capacity for social interaction involving different social cognitive skills (e.g., joint attention, common ground) and specific characteristics such as face-to-face interaction, mutual gaze and turn-taking, the exchange of rapid communicative turns. Recently, it has been argued that this turn-taking infrastructure may be a foundational and ancient mechanism of the layered system of language because communicative turn-taking has been found in human infants and across several non-human primate species. Moreover, there is some evidence for turn-taking in different mammalian taxa, especially those capable of vocal learning. Surprisingly, however, the existing studies have mainly focused on turn-taking production of adult individuals, while little is known about its emergence and development in young individuals. Hence, the aim of the current paper was 2-fold: First, we carried out a systematic review of turn-taking development and acquisition in mammals to evaluate possible research bias and existing gaps. Second, we highlight research avenues to spur more research into this domain and investigate if distinct turn-taking elements can be found in other non-human animal species. Since mammals exhibit an extended development period, including learning and strong parental care, they represent an excellent model group in which to investigate the acquisition and development of turn-taking abilities. We performed a systematic review including a wide range of terms and found 21 studies presenting findings on turn-taking abilities in infants and juveniles. Most of these studies were from the last decade, showing an increased interest in this field over the years. Overall, we found a considerable variation in the terminologies and methodological approaches used. In addition, studies investigating turn-taking abilities across different development periods and in relation to different social partners were very rare, thereby hampering direct, systematic comparisons within and across species. Nonetheless, the results of some studies suggested that specific turn-taking elements are innate, while others are acquired during development (e.g., flexibility). Finally, we pinpoint fruitful research avenues and hypotheses to move the field of turn-taking development forward and improve our understanding of the impact of turn-taking on language evolution.

Emotional authenticity modulates affective and social trait inferences from voices

The human voice is a primary tool for verbal and nonverbal communication. Studies on laughter emphasize a distinction between spontaneous laughter, which reflects a genuinely felt emotion, and volitional laughter, associated with more intentional communicative acts. Listeners can reliably differentiate the two. It remains unclear, however, if they can detect authenticity in other vocalizations, and whether authenticity determines the affective and social impressions that we form about others. Here, 137 participants listened to laughs and cries that could be spontaneous or volitional and rated them on authenticity, valence, arousal, trustworthiness and dominance. Bayesian mixed models indicated that listeners detect authenticity similarly well in laughter and crying. Speakers were also perceived to be more trustworthy, and in a higher arousal state, when their laughs and cries were spontaneous. Moreover, spontaneous laughs were evaluated as more positive than volitional ones, and we found that the same acoustic features predicted perceived authenticity and trustworthiness in laughter: high pitch, spectral variability and less voicing. For crying, associations between acoustic features and ratings were less reliable. These findings indicate that emotional authenticity shapes affective and social trait inferences from voices, and that the ability to detect authenticity in vocalizations is not limited to laughter. This article is part of the theme issue 'Voice modulation: from origin and mechanism to social impact (Part I)'.

Reasons mothers bedshare: A review of its effects on infant behavior and development

Bedsharing is controversial for nighttime caregiving in the U.S. today, as in most of the West. However, from the standpoint of evolutionary pediatrics, anthropology, and cultural psychology, bedsharing is not controversial at all, representing the context for human infant evolution and conferring a host of physiological benefits to the infant as well as the mother. In an effort to understand the rise in Western bedsharing in recent decades (and following Ball, 2002; McKenna & Volpe, 2007), Salm Ward (2015) systematically reviewed the literature on mother-infant bedsharing and identified ten reasons why mothers choose to bedshare: (1) breastfeeding, (2) comforting for mother or infant, (3) better/more sleep for infant or parent, (4) monitoring, (5) bonding/ attachment, (6) environmental reasons, (7) crying, (8) cultural or familial traditions, (9) disagree with danger, and (10) maternal instinct. The current paper offers the "review behind the review," highlighting the scientific evidence behind the reasons mothers give for their decision to bedshare, focusing on how mothers' decisions about infant sleep location influence infant behavior and development.

Romantic Love and Sleep Variations: Potential Proximate Mechanisms and Evolutionary Functions

This article provides a narrative review of what is known about romantic love and sleep variations and provides possible explanations for the association. Romantic love and sleep are described using a comprehensive, unifying framework advocated by Tinbergen. We summarise the findings of studies investigating the relationship between romantic love and sleep. Sleep variations are associated with romantic love in adolescents and young adults. We then detail some proximate mechanisms that may contribute to sleep variations in people experiencing romantic love before considering potential evolutionary functions of sleep variations in people experiencing romantic love. The relationship between symptoms of psychopathology and sleep variations in people experiencing romantic love is described. With the current state of knowledge, it is not possible to determine whether sleep variations associated with romantic love are adaptations or by-products of romantic love. We conclude by proposing areas for future research.

Aping Language: Historical Perspectives on the Quest for Semantics, Syntax, and Other Rarefied Properties of Human Language in the Communication of Primates and Other Animals

In 1980, Robert Seyfarth, Dorothy Cheney and Peter Marler published a landmark paper in Science claiming language-like semantic communication in the alarm calls of vervet monkeys. This article and the career research program it spawned for its authors catalyzed countless other studies searching for semantics, and then also syntax and other rarefied properties of language, in the communication systems of non-human primates and other animals. It also helped bolster a parallel tradition of teaching symbolism and syntax in artificial language systems to great apes. Although the search for language rudiments in the communications of primates long predates the vervet alarm call story, it is difficult to overstate the impact of the vervet research, for it fueled field and laboratory research programs for several generations of primatologists and kept busy an equal number of philosophers, linguists, and cognitive scientists debating possible implications for the origins and evolution of language and other vaunted elements of the human condition. Now 40-years on, the original vervet alarm call findings have been revised and claims of semanticity recanted; while other evidence for semantics and syntax in the natural communications of non-humans is sparse and weak. Ultimately, we are forced to conclude that there are simply few substantive precedents in the natural communications of animals for the high-level informational and representational properties of language, nor its complex syntax. This conclusion does not mean primates cannot be taught some version of these elements of language in artificial language systems - in fact, they can. Nor does it mean there is no continuity between the natural communications of animals and humans that could inform the evolution of language - in fact, there is such continuity. It just does not lie in the specialized semantic and syntactic properties of language. In reviewing these matters, I consider why it is that primates do not evince high-level properties of language in their natural communications but why we so readily accepted that they did or should; and what lessons we might draw from that experience. In the process, I also consider why accounts of human-like characteristics in animals can be so irresistibly appealing.

Infants' stress responses and protest behaviors at childcare entry and the role of care providers

During the transition from home to childcare, 70 15-month-old infants were videotaped, and their negative emotions were rated. Infants' attachments to mothers were assessed prior to child care entry and to care providers five months later using the Strange Situation Procedure (SSP). Infant heart rate was monitored at home, during adaptation to childcare (mothers present), and during subsequent separations. Respiratory sinus arrhythmia (RSA) was computed from the beat-to-beat measures of heart rate to reflect vagal tone, which is reduced during chronic states of stress, and was collected upon Arrival, during in-group Play, and when in the Group more generally. All infants responded to childcare entry with low RSA levels indicating stress. However, during adaptation with the mother present, RSA was higher for securely attached infants. On the first separation day, 35.3% of the infants fussed and cried extensively. These intense protests predicted later secure attachments to care providers, which adaptively helped to reduce stress, especially in infants who protested extensively, as if summoning their mothers back. Because extensive protest suggests limited regulatory capacities, infants risk overburdening the stress system when left unsupported.

Studying caregiver-infant co-regulation in dynamic, diverse cultural contexts: A call to action

Caregivers and infants co-regulate their physiology, emotions, and behavior in a way that is dynamically responsive to each other and the contexts in which they live. This paper is an introduction and call to action for researchers interested in understanding how to study caregiver-infant interactions in the home and diverse cultural contexts, including marginalized communities. We argue that research will be more valid, culturally relevant, and tapped-in to the daily lives of caregivers and infants if there is partnership and collaboration with the caregivers in the design of the questions, data collection and analysis, and distribution of the findings. We recommend dynamically assessing emotions, behaviors, and physiology using repeated sampling methods including ecological momentary assessments (EMA), salivary bioscience, and actigraphy. We aim to extend current practices of studying caregiver-infant co-regulation by measuring fluctuations of daily life and considering sociocultural factors that shape naturalistic caregiver-infant interactions. Using methodological advancements and community-based participatory research approaches can enable developmental scientists to measure life as it is actually lived.

Proximate and Ultimate Perspectives on Romantic Love

Romantic love is a phenomenon of immense interest to the general public as well as to scholars in several disciplines. It is known to be present in almost all human societies and has been studied from a number of perspectives. In this integrative review, we bring together what is known about romantic love using Tinbergen’s “four questions” framework originating from evolutionary biology. Under the first question, related to mechanisms, we show that it is caused by social, psychological mate choice, genetic, neural, and endocrine mechanisms. The mechanisms regulating psychopathology, cognitive biases, and animal models provide further insights into the mechanisms that regulate romantic love. Under the second question, related to development, we show that romantic love exists across the human lifespan in both sexes. We summarize what is known about its development and the internal and external factors that influence it. We consider cross-cultural perspectives and raise the issue of evolutionary mismatch. Under the third question, related to function, we discuss the fitness-relevant benefits and costs of romantic love with reference to mate choice, courtship, sex, and pair-bonding. We outline three possible selective pressures and contend that romantic love is a suite of adaptions and by-products. Under the fourth question, related to phylogeny, we summarize theories of romantic love’s evolutionary history and show that romantic love probably evolved in concert with pair-bonds in our recent ancestors. We describe the mammalian antecedents to romantic love and the contribution of genes and culture to the expression of modern romantic love. We advance four potential scenarios for the evolution of romantic love. We conclude by summarizing what Tinbergen’s four questions tell us, highlighting outstanding questions as avenues of potential future research, and suggesting a novel ethologically informed working definition to accommodate the multi-faceted understanding of romantic love advanced in this review.

The emotional canvas of human screams: patterns and acoustic cues in the perceptual categorization of a basic call type

Screams occur across taxonomically widespread species, typically in antipredator situations, and are strikingly similar acoustically, but in nonhuman primates, they have taken on acoustically varied forms in association with more contextually complex functions related to agonistic recruitment. Humans scream in an even broader range of contexts, but the extent to which acoustic variation allows listeners to perceive different emotional meanings remains unknown. We investigated how listeners responded to 30 contextually diverse human screams on six different emotion prompts as well as how selected acoustic cues predicted these responses. We found that acoustic variation in screams was associated with the perception of different emotions from these calls. Emotion ratings generally fell along two dimensions: one contrasting perceived anger, frustration, and pain with surprise and happiness, roughly associated with call duration and roughness, and one related to perceived fear, associated with call fundamental frequency. Listeners were more likely to rate screams highly in emotion prompts matching the source context, suggesting that some screams conveyed information about emotional context, but it is noteworthy that the analysis of screams from happiness contexts (n = 11 screams) revealed that they more often yielded higher ratings of fear. We discuss the implications of these findings for the role and evolution of nonlinguistic vocalizations in human communication, including consideration of how the expanded diversity in calls such as human screams might represent a derived function of language.

Clinical Evidence of Vestibular Dysregulation in Colicky Babies Before and After Chiropractic Treatment vs. Non-colicky Babies

Background: To date, after 65 years of research that was primarily directed at differentiating between normal and colicky crying, the cause of infantile colic remains elusive and no definitive cure has been found. Given the general absence of pathology, colicky crying is widely considered the extreme end of a spectrum of normal crying behavior. However, evidence gleaned from scattered sources throughout the literature suggests that infantile colic may be the behavioral expression of physiological brainstem dysregulation, particularly of the vestibular and autonomic systems. The purpose of this study is to present a five-point clinical index of vestibular (hyper) activity and its application to investigate vestibular dysregulation in colicky and non-colicky babies. Methods: One hundred and twenty consecutive colicky babies were evaluated using this index, before and after a very gentle vibratory treatment, and compared to 117 non-colicky babies. Results: Before treatment, of 120 colicky babies only 2 (1.7%) scored 0, whereas 118 (98.3%) scored 1-5. Of 117 non-colicky babies 89 (76.1%) scored 0 and 28 (23.9%) scored 1-3, none scored 4-5. The odds ratio is OR (CI 95%) 187.54 (43.52-808.09). After treatment 111 (92.5%) scored 0 and 9 (7.5%) scored 1-3, none scored 4-5. A McNemar test showed the difference before and after to be significant (χ² = 109.00, p < 0.001). For colicky babies the mean vestibular score is 2.88 (SD 1.22), compared to 0.37 (SD 0.73) for non-colicky babies, a difference of 87.2%. After treatment the score decreased from 2.88 (SD 1.12) to 0.10 (SD 0.40), or 96.5%. Conclusion: Colicky babies are not just infants who cry a lot. They also show clinical evidence of vestibular dysregulation. Treatment aimed at relaxing tight sub-occipital musculature by means of gentle vibrational stimulation may be effective in decreasing vestibular hyperactivity, signifying an improvement in brainstem regulation. The vestibular index opens the prospect for development into a tool toward an objective and practical clinical diagnosis of infantile colic.

Sucking behavior in typical and challenging feedings in association with weight gain from birth to 4 Months in full-term infants

Sucking behavior has been described as an obesity risk marker. Sucking behavior in response to challenge has not been examined as a prospective predictor of infant weight gain. Healthy, full term infants had sucking behavior assessed at ages 2 weeks and/or 2 months via a sucking pressure measurement device in two feeding conditions: during a standard feeding and during a feeding with a more challenging nipple. Weight and length were measured at 2 weeks, 2 months, and 4 months and weight-for-length z-score (WLZ) calculated. Among 45 full term infants, adjusted for age at measurement and time since last feeding, the challenging versus typical feedings differed with regard to amount consumed (54.1g vs. 65.6g, p < .05), maximum sucking pressure (121.3 mmHg vs. 99.2 mmHg, p < .05), mean burst duration (17.5s vs. 28.4s, p < .05), and feeding duration (18.51 min vs. 13.89 min, p < .01). Grams consumed in the challenging, but not typical, feeding, adjusted for age and time since last feeding, predicted rate of change in WLZ from time of measurement to age 4 months (r = 0.46, p = .013 for challenging, r = -0.07, p = .702 for typical). Nipples that are more challenging to suck from change the sucking behavior and intake among full term infants. Infants who consume more when the nipple is more challenging have greater prospective weight gain. This persistent sucking behavior in the face of challenge may reflect that a greater willingness to work for food, a known obesity risk factor, is detectable in early infancy.

The Evolution of Human Vocal Emotion

Vocal affect is a subcomponent of emotion programs that coordinate a variety of physiological and psychological systems. Emotional vocalizations comprise a suite of vocal behaviors shaped by evolution to solve adaptive social communication problems. The acoustic forms of vocal emotions are often explicable with reference to the communicative functions they serve. An adaptationist approach to vocal emotions requires that we distinguish between evolved signals and byproduct cues, and understand vocal affect as a collection of multiple strategic communicative systems subject to the evolutionary dynamics described by signaling theory. We should expect variability across disparate societies in vocal emotion according to culturally evolved pragmatic rules, and universals in vocal production and perception to the extent that form–function relationships are present.

Elimination communication contributes to a reduction in unexplained infant crying

The Normal Crying Curve refers to infants' unexplained crying from birth to a peak at about 6-8 weeks, and self-resolving by three months. However, it is known that infants signal their need to eliminate (micturate/defecate) through a variety of cues, including fussing and crying. Elimination Communication (EC) refers to a caregiver's nurturant response to infant cues, while also using timing, to gently and non-coercively cradle the infant in a supported, secure squatting position to eliminate. Such practices have been reported in ethnographic observations of hunter-gatherer care of infants, who cry less than minority world (Western) infants. We hypothesize that the current minority world practice of delayed toilet training and lack of caregiver response to elimination cues results in excessive, unexplained infant crying as infants eliminate in the constraints of diapers and in non-beneficial postures. As a corollary, we hypothesize that EC will reduce unexplained infant crying in the early months, perhaps even planating the Normal Crying Curve. To evaluate our hypothesis, we designed a pilot study to collect empirical data from mothers who practiced EC with their infants, tracking crying and fussing at Weeks 4, 6, 8 and 12 primarily utilizing a 24-hour Baby's Daily Diary. We computed baseline measures, compared our crying data with those from the literature, assessed our data for internal crying peaks, and used hierarchical multi-level modeling to evaluate cross-level interactions. We found that infants in our pilot study cried on average 50.3% less (p < 0.05), and up to 70.9% less in Week 6, compared to literature studies. Moreover, when we evaluated our data to seek out a significant crying peak across weeks, no such crying duration difference was found. Using hierarchical generalized linear modeling, we found that greater daily crying episodes predicted greater daily elimination opportunities. Shorter crying episodes predicted a greater number of daily elimination opportunities compared to longer crying episodes, especially among low baseline crying infants. Our results suggest that crying prompts caregivers to offer elimination opportunities, but when the crying continues, caregivers may try other behavioral responses, such as feeding. Additionally, our results suggest that with the practice of EC, unexplained infant crying may be significantly reduced and warrant future research with an expanded sample. If the practice of EC indeed planates the Normal Crying Curve, then such results will have a significant impact on our understanding of unexplained infant crying.

Attention bias to infant faces in pregnant women predicts maternal sensitivity

While research has shown that attention bias to infant faces is linked to parenting, this work is largely cross-sectional and limited to the postpartum period. Because the transition to motherhood from pregnancy to birth constitutes a sensitive period in cortical reorganization linked to the quality of mother-infant interactions, evaluating attention processes in the maternal cortex prior to the experience of mother-infant face-to-face interactions is critical. To assess behavioural attention and neural responses to infant faces in pregnant mothers, behavioral and electrocortical indices were collected using a Go/No Go task, in which infant and adult faces served as distractors. Results showed that heightened processing of infant faces relative to adult faces (behavioral and electrocortical indices) was related to observations of greater maternal sensitivity. These findings show that prenatal maternal attention bias to and the perceived salience of infant faces serves as an individual cognitive hallmark of maternal sensitivity that acts independently of caregiving experience.

Preterm and full term infant vocalization and the origin of language

How did vocal language originate? Before trying to determine how referential vocabulary or syntax may have arisen, it is critical to explain how ancient hominins began to produce vocalization flexibly, without binding to emotions or functions. A crucial factor in the vocal communicative split of hominins from the ape background may thus have been copious, functionally flexible vocalization, starting in infancy and continuing throughout life, long before there were more advanced linguistic features such as referential vocabulary. 2-3 month-old modern human infants produce "protophones", including at least three types of functionally flexible non-cry precursors to speech rarely reported in other ape infants. But how early in life do protophones actually appear? We report that the most common protophone types emerge abundantly as early as vocalization can be observed in infancy, in preterm infants still in neonatal intensive care. Contrary to the expectation that cries are the predominant vocalizations of infancy, our all-day recordings showed that protophones occurred far more frequently than cries in both preterm and full-term infants. Protophones were not limited to interactive circumstances, but also occurred at high rates when infants were alone, indicating an endogenous inclination to vocalize exploratorily, perhaps the most fundamental capacity underlying vocal language.

Effects of Maternal Singing Style on Mother-Infant Arousal and Behavior

Mothers around the world sing to infants, presumably to regulate their mood and arousal. Lullabies and playsongs differ stylistically and have distinctive goals. Mothers sing lullabies to soothe and calm infants and playsongs to engage and excite infants. In this study, mothers repeatedly sang Twinkle, Twinkle, Little Star to their infants (n = 30 dyads), alternating between soothing and playful renditions. Infant attention and mother-infant arousal (i.e., skin conductivity) were recorded continuously. During soothing renditions, mother and infant arousal decreased below initial levels as the singing progressed. During playful renditions, maternal and infant arousal remained stable. Moreover, infants exhibited greater attention to mother during playful renditions than during soothing renditions. Mothers' playful renditions were faster, higher in pitch, louder, and characterized by greater pulse clarity than their soothing renditions. Mothers also produced more energetic rhythmic movements during their playful renditions. These findings highlight the contrastive nature and consequences of lullabies and playsongs.

Human roars communicate upper-body strength more effectively than do screams or aggressive and distressed speech

Despite widespread evidence that nonverbal components of human speech (e.g., voice pitch) communicate information about physical attributes of vocalizers and that listeners can judge traits such as strength and body size from speech, few studies have examined the communicative functions of human nonverbal vocalizations (such as roars, screams, grunts and laughs). Critically, no previous study has yet to examine the acoustic correlates of strength in nonverbal vocalisations, including roars, nor identified reliable vocal cues to strength in human speech. In addition to being less acoustically constrained than articulated speech, agonistic nonverbal vocalizations function primarily to express motivation and emotion, such as threat, and may therefore communicate strength and body size more effectively than speech. Here, we investigated acoustic cues to strength and size in roars compared to screams and speech sentences produced in both aggressive and distress contexts. Using playback experiments, we then tested whether listeners can reliably infer a vocalizer's actual strength and height from roars, screams, and valenced speech equivalents, and which acoustic features predicted listeners' judgments. While there were no consistent acoustic cues to strength in any vocal stimuli, listeners accurately judged inter-individual differences in strength, and did so most effectively from aggressive voice stimuli (roars and aggressive speech). In addition, listeners more accurately judged strength from roars than from aggressive speech. In contrast, listeners' judgments of height were most accurate for speech stimuli. These results support the prediction that vocalizers maximize impressions of physical strength in aggressive compared to distress contexts, and that inter-individual variation in strength may only be honestly communicated in vocalizations that function to communicate threat, particularly roars. Thus, in continuity with nonhuman mammals, the acoustic structure of human aggressive roars may have been selected to communicate, and to some extent exaggerate, functional cues to physical formidability.

Implicit associations to infant cry: Genetics and early care experiences influence caregiving propensities

Adults' sensitive appraisal of and response to infant cry play a foundational role in child development. Employing a gene × environment (G × E) approach, this study investigated the interaction of genetic polymorphisms of the serotonin transporter gene (5-HTTLPR) and oxytocin receptor genes (OXTR; rs53576, rs2254298) with early parental care experiences in influencing adults' implicit associations to infant cry. Eighty nulliparous adults (40 females, 40 males) responded to the Parental Acceptance-Rejection Questionnaire (PARQ), a measure of early care experiences, and participated in a Single Category Implicit Association Task (SC-IAT) to measure implicit associations to infant cry. Independent of parental experience, the valence of the implicit response to infant cry is associated with the serotonin transporter gene polymorphism (5-HTTLPR), with LL-carriers showing more positive implicit associations than S-carriers. OXTR rs53576 moderated the relation between parental rejection and implicit appraisal of infant cry: A-carriers who experienced negative early care showed an implicit positive appraisal of infant cry, whereas in GG carriers, positive early care experiences were associated with an implicit positive reaction to infant cry. OXTR rs2254298 had no relation to implicit associations to infant cry or to early care experiences. These findings cast light on the possible interplay of genetic inheritance and early environment in influencing adults' responses to infant cry that may be incorporated into screening protocols aimed at identifying at-risk adult-infant interactions.

Towards a neural model of infant cry perception

Previous work suggests that infant cry perception is supported by an evolutionary old neural network consisting of the auditory system, the thalamocingulate circuit, the frontoinsular system, the reward pathway and the medial prefrontal cortex. Furthermore, gender and parenthood have been proposed to modulate processing of infant cries. The present meta-analysis (N = 350) confirmed involvement of the auditory system, the thalamocingulate circuit, the dorsal anterior insula, the pre-supplementary motor area and dorsomedial prefrontal cortex and the inferior frontal gyrus in infant cry perception, but not of the reward pathway. Structures related to motoric processing, possibly supporting the preparation of a parenting response, were also involved. Finally, females (more than males) and parents (more than non-parents) recruited a cortico-limbic sensorimotor integration network, offering a neural explanation for previously observed enhanced processing of infant cries in these sub-groups. Based on the results, an updated neural model of infant cry perception is presented.

Neuromodulation of maternal circuits by oxytocin

Motherhood in mammals involves tremendous changes throughout the body and central nervous system, which support attention and nurturing of infants. Maternal care consists of complex behaviors, such as nursing and protection of the offspring, requiring new mothers to become highly sensitive to infant needs. Long-lasting neural plasticity in various regions of the cerebral cortex may enable the perception and recognition of infant cues, important for appropriate caregiving responses. Recent findings have demonstrated that the neuropeptide oxytocin is involved in a number of physiological processes, including parturition and lactation and dynamically shaping neuronal responses to infant stimuli as well. Here, we review experience-dependent changes within the cortex occurring throughout motherhood, focusing on plasticity of the somatosensory and auditory cortex. We outline the role of oxytocin in gating cortical plasticity and discuss potential mechanisms regulating oxytocin release in response to different sensory stimuli.

The credibility of acted screams: Implications for emotional communication research

Researchers have long relied on acted material to study emotional expression and perception in humans. It has been suggested, however, that certain aspects of natural expressions are difficult or impossible to produce voluntarily outside of their associated emotional contexts, and that acted expressions tend to be overly intense caricatures. From an evolutionary perspective, listeners' abilities to distinguish acted from natural expressions likely depend on the type of expression in question, the costs entailed in its production, and elements of receiver psychology. Here, we investigated these issues as they relate to human screams. We also examined whether listeners' abilities to distinguish acted from natural screams might vary as a function of individual differences in emotional processing and empathy. Using a forced-choice categorization task, we found that listeners could not distinguish acted from natural exemplars, suggesting that actors can produce dramatisations of screams resembling natural vocalisations. Intensity ratings did not differ between acted and natural screams, nor did individual differences in emotional processing significantly predict performance. Scream duration predicted both the probability that an exemplar was categorised as acted and the probability that participants classified that scream accurately. These findings are discussed with respect to potential evolutionary implications and their practical relevance to future research using acted screams.

Prenatal and postnatal cortisol and testosterone are related to parental caregiving quality in fathers, but not in mothers

Testosterone and cortisol have both been implicated in human parenting behavior. We investigated the relations between observed quality of caregiving during parent-child interactions and pre- and postnatal testosterone and cortisol levels, in both mothers (N = 88) and fathers (N = 57). Testosterone and cortisol were measured before and after interaction with an infant simulator (prenatal) and with their own child (postnatal) to index basal levels as well as steroid reactivity to the interaction. Our findings are that in fathers, interactions between cortisol and testosterone are related to quality of caregiving both pre- and postnatally. Prenatally there was a stronger negative relation between T and quality of caregiving in fathers with lower cortisol levels, and postnatally there was a stronger negative relation between cortisol and quality of caregiving in fathers high in testosterone levels. Furthermore, prenatal cortisol levels were related to paternal quality of caregiving during interaction with their own child. In mothers, no associations between quality of caregiving and our endocrine measures were observed. We interpret our findings in the context of hyperreactive physiological responses observed in parents at risk for insensitive caregiving, and in light of the dual-hormone hypothesis. The current findings contribute to the growing literature on the endocrine antecedents of human caregiving behavior.

Why Only Humans Shed Emotional Tears : Evolutionary and Cultural Perspectives

Producing emotional tears is a universal and uniquely human behavior. Until recently, tears have received little serious attention from scientists. Here, we summarize recent theoretical developments and research findings. The evolutionary approach offers a solid ground for the analysis of the functions of tears. This is especially the case for infant crying, which we address in the first part of this contribution. We further elaborate on the antecedents and (intra- and interpersonal) functions of emotional tears in adults. The main hypothesis that emerges from this overview is that crying evolved as an emotional expression that signals distress and promotes prosocial behaviors in conspecifics. Further, shedding tears may influence the mood of the crier and his/her outlook on life primarily as a consequence of fulfillment of the proposed signaling function of tears. We also describe how cultural phenomena such as ritual weeping nicely fit within this framework, as they often aim to support a request for help to a powerful person or deity and promote social bonding.

Putting salient vocalizations in context: Adults' physiological arousal to emotive cues in domestic and external environments

Salient vocalizations are automatically processed and distinguished from emotionally irrelevant information. However, little is known of how contextual, gender and attentional variables interact to modulate physiological responses to salient emotive vocalizations. In this study, electrocardiogram (ECG) was utilized to investigate differences in peripheral nervous activity of men and women to infant cry (IC), infant laughter (IL) and adult cry (AC) in two different situational contexts: the domestic environment (DE) and the outside environment (OE). As the mental state of listeners can affect their response to vocalizations, a between-subject design was applied: one group was instructed to imagine being inside the scenes (Task 1: explicit task), and the other group was told to look at the scenes (Task 2: implicit task). Results revealed that females exhibited lower inter-beat interval (IBI) index in the OE condition, as compared to both males in OE and females in DE conditions, suggesting greater physiological arousal amongst females in response to vocalizations in an outside environment. Additionally, Task 1 revealed that males demonstrated higher Low Frequency/High Frequency (LFHF) index towards AC than IL. Task 2 showed the same association between these two sounds in females. The implicit task also elicited lower LFHF index in response to both IL and IC than control sound (CS), only amongst females. Findings highlight the important roles that contextual information and cognitive demand play in regulating physiological responses to salient emotive vocalizations. Integrated perspectives of physiological responses to emotive vocalizations that consider the influence of internal (adult mental states) and external (environment) contextual information will provide a better understanding of mechanisms underlying emotional processing of salient social cues.

Infant colic: mechanisms and management

Infant colic is a commonly reported phenomenon of excessive crying in infancy with an enigmatic and distressing character. Despite its frequent occurrence, little agreement has been reached on the definition, pathogenesis or the optimal management strategy for infant colic. This Review aims to delineate the definitional entanglement with the Rome IV criteria, which were published in 2016, as the leading, most recent diagnostic criteria. Moreover, neurogenic, gastrointestinal, microbial and psychosocial factors that might contribute to the pathophysiology of infant colic are explored. This Review underlines that a comprehensive medical history and physical examination in the absence of alarm symptoms serve as guidance for the clinician to a positive diagnosis. It also highlights that an important aspect of the management of infant colic is parental education and reassurance. Management strategies, including behavioural, dietary, pharmacological and alternative interventions, are also discussed. Owing to a lack of large, high-quality randomized controlled trials, none of these therapies are strongly recommended. Finally, the behavioural and somatic sequelae of infant colic into childhood are summarized.

Enhanced Sensitivity to Angry Voices in People with Features of the Broader Autism Phenotype

The present study examined whether the ability to recognize vocal emotional expressions is negatively related to features of the Broader Autism Phenotype (BAP) in the general population. We assessed 61 typically developing adults on a BAP self-report measure (Broader Autism Phenotype Questionnaire) and a purpose-developed online emotion recognition task for efficient delivery of non-linguistic vocal stimuli corresponding to the six basic emotions. Contrary to expectations, we found that higher self-ratings of rigid BAP traits correlated with better recognition accuracy and higher intensity ratings for angry voices. We interpret this anger-specific association as an advantage for enhanced threat detection in the BAP and discuss this finding in the broader context of personality research and interpersonal theory.

Computational Analysis of Neonatal Mouse Ultrasonic Vocalization

Neonatal vocalization is structurally altered in mouse models of autism spectrum disorder (ASD). Our published data showed that pup vocalization, under conditions of maternal separation, contains sequences whose alterations in a genetic mouse model of ASD impair social communication between pups and mothers. We describe details of a method which reveals the statistical structure of call sequences that are functionally critical for optimal maternal care. Entropy analysis determines the degree of non-random call sequencing. A Markov model determines the actual call sequences used by pups. Sparse partial least squares discriminant analysis (sPLS-DA) identifies call sequences that differentiate groups and reveals the degrees of individual variability in call sequences between groups. These three sets of analyses can be used to identify the otherwise hidden call structure that is altered in mouse models of developmental neuropsychiatric disorders, including not only autism but also schizophrenia. © 2018 by John Wiley & Sons, Inc.

Human infancy and parenting in global perspective: specificity

We address three long-standing fundamental questions about early human development and parental caregiving within a specificity framework using data from 796 infant-mother dyads from 11 societies worldwide. Adopting a cross-society view opens a vista on universal biological origins of, and contextual influences on, infant behaviours and parenting practices. We asked: how do infant behaviours and parenting practices vary across societies? How do infant behaviours relate to other infant behaviours, and how do parent practices relate to other parent practices? Are infant behaviours and parent practices related to one another? Behaviours of firstborn five-month infants and parenting practices of their mothers were microanalysed from videorecords of extensive naturally occurring interactions in the home. In accord with behavioural specificity, biological expectations and cultural influences, we find that infants and mothers from diverse societies exhibit mean-level society differences in their behaviours and practices; domains of infant behaviours generally do not cohere, nor do domains of maternal practices; and only specific infant behaviours and mother practices correspond. Few relations were moderated by society.

Neurobiology of culturally common maternal responses to infant cry

This report coordinates assessments of five types of behavioral responses in new mothers to their own infants' cries with neurobiological responses in new mothers to their own infants' cries and in experienced mothers and inexperienced nonmothers to infant cries and other emotional and control sounds. We found that 684 new primipara mothers in 11 countries (Argentina, Belgium, Brazil, Cameroon, France, Kenya, Israel, Italy, Japan, South Korea, and the United States) preferentially responded to their infants' vocalizing distress by picking up and holding and by talking to their infants, as opposed to displaying affection, distracting, or nurturing. Complementary functional magnetic resonance imaging (fMRI) analyses of brain responses to their own infants' cries in 43 new primipara US mothers revealed enhanced activity in concordant brain territories linked to the intention to move and to speak, to process auditory stimulation, and to caregive [supplementary motor area (SMA), inferior frontal regions, superior temporal regions, midbrain, and striatum]. Further, fMRI brain responses to infant cries in 50 Chinese and Italian mothers replicated, extended, and, through parcellation, refined the results. Brains of inexperienced nonmothers activated differently. Culturally common responses to own infant cry coupled with corresponding fMRI findings to own infant and to generic infant cries identified specific, common, and automatic caregiving reactions in mothers to infant vocal expressions of distress and point to their putative neurobiological bases. Candidate behaviors embedded in the nervous systems of human caregivers lie at the intersection of evolutionary biology and developmental cultural psychology.

Young females at risk while driving with a small child

INTRODUCTION

Previous research suggests that young mothers with little driving experience are at risk when driving with a small child passenger. In this study we examined the prevalence, characteristics and risk of fatal motor vehicle crashes involving an infant passenger under the age of one among female drivers of different ages.

METHODS

We used crash data from the US Fatality Analysis Reporting System for 1994-2013. The prevalence of fatal crashes involving infants was examined by age of female drivers and compared to the number of births among mothers of a similar age. The essential characteristics of the crashes were described, and the odds of being at fault were determined for young (16-24-year-olds) and older female drivers (25-39-year-olds) with an infant passenger or with no passengers.

RESULTS

The prevalence of fatal crashes involving infant passengers was higher among young female drivers in relation to the number of births among mothers of a similar age than among older females. Young female drivers with an infant passenger were more often at fault than older drivers (aOR=1.83, 95%, CI=1.52, 2.20). Their vehicles were older and smaller and they used proper safety seats for infants less often than the older drivers. In addition, young female drivers with an infant passenger but with no adult passenger in the vehicle were more often at fault than young female drivers with no passengers (aOR=1.27, 95% CI=1.06, 1.51). Both young and older female drivers' crashes involving an infant passenger typically occurred in ordinary driving conditions, but these drivers with infant passengers were more often reported as having fallen asleep or inattentive than those with no passengers. The presence of an adult passenger in addition to an infant passenger lowered female drivers' odds of being at fault, regardless of the driver's age.

CONCLUSIONS

Young females driving with an infant passenger, probably most often mothers, are at an elevated risk of a fatal crash, especially when they drive alone with an infant. The protective effect of an adult passenger suggests that another adult in the vehicle can assist the driver by taking care of the infant and enabling the driver to focus on driving.

A real world evaluation of a treatment for infant colic based on the experience and perceptions of 4004 parents

Infant colic (IC) is a common condition in young babies seen by primary care health professionals, especially health visitors. Nevertheless, the diagnostic criteria for IC are vague, which has resulted in a lack of clarity in published guidance on its causes and treatment. Credence has been given to alternative therapies, while health professionals are sceptical about the efficacy of over-the-counter treatments. Some 4004 parents of babies considered to have IC participated in this retrospective real world evidence study on the efficacy of a simeticone suspension in the treatment of IC. They were recruited via social media sources and were eligible for inclusion if their baby had received at least one dose of the simeticone suspension. Data were collected via an online questionnaire. The results showed that crying and discomfort-associated behaviour reduced and the babies' sleeping patterns improved following use of the suspension. More than two-thirds (69.7%) of respondents, who either used the suspension on its own or alongside another treatment, reported improvements in the signs of IC within one day. Almost all (93.2%) considered that its use was associated with either complete resolution of IC or had some effect on symptoms.

Response to Infant Cry in Clinically Depressed and Non-Depressed Mothers

BACKGROUND

Bowlby and Ainsworth hypothesized that maternal responsiveness is displayed in the context of infant distress. Depressed mothers are less responsive to infant distress vocalizations (cry) than non-depressed mothers. The present study focuses on acoustical components of infant cry that give rise to responsive caregiving in clinically depressed (n = 30) compared with non-depressed mothers (n = 30) in the natural setting of the home.

METHODS

Analyses of infant and mother behaviors followed three paths: (1) tests of group differences in acoustic characteristics of infant cry, (2) tests of group differences of mothers' behaviors during their infant's crying, and (3) tree-based modeling to ascertain which variable(s) best predict maternal behaviors during infant cry.

RESULTS

(1) Infants of depressed mothers cried as frequently and for equal durations as infants of non-depressed mothers; however, infants of depressed mothers cried with a higher fundamental frequency (f0) and in a more restricted range of f0. (2) Depressed mothers fed, rocked, and touched their crying infants less than non-depressed mothers, and depressed mothers were less responsive to their infants overall. (3) Novel tree-based analyses confirmed that depressed mothers engaged in less caregiving during their infants' cry and indicated that depressed mothers responded only to cries at higher f0s and shorter durations. Older non-depressed mothers were the most interactive with infants.

CONCLUSIONS

Clinical depression affects maternal responsiveness during infant cry, leading to patterns of action that appear poorly attuned to infant needs.