Slow weight gain in infancy is the core sign of failure to thrive. However, it is far from clear what the cause of the slow weight gain in infancy is. Failure to thrive is mostly identified late in the first year at which time it becomes problematic to ascertain its causes retrospectively. The current study was designed to investigate weight gain and behaviour in the early weeks of infancy in a prospective study. Seventy-five eight-week old infants were recruited according to their weight gain from birth to eight weeks, and classified as having slow, average or fast weight gain. Infants and their mothers were observed during two feeds. Mother-infant interaction and sucking behaviour were assessed. In addition, mothers completed questionnaires on the infant's temperament and behaviour (such as sleeping and crying), and on their own eating behaviour and adaptation to motherhood. All infants were followed up at six months and weighed again. The follow-up weight at six months allowed the identification of infants with failure to thrive as traditionally clinically defined. Six infants were identified as failing to thrive at six months, all of which had slow weight gain from birth to eight weeks. The behaviours measured through observation and the questionnaires were investigated in relation to weight gain from birth to eight weeks and six months. No significant relationship was found between weight gain and maternal adaptation, the mother's eating behaviour or infant behaviour. One sucking behaviour parameter estimate, pause length, end, was found to be significantly related to weight gain to eight weeks. This result however, was entirely attributable to the estimates of one infant. This infant had particularly poor sucking behaviour and very slow weight gain from birth to eight weeks. Infant temperament, and in particular the infant's level of fear was related to weight gain from birth to eight weeks. Infants with higher levels of fear were more likely to have slow weight gain. The length of the feed, from which the sucking behaviour was observed, was related to weight gain, with infants with long feeds being more likely to have slow weight gain.

Phonetic aspects of mother-infant interaction are discussed in light of a functionalist Mother-infant phonetic interaction (MIPhI) model. Adults addressing infants typically use a speech style (infant-directed speech, IDS) characterized by, for instance, extensive suprasegmental (prosodic) modulations. This type of speech seems to interest young infants whose active experience with the spoken language appears to focus their speech perception on the phonological properties of the ambient language during the first year of life. This thesis consists of four articles discussing phonetic modifications at the suprasegmental, segmental and phonological levels, based on data from six Swedish mothersí IDS to their 3-month-olds. The first study concerns the tonal word accent 2 in disyllabic words, and shows how the lexical, bimodal, tonal characteristics of this accent are enhanced in IDS as compared to adult-directed speech (ADS). The second is a cross-linguistic investigation of vowel formant frequencies in Swedish, Am. English and Russian IDS. It shows that vowels like /i/, /u/, and /a/ are more clearly separated in IDS than in ADS, in all three languages. The third study addresses the voiced /voiceless contrast in stop consonants as measured by voice onset time (VOT) and shows that stop consonants seem to be poorly separated in early IDS samples. The fourth study investigates the quantity distinction in V:C and VC: sequences and indicates that this phonological contrast is well maintained in the IDS. Adult data are discussed within the MIPhI model, assuming that suprasegmental and segmental specifications in IDS follow different phonetic specification paths adapted to the infantsí capacities as these develop over the first 18 months of life. The adultsí phonetic adaptations appear to reflect a selective strategy of presenting linguistic structure in a ìgift-wrappingî that is attractive and functional for the infant. / För att köpa boken skicka en beställning till exp@ling.su.se/ To order the book send an e-mail to exp@ling.su.se

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Orientador: Olga Maria Piazentin Rolim Rodrigues / Resumo: Compreender os processos envolvidos desde o início do desenvolvimento da linguagem tem sido o desafio de múltiplas áreas do conhecimento devido a sua complexidade e a gama de variáveis que podem estar correlacionadas. Para alguns estudiosos, as interações iniciais que o ser humano é exposto, desempenha papel fundamental no desenvolvimento de habilidades linguísticas. Culturalmente, a mãe está no cenário das primeiras relações com maior frequência e, por isso, acaba viabilizando mais oportunidades de interação com o bebê. Considerando assim, o presente estudo propôs-se a descrever e relacionar aspectos da interação mãe-bebê no desenvolvimento da linguagem expressiva e receptiva de bebês de três meses. Participaram deste estudo trinta mães e seus bebês com três meses que frequentam um serviço de acompanhamento do desenvolvimento infantil no primeiro ano de vida, em uma universidade pública do interior do estado de São Paulo. Para a avaliação da interação mãe-bebê, a díade foi filmada em situação estruturada em um episódio de três minutos. Para a avaliação das habilidades comunicativas foi utilizada a Escala de Desenvolvimento Bayley-III, contemplando apenas as áreas de Linguagem Expressiva e Linguagem Receptiva. As filmagens foram analisadas através da cotação de comportamentos interativos maternos e do bebê por segundo, utilizando o protocolo Interadíade. Os resultados demonstraram que, tanto as mães quanto os bebês, apresentaram maior frequência de comportamentos positivos na... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Understanding the processes involved since the beginning of language development has been the challenge of multiple areas of knowledge due to their complexity and range of variables that may be correlated. For some studies, the initial interactions that the human being is exposed plays a fundamental role in the development of language skills. Culturally, the mother is in the scene of the first relationships with more frequency and for this reason it ends up making viable more opportunities of interaction with the baby. Considering this, the present study aimed to describe and relate aspects of the mother-baby interaction in the development of expressive and receptive language of three-month-old babies. Thirty mothers and their three-month-old infants attending a child development follow-up service in the first year of life at a university in the interior of the state of São Paulo participated in this study. For the evaluation of the mother-baby interaction, the dyad was filmed in a structured situation in a three-minute episode. For the evaluation of communicative abilities, the Development Scale Bayley-III was used, considering only the areas of Expressive Language and Receptive Language. Filming was analyzed through the quotation of interactive maternal and baby behaviors per second. The results showed that both mothers and infants had a higher frequency of positive behaviors in the dyad. Babies had more mother-to-be-behaving behaviors with neutral or positive sounds, and m... (Complete abstract click electronic access below) / Mestre

Há décadas discute-se a importância da qualidade da interação mãe-bebê para um desenvolvimento saudável. Estudos têm demonstrado que prejuízos na interação mãe-filhote podem resultar em danos hormonais e comportamentais, além de desregulação emocional em diversos mamíferos. Estes dados sugerem adaptação evolutiva de mecanismos neurofisiológicos que mantém altos os níveis de comportamentos pró-sociais. Estudos com humanos evidenciaram que desde o nascimento, bebês apresentam habilidades que permitem a comunicação inicial por meio do olhar, voz, expressão facial, gestos e toque. O objetivo da Tese de Doutorado foi aprofundar conhecimento sobre a interação inicial por meio do estudo dos comportamentos da mãe e do recém-nascido imediatamente após o parto, em situação naturalística, e investigar a influência de procedimentos hospitalares, condições emocionais e sociais maternas, e das características físicas do bebê, além de averiguar as concentrações hormonais de cortisol e DHEA-s. Este estudo foi realizado em parceria com o Hospital Universitário da Universidade de São Paulo para a gravação de vídeos dos primeiros minutos de vida de 120 recém-nascidos e suas mães. A codificação do comportamento dos bebês considerou: choro, atividade motora, acalmar-se e permanecer de olhos abertos e, para a mãe, olhar para o bebê, falar com ele, tocá-lo de forma afetuosa e sorrir. A frequência dos comportamentos foi transformada em variáveis ordinais com base nos valores dos quartis. Regressões ordinais foram usadas com o intuito de prever a influência das variáveis de interesse na frequência dos comportamentos da díade. Adicionalmente, análises de variância foram usadas para investigar as concentrações hormonais de cortisol e DHEA-s em função das condições emocionais maternas e da frequência dos comportamentos. Os resultados apontaram contribuição importante dos procedimentos hospitalares em promover a interação inicial. Bebês nascidos de parto normal tiveram maior chance de apresentar atividade motora em comparação aos de parto fórceps e ao contrário do esperado os bebês que foram colocados em contato pele a pele com a mãe apresentaram menor chance de chorar em comparação aos que receberam este contato físico. A influência das condições emocionais maternas sobre os comportamentos justificou maior atenção e investimento no bem-estar das gestantes: piores condições emocionais foram preditores de maior frequência de choro do recém-nascido e mulheres que relataram conflito com o pai do bebê apresentaram menor chance de olhar e falar com o bebê. Os resultados apontaram diferenças relativas ao sexo, logo ao nascer: bebês do sexo masculino tiveram mais chance de chorar em relação aos de sexo feminino. As mães, por sua vez, mostraram mais chance de acariciar e falar com os bebês do sexo masculino. Maior concentração de cortisol foi observada em bebês filhos de mães em piores condições emocionais, sugerindo influência hormonal durante a gestação. Estes resultados evidenciaram o papel ativo dos indivíduos desde os primeiros momentos de vida e lançaram luz sobre as complexas interações que influenciam sua trajetória de desenvolvimento desde o nascimento, e possivelmente antes. Assistência à mãe, desde a gestação, salientou-se como ferramenta essencial para a saúde física e psicológica do indivíduo / The quality of early interaction plays a crucial role in child development. Findings from animal and human studies demonstrate hormonal, behavioral and emotional impairment as a result of an impoverished interaction. These results suggest an evolutionary adaptation of mechanisms to maintain high levels of prosocial behaviors. Babies communicate from birth, through gaze, voice, facial expression, gestures, and touch. The aim of the Ph.D. thesis was to improve knowledge of initial interaction through the study of the mother and infant behavior immediately after birth in a naturalistic situation and to investigate the influence of hospital procedures, emotional and social conditions from the mother, infant characteristics as well as average hormonal concentrations of cortisol and DHEA-s. This study was conducted in association with the University of São Paulo Hospital in order to record videos from the first minutes of life of 120 newborns with their mothers. Behaviors were coded every ten seconds focused on: a) infant: motor activity, cry, soothing and open eyes; b) mother: affectionate touch, smile, talking and looking at the baby. The frequency of each behavior was converted into quartiles. Multiple ordinal regressions were performed to predict independent variables and analyses of variances were performed to investigate mean differences of hormonal concentrations. The results pointed out an important contribution of the hospital procedures in promoting early interaction. In general, babies born by normal birth were more likely to show physical activity compared to those born by instrumental delivery, contrary to our initial hypothesis, infants that were not placed skin-to-skin on mothers chest were less likely to cry compared to those who had this skin contact. Worse maternal emotional state predicted increased frequencies of infants\' cry, highlighting the need to promote well-being during pregnancy. Women who reported conflict with the childs fathers showed less chance to look and talk to the baby in the delivery room. The analyses yielded differences at birth related to sex: male infants showed a greater chance of crying than females. Mothers, in turn, showed a greater chance of caressing and talking to male babies. Infants whose mothers were in worse emotional condition showed higher concentrations of cortisol, suggesting an influence from mothers hormones on the fetus during pregnancy. These results showed the active role of individuals from the first moment of their lives, shedding light on the complex interactions that influence their developmental trajectory since their birth. Thus, assistance to the mother during her pregnancy has been emphasized as an essential tool for her physical and psychological health

Mutual regulation of attention was investigated in a group of prenatally cocaine-exposed and non-exposed mother-infant dyads during a 5-minute videotaped free play session. Mutual regulation was measured using a state-based coding scheme designed to categorize dyadic interactions into three mutually exclusive and exhaustive states: maternal bid, mutual engagement, and non-involved. Results revealed no significant differences between cocaine-exposed and non-exposed dyads in overall amount of mutual engagement displayed. Cocaine-exposed dyads exhibited significantly longer mutual engagement episodes. Mothers in the two groups did not differ in the number or quality of bids for mutual engagement, and infants in both groups were equally responsive to maternal bids. No ecological variables were found to predict mutual engagement.

Early sensitive caregiver (typically mother)-infant interactions form an important foundation for infant development. When sensitive, mothers behave with the apparent goal to keep their infants happy and engaged. Mutual enjoyment is thought to motivate proximity and continued interactions. The main focus in the literature has been on the influence of stable/pathological maternal negative emotions on parenting, with parenting often assessed on one occasion, in an unnatural setting, or with a researcher present. The primary objective of this research was to explore what accounts for the variability in typical mothers’ sensitivity with their 15- to 28-week-old infants across interactions. Specific goals were to develop a novel methodology to increase the ecological validity and acceptability of assessments by having mothers themselves videotape their infant interactions in their homes, to explore the effect of mothers’ emotion states and fatigue on their ensuing sensitivity, and to evaluate if infant engagement determined whether mothers felt better (i.e., were reinforced) the more sensitively they behaved. A feasibility study was conducted with 9 mother-infant dyads, and a main study with an additional 40 dyads. Mothers completed a brief emotion and fatigue rating scale (Profile of Mood States – 15; Cranford et al., 2006) before and after each interaction, twice daily, over five to seven days. Interviews with feasibility study mothers indicated that most found the procedure acceptable, though not representative of their typical interactions. Little data were missing or uncodeable. Methodological changes are proposed to enhance the representativeness of observed interactions and to further minimize data loss. Contrary to predictions, pre-interaction emotion and fatigue states did not individually or jointly account for the significant within-subject variability in sensitivity across interactions. Mothers felt better after interacting and, the more sensitively they behaved, the more engaged their infants were, and the more positive mothers felt thereafter. However, infant engagement did not account for the relationship between sensitivity and how mothers then felt. Results suggest mothers can behave sensitively irrespective of how they feel; then, upon behaving sensitively, feel better regardless of their infants’ engagement. Interacting effects of maternal stress, cognitions, specific emotion behaviour relations, and methodology remain to be further investigated.

O estudo das interações iniciais entre mãe e bebê é fundamental para a compreensão da ontogênese humana (Seidl-de-Moura, et al., 2008) e para ajudar a promover a saúde relacional da díade. Nos estudos sobre as interações inicias entre mãe e bebê prematuro, ainda há um questionamento sobre se o nascimento prematuro e a internação em uma UTI-Neonatal fortalecem ou enfraquecem as trocas entre os membros da díade. Assim, neste estudo observou-se e analisou-se as interações iniciais entre mãe e bebê prematuro na UTI-Neonatal, observou o desenvolvimento das interações ao longo de dois meses, e comparou com interações de um grupo de mães-bebês nascidos a termo, de acordo com categorias predefinidas para a análise de vídeos. Também analisou, através de entrevistas, as características que as mães de cada tipo de díade relataram sobre seus filhos, bem como as metas de desenvolvimento apontadas e as emoções que expressaram em relação ao bebê. Participaram da pesquisa 20 díades mãe-bebê de nascidos a termo, e 20 díades de mãebebê de prematuros, nascidos entre 28 e 36 semanas de idade gestacional. Entre outras evidências, enquanto os bebês estavam na UTI-Neonatal, foram encontradas associações significativas entre as características maternas e as do bebê. Após a alta hospitalar, houve associações significativas entre a sincronia da díade e os comportamentos dos bebês. Não houve diferenças significativas entre as características de interações quando a díade estava na UTI-Neonatal e após dois meses. Não foram observadas diferenças significativas entre as díades de mães-bebês prematuros e mães-bebês a termo em relação à sincronia da díade, nem tampouco entre os comportamentos maternos nos dois momentos de observação, mas uma diferença significativa foi encontrada entre os comportamentos autorregulatórios dos bebês nascidos a termo e os dos prematuros. Verificou-se que para os dois grupos de mães, as emoções mais frequentemente relatadas foram as de amor e apego. As metas de desenvolvimento mais apontadas enquanto as mães estavam com seu bebê na UTI-Neonatal foram voltadas para o desenvolvimento físico do bebê, e quando os bebês estavam com dois meses, as metas eram mais voltadas para o desenvolvimento emocional, da mesma forma como ocorreu com as mães de bebês a termo. As características mais apontadas pelas mães ao pensarem em seus bebês enquanto eles estavam na UTI-Neonatal foram as físicas, enquanto após a alta, foram as pessoais e emocionais, assim como ocorreu com as mães de bebês nascidos a termo. Os resultados se contrapõem a afirmações de que em episódios de interação as mães de prematuros são menos sensitivas, mais intrusivas, e seus bebês, menos atentos e responsivos. Apontaram, ao contrário, para uma certa continuidade entre o que se observou na UTI-Neonatal e aos dois meses. Também não foram identificadas diferenças significativas na maioria das características de interações entre mães e bebês prematuros e mães e bebês nascidos a termo. Assim, tais resultados suavizam possíveis estigmatizações sobre estas mães e apontam a importância de se fortalecer essa relação na UTI-Neonatal através de estratégias de promoção de saúde. / The study of early interactions between mother and baby is fundamental to understanding human ontogeny (Seidl-de-Moura, et al., 2008) and to help promote the health of the relational dyad. In initial studies on the interactions between mothers and premature infants, there is still a question about whether premature birth and hospitalization in a neonatal intensive care unit strengthen or weaken the exchanges between members of the dyad. Thus, in this study we observed and analyzed the initial interactions between mother and premature baby in the neonatal intensive care unit, noted the development of interactions over two months, and compared with interactions of a group of mothers-term infants, according to predefined categories for the analysis of videos. Also examined, through interviews, features that mothers of each type of dyad reported on their children, as well as the development goals outlined and the emotions expressed in relation to the baby. Participants were 20 mother-infant dyads of term infants, and 20 mother-infant dyads in premature babies, born between 28 and 36 weeks gestational age. Among other evidence, while the babies were in the neonatal intensive care unit, significant associations were found between maternal characteristics and the baby. After hospital discharge, there were significant associations between dyadic synchrony and behavior of babies. There were no significant differences between the characteristics of interactions when the dyad was in the neonatal intensive care unit and after two months. There were no significant differences between dyads of mothers-term infants and mothers-preterm infants at term in relation to the timing of the dyad, nor between maternal behaviors in the two periods of observation, but a significant difference was found between the behaviors of autorregulatory in infants born at term and preterm infants. It was found that for both groups of mothers, the emotions most frequently reported were those of love and attachment. The goals of developing more pointed while mothers were with their baby in the neonatal intensive care unit were focused on the physical development of the infant, and when the infants were two months, the goals were more focused on emotional development, just as occurred with mothers of term infants. The characteristics most cited by the mothers think about their babies while they were in the neonatal intensive care unit were physical while after discharge, were the personal and emotional, as did mothers of term infants. The findings go against the claims that episodes of interaction in mothers of preterm infants are less sensitive, more intrusive, and their babies, less attentive and responsive. They pointed instead to a certain continuity between what was observed in the neonatal intensive care unit and two months. There were also no significant differences in most characteristics of interactions between mothers and premature babies and mothers and term infants. Thus, these results understate possible stigmatization on these mothers and indicate the importance of strengthening this relationship in the neonatal intensive care unit through health promotion strategies.

Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / Esta tese teve como objetivos: (I) propor uma articulação teórica para o estudo do sorriso contemplando a dimensão histórica, sociocultural e evolutiva da espécie humana e seu aparato biológico; (II) realizar dois estudos empíricos, um longitudinal, da terceira semana ao sexto mês de vida de dois bebês e outro transversal, com bebês de um, dois e cinco meses de nascidos, com o propósito de: (II.1) investigar se há algum padrão de sorrisos em termos de freqüência, duração e características morfológicas, e se ocorrem transformações nesse padrão nos seis primeiros meses de vida; (II.2) analisar padrões de sorriso apresentados na presença de comportamentos afetivos da mãe, nesse período; e (II.3) verificar se os bebês respondem de modo contingente, com sorrisos, aos comportamentos afetivos da mãe, e se há padrões diferenciados por tipo de sorriso. Participaram do estudo longitudinal duas díades mãe-bebê, filmadas em suas residências, semanalmente. Do estudo transversal, para cada grupo de diferentes idades, participaram vinte díades mãe-bebê, também filmadas em suas residências. As categorias de observação, comuns aos dois estudos, foram codificadas em duas partes, sendo a referente aos sorrisos do bebê com comportamentos mutuamente exclusivos e exaustivos. Os índices de Kappa de Cohen e de concordância indicaram boa fidedignidade entre os observadores. Entre outras evidências, verificou-se tendência de trajetória de curva ascendente para os sorrisos dos bebês no período estudado, F(1,22) = 6,77, p<0,05, para um dos bebês do estudo longitudinal, e, F(1,23) = 7,85, p<0,05, para o outro. Os dois bebês revelaram uma tendência particular a exibir com mais freqüência um ou dois tipos de sorrisos. Os sorrisos da mãe, como demais comportamentos afetivos, mostraram-se potenciais eliciadores de sorrisos de tipos variados nos bebês. Correlações significativas foram encontradas, na pesquisa longitudinal, entre os tipos mais freqüentes de sorrisos dos bebês e os sorrisos de suas mães (r=0,77, p<0,0017, para um dos bebês, e r=0,62, p<0,0017, para o outro). Também no estudo transversal foi verificada correlação entre o sorriso simples e o sorriso da mãe (r=0,70, p<0,0007). Sorrisos de diferentes tipos foram exibidos pelos bebês, tanto no estudo longitudinal, quanto no transversal, como respostas contingentes aos comportamentos maternos observados. Esses e outros resultados indicam uma associação significativa entre os sorrisos dos bebês e comportamentos afetivos das mães. A relevância da temática desse trabalho contrasta com a carência de estudos brasileiros sobre o tema. Entende-se que essa lacuna precisa ser superada, e esta tese representou um movimento nessa direção. / This doctoral dissertation had the following purposes: (I) to propose an approach to the study of smile that integrates a historical, socio-cultural and evolutionary, and biological dimmension; (II) to carry out two empirical studies, the first one longitudinal, reaching from the third week to the sixth lifes month of two babies, and the second one, a transversal studie, at the first, the second and the fifth months of life, with the proposition of: (II.1) to investigate any eventual standard of smile exibition in terms of frequency, duration and morfological characteristics, and any possible transformation in this standard during the first six months of life; (II.2) to analyze the smile standards observed in the presence of mothers affective behaviors during the first six months of life; and (II.3) to verify if the babies can answer contingently, with smiles, to the mothers affectives behaviors, and also if there are specific standards for each kind of smile. Two mothers and their babies participated in the longitudinal study and were videotaped at home. Twenty mothers and their babies participated, for each of the three groups of different ages in the transversal study, and were videotaped at home. The observation categories in these two studies are codified in two parts. The first part had mutually exclusive and exhaustive behaviors (babys smiles). The Cohens Kappa and the agreement indexes indicated good reliability inter observers. Among the evidences, it was verified a incrising curve trajetorial tendency for the babiess smiles in the period studied, F(1,22) = 6,77, p<0,05 for the first baby, and F(1,23) = 7,85, p<0,05 for the second one, both of them in the longitudinal study context. The two babies have revealed a particular tendency to frequentely display one or two kinds of smile. Babies also answered contingently with smiles to mothers affective behaviors in the two studies. In the longitudinal resourch, correlations between the more frequent kinds of the babies smiles and his mothers smiles were verified (r=0,77, p<0,0017 for one baby, and r=0,62, p<0,0017 for the other). In the transversal research, correlations between the simple smile and the mothers smile were verified (r=0,70, p<0,0007). Differents kinds of smiles have been exibited from the babies, in the both studies, longitudinal and transversal, as contigencial anwers to the mothers observed behaviors. This and others results sinalize to an association between the babies smile and his mothers affective behaviors. The relevance of investigating babiessmile contrats with the lack of Brazilian studies on this theme. This dissertation intended to contributeas an effort to supply this gap.

Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / Esta tese teve como objetivos: (I) propor uma articulação teórica para o estudo do sorriso contemplando a dimensão histórica, sociocultural e evolutiva da espécie humana e seu aparato biológico; (II) realizar dois estudos empíricos, um longitudinal, da terceira semana ao sexto mês de vida de dois bebês e outro transversal, com bebês de um, dois e cinco meses de nascidos, com o propósito de: (II.1) investigar se há algum padrão de sorrisos em termos de freqüência, duração e características morfológicas, e se ocorrem transformações nesse padrão nos seis primeiros meses de vida; (II.2) analisar padrões de sorriso apresentados na presença de comportamentos afetivos da mãe, nesse período; e (II.3) verificar se os bebês respondem de modo contingente, com sorrisos, aos comportamentos afetivos da mãe, e se há padrões diferenciados por tipo de sorriso. Participaram do estudo longitudinal duas díades mãe-bebê, filmadas em suas residências, semanalmente. Do estudo transversal, para cada grupo de diferentes idades, participaram vinte díades mãe-bebê, também filmadas em suas residências. As categorias de observação, comuns aos dois estudos, foram codificadas em duas partes, sendo a referente aos sorrisos do bebê com comportamentos mutuamente exclusivos e exaustivos. Os índices de Kappa de Cohen e de concordância indicaram boa fidedignidade entre os observadores. Entre outras evidências, verificou-se tendência de trajetória de curva ascendente para os sorrisos dos bebês no período estudado, F(1,22) = 6,77, p<0,05, para um dos bebês do estudo longitudinal, e, F(1,23) = 7,85, p<0,05, para o outro. Os dois bebês revelaram uma tendência particular a exibir com mais freqüência um ou dois tipos de sorrisos. Os sorrisos da mãe, como demais comportamentos afetivos, mostraram-se potenciais eliciadores de sorrisos de tipos variados nos bebês. Correlações significativas foram encontradas, na pesquisa longitudinal, entre os tipos mais freqüentes de sorrisos dos bebês e os sorrisos de suas mães (r=0,77, p<0,0017, para um dos bebês, e r=0,62, p<0,0017, para o outro). Também no estudo transversal foi verificada correlação entre o sorriso simples e o sorriso da mãe (r=0,70, p<0,0007). Sorrisos de diferentes tipos foram exibidos pelos bebês, tanto no estudo longitudinal, quanto no transversal, como respostas contingentes aos comportamentos maternos observados. Esses e outros resultados indicam uma associação significativa entre os sorrisos dos bebês e comportamentos afetivos das mães. A relevância da temática desse trabalho contrasta com a carência de estudos brasileiros sobre o tema. Entende-se que essa lacuna precisa ser superada, e esta tese representou um movimento nessa direção. / This doctoral dissertation had the following purposes: (I) to propose an approach to the study of smile that integrates a historical, socio-cultural and evolutionary, and biological dimmension; (II) to carry out two empirical studies, the first one longitudinal, reaching from the third week to the sixth lifes month of two babies, and the second one, a transversal studie, at the first, the second and the fifth months of life, with the proposition of: (II.1) to investigate any eventual standard of smile exibition in terms of frequency, duration and morfological characteristics, and any possible transformation in this standard during the first six months of life; (II.2) to analyze the smile standards observed in the presence of mothers affective behaviors during the first six months of life; and (II.3) to verify if the babies can answer contingently, with smiles, to the mothers affectives behaviors, and also if there are specific standards for each kind of smile. Two mothers and their babies participated in the longitudinal study and were videotaped at home. Twenty mothers and their babies participated, for each of the three groups of different ages in the transversal study, and were videotaped at home. The observation categories in these two studies are codified in two parts. The first part had mutually exclusive and exhaustive behaviors (babys smiles). The Cohens Kappa and the agreement indexes indicated good reliability inter observers. Among the evidences, it was verified a incrising curve trajetorial tendency for the babiess smiles in the period studied, F(1,22) = 6,77, p<0,05 for the first baby, and F(1,23) = 7,85, p<0,05 for the second one, both of them in the longitudinal study context. The two babies have revealed a particular tendency to frequentely display one or two kinds of smile. Babies also answered contingently with smiles to mothers affective behaviors in the two studies. In the longitudinal resourch, correlations between the more frequent kinds of the babies smiles and his mothers smiles were verified (r=0,77, p<0,0017 for one baby, and r=0,62, p<0,0017 for the other). In the transversal research, correlations between the simple smile and the mothers smile were verified (r=0,70, p<0,0007). Differents kinds of smiles have been exibited from the babies, in the both studies, longitudinal and transversal, as contigencial anwers to the mothers observed behaviors. This and others results sinalize to an association between the babies smile and his mothers affective behaviors. The relevance of investigating babiessmile contrats with the lack of Brazilian studies on this theme. This dissertation intended to contributeas an effort to supply this gap.