Within-litter variance in early rat pup-mother interactions and adult offspring responses to novelty.

Siblings share similar genetics and environments, however, their behavior can be quite different. To determine if within-litter variance in neonatal-maternal interactions predict adult sibling behavioral variance, we observed mother-pup interactions during postnatal days 1-8 in four Sprague-Dawley rat litters and measured adult offspring behavioral responses to social and physical novelty. Our results indicate that pup and maternal behavior varied by at least twofold within each litter, and that specific pup behaviors within each litter (perioral contact) were associated with increased maternal licking. Furthermore, siblings that received more licks and made more perioral contact during postnatal days 1-8 had longer latencies to approach novel objects in adulthood than siblings that received less licking and made less perioral contact. This within-litter variance in postnatal mother and pup behavior and offspring adult behavior indicates that early social dynamics within families are an important area to examine to understand the development of sibling variance.

Toward a developmental model of child compliance: the role of emotion regulation in infancy.

The present study examined the relation between early emotion regulation and later compliance. When infants were 5, 10, and 18 months of age, they participated in a frustration task. The degree to which they reacted negatively to the stimuli and the behaviors they used to regulate that response were coded. Baseline heart rate also was recorded and a measure of cardiac vagal tone (VNA) was derived. Several tasks (electrode placement, toy clean-up, and test situation) were administered to elicit compliance/noncompliance when the participants were 30 months of age. Results revealed that infants who demonstrated low levels of regulatory behavior were more likely to be noncompliant as toddlers. Several interaction effects suggested that the prediction to later noncompliance was also dependent upon the infants' level of reactivity. Cardiac vagal tone also was related to compliance but in a contradictory fashion. High VNA was related to noncompliance to toy clean-up, whereas low VNA was related to noncompliance to electrode placement. The data provide support for a developmental model of compliance that includes the ability to regulate emotional arousal.

Sleep state and vagal regulation of heart period patterns in the human newborn: an extension of the polyvagal theory.

The influence of sleep state (i.e., active and quiet) on heart period, heart period variability, respiratory sinus arrhythmia (RSA), and the coupling between RSA and heart period was evaluated in 24 healthy full-term newborns. Electrocardiogram (ECG) data were collected, and sleep state was coded 1 hr after feeding until at least 10 min of data were collected in states of active and quiet sleep. ECG data were analyzed for the first five continuous minutes of each sleep state. Relative to active sleep, quiet sleep was associated with significantly higher amplitude RSA, lower heart period variability, and longer heart periods. Because RSA amplitude reflects the functional output of vagal pathways originating in the nucleus ambiguus, it was hypothesized that sleep state would influence how these vagal pathways regulate instantaneous changes in heart period. A new method, evaluating the instantaneous coupling of RSA and heart period, demonstrated that coupling was significantly greater during active sleep. The neurophysiological explanation extends the polyvagal theory to include potential cortical-brain stem connections.

Negative emotionality and cortisol during adolescent pregnancy and its effects on infant health and autonomic nervous system reactivity.

This research examined the relations among maternal emotionality, biology, and infant outcome and autonomic nervous system reactivity (cardiac vagal tone). The sample consisted of 27 pregnant adolescents and their 3-week-old infants. Measures of anxiety, depression, anger, and saliva cortisol were obtained from the adolescents both pre- and postnatally. Infant outcome measures consisted of gestational age at delivery, birth weight, number of risk factors at birth and at 24 hr, Apgar score at 1 and 5 min, abnormalities on newborn physical exam, number of resuscitation measures used on the infant, and cardiac vagal tone. Significant relations were found among the adolescent's emotionality, infant physical outcomes, and cardiac vagal tone. Higher concentrations of adolescent cortisol were associated with lower infant Apgar scores and an increased need for resuscitation measures performed on the infant. The positive association between negative emotions and better infant outcomes also was found and may reflect the sensitivity of the adolescents to their feelings and needs during pregnancy. Social support during pregnancy mediated the effects of maternal negative emotionality and infant cardiac vagal tone.

The effect of infant colic on maternal self-perceptions and mother-infant attachment.

Mothers of infants who developed colic were compared with mothers of non-colic infants on their perceptions of parenting self-efficacy, and separation anxiety as well as their attachment relationship with their infants. Colic was identified prospectively through telephone contacts with mothers. Questionnaires on self-efficacy and separation anxiety were completed when infants were 5 months of age. At 18 months of age mothers and infants (colic and non-colic) participated in a laboratory situation to measure attachment. Results revealed that mothers of colic infants reported feeling less competent as mothers. In addition, while mothers of colicky infants tended to have more separation anxiety than mothers of non-colic infants, they felt that these separations did not have a negative effect on their child. Finally, no differences were revealed for attachment classifications between colic and non-colic infants at 18 months.

Infants' responses to frustrating situations: continuity and change in reactivity and regulation.

We examined continuity, stability, and change in behaviors reflecting infant reactivity and regulation. Healthy infants were observed in laboratory situations designed to elicit frustration when they were 5 (N = 87) and 10 months of age (N = 82). Behaviors indicative of reactivity included objective ratings of average intensity cry, peak intensity cry, and latency to cry. In addition, durations of orienting, avoidant, and nonnegative communicative behaviors were assessed as measures of regulation at each age. Results showed that several behaviors changed in level over time. In addition, Confirmatory Factor Analysis revealed both structural continuity and discontinuity: Behaviors were organized into 2 similar factors at 5 and 10 months (Reactivity and Regulation), but the relation between reactivity and regulation became increasingly independent over time, such that reactivity and regulation were negatively correlated at 5 months but not at 10 months. Finally, model-fitting revealed cross-dimension but not within-dimension stability (5-month reactivity predicted 10-month regulation).

Psychophysiological correlates of infant temperament: stability of behavior and autonomic patterning from 5 to 18 months.

The stability of infant temperament and autonomic patterning (heart period and cardiac vagal tone) was examined longitudinally when infants were 5, 10, and 18 months of age. Behavioral measures of reactivity and regulation to frustration tasks, and maternal perceptions of infant temperament were obtained at each age along with baseline measures of cardiac activity. No stability was found from 5 to 10 months while some stability of behavior and autonomic patterning was identified from 10 to 18 months, with the exception of negative reactivity. High levels of cardiac vagal tone (V) were associated with negative reactivity at 18 months. When examining groups based on degrees of reactivity and regulation, we found infants who responded negatively to frustration but who also displayed more regulatory behavior to have higher V.

Linking employment to attachment: the mediating effects of maternal separation anxiety and interactive behavior.

This study examined the effects of maternal employment and separation anxiety on maternal interactive behavior and infant attachment. 73 mother-infant pairs participated in a laboratory free-play session when infants were 5 and 10 months of age and in the Strange Situation when the infants were 18 months of age. Maternal feelings about being separated from her infant were assessed by questionnaire at 5 months. Employed mothers returned to work before the infants' fifth month, and nonemployed mothers did not work outside the home through their infants' tenth month. Employed mothers who reported high levels of separation anxiety were more likely to exhibit intrusive behaviors at 10 months. While employment was not directly related to attachment, we found infants of high-anxiety employed mothers to develop anxious-avoidant attachments. The results suggest that maternal separation anxiety and interactive style may be important mediators between employment and later infant outcome.

Conditions of continuity and discontinuity in infant negative emotionality: newborn to five months.

This study investigated infant and caregiving-environment variables associated with continuity and discontinuity in infant negative emotionality between the newborn period and 5 months of age. Comparisons were made between groups of infants who evidenced similar levels of crying as neonates but differed by 5 months of age. For initially high-crying infants, mother personality traits, marital quality, and infant variables measured neonatally discriminated stable from changing infants. Ratings of mother sensitivity and infant responsiveness made at 5 months of age also related to continuity and discontinuity in negative emotionality over the first 5 months.