Relationships between regulatory temperament dimensions and self-regulatory behaviors at 4 and 6 months of age

Relationships between regulatory temperament dimensions and self-regulatory behaviors at 4 and 6 months of age

Infant Behavior & Development 38 (2015) 162–166 Contents lists available at ScienceDirect Infant Behavior and Development Brief report Relationshi...

380KB Sizes 1 Downloads 58 Views

Infant Behavior & Development 38 (2015) 162–166

Contents lists available at ScienceDirect

Infant Behavior and Development

Brief report

Relationships between regulatory temperament dimensions and self-regulatory behaviors at 4 and 6 months of age Tiziana Aureli a,∗ , Gabrielle Coppola a , Laura Picconi b , Annalisa Grazia a , Silvia Ponzetti a a b

Department of Neuroscience, Imaging and Clinical Sciences, University of Chieti-Pescara, Chieti, Italy Department of Psychological, Human and Hearth Sciences, University of Chieti-Pescara, Chieti, Italy

a r t i c l e

i n f o

Article history: Received 16 March 2014 Received in revised form 4 August 2014 Accepted 11 December 2014 Available online 6 February 2015 Keywords: Regulatory functioning development Temperament–behavior relationships Early dyadic interactions

a b s t r a c t The present study focused on relationships between temperament and behavior in early regulation development. Unlike most studies on the topic, we observed infant behavior in a naturalistic playful situation rather than in experimental stressful procedure, and employed temperament measures uniquely reflecting regulatory dispositions rather than a global measure of reactivity. The infant’s self-regulatory behaviors were observed at 4 and 6 months during face-to-face interactions and regulatory dimensions were assessed at 4 months. We found that low intensity pleasure and soothability dimensions, related to the infant physical and social experience, respectively, significantly affected regulatory behavior and their influence showed to depend on the infant’s age, with the former dimension being influential at the earlier age and the latter being influential when the behavior was observed at the later age. Results are interpreted on the light of a dynamic view of regulation development. © 2015 Elsevier Inc. All rights reserved.

The ability to regulate attention, arousal and emotion starts to develop very early in human ontogeny and it is foundational for organizing individual adaptive functioning throughout life (Sameroff & Emde, 1989; Sroufe, 1996). It develops through the myriad of interactions with the primary caregiver which occur from the birth on and provide the infants with self- and other-generated resources for managing both the internal and external stimulations in a safe and controlled manner. A number of experimental procedures have been devised to investigate early regulatory behaviors. They include still-face (Mesman, van Ijzendoorn, & Bakermans-Kranenburg, 2009); arm restraint, toy-removal and plastic barrier task (BraungartRieker & Stifter, 1996; Buss & Goldsmith, 1998; Calkins, Dedmon, Gill, Lomax, & Johnson, 2002; Moscardino & Axia, 2006; Stifter & Braungart, 1995; Stifter & Spinrad, 2002); fear episodes (Buss & Goldsmith, 1998); stranger approach (Buss & Goldsmith, 1998; Mangelsdorf, Shapiro, & Marzolf, 1995); and competing demanding (Diener, Mangelsdorf, McHale, & Frosch, 2002). All of these procedures employ a distress-inducing episode, based on the assumption that, once an infant is faced with a negative affect, the behaviors that follow, and lead to the lowering of the distress level, can be regarded as reflecting regulatory functions. Although this assumption is plausible and has been capable of providing a broad range of validated procedures, it has had the effect of restricting the observation of regulatory behaviors to situations that occur quite infrequently in the infant’s ordinary life. How the infant regulates in contexts that approximate more to daily interactions needs to be investigated further (for a notable exception, see Miller, McDonough, Rosemblum, & Sameroff, 2002).

∗ Corresponding author. E-mail address: [email protected] (T. Aureli). http://dx.doi.org/10.1016/j.infbeh.2014.12.013 0163-6383/© 2015 Elsevier Inc. All rights reserved.

T. Aureli et al. / Infant Behavior & Development 38 (2015) 162–166

163

Temperament is generally thought of as reflecting constitutionally-based dispositions to cope with emotional arousal and therefore it has often been associated with regulatory behaviors. In particular, according to Rothbart’s psychobiologically oriented approach (Rothbart & Derryberry, 1981), two areas of infant functioning are involved: reactivity and self-regulation, the former concerning the emotional responses to the external environment and the latter concerning the recovery from distress. To better capture the most theoretically relevant dimensions in the above areas, the Infant Behavior Questionnaire (IBQ-R; Gartstein & Rothbart, 2003) has been construed as a revised version of a previous instrument (Rothbart, 1981). It includes 14 temperamental scales, four of them – i.e. low intensity pleasure, duration of orienting, cuddliness/affiliation, and soothability – loading on the so-called Regulatory factor, one of three overarching dimensions that were found to organize the factorial structure of the instrument (Gartstein & Rothbart, 2003). The influence of temperament on the infant’s capacity to deal with frustrating stimuli (Braungart-Rieker, Garwood, Powers, & Notaro, 1998; Calkins et al., 2002; Mangelsdorf et al., 1995; Tarabulsy et al., 2003) has been consistently demonstrated by a number of studies, with the more negative infants showing less self-comforting behaviors in stressful experimental procedures than easier infants. Temperament was also found to affect the quality of dyadic interactions since mothers are more intrusive when faced with difficult infants as well as poorly responsive to their communicative signals (Field, Adler, Vega-Lahr, Scafidi, & Goldstein, 1987; Mäntymaa, Puura, Luoma, Salmelin, & Tamminen, 2006; Szabó et al., 2008; van den Boom & Hoeksma, 1994). In both cases, the temperament’s effect on the infant’s and the mother’s behavior has been related to infant’s negative reactivity. How more specific dimensions, such as those associated with the regulatory factor identified by Gartstein and Rothbart (2003), impact regulatory behaviors needs to be detailed further. The present study fills a gap in the literature by observing the infant’s regulatory behaviors in naturalistic playful situations rather than in experimental stressful procedures, and by employing temperament measures uniquely reflecting regulatory dispositions rather than a global measure of reactivity. We expected to find relationships between temperament and behavior. In particular, soothability, which measures the infant’s disposition to reduce “fussing, crying, or distress when soothing techniques are used by the caregiver” (Gartstein & Rothbart, 2003, p. 72), could be strictly related to the infant’s ability to find regulatory strategies by him/herself when interacting with the mother. We also expected that the relationships between temperamental dimensions and regulatory behaviors would modify over time. In fact, some temperamental dispositions could be more influential at a later age than at an earlier one, due to a developmental change in the infant’s abilities to deal with internal and external reality. Plausible though the proposal might be, no hypothesis has been advanced. Nevertheless, we explored that issue by observing the infants longitudinally, at four and six months of age, i.e. in a period characterized by a dramatic increase of the infant’s skills in domains, such as attentional, motor and emotional, which are strictly related to regulatory development. Sixty-five mother–infant dyads attended the Baby Lab of the University of Chieti (Italy) twice, when the infant was four and six months old, and were videotaped when interacting in a three-minute face-to-face session. Mothers were recruited at the hospital of Chieti within two days of the baby’s birth and they were approached to obtain their agreement to participate. The mothers’ mean age was 34.05 years (SD = 4.74; range = 20–44), the average number of years of education was 15.31 (SD = 2.94; range = 8–18), and 74% (N = 48) of them were employed. For the infants, 48% were male (N = 31) and 71% (N = 46) were firstborns. All infants were born full-term and none of them had medical complications at birth, had experienced hospitalisations or had been diagnosed for medical or psychological delays/disorders. They all belonged to bi-parental Italian families, their mothers were their primary caregivers and their fathers were actively engaged in their care. Infant behaviors were analysed from the videotaped sessions by the following codes provided by Tronick et al. (2005) to capture self-regulatory behaviors during interaction: oral self-comforting (the infant sucks on or brings to the mouth their body, the strap of a chair, their clothing, or the mother’s hand or finger, to provide self-stimulation), self-clasp (the infant’s two hands are touching, clasped together), distancing (the infant attempts to increase their physical distance from the caregiver by turning and twisting away from them) and autonomic stress indicators (e.g., hiccups, spitting up). Since our infants showed no behaviors in the last two codes, at either four or six months of age, those codes were removed from the analysis. Inter-observer reliability was calculated on 20% of the entire data set. We assessed the agreement by the Interval by Interval index (IxI; Birkimer & Brown, 1979), which is typically used when behaviors can occur in the same interval, as in our case, and is based on the presence/absence of each code across each one-second interval. The agreement at four months was .99 for oral self-comforting and .98 for self clasp; the score at six months was 1.00 for both categories. Infant temperament was measured by means of the Infant Behavior Questionnaire-Revised (IBQ-R, Gartstein & Rothbart, 2003), which the mothers were asked to complete within a week after the first observational session, and to bring with them to the second session when the infant was six months old. As no official Italian version of the instrument was available at the time we began the study, we used our own version, which was derived from a translation and back translation of the original form (Picconi & Aureli, 2012). After validating the full form, we created a shorter form to make the instrument less demanding for the mothers. A new validation process was then undertaken, which produced an instrument with 103 items and 14 scales, the same as in the full version (Activity Level, Distress to Limitations, Fear, duration of orienting, Smiling and Laughter, High Intensity Pleasure, low intensity pleasure, soothability, Falling Reactivity/Rate of Recovery from Distress, cuddliness, perceptual sensitivity, Sadness, Approach, and Vocal Reactivity). A factorial structure of the questionnaire was also computed, which resulted in accordance with the three-factor structure revealed by Gartstein and Rothbart (2003). In particular, Positive Affectivity/Surgency, Negative Emotionality, and Orienting/Regulatory Capacity included loadings for the same dimensions as in the original study. As exceptions, low intensity pleasure and duration of orienting were associated

164

T. Aureli et al. / Infant Behavior & Development 38 (2015) 162–166

Table 1 Pearson’s correlations between temperamental dimensions at 4 months and self-regulatory behavior in face to face interaction at 4 and 6 months of age.

Oral self-comforting Self-clasp

Cuddliness

Soothability

Low intensity pleasure

Duration of orienting

Perceptual sensitivity

.03 (.09) −.12 (−.16)

.08 (.26* ) −.08 (−.02)

.44** (.16) .05 (−.07)

−.07 (.12) −.04 (−.04)

.06 (.00) −.10 (.00)

Note. Correlations with measures at 4 months are out of brackets; those at 6 months are in brackets. ** p < .001. * p < .05.

with very small loadings on any factor, rather than being included in the third factor (Orienting/Regulation), and perceptual sensitivity loaded on the third factor rather than on the first (Surgency/Extraversion). The mothers involved in the present study completed the short 103-item instrument. Because of our interest in the infants’ regulatory strategies, only dimensions included in the Orienting/Regulation factor were considered. They were the following: cuddliness (the baby’s expression of enjoyment and moulding of the body when being held by a caregiver), soothability (the baby’s reduction of fussing, crying, or distress when soothing techniques are used by the caregiver), perceptual sensitivity (the baby’s detection of slight, low intensity stimuli from the external environment), low intensity pleasure (amount of pleasure or enjoyment related to low stimulus intensity, rate, complexity, novelty, and incongruity) and duration of orienting (the baby’s attention to and/or interaction with a single object for extended periods of time). All the above dimensions loaded on regulatory factor in both Garnstein and Rotbarth’ study (2003) and own our study or in either of them. We completed a preliminary test for possible differences on the temperamental and regulatory measures as a function of the infant’s gender. Since no differences were found, the main analyses were conducted on the whole sample, with no control on the gender effect. A set of Pearson correlation analyses (2-tailed) was first computed. We tested the associations between the five dimensions loaded on the orientation/regulation factor, i.e. cuddliness, soothability, duration of orienting, perceptual sensitivity and low intensity pleasure, assessed at four months of age, and proportional durations of the two selfregulatory behaviors of Oral Self-Comforting and Self Clasp, observed at both four months (M = .21, SD = .32; M = .26, SD = .35, respectively) and six months (M = .14, SD = .32; M = .08, SD = .25, respectively). In order to protect against capitalising of chance, the Bonferroni-corrected alpha level was used, according to the number of associations that were tested at each age for each of the two regulatory codes. We found that two temperamental dimensions, low intensity pleasure and soothability, correlated with a single regulatory behavior, oral self-comforting (see Table 1), the former correlation being significant when the behavior was observed at four months (r = .44, p < .000) and the latter one being significant when that behavior was observed at six months (r = .26, p < .05). In order to find whether age moderated the above associations, we then tested the differences between the coefficients for the associations of each temperamental dimension with oral self-comforting at both four and six months (see Baron & Kenny, 1986). In order to reject the null hypothesis concerning the equivalence of the two correlation coefficients, the coefficients were converted into z-scores using the Fisher r-to-z transformation. Then, making use of the sample size employed to obtain each coefficient, these z-scores were compared (Cohen & Cohen, 1983). As showed by Table 1, the correlation between low intensity pleasure and oral self-comforting observed at four months was significantly higher than the same correlation when behavior was observed at six months (z = 1.73, 1-tailed p = .04). No significant differences between the two ages were found for the soothability and oral self-comforting correlation (z = −1.04, 2-tailed p = .30; 1-tailed p = .15). Therefore, age worked as a significant moderating variable on the association between temperament and behavior when low intensity pleasure was considered. Given the above results two points seem to be worthy of consideration. First, the relationships between temperament and behavior appeared to be quite specific. Looking at the temperament side of that relationships, only two out of the five scales associated with the Regulatory factor were involved, i.e. soothability, as expected, and low intensity pleasure. With reference to Gartstein and Rothbart’s (2003) suggestion that self-regulation entails aspects that are addressed by different dimensions, the five regulatory scales might influence the infant behavior limited to the addressed aspect. In particular, perceptual sensitivity and duration of orienting, which concern the infant’s ability to notice slight external stimuli and to be attentive to the physical environment, respectively, involve the cognitive rather than the emotional side of the regulatory factor; the third dimension, cuddliness, which reflects the infant’s pleasure in being held by the caregiver, relates instead to the affiliativeness facet of temperament. Therefore, perceptual sensitivity, duration of orienting and cuddliness would likely affect regulation when the infants are involved in a physical-oriented or caring-oriented contexts, rather than in a stressful situation. On the other hand, low intensity pleasure and soothability, which are thought to reflect the infant’s enjoyment for playing or sitting quietly, as to the former dimension, and the infant’s propensity to reduce distress, as to the latter, apply to the emotional side of regulation. Therefore they can be particularly effective when the infants are presented with a negative affect, perhaps helping them to escape from the emotional arousal caused by an adverse situation, or to find strategies for controlling that emotion, respectively. Looking at the behavioral side of the temperament–behavior relationships, only the oral strategy was significantly affected by temperament. It may be that the relevance of the mouth for the psychobiological functioning in the first half of the first year of life makes the oral strategy more likely to be affected by constitutional features during that period than the manual strategy. That one would be influenced later in development, when the mouth will leave room for the hands, i.e. once the

T. Aureli et al. / Infant Behavior & Development 38 (2015) 162–166

165

hands become the primary medium of action. This finding, distinguishing oral and manual in regulatory development, is consistent with a previous study by Coppola, Aureli, Grazia, and Ponzetti (2010), which also showed a distinction between the two behaviors in affective development. They found that oral self-comforting and self clasp, both observed at four months during the still-face procedure, related to different attachment behaviors during the Strange Situation Procedure at 15 months (Ainsworth, Blehar, Waters, & Wall, 1978). With reference to the proposal advanced by Gianino and Tronick (1988) aimed at distinguishing the self- from the other-directed strategies in the infant regulatory repertoire, a further distinction could be thus suggested within the former group. Actually, oral and manual strategies, although both grounded in the self, seem to relate to different aspects of the infant’s psychological functioning, at both the individual (temperament) and interpersonal (attachment) level. The second point to discuss concerns the temperament–behavior relationships as a function of age. We found that both low intensity pleasure and soothability dimensions were associated with oral self-comforting, the former at four months and the latter at six months. It may be that low intensity pleasure, as expressing the tendency to appreciate soft and calm situations, helps the infants to self-regulate at an earlier age rather than later, since younger infants are less capable of dealing with highly exciting stimuli than older. Relationships between soothability and regulatory behaviors were expected, but proved to be effective only when oral self-comforting was observed at six months. It may be that the tendency to enjoy maternal support in the caring context at an earlier age helps the infant to regulate a few months later when interacting with the mother, in line with the infant’s growing abilities to manage the dyadic experience in that period compared to the previous one. Further research is needed to elucidate the reasons why the temperament–behavior association varies with age. In any event, age did matter, since low intensity pleasure affected behavior at an earlier age and soothability at a later age: indeed, in the former case, it operated as a moderating factor. Therefore, the evidence we found, although not conclusive on the role played by age in regulatory development, nevertheless provides some hints for undertaking that issue. According to a dynamic view of human development as a time-dependent outcome (Thelen & Smith, 1994; see also Lerner, 2002), age showed to act in the regulatory process not as a neutral background to the deployment of the infant skills, but as a variable intimately interwoven with those skills, and thus can be regarded as a key component of that process. This is one of the very few studies investigating the infant’s regulation development in an ordinary context. As the most intriguing result, we found that self-regulatory behaviors emerge during a playful face-to-face interaction. What events caused the need for the infant to regulate in an apparently non distressing situation cannot be revealed by our data and that is the major limitation of the study. To speculate, mismatches occurring in normal interactions (Weinberg and Tronick, 1996) would matter, since the temporary rupture of the interactional synchrony has been associated with the infant’s negative affect (Cohn and Tronick, 1987). However, maternal negativity towards the infants very rarely has been observed in typical samples; so what causes negativity in the infants cannot be easily referred to the mother’s adverse behavior. Actually, also positive bids, when excessive, could force the infants to adopt some strategies for adjusting in order to reduce the increase of the arousal, and therefore opposite behaviors could have the same disturbing effect. However, the timing of the maternal input instead of its content could act as the influencing factor: may be that an otherwise appreciated positive behavior occurring at the end of a specially exciting sequence leads the infant to get that time disturbed. Alternatively, internal factor could cause the infants to become troubled during interaction, since the age we observed falls in a developmental period especially critical for the attainment of regularities in the infant’s biological assessment. Contingency analyses might be helpful to investigate the issue and, given the dynamic of interaction, they would be especially informative if taking into account the position of a single turn with respect to the whole sequence and not only to the immediately preceding turn. To our knowledge, no study investigated that issue. Based on our results showing the occurrence of self-regulatory behaviors in the usual face-to-face interactions, new insights on the regulatory development could be gained by opening this research interest. References Ainsworth, M. D. S., Blehar, M. C., Waters, E., & Wall, S. (1978). Patterns of attachment: A psychological study of the strange situation. Hillsdale, NJ: Erlbaum. Baron, R. M., & Kenny, D. A. (1986). The moderator–mediator variable distinction in social psychological research: Conceptual, strategic, and statistical considerations. Journal of Personality and Social Psychology: 5., 1173–1182. http://dx.doi.org/10.1037/0022-3514.51.6.1173 Birkimer, J. C., & Brown, J. H. (1979). A graphical judgmental aid which summarizes obtained and chance reliability data and helps assess the believability of experimental effects. Journal of Applied Behavior Analysis: 12., (4), 523–533. Braungart-Rieker, J. M., & Stifter, C. A. (1996). Infants’ responses to frustrating situations: Continuity and change in reactivity and regulation. Child Development: 67., (4), 1767–1779. Braungart-Rieker, J., Garwood, M. M., Powers, B. P., & Notaro, P. C. (1998). Infant affect and affect regulation during the still-face paradigm with mothers and fathers: The role of infant characteristics and parental sensitivity. Developmental Psychology: 34., (6), 1428–1437. Buss, K. A., & Goldsmith, H. H. (1998). Fear and anger regulation in infancy: Effects on the temporal dynamics of affective expression. Child Development: 69., (2), 359–374. Calkins, S. D., Dedmon, S. E., Gill, K. L., Lomax, L. E., & Johnson, L. M. (2002). Frustration in infancy: Implications for emotion regulation, physiological processes, and temperament. Infancy: 3., (2), 175–197. Cohen, J., & Cohen, P. (1983). Applied multiple regression/correlation analysis for the behavioral sciences (2nd ed.). Hillsdale, NJ: Erlbaum. Cohn, J. F., & Tronick, E. (1987). Mother-infant face-to-face interaction: The sequence of diadi states at 3, 6, and 9 months. Developmental Psychology: 23., 68–77. Coppola, G., Aureli, T., Grazia, A., & Ponzetti, S. (2010). Relazioni fra dimensioni affettive e comportamenti regolatori nel primo anno di vita [Relationships between affect and regulatory behaviors in the first year of life]. Età evolutiva: 96., 51–63. Diener, M. L., Mangelsdorf, S. C., McHale, J. L., & Frosch, C. A. (2002). Infants’ behavioral strategies for emotion regulation with fathers and mothers: Associations with emotional expressions and attachment quality. Infancy: 3., (2), 153–174.

166

T. Aureli et al. / Infant Behavior & Development 38 (2015) 162–166

Field, T., Adler, S., Vega-Lahr, N., Scafidi, F., & Goldstein, S. (1987). Temperament and play interaction behavior across infancy. Infant Mental Health Journal: 8., (2), 156–165. Gartstein, M. A., & Rothbart, M. K. (2003). Studying infant temperament via the Revised Infant Behavior Questionnaire. Infant Behavior & Development: 26., 64–86. Gianino, A., & Tronick, E. Z. (1988). The mutual regulation model: The infant’s self and interactive regulation, coping, and defensive capacities. In T. Field, P. McCabe, & N. Schneiderman (Eds.), Stress and coping across development (pp. 47–68). Hillsdale, NJ: Erlbaum. Lerner RM. (2002). Concepts and theories of human development (3rd ed.). Mahwah, NJ: Erlbaum. Mangelsdorf, S. C., Shapiro, J. R., & Marzolf, D. (1995). Developmental and temperamental differences in emotion regulation in infancy. Child Development: 66., (6), 1817–1828. Mäntymaa, M., Puura, K., Luoma, I., Salmelin, R. K., & Tamminen, T. (2006). Mother’s early perception of her infant’s difficult temperament, parenting stress and early mother–infant interaction. Nordic Journal of Psychiatry: 60., (5), 379–386. Mesman, J., van IJzendoorn, M. H., & Bakermans-Kranenburg, M. J. (2009). The many faces of the still-face paradigm: A review and meta-analysis. Developmental Review: 29., 120–162. Miller, A. L., McDonough, S. C., Rosenblum, K. L., & Sameroff, A. J. (2002). Emotion regulation in context: Situational effects on infant and caregiver behavior. Infancy: 3., (4), 403–433. Moscardino, U., & Axia, G. (2006). Infants’ responses to arm restraint at 2 and 6 months: A longitudinal study. Infant Behavior & Development: 29., 59–69. Picconi, L., & Aureli, T. (2012). IBQ-R for 4-month-old Italian infants. Chieti scalo (I): Chieti-Pescara University (Unpublished Manuscript). Rothbart, M. K. (1981). Measurement of temperament in infancy. Child Development: 52., 569–578. Rothbart, M. K., & Derryberry, D. (1981). Development of individual differences in temperament. In M. E. Lamb, & A. L. Brown (Series Eds.) &, Advances in developmental psychology : vol. 1. (vol. 1) (pp. 37–86). Hillsdale, NJ: Erlbaum. Sameroff, A. J., & Emde, R. N. (1989). Relationship disturbances in early childhood. New York, NY: Basic Books. Sroufe, L. A. (1996). Emotional development: The organization of emotional life in the early years. Cambridge: Cambridge University Press. Stifter, C. A., & Braungart, J. M. (1995). The regulation of negative reactivity in infancy: Function and development. Developmental Psychology: 31., (3), 448–455. Stifter, C. A., & Spinrad, T. L. (2002). The effect of excessive crying on the development of emotion regulation. Infancy: 3., (2), 133–152. ´ M., van Aken, C., Verhoeven, M., van Aken, M. A. G., & Junger, M. (2008). The relations among child negative interactive behavior, child Szabó, N., Dekovic, temperament, and maternal behavior. Early Childhood Research Quarterly: 23., 366–377. Tarabulsy, G. M., Provost, M. A., Deslandes, J., St-Laurent, D., Moss, E., Lemelin, J. P., et al. (2003). Individual differences in infant still-face response at 6 months. Infant Behavior & Development: 26., 421–438. Thelen, E., & Smith, L. B. (1994). A dynamic systems approach to the development of cognition and action. Cambridge, MA: MIT Press. Tronick, E. Z., Messinger, D. S., Weinberg, M. K., Lester, B. M., Lagasse, L., Seifer, R., et al. (2005). Cocaine exposure is associated with subtle compromises of infants’ and mothers’ social-emotional behaviorand dyadic features of their interaction in the face-to-face still-face paradigm. Developmental Psychology: 41., (5), 711–722. van den Boom, D. C., & Hoeksma, J. B. (1994). The effect of infant irritability on mother–infant interaction: A growth-curve analysis. Developmental Psychology: 30., (4), 581–590. Weinberg, M. K., & Tronick, E. Z. (1996). Infant affective reactions to the resumption of maternal interaction after the still-face. Child Development: 67., 905–914.