Fixed ratio and extinction performance of infants in the second year of life

Five 14(1/2)- to 19(1/2)-month-old infants were trained to lever press for snacks on small fixed ratio schedules of reinforcement. Within four to nine sessions, responding under FR 10 was established for four subjects and FR 15 for the other. Each subject's last session revealed behavioral patterns similar to animal and human FR trained subjects-a high and constant ratio rate, mixed with a zero rate following reinforcements. Deviations were mostly in the form of prolonged and variable post-reinforcement pauses. These and other irregularities were probably due to the limited deprivation conditions and improper training procedures in which the ratio (for two subjects) was ascended too early and too quickly. Extinction was instituted during the last session. The degree to which extinction performance matched that of other organisms depended upon how stable and "ratio-like" performance was during conditioning.     

The emergence of tool use during the second year of life

Despite a growing interest in the question of tool-use development in infants, no study so far has systematically investigated how learning to use a tool to retrieve an out-of-reach object progresses with age. This was the first aim of this study, in which 60 infants, aged 14, 16, 18, 20, and 22months, were presented with an attractive toy and a rake-like tool. There were five conditions of spatial relationships between the toy and the tool, going from the toy and tool being connected to there being a large spatial gap between them. A second aim of the study was to evaluate at what age infants who spontaneously fail the task can learn this complex skill by being given a demonstration from an adult. Results show that even some of the youngest infants could spontaneously retrieve the toy when it was presented inside and touching the top part of the tool. In contrast, in conditions with a spatial gap, the first spontaneous successes were observed at 18months, suggesting that a true understanding of the use of the tool has not been fully acquired before that age. Interestingly, it is also at 18months that infants began to benefit from the demonstration in the conditions with a spatial gap. The developmental steps for tool use observed here are discussed in terms of changes in infants' ability to attend to more than one item in the environment. The work provides insight into the progressive understanding of tool use during infancy and into how observational learning improves with age.     

An exploratory study of mother-child interaction during the second year of life

The aim of this study was to further understanding of development during the crucial second year of life. The study employed a naturalistic, semistructured situation for the observation of mother-child behavior. The experimental stimulus was the progressive diversion of the mother's attention away from her child. This diversion evoked separation anxiety in the child and the individual and interactive regulatory behaviors of the mother-child pair. Concurrently, the child's behavior was observed in a play group situation. One set of rating scales was devised for assessment of the mother-child interaction, and another set for assessment of the child's functioning in the play group. The major hypothesis was that maternal and child behaviors that foster the child's successful handling of phase-specific stresses and developmental tasks will be positively correlated with the child's functioning in the play group. This hypothesis is supported by the findings of the study.     

Memory reactivation in the second year of life

Memory reactivation has not been systematically studied with infants older than 1 year. Currently, three experiments examined the effects of a reactivation treatment (priming) on retention throughout the second postnatal year. Fifteen- and 18-month-olds learned an operant train task, forgot it, received a 2-min or 10-s prime, and later were tested for retention. Although the longer prime was effective for 15-month-olds, 18-month-olds required the shorter prime (Experiment 1). The memory was reactivated after delays two (18 months) and three (15 months) times longer than infants originally remembered it (Experiment 2). The reactivated memory was forgotten as fast as the original memory after the 2-min prime and twice as fast after the 10-s prime (Experiment 3). The fact that reactivation changes quantitatively but not qualitatively throughout infancy suggests that the same mechanism mediates it at all ages. These findings have major implications for the impact of early experience on cognitive development.     

Language specific prosodic preferences during the first half year of life: Evidence from German and French infants

There is converging evidence that infants are sensitive to prosodic cues from birth onwards and use this kind of information in their earliest steps into the acquisition of words and syntactic regularities of their target language. Regarding word segmentation, it has been found that English-learning infants segment trochaic words by 7.5 months of age, and iambic words only by 10.5 months of age [Jusczyk, P. W., Houston, D. M., & Newsome, M. (1999). The beginnings of word segmentation in English-learning infants. Cognitive Psychology, 39, 159–207]. The question remains how to interpret this finding in relation to results showing that English-learning infants develop a preference for trochaic over iambic words between 6 and 9 months of age [Jusczyk, P. W., Cutler, A., & Redanz, N. (1993). Preference for the predominant stress patterns of English words. Child Development, 64, 675–687]. In the following, we report the results of four experiments using the headturn preference procedure (HPP) to explore the trochaic bias issue in German- and French-learning infants. For German, a trochaic preference was found at 6 but not at 4 months, suggesting an emergence of this preference between both ages (Experiments 1 and 2). For French, 6-month-old infants did not show a preference for either stress pattern (Experiment 3) while they were found to discriminate between the two stress patterns (Experiment 4). Our findings are the first to demonstrate that the trochaic bias is acquired by 6 months of age, is language specific and can be predicted by the rhythmic properties of the language in acquisition. We discuss the implications of this very early acquisition for our understanding of the emergence of segmentation abilities.     

Working mother-infant interactions across the second year of life

Play interactions between 36 college-educated, middle-income, working mothers and their infants, who had attended nursery school since 1 month of age, were videotaped when the infants were 12, 18, and 24 months of age. The videotapes were coded for mother and infant looking at each other, vocalizing, affectionate play, and constructive play. Changes noted in the infants' play behaviors across this period included an increase in infant vocalizations and constructive play and a decrease in affectionate play. These results, together with corresponding decreases in the mothers' constructive and affectionate play behavior, suggest growing autonomy of the infants' play and encouragement of autonomy by the mothers. Stability of behaviors across this period and stability of relations between infant and mother behaviors were only moderate. Comparison of these data with data from a study by Clarke-Stewart and Hevey (1981) suggested greater frequency of interactive behavior among working mothers and their infants than among nonworking mothers and their infants.     

The Gesell developmental schedule in hispanic low-birth weight infants during the first year of life

The Gesell Schedule was administered to 143 low birthweight, high-risk, Hispanic infants of low-socioeconomic status to determine if this test was appropriate for this population. All but 5 were preterms, 73 females, 70 males. The infants were evaluated at 20 and 40 weeks corrected chronological age (CCA). The Gesell appears to be a useful developmental test for this population. Values for the overall developmental quotient (DQ) did not deviate from the Gesell norms, despite the infants' relatively poor growth pattern. Slight deviations from the norm in gross motor, fine motor, and language subscales were observed at 40 weeks CCA. Repeated measure analyses of variance revealed a significant decline in overall developmental, language, and fine motor quotients from 20 to 40 weeks. Birth-weight (BW) and small-for-gestational-age (SGA) categories influenced the outcome.     

Effects of tactile stimulation on low and very low birthweight infants during the first week of life

Thirty-one low and very low birthweight infants were given tactile stimulation during the first week of life. Compared with the control group of 35 they showed less weight loss. When stimulation was started within the first 48 hours, there was significantly less weight loss than when it was started in the interval 49 to 120 hours. Gratitude is due also to the High Wycombe General Hospital, the Ashford (Middlesex) Clinic, Queen Charlotte’s Hospital for Women, the South London Hospital, and particularly St. George’s Hosptial (Tooting) for support and for access to their facilities; without them, and the participation of the mothers and their babies, this work could not have been accomplished.     

Developmental changes in facial expressions of emotions in the strange situation during the second year of life

Infants' expressions of discrete emotions were coded during the more stressful episodes (4 through 8) of the Strange Situation at 13 and 18 months. The data showed a significant decrease in full-face expressions (more complex configurations of movements) and a significant increase in component expressions (simpler and more constrained patterns of movements). The authors interpreted this trend as a developmental change toward more regulated and less intense emotions. Consistent with this view, the aggregate index of infants' full-face negative emotion expressions, interpreted as reflecting relatively unregulated intense emotions, correlated significantly with maternal ratings of difficult temperament. The authors discuss alternative interpretations of the findings in terms of changes in reactivity/arousability and the emerging capacity for self-regulation.     

Infants in group care: their interactions with professional caregivers and parents across the second year of life

Seventy children were observed during structured play with their primary professional caregivers and three peers in the child care center and with their primary caregiving parents at home at 15 and 23 months of age. The same structured play tasks were used in the two settings and the quality of the children's interactions with caregivers and parents was rated using the same 7-point scales. As expected, the quality of caregiver–child interactions significantly increased between 15 and 23 months. At 15 months, the quality of caregiver–child interactions was significantly lower than the quality of parent–child interactions, particularly with regard to caregiver supportive presence and respect for the child's autonomy. At 23 months, however, the quality of caregiver–child interactions was no longer lower and in some respects even higher than the quality of parent–child interactions. At both ages, the children expressed more negativity towards their parents than towards their professional caregivers.     

Parent-child interaction during the first year of life in infants at elevated likelihood of autism spectrum disorder

Autism spectrum disorder (ASD) likely emerges from a complex interaction between pre-existing neurodevelopmental vulnerabilities and the environment. The interaction with parents forms a key aspect of an infant’s social environment, but few prospective studies of infants at elevated likelihood (EL) for ASD (who have an older sibling with ASD) have examined parent-child interactions in the first year of life. As part of a European multisite network, parent-child dyads of free play were observed at 5 months (62 EL infants, 47 infants at typical likelihood (TL)) and 10 months (101 EL siblings, 77 TL siblings). The newly-developed Parent-Infant/Toddler Coding of Interaction (PInTCI) scheme was used, focusing on global characteristics of infant and parent behaviors. Coders were blind to participant information. Linear mixed model analyses showed no significant group differences in infant or parent behaviors at 5 or 10 months of age (all ps≥0.09, d≤0.36), controlling for infant’s sex and age, and parental educational level. However, without adjustments, EL infants showed fewer and less clear initiations at 10 months than TL infants (p = 0.02, d = 0.44), but statistical significance was lost after controlling for parental education (p = 0.09, d = 0.36), which tended to be lower in the EL group. Consistent with previous literature focusing on parent-infant dyads, our findings suggest that differences between EL and TL dyads may only be subtle during the first year of life. We discuss possible explanations and implications for future developmental studies.     

Videotaping effects on the behaviors of low income mothers and their infants during floor-play interactions

Interaction behaviors and language measures of low income mothers and their 12-month-old infants were compared for floor-play situations in which the mother was aware and unaware of being videotaped. When the mothers were aware of being videotaped, they were more proximal to their infants, offered and demonstrated toys more frequently, engaged in more frequent interaction games, vocalized more frequently, emitted a greater number of words as well as declarative and imperative utterances, and their infants engaged in more constructive play. Combining the analysis of variance and correlational analyses results suggested that the verbal behaviors of mothers were inflated and their non-verbal behaviors were distorted when they were aware of being videotaped. The implications of these data for the use of videotaping as an assessment and intervention tool are discussed.     

Children's understanding of communicative intentions in the middle of the second year of life

Two tasks were administered to 40 children aged from 16 to 20 months (mean age = 18;1), to evaluate children's understanding of declarative and informative intention [Behne, T., Carpenter, M., & Tomasello, M. (2005). One-year-olds comprehend the communicative intentions behind gestures in a hiding game. Developmental Science, 8, 492–499; Camaioni, L., Perucchini, P., Bellagamba, F., & Colonnesi, C. (2004). The role of declarative pointing in developing a theory of mind. Infancy, 5, 291–308]. In the first task, children had to respond to the experimenter who pointed at a distal object; in the second task, children had to find a toy in a hiding game after the experimenter indicated the correct location either by pointing or by gazing. In the first task, most children responded to the declarative gesture by “commenting” on the pointed object instead of just looking; however, looking responses were more frequent than commenting responses. In the second task, children chose the correct location of the object significantly more frequently when the informative gesture was the point than when it was the gaze; moreover, there were significantly more correct choices than incorrect choices in the point but not in the gaze condition. Finally, no significant relation was found between tasks. Taken together, the findings support the view that infants’ developing understanding of communicative intention is a complex process in which general cognitive abilities and contextual factors are equally important.     

Generalization of deferred imitation during the first year of life

Infants first generalize across contexts and cues at 3 months of age in operant tasks but not until 12 months of age in imitation tasks. Three experiments using an imitation task examined whether infants younger than 12 months of age might generalize imitation if conditions were more like those in operant studies. Infants sat on a distinctive mat in a room in their home (the context) while an adult modeled actions on a hand puppet (the cue). When they were tested 24 h later, 6-month-olds generalized imitation when either the mat or the room (but not both) differed, whereas 9-month-olds generalized when both the mat and the room differed. In addition, 9-month-olds who imitated immediately also generalized to a novel test cue, whereas 6-month-olds did not. These results parallel results from operant studies and reveal that the similarity between the conditions of encoding and retrieval-not the type of task-determines whether infants generalize. The findings offer further evidence that memory development during infancy is a continuous function.     

A longitudinal examination of the transition to symbolic communication in the second year of life

Between 10 and 24 months of age, children progress from communicating through conventional signals to communicating through symbols in a variety of situations. The present study investigates this transition analysing mother–child communication frames and the child's communicative acts, and tracing the developmental changes in both frames and communicative acts. Four children (2 girls, 2 boys) and their mothers were observed longitudinally and extensively, from 10 to 24 months of age, using a multiple case‐study method. Through the detailed investigation of these single cases, clear developmental rajectories were found, showing that conventional frames and representational gestures ‘bridge’ the transition from attentional to symbolic communication. There were significant differences between dyads and children in the developmental trajectories for several frames and communicative acts. The results not only confirm previous findings on the development of verbal and gestural communication, but provide new insights into the transition to symbolic communication in the second year of life, first because of the use of frame analysis and second because of a focus on individual trajectories in development. Copyright © 2003 John Wiley & Sons, Ltd.     

Shared focus in mother—child joint activity in the second year of life

Shared focus between mother and child during joint activity was examined. Ten dyads were observed at 16 and 20 months. We found that the level of conventionality expressed by shared focus increases with age. The activity becomes more oriented towards the cultural aspects of the objects than to material aspects, and social games become more oriented towards symbolic and linguistic aspects than to practical ones. Moreover, we found that the content of the game influences the function of the child's utterances both at 16 and at 20 months. These results point to the cultural specification of joint activity, which can be viewed as mediating the development of intersubjectivity as well as individual behaviour.