Re-enactment of intended acts from a video presentation by 18- and 24-month-old children

We used the Re-enactment of intention paradigm to investigate whether children would re-enact what an adult intended to do in a video presentation as they do when presented with a live demonstration (Meltzoff in Dev Psychol 31(5):838-850, 1995). Unlike the 18-month-old infants studied by Meltzoff (Dev Psychol 31(5):838-850, 1995), the 18- and 24-month-olds in the current study did not frequently imitate unsuccessful goal-directed actions presented in a video model. Children who performed better in the task also tended to share more of their attention with the experimenter during co-viewing of the video. Performance on the Re-enactment of intention task was positively related to categorization score, an independent measure of cognitive functioning.     

Lexical stress and phonetic processing in word learning in 20- to 24-month-old English-learning children

To investigate the interaction between segmental and supra-segmental stress-related information in early word learning, two experiments were conducted with 20- to 24-month-old English-learning children. In an adaptation of the object categorization study designed by Nazzi and Gopnik (2001), children were presented with pairs of novel objects whose labels differed by their initial consonant (Experiment 1) or their medial consonant (Experiment 2). Words were produced with a stress initial (trochaic) or a stress final (iambic) pattern. In both experiments successful word learning was established when the to-be-remembered contrast was embedded in a stressed syllable, but not when embedded in unstressed syllables. This was independent of the overall word pattern, trochaic or iambic, or the location of the phonemic contrast, word-initial or -medial. Results are discussed in light of the use of phonetic information in early lexical acquisition, highlighting the role of lexical stress and ambisyllabicity in early word processing.     

Object retrieval through observational learning in 8- to 18-month-old infants

Observational learning was studied in 8-, 10-, 12-, 15- and 18-month-old infants. Using object-retrieval tasks of relatively comparable difficulty for each age group, we showed that between 10 and 12 months there is a change in the capacity to learn a new skill by observation.     

The production of bimanual percussion in 12- to 24-month-old children

Bimanual coordination represents a complex self-organizing system that is subject to both internal and contextual constraints. Although there has been interest in examining bimanual development throughout the lifespan, few data exist relative to the bimanual activity of children between 1 and 4 years of age. The study reported here represents an initial effort to address this gap. Twenty-seven children who were either 12, 18 or 24 months old were videotaped while drumming with sticks on a plastic drum. Two independent observers recorded bout length as well as number and phase relation of movement cycles within bouts. Kinematic analysis provided more detailed information about the timing and form of children's activity. Results indicate that bimanual drumming becomes preferred over unimanual drumming by 2 years of age, that the proportions of different phase relations exhibited by children change between 1 and 2 years of age, and that the behavior appears to go through periods of stability and variability within this age range. These results are discussed in the context of the child's physical development and interactions with the environment during this period.     

Foetal testosterone and vocabulary size in 18- and 24-month-old infants

Amniotic fluid, obtained from 87 pregnant women for routine amniocentesis, was analysed for foetal testosterone (FT) level. Their infants (40 girls and 47 boys) were followed up 18 and 24 months after birth and their vocabulary size was assessed. Girls were found to have a significantly larger vocabulary than boys at both ages. This replicates previous findings of a female advantage in language ability, but reveals this sex difference at the earliest point of development. Additionally, FT was an inverse predictor of vocabulary size when data from both sexes was examined together, but not within sex. The lack of a significant correlation between FT and vocabulary within each sex may reflect the relatively small sample size. However, the significant correlation between FT and vocabulary when the sexes were combined suggests FT might be involved in shaping the neural mechanisms underlying communicative development.     

Televised social interaction and object learning in 14- and 18-month-old infants

We examined object learning in infants who viewed a televised adult speaking about a novel toy in videos that varied in the social cues provided. Novelty preference in following test trials differed as a function of televised social cues in 18-month-old, but not 14-month-old infants.     

12- and 18-month-old infants follow gaze to spaces behind barriers

Infants follow the gaze direction of others from the middle of the first year of life. In attempting to determine how infants understand the looking behavior of adults, a number of recent studies have blocked the adult's line of sight in some way (e.g. with a blindfold or with a barrier). In contrast, in the current studies an adult looked behind a barrier which blocked the child's line of sight. Using two different control conditions and several different barrier types, 12- and 18-month-old infants locomoted a short distance in order to gain the proper viewing angle to follow an experimenter's gaze to locations behind barriers. These results demonstrate that, contra Butterworth, even 12-month-old infants can follow gaze to locations outside of their current field of view. They also add to growing evidence that 12-month-olds have some understanding of the looking behaviors of others as an act of seeing.     

Child and maternal correlates of impulse control in 24-month-old children

In two studies, we assessed the ability of 24-month-old children (N = 82) to delay a response to an attractive stimulus on a series of tasks administered by either the child's mother or a female adult stranger. In both studies, delay performance was consistent across tasks, but findings were inconsistent as to the effect on delay performance of a child's gender or the examiner's relationship to the child. Mothers' ratings of their children's personality predicted delay performance; superior performance was associated with low impulsivity, high attention span/persistence, and low sociability. Superior delay performance was also associated with low maternal directiveness as assessed on compliance tasks, and with mothers' encouragement of independence as assessed on a child-rearing attitude questionnaire.     

Generalization of equivalence relations from photos to objects by preschool children

Generalized equivalence classes are stimulus classes that consist of equivalent stimuli and other physically similar class‐member stimuli. The present study evaluated whether preschool children would form equivalence classes among photos of abstract objects (2D) and show equivalence generalization to the corresponding objects (3D), printed photos (2D stimuli), and to black‐and‐white drawn pictures (2D stimuli). Six typically developing children were taught arbitrary relations to establish three 3‐member equivalence classes with 2D stimuli presented on a computer screen. AB‐AC baseline relations (for half of the participants) and AB‐BC relations (for the other half) were taught using a multiple‐probe design to assess taught and tested relations. After class formation, three types of generalization probes were conducted: generalization to 3D stimuli, generalization between 2D (printed photos) and 3D stimuli, and generalization to drawn pictures (2D). All of the participants formed the equivalence classes. Two participants met the criterion for all three generalization probe types. Two participants presented mixed results across tests, and two participants did not exhibit equivalence generalization. The results demonstrated equivalence generalization from 2D to 3D stimuli in preschool children, although the variability across participants suggests that such generalization cannot be assumed a priori.     

Concurrent relations between inhibitory control,vocabulary and internal state language in 18- and 24-month-old Italian-speaking infants

The aim of this study was to investigate the concurrent relations between 18- and 24-month-olds' performance on tasks measuring inhibitory control, word production, and internal state vocabulary. Two tasks were used to measure inhibitory control, the Reverse Categorization task (a conflict task), and the Gift task (a delay task). Expressive vocabulary was assessed with the Italian version of the MacArthur Communicative Development Inventory (Words and Sentences), and internal state vocabulary was assessed with a checklist of 78 mental state terms adapted from the English Internal State Language Questionnaire. Expressive vocabulary was associated to Internal State Language and to the Reverse Categorization task, but not to the Delay task. Our findings document internal state language abilities in a sample of 61 Italian-speaking children, and show that internal state vocabulary is significantly and specifically related only to performance on the conflict measure of inhibitory control, even when vocabulary size is controlled for. Results of our study extend to an Italian sample of children previous findings on an early association between self-control and theory of mind and suggest that a link between inhibitory control processes and internal state language may be present at a very young age.     

Categorization of two-dimensional and three-dimensional stimuli by 18-month-old infants

In two experiments, 18-month-old infants’ categorization of 3D replicas and 2D photographs of the same animals and vehicles were compared to explore infants’ flexibility in categorization across different object representations. Using a sequential touching procedure, infants completed one superordinate and two basic-level categorization tasks with 3D replicas, 2D cut out photographs, or 2D images on photo cubes (“2D cubes”). For superordinate sets, 3D replicas elicited longer mean run lengths than 2D cut outs, and 3D replicas elicited equivalent mean run lengths as 2D cubes. For basic-level sets, infants categorized high-contrast animal sets when presented with 3D replicas, but they failed to categorize any of the 2D photograph sets. Categorization processes appear to differ for 3D and 2D stimuli, and infants’ discovery of object properties over time while manipulating objects may facilitate categorization, as least at the superordinate level. These findings are discussed in the context of infants’ representation abilities and the integration of perception and action.     

An examination of spontaneous pointing in 20- to 50-month-old children.

Occurrences of spontaneous pointing in 20-, 30-, 40-, and 50-mo.-old children were observed during the children's indoor or outdoor free-play periods. Observers recorded the sex of the pointer, the behavioral pattern observed, the reason for the point, the response of the adult, and the distance of the child from the adult at the time of a point. Analysis indicated a significant dip in the rate of pointing among the 30-mo.-olds while the 20- and 50-mo.-olds were observed to point most often. With the exception of the 30-mo.-olds, pointing was significantly more likely to be observed in boys. For all age groups, the point was used primarily to name. After 20 months adults were significantly less likely to respond to the point, and when they did respond they were more likely to name or demonstrate irrespective of the apparent reason for the child's point. Finally, the probability of adults' response appeared to be unrelated to the distance from the child to the adult, and further, the likelihood of an adult's response appeared to exert little influence on the rate of pointing. The results suggest that pointing may be an expressive act that can be used as a communicative gesture, but there was little evidence that any of these age groups were using the point as a ritualized gesture, that is, as an action conventionalized within the context of social interaction.     

Comparison of Egyptian and Canadian children on a picture apperception test

Individualism-collectivism theory predicted that Egyptian and Canadian children's performance would differ on relevant scales of the Roberts Apperception Test for Children (RATC). The RATC was administered to 34 Egyptian and 34 Canadian children ages 6-13 years. Canadian children scored higher on autonomy and lower on receiving support from others and parental limit setting. At older ages, Egyptian children manifested less rejection, desire for help from others, and aggression. There were no cultural differences in anxiety or depression and few differences on indicator and resolution scales related to understanding the task and resolving problems. The findings validated cross-cultural use of the RATC and demonstrated that the increasingly general theory of collectivism allowed meaningful predictions about personality and clinical traits.     

Long-term transfer of learning from books and video during toddlerhood

Television viewing and picture book reading are prevalent activities during toddlerhood, and research has shown that toddlers can imitate from both books and videos after short delays. This is the first study to directly compare toddlers' long-term retention rates for target actions learned from a video or book. Toddlers (N=158) at 18- and 24-months of age saw an experimenter demonstrating how to make a novel three-step toy rattle via a prerecorded video or a picture book. The toddlers' imitation of the target actions was tested after a specific delay (e.g., 2, 4 weeks), and their performance was compared with that of age-matched controls who did not see a demonstration. The 18-month-olds retained the target actions for 2 weeks, exhibiting forgetting at 4 weeks, whereas the 24-month-olds retained the information for up to 4 weeks, exhibiting forgetting at 8 weeks. Retention rates for books and videos did not differ at either age. These findings demonstrate very impressive retention from a brief two-dimensional media demonstration, and they contribute to our overall understanding of long-term memory processes during infancy.     

Communicative skills in relation to gender, birth order, childcare and socioeconomic status in 18-month-old children

Variation in communicative skills, defined as gestures, vocabulary comprehension and vocabulary production, was examined as a function of gender, birth order, childcare and socioeconomic status (SES) in 1,019 18-month-old children. The children were recruited at their regular check-up at a number of randomly selected Child Health Care centers in a Swedish county. The participation rate was 88%. The children were assessed by their mothers using a short version of the Swedish Early Communicative Development Inventories. The results demonstrate significant effects of gender and birth order on vocabulary comprehension and vocabulary production. Girls scored higher than boys and first-born children scored higher than later-born children. Type of childcare (family care, care at home and day-care centers) interacted with gender and birth order on vocabulary production and indicated that family care is not as advantageous as care at home or at day-care centers. SES had no effect on children's communicative skills at this age.     

18- and 24-month-olds' discrimination of gender-consistent and inconsistent activities

18- and 24-month-olds' ability to discriminate gender-stereotyped activities was assessed. Using a preferential looking paradigm, toddlers viewed male and female actors performing masculine and feminine-stereotyped activities. Consistent with our predictions, and previous research, 24-month-olds, but not 18-month-olds, looked longer at the gender-inconsistent activities than the gender-consistent activities. Results are discussed in terms of toddlers emerging gender stereotypes and perception of everyday events.     

Stability of deferred imitation in 12- to 18-month-old infants: A closer look into developmental dynamics

Deferred imitation is used to assess declarative memory in infants. Although a lot of studies show that infants from 6 months onwards are able to re-enact actions following a delay, only a few studies describe early declarative memory longitudinally. From a variable-centred approach, these studies found a modest relationship between measurement occasions that increases with age. However, no studies have analysed the differential aspect of memory development from a person-centred perspective. The present study analyses memory stabilities both from a variable-centred and person-centred approach within a sample of N = 87 infants of a 2-wave longitudinal design (12- and 18-month-olds). From a variable-centred perspective, the results indicate that, first, there was a significant increase in infants' memory performance and, second, that although reliable, the stability of infants' memory performance was relatively low. From a person-centred perspective two vs. three groups of infants were differentiated showing different developmental growth trajectories and stability correlations but no differences in language, cognitive and motor development. The implications of those results in terms of further test development are discussed. Furthermore, important methodological expansions for the analysis of infants' memory data are presented and discussed.