Features of Interaction in Infant Twins

Social Interaction between a Pair of Infant Twins

The development of social competence was studied by observing the free-play behaviour of a pair of twin boys. Videotape recordings of monthly free-play sessions in a laboratory from age 8 months to 2 1/2 years were analysed according to a combination of Mueller and Lucas's stage categories of toddler interaction and Parten's levels of social participation. Previous findings regarding these stages were replicated in play with objects, with the first example of a co-operative sequence occurring at 22 months. However, non-object-centred sequences exhibited features of co-operative behaviour as early as 10 months. These sequences showed conversation-like vocal exchanges and distracting — consoling behaviour. It is suggested that when peers are completely familiar, they may be capable of a social competence which is not based on objects and which can therefore develop before skill with objects is likely.

Eight-Year Follow-up of Cognitive Development in 33 Twin Pairs

This is a follow-up study of twins, including 33 twinpairs from the Stockholm area, aiming to study the cognitive development of twins at eight years of age. The twins have been followed at different ages from birth onwards. All children were tested with the Wechsler Intelligence Scale for Children in a Swedish translation (WISC). The WISC test consists of a Verbal and a Performance Scale. There were no significant differences between twin girls and twin boys on these Scales. On the Performance subtests Block Design, Object Assembly, and Coding, however, the twin girls performed significantly better than the twin boys. In comparing cognitive development for twins and singletons, the twin group had somewhat lower average scores than the singletons. Prematurity and low birth weight continued to be related to cognitive development at eight years of age. Also at this age the school teacher completed a questionnaire about the twins social behaviour and some personality traits. There was a relation between one questionnaire factor, a low score of assertiveness, and the mother's negative or ambivalent expectations concerning the twin pregnancy. The twin group with the mother's negative expectations also had significantly lower results on the subtests Comprehension and Coding. Negative mothers had more premature twins than mothers who were positive toward the twin pregnancy.

Late language emergence in 24 month twins: Heritable and increased risk for LLE in twins

Purpose

This study investigated the etiology of Late Language Emergence (LLE) in 24-month-old twins considering possible twinning, zygosity, gender, and heritability effects for vocabulary and grammar phenotypes.

Method

A population-based sample of 473 twin pairs participated. Multilevel modelling estimated means and variances of vocabulary and grammar phenotypes, controlling for familiality. Heritability was estimated with DeFries-Fulker regression, and variance components models, to determine effects of heritability, shared-environment, and non-shared environment.

Results

Twins had lower average language scores than norms for singleborn children, with lower average performance for MZ than DZ twins, and lower for boys than girls, although gender and zygosity did not interact. Gender did not predict LLE. Significant heritability was detected for vocabulary (.26) and grammar phenotypes (.52/.43 for males/females) in the full sample, and in the sample selected for LLE (.42 and .44). LLE and the appearance of Word Combinations were also significantly heritable (.22-.23).

Conclusion

The findings revealed an increased likelihood of LLE in twin toddlers compared to singleborn children that is modulated by zygosity and gender differences. Heritability estimates are consistent with previous research for vocabulary and add further suggestion of heritable differences in early grammar acquisition.

Comparative Development of Surviving Co-Twins of Vanishing Twin Conceptions, Twins and Singletons

Early loss of one fetus in a multiple gestation as a ‘vanishing’ twin is a well recognized phenomenon. It is uncertain whether this has an impact on the development of the surviving co-twin. The aim of this study is to compare the development of singletons, twins and the surviving co-twins of a vanishing twin. The 324 children born to 229 women who were recruited into the study between 1999 and 2001 formed the study population. Children were assessed at 1 year of age with Griffiths Mental and Developmental Scales. A neurological examination was performed using an optimality score to exclude those with severe neurodisability. Three hundred and five children (92 singletons, 180 twins and 33 survivors with a vanishing twin) were included. The sub- and general quotient scores in singletons and surviving co-twins of a vanishing twin did not differ significantly. Twins had significantly lower scores than singletons in all areas of development and were more likely to be born early with lower birthweights. Following adjustment for gestation and birthweight, the difference between the two groups was nullified suggesting that the slower development of twins is related to their prematurity and lower birthweight.

Examining the Dimensions of Intimacy in Twin and Peer Relationships

While it is widely assumed that twinship involves high levels of intimacy to the detriment of other relationships, an examination of twinship using measures of intimacy has not yet been conducted. Participants were 214 individual twins (128 MZ, 62 DZ same-sex, and 24 DZ mixed-sex) between 16–73 years of age. Twins completed measures of intimacy in reference to their co-twin, their closest same-sex friend, and their closest other-sex friend. As expected, the highest level of intimacy was reported for the co-twin. Contrary to expectation, MZ twins did not report significantly higher levels of intimacy with their co-twin, or significantly lower levels of intimacy with their closest friends when compared to DZ same-sex or DZ mixed-sex twins. Furthermore, twins who reported high levels of intimacy with their co-twin did not report significantly lower levels of intimacy with their closest friends. Implications and directions for future research are discussed.

Twins Have Slightly Higher Self-Concepts Than Singletons in the Elementary School Period: A Study of South Korean Twins and Singletons

The twin method assumes that the trait under study is similar in twins and singletons so that the results from twin samples can be generalized to the singleton population. The purpose of the present study was to compare self-concept in twins and singletons matched in parental level of education. The 6 cluster scales of the Piers-Harris Children's Self-Concept Scale (P-H) were administered to 630 singleton children and 635 twins aged 7 to 12 years. Model-fitting analyses yielded two conclusions. First, self-concept was generally similar between first- and second-born twins and between monozygotic and dizygotic twins across the 6 cluster scales of the P-H. Second, twins consistently exceeded singletons for all 6 cluster scales of the P-H. However, the effect sizes of differences between twins and singletons were small except for one scale, Physical Appearance and Attributes.

Twin and Genetic Effects on Life Events

Twin studies that examine the effect of specific environmental risk factors on psychiatric disorders assume that there are no differences in prevalences of these risk factors between twins and singletons. Violation of this assumption signifies that the results from twin studies might not generalize to singletons. Another assumption, not only often underlying twin studies but also epidemiological research, is that life- events are not influenced by familial factors. We tested differences in prevalences of experienced life events in a Dutch sample of 2086 monozygotic (MZ) twins, 2090 dizygotic (DZ) twins and 1307 of their siblings. Self-reported data on life events (illness of self, illness of a significant other, spouse/romantic relationship, divorce/break-up of a relationship, death of a significant other, traffic accident, robbery, violent assault, sexual assault) were available from a survey- study. We further investigated whether familial resemblance was present for the exposure to these life events and, if so, whether this resemblance was due to genetic or common environmental factors. No differences were found in the prevalences of life events between MZ twins, DZ twins and their siblings. There was evidence for familial aggregation of all life events, except for traffic accidents in women. Results indicated genetic control on the presence of a spouse or involvement in a relationship. Familial resemblance of illness and death of a significant other was mainly due to common environment. For the other life events, it was not possible to distinguish between genetic and common environmental effects.

Twins as a natural experiment to study the causes of mild language delay: I: Design; twin-singleton differences in language, and obstetric risks

BACKGROUND

Twins tend to lag behind singletons in their language development, but the causes were unknown. The possibilities suggested include obstetric complications, twin-specific features, and postnatal differences in family interaction. The present study was designed to pit these alternatives against one another as possible causal influences.

METHOD

The Avon Longitudinal Study of Parents and Children (ALSPAC) was used to identify the 116 twin pairs (of whom 96 participated) and 114 pairs of singletons (of whom 98 participated) whose ages were no more than 30 months apart. The McArthur Communicative Development Inventory was completed at 20 months, and the Pre-School Language Scales (PLS-3), and the McCarthy Scales of Children's Abilities at 36 months. Obstetric and perinatal complications were assessed on the basis of detailed systematic parental reports, together with a systematic coded abstraction of all medical records dealing with pregnancy and the neonatal period. Family background details were assessed from parental reports, and the primary carer's verbal functioning was assessed by the Mill Hill Vocabulary Scale. Congenital anomalies were assessed using the method of Waldrop and Halverson.

RESULTS

The language of twins was 1.7 months below that of singletons at 20 months and 3.1 months at 3 years. The verbal cognitive score of twins was about half a standard deviation lower than that of singletons. The twin-singleton differences in language level were found tobe unassociated with obstetric/perinatal features as assessed from both parental reports and medical records, to birthweight or gestation, to birthweight discrepancy within the twin pair, or to congenital anomalies.

CONCLUSION

It is concluded that obstetric/perinatal features do not account for the slower language development in twins as compared with singletons, within a sample born after at least 33 weeks gestation.

Depression scale scores in 8-17-year-olds: effects of age and gender

BACKGROUND

The excess of unipolar depression in females emerges in adolescence. However, studies of age effects on depression scale scores have produced divergent estimates of changes from childhood to adolescence.

METHOD

We explored possible reasons for this discrepancy in two large, longitudinal samples of twins and singletons aged 8-17.

RESULTS

There were no differences between twins and singletons in their scores on the Short Mood and Feelings Questionnaire (SMFQ), a 13-item self-report depression scale. SMFQ scores for boys fell over this age-range, while those for girls fell from age 9 to age 11 and then increased from age 12 to age 17. The mean scores of girls under 12 and those 12 and over differed by only around one-fifth of a standard deviation. However, given the non-normal distribution of the scores, a cut point that selected the upper 6% of scores created the expected female:male ratio of 2:1.

CONCLUSIONS

Implications for future research on adolescent depression are discussed.

Heritability of poor language achievement among twins

In order to examine the basis of familial associations with poor language achievement, 62 twinship pairs and 3 sets of triplets were studied in which at least one member presented poor oral language status in the absence of other developmental or sensory impairments. Rates of concordance for poor language were compared between the monozygotic (MZ) and dizygotic (DZ) pairs. Concordance for the MZ pairs was .96, whereas it was .69 for the DZ pairs. The DeFries-Fulker method for computing heritability of extreme scores was employed yielding a h2g of .45. Similar results were obtained for those pairs containing only children with performance IQs above 85, but with at least one member having language below -1 SD. A comparison of DZ twins with singleton sibling pairs with at least one affected member and of similar age showed that DZ twins were more similar with respect to language achievement than singleton pairs. Thus, twinning appeared to have influenced twin resemblance among those where at least one member presented poor language achievement. These results support the hypothesis that genetic factors contribute to the liability of poor language achievement in children who do not present other developmental or sensory disorders.

Emotional availability in mother-twin dyads: effects on the organization of relationships

The term "emotional availability" has evolved primarily in therapeutic contexts where it refers to the sensitive engagement of the therapist in the patient's narrative of life experiences and openness to the patient's emotional expressions (Emde 1980). In the therapeutic situation, emotional availability refers to the quality of the therapist in supporting the growth or development of the patient. It is anticipated that the outcome of the therapeutic experience will include an enhanced capacity for reciprocal emotional availability with others.

Effects of early mother-twin relationships from birth to age 3, on twin bonding

Findings from an earlier phase of this research project clearly pointed to the mother's psychological adaptation inherent to the specificities of triadic interaction. Mothers' attitudes were classified in a typology ranging from "early twinness" where the two babies are treated as though they were a single unit, to attempt to create two dyadic relationships. The current program deals with the effects of the type of parent-child relationship at one year on the emergence of twin bonding. Sixty-eight families of twins (26MZ, 24DZ same sex, 18DZ different sex) are followed up from birth to the age of 3 using a method based on clinical interviews, videotaped observations, and questionnaires. The data cover mothers' rearing attitudes towards organization of babycare and outward signs of twinness, maternal representations of the relationship between the twins and observation of the children's interaction in a standardized game situation. The findings are discussed in terms of zygosity, and parental SCS.

Mother-twin interaction during early childhood

The components of a research program focusing on early mother-twin interaction is described. Preliminary data obtained from a questionnaire at two months post term, cross-sectional observations at the age of one year, a follow-up study involving home observation and parental interviews from birth to the age of 3, point to the specificity of this triadic situation. During the first months of life, the burden of material tasks and the increase in baby care leave little time for starting a relationship based on pleasure or play. The impossibility of responding simultaneously to the needs of two babies and the difficulty of forming relationships on an individual basis foster early concerns for egalitarianism. The degree of physical resemblance between the babies creates the problem of differentiating them. To tell twins apart, mothers rapidly tend to rely on behavioral characteristics to which they attribute a genetic basis. In contrast, differences in development between the babies that introduce the eventuality of the dominance of one of the twins are often denied. In this highly specific situation, mothers arrive at personal solutions of adjustment over the first 3 years, manifest in a certain number of psychological and educational attitudes. Analysis of these maternal attitudes may help to shed light on some of the features of later psychoemotional development in twins.