Twins' and Singletons' Linguistic Environment: A Systematic Review

Abstract

Background: Among twins, lower linguistic skills emerged when compared with singletons. Considering the association found between parental linguistic input and children's language development, exploring the differences between twins and singletons' linguistic environments could find variables that are potentially associated with the lower linguistic skills of twins.Aim: The current systematic review aims to analyze and systematize the existing literature focused on the comparison of twins' and singletons' linguistic environments within their first 3 years of life. Methodological issues (i.e., the procedure used to assess the linguistic environment, the coding of the linguistic environment's features, the computational method employed to assess the parental linguistic input, and participant characteristics) and differences found among twins and singletons regarding their linguistic environment (i.e., linguistic input quantity, linguistic input complexity, linguistic features of child-directed speech, parental responsiveness, and directiveness, joint attention, and book reading) were highlighted.Method: The Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement was followed. Eligible studies were searched through EBSCO, PubMed, and Web of Science. From this search, 1,347 study results emerged, and 8 studies were included.Results: To our knowledge, this is the first systematic review focused on the comparison of twins' and singletons' linguistic environments. Differences between the groups were found in all of the included studies. Data against twins were generally identified regarding all the considered linguistic environment's features. However, conflicting results within and between the included studies emerged, mainly according to the computational method employed (i.e., twin moms value, twin direct dyadic value, twin direct dyadic + both value, and input directed toward both children simultaneously).Conclusion: The disadvantaged linguistic environment of twins is likely due to limited parental resources and demands associated with the management of two children of the same age. However, the limited and conflicting data found did not allow for a firm conclusion to be drawn on the differences in the twins' and singletons' linguistic environments. Further studies on the topic are needed.

Effect of Twinning on Chinese and English Vocabulary Knowledge

“…These findings provide support for a twinning effect on native language development in middle to late childhood (Dʼhaeseleer et al, 2016;Tsou et al, 2008) in the area of vocabulary knowledge. They are also consistent with the assumption that the effect stems from enhanced competition for parental attention and linguistic interaction for twins compared with singletons (Thorpe, 2006;Trombetta et al, 2019), since the effect is reduced considerably in a non-native language primarily learned in school and thus much less affected by family interactional factors. An additional age analysis revealed that the pattern of results remained the same in a younger subgroup with a mean age of around 7 years, whereas a slightly weaker twinning effect on Chinese vocabulary was shown in an older subgroup with a mean age of 8 years and 8 months.…”

“…This conclusion is corroborated by studies demonstrating the effect even after controlling for twin‐specific and perinatal factors (e.g., Rutter et al, 2003). In a more recent review, Trombetta et al (2019) identified quantity and complexity of linguistic input, features of child‐directed speech, parental responsiveness, joint attention, and book reading as the main family interactional dimensions on which twinning may have a negative impact, leading to delayed language development for twins compared with singletons. Hence, as to the question of what causes the twinning effect, there has been good agreement among previous authors that family interactional factors play an important role.…”

Neurodevelopmental outcome of low-risk moderate to late preterm infants at 18 months

“…When the MLP group was subdivided by pregnancy type, differences were evident in Subscale B (Language and Communication) in which MLP infants from singleton pregnancies significantly outperformed MLP infants born from a multiple pregnancy ( p = 0.040). A systematic review comparing the outcome of infants from twin and singleton pregnancies described differences in language and communication but proposed that the likely cause was due to the parental demands of managing two infants ( 30 ). Thorpe identified language delay in twins as mild but prevalent especially in male infants ( 31 ).…”

Intra- and Inter-Group Differences in the Cognitive Skills of Toddler Twins with Birth Weight Discordance: The Need to Enhance Their Future from Early Education

“…This is complicated for twin children. These families tend to be more overwhelmed and present higher levels of stress in the face of increased demands when caring for twins infants [88]. This sometimes makes it difficult for them to find time to meet-in addition to the child's demands-the 'demands generated by the researchers'.…”

“…Although all the participants began the study with a mental age of 18 months, it is not known how each of these two contexts could have affected their cognitive skills during the time that this research lasted and when the data was being collected. Although the two twins from each couple share a family and school, this does not mean that, in each context, the two siblings are cared for and stimulated equally, or, even if they are, the effects on their cognitive development could be different [19,88]. As such, it would be worth analyzing the type of interactions that both families and teachers establish with each of the twins and establishing what the effects are on their cognitive skills.…”