Developmental Differences Between Twins and Singletons: A New Study Reveals Early Gaps and Later Reversals
New research published in Child Development highlights developmental differences between twins and their singleton siblings, revealing early gaps in language, cognition and social-emotional development that often reverse in later childhood. The study, which analyzed data from 851 families, emphasizes that these differences stem from the unique environment experienced by twins—such as shared parental attention and resources—rather than parenting quality.
Early Developmental Gaps
Researchers found that twins consistently scored lower than their singleton siblings in language, cognition, and social-emotional development at ages two, three, and four. These findings align with previous research indicating that twins may face unique challenges due to the dynamics of their shared environment. The study is the first to compare twins to their younger, single-born siblings within the same household, allowing researchers to isolate the twin experience from other factors like socioeconomic status.
Language Development: A Reversal in Later Childhood
Interestingly, the study revealed a significant reversal in language abilities around age seven. After this age, twins demonstrated language skills that surpassed those of their singleton siblings. This suggests that the early language delays experienced by twins may be compensated for as they mature, potentially due to increased social interaction and cognitive development.
Cognitive and Social-Emotional Development: Persistent Differences
Despite the language catch-up, twins continued to exhibit lower scores in cognitive and social-emotional areas as they approached school age. Specifically, the research indicated that twins experienced more peer-related difficulties compared to singletons. This suggests that the challenges of navigating social interactions as part of a pair may persist into later childhood.
The Unique Challenges of the Twin Experience
Emily Wood, the lead author of the study from the University of York, explained that the twin experience presents specific challenges often overlooked. “When you have two children of the exact same age, they are in direct competition for everything—from toys and food to a parent’s one-on-one attention. This is a challenge inherent to being a twin, and it’s something parents of single children don’t have to navigate in the same way,” she stated. The research suggests that the demanding rearing environment for twin families may necessitate targeted support in the early years to help bridge developmental gaps before school entry.
Social-Emotional Development: Challenging Assumptions
Sophie von Stumm, senior author and Professor of Psychology in Education at the University of York, highlighted surprising findings regarding social-emotional development. “There is a common assumption that twins might have an advantage here because they grow up with a built-in companion, which could lead to better sharing skills or higher empathy. However, we found the opposite: twins actually reported more peer problems than singletons as they got older,” she noted. This suggests that growing up as a pair does not automatically translate to easier socialization with others.
Rising Twin Births and the Necessitate for Support
The findings are particularly relevant given the increasing rates of twin births in Western populations, linked to factors such as older maternal age and the increased use of in-vitro fertilization (IVF). More advanced medical care has also contributed to higher survival rates for twin pregnancies.
Implications for Healthcare and Education
The researchers hope their findings will encourage a shift in how healthcare and education providers approach twin development. Currently, support is often concentrated on pregnancy, and birth. Professor von Stumm emphasized the need to raise awareness that being a twin presents ongoing challenges that extend beyond infancy. She suggests that offering twins additional support in areas like cognition and social play could help ensure they are not at a disadvantage when starting school.
Publication Details
Emily Wood et al, Twins and their singleton siblings differ in language, cognition, and social-emotional development, Child Development (2026). DOI: 10.1093/chidev/aacaf029
Journal information: Child Development