The Similarity of Siblings' Attachments to Their Mother

Abstract

Do siblings develop similar attachment relationships with their mother? Attachment theory suggests that brothers and sisters growing up in the same family are likely to relate in similar ways to their parents, at least when parental attachment representations and interactive styles remain stable across time. In the current study, sibling attachment data from three research groups (from Pennsylvania State University, Leiden University, and the University of Western Ontario) have been pooled to assemble a sufficiently large sample of observations (N = 138 sibling pairs) for a detailed comparison of sibling attachment relationships. Spacing between the births, differences in maternal sensitivity, and gender of siblings were examined as possible sources of concordance of nonconcordance. Attachment security (including disorganized attachment) of each sibling was assessed with the Strange Situation procedure between 12 and 14 months after birth. Maternal sensitivity was observed with the same rating scale in a laboratory play session in one of the studies and in home observations in the others. Sibling relationships were found to be significantly concordant when classified as secure/nonsecure (62% concordance, p < .01, 1-tailed, intraclass correlation = .23) but not when further subcategorized. Maternal insensitivity to both siblings (shared environment) was associated with concordance of sibling nonsecurity. Siblings of the same gender were more likely to form concordant relationships with their mother (68%; p < .01, 1-tailed, intraclass correlation = .37) than those of opposite gender. Same-sex sibling concordance was comparable to the concordance found for monozygotic twins in earlier studies. Genetic factors may, therefore, play a relatively small role in the development of attachment.

Concordance of Attachment Representations in Preschool Siblings Assessed by the Attachment Story Completion Task

“…This concordance rate was not significant and close to the concordance rate expected by chance. This is in contrast to the study by van IJzendoorn et al (2000) based on the data of 2014 normal children of 15 US samples assessed using the Strange Situation Procedure reporting a significant 62% concordance rate between infant siblings which was also significantly higher than expected by chance (52%). A 60% concordance rate, but not significant in every case, was also found in other studies with younger sibling pairs and twins measured in the Strange Situation Procedure (Bokhorst et al, 2003;Fearon et al, 2006;O'Connor & Croft, 2001;Teti & Ablard, 1989;Ward et al, 1988).…”

“…The lack of influence of gender differences and birth spacing are similar to results reported in studies on attachment concordance in younger children (Ward et al 1988;van IJzendoorn, 2000). Still, the latter study indicated that mothers displayed less sensitivity towards the second-born child, a variable that we did not assess directly but that could potentially explain the non-significant concordance rate found in our study.…”

“…Fourth, maternal sensitivity is known to be one of the strongest predictors of child attachment security. Van IJzendoorn et al (2000) reported that birth order was significantly related to maternal sensitivity even though no significant effect of birth order on attachment security was found. The results of that study indicated that mothers displayed less sensitivity with their younger than with their older children (van IJzendoorn et al, 2000).…”

“…In contrast to former studies, sibling pairs of the same sex showed higher concordance rates (68%) than sibling pairs of the opposite sex (56%). Birth order was not related to attachment distributions but was significantly related to maternal sensitivity, as mothers displayed less sensitivity toward (van IJzendoorn et al, 2000). Spacing between the births was not related to concordance of attachment security of the siblings, but longer birth spacing was associated with higher sensitivity to the younger sibling, and shorter birth spacing was associated with higher sensitivity to the elder sibling.…”

“…However, child-related features were not discussed. Van IJzendoorn et al (2000) pooled data on sibling attachment from two US and one Dutch sample to examine attachment concordance in 138 sibling pairs. All children had been assessed with the Strange Situation between the ages of 12 and 14 months.…”