In search of shared and nonshared environmental factors in security of attachment: A behavior-genetic study of the association between sensitivity and attachment security.

Abstract

The current article presents results from a twin study of genetic and environmental components of maternal sensitivity and infant attachment and their association. The sample consisted of 136 twin pairs from 2 sites: Leiden, the Netherlands, and London, UK. Maternal sensitivity was assessed in the home at 9-10 months, and infant attachment security was observed in the laboratory at 12 months. The study yielded little evidence that genetic factors are involved in variations between twins in maternal sensitivity ratings but did find that shared variance in maternal sensitivity was able to account for some of the similarity between twins in attachment security. Weak nonshared associations between sensitivity and attachment appeared to suppress the magnitude of the correlation between attachment and sensitivity in twin children. The results could indicate that the attachment security of one twin may depend on the relationship the parent has with the other twin. The results are brought to bear on the validity of attachment theory as a theory of primarily shared environmental effects in children's development and the continuing challenge posed to attachment theory by within-family differences in socioemotional processes.

A sibling adoption study of adult attachment: The influence of shared environment on attachment states of mind

“…The lack of variation in genetic relatedness within sibling pairs (e.g., MZ or DZ twins, biologically related siblings) and between sibling pairs and the parent generation limit our conclusions regarding possible genetic influences on sources of environmental influence (e.g., shared, nonshared) (Reiss et al, 1994;Turkheimer & Waldron, 2000). The untested possibility remains that genetic differences between siblings influenced or were differentially influenced by qualities of the parent -child relationship (e.g., parental sensitivity) and/or impacted potential intervening influences on attachment in adulthood (e.g., romantic relationships) (Fearon, van IJzendoorn, Fonagy, Bakermans-Kranenburg, Schuengel, & Bokhorst, 2006;Torgerson, Grova, & Sommerstad, 2007). Unfortunately, our sample size and study design preclude examination of these processes with our data.…”

Attachment-Related Mentalization Moderates the Relationship Between Psychopathic Traits and Proactive Aggression in Adolescence

“…Moreover, approximately one-third of the variance in psychopathic tendencies in childhood are attributable to nonshared environmental influences (Viding et al, 2005). Mentalization therefore, with its ties to attachment (Fonagy, Redfern, & Charman, 1997;Fonagy, Steele, Steele, & Holder, 1997;Hill, et al, 2008), largely mediated by shared and nonshared environmental factors 13 (Fearon, et al, 2006;Roisman & Fraley, 2008), may add to the understanding of etiological factors in psychopathy.…”

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

“…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). However, methodological differences between the studies make it difficult to compare the concordance rates.…”