ABSTRACT
Virtual twins (VTs) are same-age unrelated siblings reared together from early infancy. These unique sibling sets replicate twinship, but without the genetic link. The first VT pair was identified and studied at the University of Minnesota in 1990, launching the development of the Fullerton Virtual Twin Study at California State University, Fullerton (CSUF) in 1991. The registry currently includes 151 pairs, mostly children, with new pairs identified on a continuous basis. Research with VTs includes studies of general intelligence, body size, interpersonal trust, social coordination, social networks, and parenting. In some cases, VTs have been studied in conjunction with pairs of monozygotic twins, dizygotic twins, full siblings, and friends as part of TAPS (Twins, Adoptees, Peers and Siblings), a collaborative project conducted between CSUF and the University of San Francisco, 2002-2006. VTs will also serve as a comparison group for epigenetic analyses of young Chinese twins reared apart and together.
Subject(s)
Adoption , Siblings , Twins, Dizygotic/psychology , Twins, Monozygotic/psychology , Adolescent , Adult , California/epidemiology , Child , Child Rearing , Child, Preschool , Cohort Studies , Female , Humans , Intelligence , Male , Middle Aged , Personality , Social Environment , Young AdultABSTRACT
The Fullerton Virtual Twin Study has been assessing the behaviors of an unusual sibship since 1982. Virtual twins (VTs) are same-age, unrelated siblings reared together since infancy. They replicate the rearing situation of twins but without the genetic link, enabling direct assessment of shared environmental effects on behavior. An updated analysis of IQ data, based on an increased sample of 142 VT pairs (7.87 years, SD=8.22), is presented. Intraclass correlations of .28 (IQ) and .11 (subtest profile) indicated modest shared environmental influences on intelligence. Findings from the Twins, Adoptees, Peers and Siblings (TAPS) project that studies virtual twins and other kinships are described.
ABSTRACT
Virtual twins (VTs) are same-age unrelated siblings reared together from infancy who replicate twinship, but without the genetic relatedness. A 2005 report from the ongoing Fullerton Virtual Twin Study found an IQ intraclass correlation of .26 (p < .01, n = 113 pairs) and a within-pair difference of 13.22 IQ points. The average age of VTs in that study was 8.10 years (SD = 8.56, range: 4.01-54.84 years). An opportunity to retest members of 43 VT pairs, 1.70-8.96 years after their time 1 assessment, allowed additional analyses of genetic and environmental influences underlying general intellectual development. A decrease in the VT IQ correlation and an increase in the within-pair difference were indicated, consistent with increasing genetic and/or non-shared environmental influences and decreasing shared environmental influence on general intellectual development throughout childhood.
