Pedersen N L, Friberg L, Floderus-Myrhed B, McClearn G E, Plomin R
Acta Genet Med Gemellol (Roma). 1984;33(2):243-50. doi: 10.1017/s0001566000007285.
A sample of twins separated early in life has been identified in the Swedish Twin Registry. When the registry was compiled in 1961 (old cohort) and 1973 (young cohort), one or both members of 961 pairs indicated that they were separated by the age of 10. In May 1979, both members of 698 pairs were alive and were sent a questionnaire concerning the circumstances of separation. Items included reasons and timing of separation, biological relatedness of rearing parents, degree of contact after separation (including whether they lived in the same area, attended the same school, or lived together again), rough measures of selective placement, and current frequency of contact. An attempt was then made to categorize the pairs based on degree of separation. A total of 257 pairs met the criteria: rearing parents of one twin biologically unrelated to rearing parents of the cotwin, twins not living together again after separation, and contact after separation a few times a year or less. As much as 50% were separated by their first birthday, and 80% by the age of five. Various data from the twin registry are presented describing the entire sample of early separated twins as compared to a matched sample of twins reared together.
瑞典双胞胎登记处已识别出一组自幼便被分开抚养的双胞胎样本。1961年（老年队列）和1973年（青年队列）编制该登记处时，961对双胞胎中的一方或双方表示他们在10岁之前就已分开。1979年5月，698对双胞胎中的双方都在世，并收到了一份关于分开情况的问卷。问卷内容包括分开的原因和时间、抚养父母的生物学亲属关系、分开后的联系程度（包括他们是否住在同一地区、是否就读于同一所学校或是否再次共同生活）、选择性安置的大致衡量标准以及当前的联系频率。随后尝试根据分开程度对这些双胞胎对进行分类。共有257对符合标准：其中一个双胞胎的抚养父母与另一个双胞胎的抚养父母没有生物学亲属关系，双胞胎分开后不再共同生活，且分开后每年联系次数为几次或更少。多达50%的双胞胎在一岁生日前就已分开，80%在五岁前分开。文中呈现了来自双胞胎登记处的各种数据，描述了早期分开抚养的双胞胎的整个样本，并与一起抚养的匹配双胞胎样本进行了比较。
