A contribution to the psychological study of interpersonal relations in twins

A sample of 71 pairs (32 MZ, 39 DZ), of mean age 9.7 years, has been studied through various techniques in order to better understanding the interpersonal relation of twins, both within the pair and with repect to the members of the family group, and especially the mother. Zygosity, dominance, and birth order have been taken into account. The relation between MZ twins appears to be somehow less special than believed, whereas a special triadic relation appears to exist with the mother. A differentiated research of identity in MZs and autonomy in DZs is also noted (which contributes to a better understanding of problems of schizophrenia in twins). Finally, the relation between MZ cotwins shows mutual similarity and attachment to be lower than foreseen and, anyhow, of a far from mysterious nature.