Virtual twins are same age siblings who are reared together since birth, but without any genetic or biological relations. These virtual twins can either be both adopted by the rearing parents, or one is adopted while the other is a biological child. Although these virtual twins don't share any genetic relationship, the rearing situation and home environment of these “twins” are the same since they grew up in the same house under the same parental supervision.
A study showed that the influence of shared environment, particularly home life, in the intellectual development of these virtual twins decreases in early and middle childhood. Genetic and non-shared environmental factors affect the intellectual difference between these genetically unrelated twins, and the difference becomes increasingly apparent as the twins grow up. This study supports the phenomenon “nature versus nurture”, and nature has obviously won. Genes still play a large role in the mental and intellectual development of children.
Other studies have been conducted relating to virtual twins, and how the environment plays a big role in the personality and character development of children. One pair of virtual twins, Sara and Julie, showed extreme differences in personality and behavior. Sara goes to church while Julie does not. Sara has six studs on each ear while Julie rarely wears any jewelry. Sara wears glasses and likes dressing up, while Julie wears contacts and loves casual wear. This study proves that shared environment has little or no effect at all to the personality development and behavior of virtual twins.