"I am returning this otherwise good typing paper to you because someone has printed gibberish all over it and put your name at the top." - An English Professor, Ohio University

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UMN Dept of Psychology: Labs: Minnesota Twin Family Study

"Similarity in twins reared together is due to genes and environment. Similarity in twins reared apart is due only to genes because they don't share experiences together. Most people would guess that twins reared together would be more alike than twins reared apart. But are they?..

[Identical] twins reared apart were about 50% similar in personality... [Identical] twins reared together are also about 50% similar in personality...

Similarities between twins are due to genes, not the environment... the environment, rather than making twins reared together alike, makes them different...

1. The spouses of [Identical] twins are no more alike than the spouses of [fraternal] twins and hardly more alike than random pairs of people!
2. When we asked male twins how they felt about their co-twin's spouse, two-thirds of the twins said they were indifferent to their twin's mate or actively disliked her!

Our choice of mate is one of the most important choices we ever make and yet it seems to be a random affair, not strongly influenced by genes or upbringing. The person that we end up with is determined by a kind of lottery, by whom we happen to be near when Cupid's arrow strikes!...

By asking twins about divorces in their families, a divorce risk was calculated according to which family member was divorced...

Identical (MZ) twins thus have very similar personalities.

We believe their similar divorce rates are due to their having genetically influenced personality characteristics that contribute to marital adjustment...

As twins grow older, do they become less similar to one another?

MZ (identical) twins become less similar in terms of physical traits like looks and weight over time. However, we recently found that MZ twins become more similar with respect to abilities such as vocabularies and arithmetic scores...

As DZ (fraternal) twins get older, as they leave their rearing home, marry, start careers and families, and develop their own circle of friends, they become less similar with respect to vocabularies and arithmetic scores."


Ah, the power of socialisation!