Minnesota Twin StudyMinnesota Twin Study

Paulina & PatrickPaulina & Patrick

AIM OF STUDYAIM OF STUDY

• It seeks to identify the genetic & environmental influences on the development of psychological traits.

WHY USE TWINS?WHY USE TWINS?

• Twins are valuable to researchers because identical twins share 100% of their genes & fraternal twins share, on average, 50% of their genes

• Both types of twins share certain aspects of their environment, allowing researchers to estimate the heritability of certain traits.

METHOD & METHOD & COLLECTING DATACOLLECTING DATA

• Longitudinal study of 11-17 year-old twins, started in 1979. Involved a week-long of medical & psychological assessment or identical and fraternal twins separated in early life.

• Medical Assessment:- Psychiatric interview- Medical life history- Standard blood test- Detailed dental & periodontal exams

METHOD &METHOD &COLLECTING DATACOLLECTING DATA

• Psychological Assessment:-Academic ability-Personality & Interests-Family & Social relationships-Mental & Physical health-Psychological Measurements

• A systematic assessment of aspects of the twin's rearing environments that might have had causal roles in their psychological development is also carried out.

• This study provided many examples of separated identical twins showing multiple similarities.

FINDINGS (EXAMPLES)FINDINGS (EXAMPLES)

• Twins reared apart: Thomas Bouchard found that an identical twin reared away from their co-twin seemed to have about an equal chance of being similar to their twin in personality, interests & attitudes as on who has been reared with his/her co-twin.

FINDINGS (examples)FINDINGS (examples)

- Separated as infants, twins Gerald (Jerry Levey) and Mark Newman grew up to share characteristics ranging from their firefighting avocation to taste in beer.

- Neither of them knew of the others existence- When they first met, they saw their reflection in the other

person.- Grew same mustache, wore the same glasses.- Both worked in supermarkets for a while.- Both men are bachelors and are attracted to the same kind

of woman.- Both volunteer fire fighters.- Both brought up in the Jewish faith but neither is particularly

religious- Both men drink only Budweiser Beer. ( They even hold the

can in the same way)- Quote - “we kept making the same remarks at the same time

and using the same gestures. It was spooky...He is he and I am I, and we are one.”

CONCLUSIONCONCLUSION

The study of reared-apart twins led to two general conclusions concerning the sources of the psychological differences and behavioral variation between twins:

1) Generic factors exert a prominent and universal influence on behavioral differences2) The effect of being reared in the same home is not that important for many psychological traits.

This leads to the conclusions that most similarities between twins are due to genes rather than from the environment they live in. This is because the similarities of twins which had been reared apart must’ve been due to their environment.

PROBLEMS WITH THE PROBLEMS WITH THE STUDYSTUDY

- Bouchard relied on media coverage to recruit participants.-There are some ethical concerns about the way he reunited the twins.-There was no adequate control to establish the frequency of contact between the twins prior to the study.-We cannot assume that twins who are raised together experience the same environment .