Why Researchers Study Twins

The special relationship between twins allows researchers to examine the differences between genetic and environmental influences on both physical and mental health, as well as traits and behaviors, in the general population. Ultimately, twin research helps answer questions not only about how humans differ, but why.

Since identical (monozygotic) twins develop from the same fertilized egg, they are the same sex and share 100 percent of their genes. Some of their similarities provide evidence of a high degree of genetic influence. But since fraternal (dizygotic) twins develop from two different eggs fertilized by separate sperm cells, they generally share only about 50 percent of their genes and, in that sense, are more like typical brothers and sisters. Similarities found between sets of identical and fraternal twins suggest more environmental influences than genetic.

The information gathered from twin studies lays the groundwork for future genetic research, including the degree to which any and all aspects of life are determined by genetics, the location of specific genes, and the prevention and treatment of genetic disorders.

Recent posts on Twins

On Your Own

By Barbara Klein Ph.D., Ed.D. on November 16, 2017 in Twin Dilemmas
Does twin loneliness come to an end?

Why Is It So Hard to Separate from My Twin?

By Barbara Klein Ph.D., Ed.D. on October 22, 2017 in Twin Dilemmas
Helpful tips for dealing with separating from your twin.

Twins and More: Too Much of a Good Thing?

By Robert D. Martin Ph.D. on July 25, 2017 in How We Do It
Multiple pregnancies bring more bundles of joy, but premature birth is more common. Delayed motherhood and fertility treatments are boosting the frequency of multiple births.

Twins With Two Daddies

By Robert D. Martin Ph.D. on June 22, 2017 in How We Do It
Paternity suits triggered by strikingly different fraternal twins have revealed bizarre cases with two different fathers. Split paternity is the visible tip of a sizeable iceberg.

Do Twins Read Each Other's Minds?

By Nancy L. Segal Ph.D. on March 30, 2017 in Twofold
Some people think twin communicate telepathically, but research shows otherwise.

Twins: Individual Identities and Common Bonds

By Nancy L. Segal Ph.D. on January 26, 2017 in Twofold
Does a close twin relationship take away from individual identity?

Twin Research and the Arts: How Are They Connected?

By Nancy L. Segal Ph.D. on December 10, 2016 in Twofold
Which comes first? The science or the work of art?

3 Reasons Twins Live Longer (and How You Can, Too)

By Guy Winch Ph.D. on August 24, 2016 in The Squeaky Wheel
A new study examines why twins live longer; non-twins can benefit from their findings as well.

The Psychology of Parenting Twins

By Kristi Pikiewicz Ph.D. on September 29, 2014 in Meaningful You
The number of families with twins is increasing these days. But, parenting twins is a challenge!

Confessing for Two

By Abigail Pogrebin on October 26, 2009 in One and the Same
How does one write personally about being an identical twin without exposing one's twin in the process? I discovered it's impossible.