Twofold

The Singular World of Twins and Twin Studies.

by Dr. Nancy L. Segal

International Twin Congress and More

Twin research never stops! Read More

Twin Studies: Solvent Exposure, Parkinson’s Disease and Gender Identity Disorder

What twins tell us about chemicals in our environment. Read More

When a Twin Dies

A twin-based perspective on organ donation and its aftermath. Read More

Twin Tidbits

Twins have twice as many tidbits! Read More

Twins and Non-Twins Switched at Birth: How Rare?

Switched-at-birth twins: how and when do they occur? Read More

Twin Research: Misperceptions

Twin research is fraught with misperceptions that need correcting. Read More

Twin Injuries -- Genes or Environments?

Are your genes behind your injuries? Read More

Twin Typing by Self-Report

Twins: identical or fraternal? Who knows best? Read More

It may not be surprising that twin conferences come in pairs. In May and June of 2010 I attended two truly excellent meetings organized around twin studies. The first one, held at the University of California, Los Angeles was targeted to the general public, while the second one, held in Seoul, South Korea was aimed at research professions. Read More

Are Younger Looking Twins Healthier?

Does how you like reflect your general physical health? Twins studies can provide answers. Dr. Kaare Christensen and his colleagues in the United States, New Jersey, England, Germany and The Netherlands have produced an important and creative twin study on perceived aging as a marker of biological aging (Christensen, Thinggaard, McGue, Rexbye, Hjelmborg, Aviv, et al., 2009). Read More

DNA Dilemmas: New Riddles from Twins

Identical twins’ shared DNA has led to some extraordinary dilemmas when it comes to assigning paternity or assigning blame. For example, I am aware of several cases in which women have had sexual relations with both members of an identical males twin pair, such that the biological father of their children cannot be identified. Strangely, the identity of the child’s maternal grandmot Read More

Are These Two Children Twins?

Investigators at the National Embryo Center in Knoxville, TN have reported an unusual delivery--the first case of twins unrelated to their mother and to each other. The pair resulted from the transfer of three embryos from two different donors to a forty-two-year old woman with an infertility history. Read More

Loss of a Twin

Twin Loss: The Annual Convention

Triplets--An Unusual Case

This article is reprinted, in part, from a longer one in a recent issue of the journal Twin Research and Human Genetics. Read More

DNA Dilemmas: New Riddles from Twins

More Octuplets: Combinations and Permutations

Multiple births are a great addition to research addressing genetic and environmental influences on behavior. It occurred to me that the new octuplets offer some amazing possibilities: The eight babies include:

28 twin pairs 56 triplet sets 70 quadruplet sets 56 quintuplet sets

29 sextuplet sets

8 septuplet sets

Why Some Identical Female Twins Are Different

Behavioral and physical differences between identical twins are fascinating because they are unexpected. Many people assume that when identical twins differ they do so because they are treated differently by others, or because they try to differentiate from one another in order to carve out a separate identity. Read More

Octuplets: Views From One Who Studies Two

The recent birth of the Suleman octuplets in southern California has attracted unprecedented attention from physicians, parents and publishers around the world. It is a frequent topic of conversation in coffee shops and classrooms. Issues surrounding the octuplets' child care, health expenses, biological origin and future development-all important and timely--have been debated endlessly. Read More

Political Pairs

It's the new hot topic in psychological twin research-to what extent do genes affect our interest and participation in politics? With the November election looming in the very near future, this is an opportune time to examine the research.

Studies by James Fowler at the University of California, San Diego address a host of relevant questions.

Twins Reared Apart--But Together Again

I have always believed that twins belong together, and still do. Twins meeting for the first time as adults describe anger, resentment and sadness at having been raised apart, often for the convenience of others. Read More