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Intellectual similarity of virtual twin pairs: Developmental trendsVirtual twins (VTs) are same-age unrelated siblings reared together from infancy who replicate twinship, but without the genetic relatedness. A 2005 report from the ongoing Fullerton Virtual Twin Study found an IQ intraclass correlation of .26 (p .01, n = 113 pairs) and a within-pair difference of 13.22 IQ points. The average age of VTs in that study was 8.10 years (SD = 8.56, range: 4.01–54.84 years). An opportunity to retest members of 43 VT pairs, 1.70–8.96 years after their time assessment, allowed additional analyses of genetic and environmental influences underlying general intellectual development. A decrease in the VT IQ correlation and an increase in the within-pair difference were indicated, consistent with increasing genetic and/or non-shared environmental influences and decreasing shared environmental influence on general intellectual development throughout childhood. 2006 Elsevier Ltd. All rights reserved. Get the article from sciencedirect.comTo participate in the study please e-mail Dr Segal at This email address is being protected from spambots. You need JavaScript enabled to view it. |
Nancy L Segal, Ph.D.
657-278-2142
nsegal@fullerton.edu
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Dr. Nancy L. Segal
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This volume is an annotated collection of original, informative, and moving photographs of the twins who survived the brutal medical experiments conducted at the Auschwitz-Birkenau death camp (1943-1945). The experiments were conducted by the infamous physician, Josef Mengele.
Order at Academic Studies Press.
Andrew from the United States and Elad Dvash-Banks from Israel married in Canada in 2010 when gay couples could not marry in these countries. The couple conceived fraternal twins, Aiden and Ethan, with a Canadian surrogate by means of egg and sperm donation. The two boys were born just four minutes apart. Aiden was conceived with a donated egg and Andrew's sperm cell, and Ethan was conceived with a donated egg (from the same woman) and Elad's sperm cell.
Order on Amazon.
Takes the first in-depth look at the New York City adoption agency that separated twins and triplets in the 1960s, and the controversial and disturbing study that tracked the children’s development while never telling their adoptive parents that they were raising a “singleton twin.”
Order on Amazon, Roman and Littlefield, BAM (Books a Million) or Powell’s.
The identical “Jim twins” were raised in separate families and met for the first time at age thirty-nine, only to discover that they both suffered tension headaches, bit their fingernails, smoked Salems, enjoyed woodworking, and vacationed on the same Florida beach.
Order on Amazon, Harvard University Press.
The riveting story of two sets of twins separated at birth and improbably reunited as adults, a dream case for exploring nature vs. nurture. Accidental Brothers tells the unique story of two sets of identical Colombian twin brothers who discovered at age 25 that they were mistakenly raised as fraternal twins ― when they were not even biological brothers.
Order on Amazon, Barnes and Noble, Books-A-Million and IndieBound.
Listen to a apple podcast about twins!
https://podcasts.apple.com/za/podcast/426-twins-clones-and-the-bond-we-all-crave-my-dads/id1525296416?i=1000705295678
Two new articles! Twins problem behaviors
and Twins IQ: Test of Draw-a-Person Task
https://www.tandfonline.com/eprint/USPQJ6BXKBAZFEPRKX2R/full?target=10.1080/00221325.2025.2487501#d1e230
https://www.sciencedirect.com/science/article/pii/S0022096525000785
See my tribute to the late Dr. Helen E. Fisher,
Anthropologist and Identical Twin
https://authors.elsevier.com/c/1kuTF3tz49AMkJ
See the just released film, THE ACCIDENTAL TWINS,
Doc film on doubly switched Colombian twins, Netflix;
https://www.netflix.com/title/81627034?trkid=13747225&s=i&vlang=en&clip=81776819; www.netflix.com/title/81627034
Watch my Opening Address, International
Twin Congress. September 26, 2024, Assisi, Italy
https://www.youtube.com/watch?v=Gmthl0i-Bhs&t=1433s
start at about 23 minutes
See my newest article on repeat measure of IQ in two reared-apart twin samples and a sample of virtual twins (same-age unrelated siblings reared together).
https://authors.elsevier.com/sd/article/S0191-8869(24)00211-3
See my new article that describes two new parenting concepts: "Assortative Parenting and Assortative Cross-Parenting: New Views of Parental Preference for Selected Children. https://www.sciencedirect.com/science/article/pii/S0378378223001998
Listen to an April 17, 2024 NPR-1A program about twins.
https://the1a.org/segments/the-tea-on-twins/
C-SPAN-2, Book TV! WATCH THE SHOW! Gay Fathers, Twin Sons: The Citizenship Case That Captured the World, and The Twin Children of the Holocaust: Stolen Childhood and the Will to Survive.
https://www.c-span.org/video/?530176-1/gay-fathers-twin-sons-citizenship-case-captured-worldWatch my Skeptic September 1, 2023 interview about my 2 recent books,
hosted by Michael Shermer
https://www.skeptic.com/michael-shermer-show/nancy-segal-twins-behavior-genetics-eugenics-human-behavior/
Listen to my August 17, 2023 interview on Gay Fathers, Twin Sons
with host Larry Mantle on AirTalk: start at 33:38
https://podcasts.apple.com/us/podcast/airtalk/id73329334
You can hear my 8/2023 conversation with Chris Williamson, of Modern Wisdom Podcast
https://www.youtube.com/watch?v=rRjXwdEI-lY
Please see this news article about an extraordinary July 16 event--i spoke here at the book launch of the world's oldest survivor of Mengele's Auschwitz experiments.
https://www.australianjewishnews.com/memoir-highlights-survivors-amazing-life/
Listen to my interview on NPR (AirTalk with Larry Mantle, on my new 2023 book, The Twin Children of the Holocaust: Stolen Childhood and the Will to Survive. (Scroll down to 7th segment). Lasts about 17 minuteshttps://www.kpcc.org/podcast/airtalk/people-want-to-know-what-mayor-bass-is-going-to-do-about-homelessness-heres-what-she-said-during-the-state-of-the-city-address
PROGRAMS AND PAST EVENTS
Watch and read about this fascinating story of identical twins' alleged cheating and lawsuit that followed.
CNN Evening News, December 13, 2022
November 2021 release of
Nancy Segal's 7th book:
WATCH THE HALF-HOUR BBC DOCUMENTARY on Deliberately Divided, July 23, 2022. — AIRED ON 200 TV STATIONS WORLDWIDE
https://www.bbc.com/reel/playlist/split-at-birth-twins-divided
LISTEN TO MY JUNE 30, 2022 EPISODE OF MALCOLM GLADWELL'S REViSIONIST HISTORY ON TWIN EXPERIMENTS
Listen here...
LISTEN TO A RECENT NPR RADIO INTERVIEW ABOUT TWINS AND DELIBERATELY DIVIDED
Listen here...
Nature-Nurture BBC Mini-Series (Episode 1), February 10, 2022
Watch here...
Controversy! Ethical Issues Surrounding the 1960-70s New York City Study of Twins Deliberately Adopted Apart
April 14, 2022: 9:00 am Pacific time; noon Eastern time; 4:00pm UK; 5:00pm Europe
Zoom link: To come!
Sibling Revelry, Interview with actors Kate and Oliver Hudson, March 31, 2022
Listen to an interview about Deliberately Divided and many aspects of twinship
Listen here...
The Weekend University, London, UK (virtual):
https://theweekenduniversity.com/
NPR: AirTalk with Larry Mantle, KPCC 89.3
November 10, 2021, 11:40 am PT
Deliberately Divided: Inside the Controversial Study of Twins and Triplets Adopted Apart
Rowman & Littlefield
Read a review--two-page spread--in the New York Post
December 12, 2021
Read on NY Post...
See an interview with Twins Magazine about Deliberately Divided, December 2021
Read on Twins Magazine
Watch the December 19, 2021 lecture at Weekend University
Nature or Nurture?
Watch on Google Drive
Xploration Station, Season 2, Episode 1
Human Cloning and Twins, 2021
Watch here...
I look at twins as scientific treasures. Because just by acting
naturally in different research contexts, twins tell us so much about our
human behavior and how we got that way...
Bringing together the latest, cutting-edge research, with illustrative case histories of twins and their families, preeminent twin researcher Dr. Nancy L. Segal explores ways in which twins enhance our knowledge of human behavioral and physical development.
Identical twins Delia and Begona were born thirty-seven years ago in Spain's Canary Islands. Due to chaotic conditions at the hospital or simple human error, Delia was unintentionally switched with another infant in the baby nursery.
This collection of case studies, following up on Entwined Lives: Twins and What They Tell Us About Human Behavior, feeds our fascination with "the tiny twists and great puzzles behind individuals' similarities and differences."
Students and scholars interested in the twists and bedrocks of human development will find in this volume a stimulating sampler of cutting-edge research on the topics that define Freedman's career: behavior genetics, human ethology, evolutionary psychology, and culture.
Coming Soon!
Shedding new light on over 70 commonly held ideas and beliefs about the origins and development of identical and fraternal twins. Using the latest scientific findings from psychology, psychiatry, biology, and education, the book separates fact from fiction.
The identical “Jim twins” were raised in separate families and met for the first time at age thirty-nine, only to discover that they both suffered tension headaches, bit their fingernails, smoked Salems, enjoyed woodworking, and vacationed on the same Florida beach.