Pairs of Genetically Unrelated Look-Alikes : Further Tests of Personality Similarity and Social Affiliation

Commentary: Assortative parenting and assortative cross-parenting: New views of parental preference for selected children

The commentary delves into the implications of "assortative parenting" and "assortative cross-parenting," as introduced by N. L. Segal, and situates these concepts within the framework of current research. It addresses the joys and complexities of raising twins, highlighting how their concurrent development stages can amplify parental favoritism and heighten the challenge of addressing each twin's unique needs. This interplay provides a rich context to investigate assortative parenting practices. Additionally, this paper contemplates the broader picture of twin studies, particularly how the care of monozygotic twins (who share 100 % of their genes) and dizygotic twins (who share 50 % of their genes, on average) may reveal the intertwined nature of genetics and environment in parenting strategies. It also proposes that twins' interactions with other family members, their spouses, and peers can offer profound insights into the phenomena of phenotypic assortative affiliation, enriching our understanding of close relational bonds.

Twins Standing in for Co-Twins: Explanation and Speculation/Twin Research Reviews: Single v. Multiple Embryo Transfer; Neurimaging of Twins with Periventricular Nodular Heterotopia; Twin Dietary Study; New Hungarian Text on Twins/Human Interest: Valedictorian and Salutatorian Twins; Twin Mother at Age Seventy; Twins Reunited by Tiktok; New Film on Twins with Selective Mutism; Becoming Twin Doctors

An overview of circumstances in which twins take the place of their co-twin is presented. Various explanations and speculations are proposed for understanding twins' willingness to do so in certain situations. This section is followed by reviews of timely twin research, namely single versus multiple embryo transfer; neurimaging of twins with periventricular nodular heterotopia; a twin dietary comparison; and a new book of twin-related readings from Hungary. The final portion of this article concerns human interest stories that both inform and entertain. They involve valedictorian and salutatorian twins; a mother delivering twins at age seventy; twins reunited by TikTok; a new film about twins with selective mutism; and twins becoming doctors.

The 18th International Twin Congress, and a Look at Twin Research in Wales/Twin Research Reviews: Temperamental Similarities and Twin Relations; Maximizing Twin Designs; Rare Tubal Ectopic Pregnancy; Twins' Academic Self-Concept Formation/In the Media: Identical Infant Twins Reunited; Birth of Identical-Fraternal Quadruplets; Identical Twin Comedians; 'Twice in a Lifetime': Meeting an Unrelated Look-Alike; Twins in the Tour de France

The 18th International Society for Twin Studies convention took place between June 15-17, 2023, in Budapest, Hungary. A selective sampling of highlights from the meeting are presented. This is followed by a brief overview of ongoing twin research at the University of Aberystwyth in Wales and some twin treasures in the National Library. Next, reviews of timely research that examine temperamental similarities and twin relations, the maximization of twin research designs, a rare ectopic twin pregnancy, and twins' academic self-concept formation are presented. The final section covers stories appearing in various media sources that are informative, enlightening, and interesting, namely a reunion of identical infant twins, the birth of identical-fraternal quadruplets, identical twin comedians, meeting an unrelated look-alike, and twins in the Tour de France.

The Garden of Forking Paths; An Evaluation of Joseph's 'A Reevaluation of the 1990 "Minnesota Study of Twins Reared Apart" IQ Study'

Joseph has written what purports to be a refutation of studies of Twins Reared-Apart (TRAs) with a singular focus on the Minnesota Study of Twins Reared-Apart (MISTRA). I show, in detail, that (a) his criticisms of previous TRA studies depend on sources that were discredited prior to MISTRA, as they all failed the test of replicability, (b) the list of biases he uses to invalidate MISTRA do not support his arguments, (c) the accusations of questionable research practices are unsubstantiated, (d) his claim that MISTRA should be evaluated in the context of psychology's replication crisis is refuted. The TRA studies are constructive replications. Like many other scholars, past and present, he has been misled by the variation introduced by small samples (sampling error) and the distortion created by walking in the garden of forking paths. His endeavor is a concatenation of elision and erroneous statistical/scientific reasoning.

Quadruplets: Risks, Outcomes and a Set of Four/Twin Research Reviews and a Lawsuit: Antenatal Corticosteroids and Twins' Neonatal Outcomes; Fathers of Twins; Doppelgängers and Similarity; Monozygotic Co-Twin Difference in Asymmetric Pigmented Paravenous Chorioretinal Atrophy/In the News: Opposite-Sex Twin Holocaust Survivors; Twin Models at Gucci; Twins With Different Fathers; Reunited Twins Enter Same Convent; Death of a Twin Soldier During Training; Surgical Separation of Conjoined Twins

Quadruplets are at elevated physical risks at prenatal, perinatal, and postnatal levels, relative to twins. A brief review of this area is followed by discussion of a female quadruplet with three co-quadruplet brothers. Next, several timely twin research reports are examined. The topics include antenatal corticosteroids and twins' neonatal outcomes, the meaning of fatherhood in families with twins, what doppelgängers (look-alikes) reveal about physical and behavioral similarity, and monozygotic (MZ) co-twin discordance for asymmetric pigmented paravenous chorioretinal atrophy. A lawsuit involving alleged cheating on a medical school examination by identical twins is also reviewed. General interest stories cover opposite-sex twin Holocaust survivors, twin models at a Gucci fashion show, twins with different fathers, reunited female twins who entered the same convent, the death of an MZ female twin soldier during training, and the surgical separation of conjoined twins in Brazil.

Classroom Placement and Twins' Social Behaviors in Elementary School: Providing Empirical Evidence to Inform Educational Policy

Classroom placement of twins is an ongoing issue for educational policy. Many educational jurisdictions have standard policy most commonly founded in the belief that separation supports individual identity, personal development and academic opportunity. This study examined the effects of classroom placement in a sample of 560 twin pairs whose behaviors were assessed from ages 5 to 12 years. We found no detrimental effect of classroom sharing on twins' social development. In contrast, this study provides evidence that educating twins together is associated with modest positive twins' behaviors and social functioning at school. Implications for educational policies are further discussed.

Reared-Apart and Reunited: Extraordinary Dynamics/Twin Research Reviews: Twin Bereavement and Lifespan Associations; Identifying Novel Mutations in Twins; Parenting Premature Multiples; Conjoined Twins in Cross-Cultural Context/In the News: Madeline Albright, Mother of Twins, Passes Away; Identical Twin Songwriters Compose New Musical; Visually Impaired Twin Skiers; Identical Twin Brothers Undergo Heart Transplants; Naming the Genain Quadruplets

The focus of this article is on insights gained from the extraordinary dynamics that took place between a pair of reunited monozygotic female twins from Greece. Topics include visualizing the co-twin prior to meeting, the unique love and attraction between the twins, a mother's response to discovering her child's cotwin and the challenges posed by insufficient kinship categories. The following section of this article surveys four recent twin research reports. They include Bereavement and Lifespan Associations; Novel Mutations in Twins; Parenting Premature Multiples; and Conjoined Twins. The final part of this article presents interesting and informative news about twins from popular sources. The topics covered are the passing of Madeline Albright (Secretary of State and mother of twins); identical twin songwriters; visually impaired twin and sibling skiiers; identical twin brothers who both received heart transplants; and the naming of the Genain quadruplets.

Reared-apart/reared-together Chinese twins and virtual twins: Evolving research program and general intelligence findings

China's One-Child Policy (1979-2015) limited rural families to two children and urban families to one child. This practice, which led to the abandonment of hundreds of thousands of female infants, is indirectly responsible for the separate placement of infant twins. The availability of this sample launched the first prospective study of these pairs. Participants include families and twins comprising 15 monozygotic (MZA) pairs and 7 dizygotic (DZA) pairs from countries throughout the world. The research program is described, and the initial wave of IQ scores for MZA and DZA twin pairs is examined in the first comprehensive report from this study. The twins' mean age at participation was 9.41 years (SD = 6.36), and their ages ranged from 3.19 to 24.98 years. Informative contrasts with adopted-together Chinese twins and virtual twins (same-age unrelated individuals reared together) highlight shared genetic and environmental effects on intellectual development. Applied directions based on findings from these novel samples are described.