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Virtual twins (VTs) are defined as same-age unrelated siblings raised together from early infancy. This special class of adoptive siblings replays the rearing situation of twins, absent genetic relatedness. The first such pair was identified and studied in 1990 at the University of Minnesota, leading to the creation of the Fullerton Virtual Twin Study (FVTS) at California State University, Fullerton (CSUF) the following year. The registry currently includes 169 VT pairs, mostly children, with new pairs identified on a regular basis. These sibling sets provide a direct estimate of environmental influences on developmental traits and, as such, offer informative comparisons with ordinary monozygotic and dizygotic twins, full siblings and adoptive brothers and sisters. The sample characteristics, assessment battery and findings to date are summarized in this 2019 update.
The University of São Paulo Twin Panel (Painel USP de Gêmeos), based at the Institute of Psychology of the University of São Paulo, started formally in 2017. Our registry is new, but in only two years of formal existence, it comprises a volunteer sample of 4826 registered individuals (98% twins and 2% higher-order multiples), recruited at the University of São Paulo and by social media campaigns. Our main aim is to conduct and promote research with twins on psychological processes and behavior. The University of São Paulo is the largest higher education and research institution in South America, and the Painel USP de Gêmeos has great potential for fostering research on twin-related issues from a psychological perspective in Brazil and South America.
Co-twin control is a well-known methodological twin research design, but its variations and complexities are less well known. Various issues and illustrations are presented with reference to studies involving natural events, experimental interventions and rare happenings that underlie monozygotic (MZ) twins’ environmental differences. This discussion is followed by summaries of recent twin research pertaining to cancer risk in overweight twins, the physical risk to surviving twins after fetal loss of a co-twin, a 20-year update of twin concordance for Parkinson’s disease, and neuroanatomical differences in musically discordant MZ twin pairs. Several twin-related items that have attracted attention in the news are also summarized.
This case study examined the hypothesis that longer outdoor time results in normal vision and refractive status, using unique genetically informative kinships. The participants were the members of 29-year-old doubly exchanged monozygotic male twin pairs from Bogotá, Colombia, in South America. Comprehensive ophthalmological examinations, including uncorrected and corrected visual acuity, refraction and keratometry, and visual life history interviews were undertaken; all examinations were conducted by two ophthalmologists blind to the hypothesis, relatedness, and rearing status of the four participants. Normal uncorrected vision and refractive status were present in the two rural-raised, unrelated brothers, relative to their urban-raised counterparts. Uncorrected visual acuities were 20/160 and 20/200 for the city-raised twins and 20/20 and 20/30 for the country-raised twins. Premature birth, low birth weight, computer use, and reading time could not explain these differences. It was concluded that time spent outdoors appears to be a significant factor in the development of myopia, reinforcing extant findings via a novel experimental approach.
The second recorded case of sesquizygotic (SQZ) twins is summarized. It is suspected that SQZ twins result from the fertilization of an egg by two separate spermatozoa, followed by division of the fertilized ovum. Next, recent studies examining how differences in parental affection affect co-twins’ personality profiles, the prenatal demise of fetuses during twin pregnancy, a forensic case of heteropaternal superfecundation and selective feticide in dichorionic twins are reviewed. Finally, summaries of newsworthy items featuring an identical twin Oscar winner, a case of ‘superfecundated’ twins born to a gay couple, identical twins who try partly living apart and new molecular techniques to distinguish an innocent identical twin from his or her guilty co-twin are presented.
Introduction: 9-1-1 telecommunicators receive minimal education on agonal breathing, often resulting in unrecognized out-of-hospital cardiac arrest (OHCA). We successfully piloted an educational intervention that significantly improved telecommunicators’ OHCA recognition and bystander CPR rates in Ottawa. We sought to better understand the operations of Canadian 9-1-1 communications centers (CC) in preparation for a multi-centre study of this intervention. Methods: We conducted a National survey of all Canadian CCs. Survey domains included information on organizational structure, dispatch system used, education curriculum, and performance monitoring. It was peer-reviewed, translated in French, pilot-tested, and distributed electronically using a modified Dillman method. We designated respondents in each CC before distribution and used targeted follow-up and small incentives to increase response rate. Respondents also described functioning of neighboring CCs if known. Results: We received information from 51/51 provincial and 1/25 territorial CCs, representing 99.7% of the Canadian population. CCs largely utilize the Medical Dispatch Priority System (MPDS) platform (93%), many are Province/Ministry regulated (50%) and most require a High School diploma as minimum entry level education (78%). Telecommunicators receive initial in-class training (median 1.3 months, IQR 0.3-1.9; range 0.1-2.2), often followed by a preceptorship (84.4%) (median 1.0 months, IQR 0.7-1.7; range 0.4-6.0). Educational curriculum includes information on agonal breathing in 41% of CC, without audio examples in 34%. Among responding CCs, over 39,000 suspected OHCA 9-1-1 calls are received annually. Few CCs maintain local performance statistics on OHCA recognition (25%), bystander CPR rates (25%) or survival rates (50%). Most (97%) expressed interest in future research collaborations. Conclusion: Most Canadian telecommunicators receive no or minimal education in recognizing agonal breathing. Further training and improved OHCA monitoring may assist recognition and enhance outcomes.
Findings related to visual functioning, drawn from early reared-apart twin studies, are summarized. These data are supplemented by more recent research from similar investigations. This section is followed by a survey of findings and conclusions from a special issue of the journal Seminars in Perinatology concerning the challenges and management of conjoined twins. An early case report on thoracopagus-conjoined twin cattle is also presented, as are neuroanatomical findings from a study of monozygotic twins discordant for musical training. Items noted in the news include college benefits for twin parents, an update on octomom, claims of gene editing of infant twins, the nature of quarternary marriages and an unusual planned twin pregnancy.
Twin studies have shown that our sense of humor has an underlying genetic component, but less investigation of the origins of stand-up comedy has been undertaken. This article briefly reviews twin research findings on humor, then describes the working partnership and social affiliation of a pair of monozygotic male twins who perform together as stand-up comedians. The abilities, personalities and temperaments of these twins suggest future avenues for research in this interesting area. Next, findings from twin studies and case reports of twins with cleft lip and palate, dental caries, noninvasive prenatal testing and Capgras syndrome (with folie à deux) are summarized. In conclusion, recent news about athletic twins, transgendered twins, crib-sharing and career choice are presented.
The Brazilian Household Food Insecurity Measurement Scale (EBIA) has eight general/adult items applied in all households and six additional items exclusively asked in households with children and/or adolescents (HHCA). Continuing an investigation programme on the adequacy of model-based cut-off points for EBIA, the present study aims to: (i) explore the capacity of properly stratifying HHCA according to food insecurity (FI) severity level by applying only the eight ‘generic’ items; and (ii) compare it against the fourteen-item scale.
Latent class factor analysis (LCFA) models were applied to the answers to the eight general/adult items to identify latent groups corresponding to FI levels and optimal group-separating cut-off points. Analyses involved a thorough classification agreement evaluation and were performed at the national level and by macro-regions.
Data derived from the cross-sectional Brazilian National Household Sample Survey of 2013.
A nationally representative sample of 116 543 households.
In all households and investigated domains, LCFA detected four distinct household food (in)security groups (food security and three levels of severity of FI) and the same set of cut-off points (1/2, 4/5 and 6/7). Misclassification in the aggregate data was 0·66 % in adult-only households and 1·06 % in HHCA. Comparison of the scale reduced to eight items with the ‘original’ fourteen-item scale demonstrated consistency in the classification. In HHCA, the agreement between both classifications was 96·2 %.
Results indicate the eight ‘generic’ items in HHCA can be reliably used when it is not possible to apply the fourteen-item scale.
Twin research has found genetic influence underlying vocational interests, work values, and job satisfaction. In addition, numerous studies have shown that monozygotic (MZ) twins generally display greater within-pair cooperation and social closeness than dizygotic (DZ) twins. These findings are illuminated by exploring the occupational histories of two female twin pairs, one set MZ and the other set DZ. This is followed by a review of timely twin-based research reports on molar pregnancy, social support, conjoined twinning, and immune discordance. Finally, news items regarding identical twin politicians, multiple birth marriages, a new Guinness World Record for twins, and a twin-family story from the Museum of Memory and Human Rights in Santiago, Chile are both interesting and informative.
Ingham (2) has defined the following summation method. A series ∑ an will be called summable (I) to s if
where as usual [x] is the greatest integer ⩽ x. (An equivalent method was described somewhat earlier by Wintner (7), who called it “an Eratosthenian method“; however, the notation (I) and the name “Ingham summability” introduced by Hardy (1) seem to have become usual.)
Twins switched at birth are a rare subtype of twins who grow up apart. The frequency with which this event occurs, as well as selected life history events, twin relationships, and critical issues generated by the nine recorded cases are reviewed. This is followed by summaries of recent studies addressing classroom placement for twins, mirror syndrome in mothers, unusual twin types, and parenting stress. The article concludes with a review of human interest items from the general media, namely a triplet film, educational achievement, prison release, co-twin impersonation, and facial recognition technology.
Irving I. Gottesman played an important role for psychiatric genetic research in Denmark through more than 40 years of collaboration with Danish scientists, resulting in important twin and family studies based upon the unique national registers available in Denmark.
Genetic predispositions play an important role in the development of internalizing and externalizing behaviors. Understanding the mechanisms through which genetic risk unfolds to influence these developmental outcomes is critical for developing prevention and intervention efforts, capturing key elements of Irv's research agenda and scientific legacy. In this study, we examined the role of parenting and personality in mediating the effect of genetic risk on adolescents’ major depressive disorder and conduct disorder symptoms. Longitudinal data were drawn from a sample of 709 European American adolescents and their mothers from the Collaborative Studies on Genetics of Alcoholism. Results from multivariate path analysis indicated that adolescents’ depressive symptoms genome-wide polygenic scores (DS_GPS) predicted lower parental knowledge, which in turn was associated with more subsequent major depressive disorder and conduct disorder symptoms. Adolescents’ DS_GPS also had indirect effects on these outcomes via personality, with a mediating effect via agreeableness but not via other dimensions of personality. Findings revealed that the pattern of associations was similar across adolescent gender. Our findings emphasize the important role of evocative gene–environment correlation processes and intermediate phenotypes in the pathways of risk from genetic predispositions to complex adolescent outcomes.
In 1968, long before the publication of Stephen J. Gould's The Mismeasure of Man, Herrnstein and Murray's The Bell Curve, or Arthur Jensen's Bias in Mental Testing, Irving Gottesman published a book chapter that addressed head-on the issues that would define the relationship between the genetics of social behavior and large-scale social theory for the next 50 years. That he could do so with his characteristic scholarly thoroughness and scientific tough-mindedness without once lapsing into regressive hereditarianism is a testimony to the scope of his scientific knowledge and the generosity of his intellectual spirit.
One of Irving I. Gottesman's many contributions to behavior genetics, and part of his enduring legacy, was his introduction of the term ‘endophenotype’ to the field of psychiatry. Gottesman argued that focusing on endophenotypes, rather than complex heterogeneous clinical diagnoses, could help elucidate disease etiology. Although a different strategy for gene identification ultimately proved successful (that of amassing extremely large sample sizes in order to overcome the ‘noise’ of heterogeneity and have sufficient power to find genes of very small effect), the endophenotype concept continues to make a meaningful contribution to the field. The endophenotype concept forced the field to move beyond a simple disease model of finding genes ‘for’ psychiatric outcomes, and reminded us that genes are quite distal from complex behavioral outcomes and disorders. Endophenotypes called our attention to the steps along that pathway. In that process, the concept of endophenotypes evolved and expanded to include discussion of the role that other intermediary traits and psychological processes play in the development and genetic etiology of psychiatric and substance use disorders. As large-scale consortia continues to identify genes and generate genome-wide polygenic scores that are associated with behavioral outcomes, the next important step will be to characterize the pathways and mechanisms by which genetic risk unfolds. This essential step of mapping risk from genes to behavior is an evolution that follows naturally from the endophenotype concept, and could ultimately translate into improved prevention and intervention for individuals who are pre-disposed to mental health challenges.
Like families, professors transmit bits of wisdom to their students, not just by what they say but what they do. Colleagues share methods and data, but more importantly, ideas and visions. Irving I. Gottesman was unique in this respect, both brilliant in his field and wise when it came to teaching, guiding, and supporting. His academic pedigree extends across many generations and will for generations to come.
Irving Gottesman is known primarily for his work in psychopathology, but he also had a long-standing interest in understanding psychological development generally (typical and atypical). Through his mentorship, he also influenced work in gender development. Characteristics related to sex and gender are ideally suited to study the interplay of genes and environment across development. We discuss how gender development is influenced by gonadal hormones present during early life, but not in a simple way. We describe some of the challenges and opportunities to extend our understanding of the complexity of gender development. Throughout, we consider the kinds of questions Gottesman would likely have asked and emphasize his influence on our work.
Dr. Irving I. Gottesman was very creative in applying twin research designs to test hypotheses and predictions about human behavior. Two designs stand out among others: twins reared apart from birth and the twin-family study. I (NS) was inspired to incorporate both of these approaches into my own research programs at California State University, Fullerton. Gottesman's involvement and contributions to reared-apart twin research are described, followed by selected findings from the Minnesota Study of Twins Reared Apart (MISTRA), the Fullerton Study of Chinese Twins Reared Apart (CTA), a case report on separated monozygotic (MZ) female twins from South Korea, and doubly exchanged MZ male twin pairs from Colombia, South America. Recent findings from an ongoing twin-family study of social closeness, and future directions, are also presented.