Behavioral Genetics Research Articles

Genetics of Risk-Taking Behavior: Current Knowledge, Challenges and Future Directions

Genetics of Risk-Taking Behavior: Current Knowledge, Challenges and Future Directions

Genetics of Domestic Dog Behavior

Each of the nearly 450 dog breeds in existence today has a unique history and genetic profile. Early in domestication dogs were bred to perform specific behaviors such as herding, guarding and hunting. Later, fanciers developed hundreds of breeds, often displaying variation in body morphology, including shape and size in addition to coat color, skull shape, leg length, etc. Indeed, domestic dogs display the largest amount of genetic variation of any land mammal currently on earth. We are interested in understanding the genetic underpinnings of that variation, and applying those results to studies of growth regulation, normal and abnormal behavior and disease susceptibility. We have therefore assembled the largest and most diverse dataset of dog breeds and other canines to date with canines originating from six continents, reflecting the extensive phenotypic variation and heritage that coalesce in modern dogs. Building a dataset of whole genome sequence from thousands of dogs we have identified over 90 million single nucleotide variants for this purpose. In this presentation we explore the genetics underlying the evolutionary transition from wolf to domestic dog, highlighting genes that when mutated contribute to major human behavioral phenotypes. We then describe the genetics of a subset of breed behaviors.

Cognitive Creationism Compared to Young-Earth Creationism

“Cognitive creationism” is a term for ideologically based rejection of concepts from differential psychology or behavioral genetics. Various authors have compared this practice to young-Earth creationism, but the parallels between the two have not previously been subjected to an in-depth comparison, which is conducted for the first time in this paper. Both views are based on a similar set of psychological needs, and both have developed epistemologically similar worldviews, which draw certain conclusions ahead of time and then interpret all evidence in light of these assumptions. This reversal of the scientific method leads both young-Earth creationists and cognitive creationists to reject large swaths of otherwise well-established research due to its potential to support conclusions they have chosen a priori to reject. Both views also tend to rely on nonparsimonious ad hoc explanations, which are usually not able to reliably predict any future results. The risks posed by cognitive creationism will be discussed, along with potential implications for science education.

The double helix at school: Behavioral genetics, disability, and precision education

The prospect of using behavioral genetic data in schools is gaining momentum in the U.S., with some scholars advocating for the tailoring of educational interventions to students' genetic makeup (“precision education”). Public perspectives on testing for and using behavioral genetic data in schools can affect policies but are unknown. We explored public views in the U.S. (n = 419) on key issues in precision education. The introduction of a child's behavioral genetic information regarding Attention-Deficit/Hyperactivity-Disorder was associated with beliefs that such data should be considered in educational planning for the child and increased medicalization, but also a belief in treatment efficacy. Most participants expressed interest in learning about children's behavioral genetic predispositions but would disapprove of testing without parental consent. Differences by participants' race, ethnicity and educational attainment were observed. Our findings indicate the public's complex understanding of genetic information and the challenges for wide implementation of precision education in the U.S.

The Making of Long-Lasting Memories: A Fruit Fly Perspective

Understanding the nature of the molecular mechanisms underlying memory formation, consolidation, and forgetting are some of the fascinating questions in modern neuroscience. The encoding, stabilization and elimination of memories, rely on the structural reorganization of synapses. These changes will enable the facilitation or depression of neural activity in response to the acquisition of new information. In other words, these changes affect the weight of specific nodes within a neural network. We know that these plastic reorganizations require de novo protein synthesis in the context of Long-term memory (LTM). This process depends on neural activity triggered by the learned experience. The use of model organisms like Drosophila melanogaster has been proven essential for advancing our knowledge in the field of neuroscience. Flies offer an optimal combination of a more straightforward nervous system, composed of a limited number of cells, and while still displaying complex behaviors. Studies in Drosophila neuroscience, which expanded over several decades, have been critical for understanding the cellular and molecular mechanisms leading to the synaptic and behavioral plasticity occurring in the context of learning and memory. This is possible thanks to sophisticated technical approaches that enable precise control of gene expression in the fruit fly as well as neural manipulation, like chemogenetics, thermogenetics, or optogenetics. The search for the identity of genes expressed as a result of memory acquisition has been an active interest since the origins of behavioral genetics. From screenings of more or less specific candidates to broader studies based on transcriptome analysis, our understanding of the genetic control behind LTM has expanded exponentially in the past years. Here we review recent literature regarding how the formation of memories induces a rapid, extensive and, in many cases, transient wave of transcriptional activity. After a consolidation period, transcriptome changes seem more stable and likely represent the synthesis of new proteins. The complexity of the circuitry involved in memory formation and consolidation is such that there are localized changes in neural activity, both regarding temporal dynamics and the nature of neurons and subcellular locations affected, hence inducing specific temporal and localized changes in protein expression. Different types of neurons are recruited at different times into memory traces. In LTM, the synthesis of new proteins is required in specific subsets of cells. This de novo translation can take place in the somatic cytoplasm and/or locally in distinct zones of compartmentalized synaptic activity, depending on the nature of the proteins and the plasticity-inducing processes that occur. We will also review recent advances in understanding how localized changes are confined to the relevant synapse. These recent studies have led to exciting discoveries regarding proteins that were not previously involved in learning and memory processes. This invaluable information will lead to future functional studies on the roles that hundreds of new molecular actors play in modulating neural activity.

Commissioned Book Review: Michael Ryan, The Genetics of Political Behavior: How Evolutionary Psychology Explains Ideology

Commissioned Book Review: Michael Ryan, <i>The Genetics of Political Behavior: How Evolutionary Psychology Explains Ideology</i>

Action detection using a neural network elucidates the genetics of mouse grooming behavior.

Automated detection of complex animal behaviors remains a challenging problem in neuroscience, particularly for behaviors that consist of disparate sequential motions. Grooming is a prototypical stereotyped behavior that is often used as an endophenotype in psychiatric genetics. Here, we used mouse grooming behavior as an example and developed a general purpose neural network architecture capable of dynamic action detection at human observer-level performance and operating across dozens of mouse strains with high visual diversity. We provide insights into the amount of human annotated training data that are needed to achieve such performance. We surveyed grooming behavior in the open field in 2457 mice across 62 strains, determined its heritable components, conducted GWAS to outline its genetic architecture, and performed PheWAS to link human psychiatric traits through shared underlying genetics. Our general machine learning solution that automatically classifies complex behaviors in large datasets will facilitate systematic studies of behavioral mechanisms.

Housing, Husbandry and Welfare of a "Classic" Fish Model, the Paradise Fish (Macropodus opercularis).

Simple SummaryParadise fish (Macropodus opercularis) has been a favored subject of behavioral research during the last decades of the 20th century. Lately, however, with a massively expanding genetic toolkit and a well annotated, fully sequenced genome, zebrafish (Danio rerio) became a central model of recent behavioral research. But, as the zebrafish behavioral repertoire is less complex than that of the paradise fish, the focus on zebrafish is a compromise. With the advent of novel methodologies, we think it is time to bring back paradise fish and develop it into a modern model of behavioral and evolutionary developmental biology (evo-devo) studies. The first step is to define the housing and husbandry conditions that can make a paradise fish a relevant and trustworthy model. Here, we define the relevant welfare parameters for keeping a healthy population of paradise fish and provide a detailed description of our recent experience in raising and successfully breeding this species under laboratory conditions.Thanks to its small size, external fertilization and fecundity, over the past four decades, zebrafish (Danio rerio) has become the dominant fish model species in biological and biomedical research. Multiple lines of evidence, however, suggest that the reliance on only a handful of genetic model organisms is problematic, as their unique evolutionary histories makes them less than ideal to study biological questions unrelated to their historically contingent adaptations. Therefore, a need has emerged to develop novel model species, better suited for studying particular problems. The paradise fish (Macropodus opercularis) has a much more complex behavioral repertoire than zebrafish and has been a favored model animal in ethological research during the last decades of the previous century. We believe that with currently available, easily adaptable genetic toolkits, this species could be easily developed into a popular model of behavioral genetics. Despite its earlier popularity, however, the description of a detailed housing and husbandry protocol for this species is still missing from scientific literature. We present here a detailed description of how to raise and breed paradise fish successfully under laboratory conditions, and also discuss some of the challenges we faced while creating a stable breeding population for this species in our facility.

Quick detection of a rare species: Forensic swabs of survey tubes for hazel dormouse Muscardinus avellanarius urine

Abstract Effective conservation decisions rely on accurate survey data, but methods can be resource‐intensive and risk false negative results. Presence of the threatened hazel dormouse (England, UK) is typically confirmed by looking for its nest in survey tubes, over a 6‐month period. As an alternative, environmental DNA (eDNA) surveys have proven benefits in efficiency and accuracy for other taxa, but generally rely on the extraction and amplification of DNA from water, soil or sediment, which are not yet dependable samples for rare terrestrial mammals like the hazel dormouse. At a known occupancy site, paper‐lined survey tubes were used to capture a DNA sample. Like other species of rodent, the hazel dormouse excretes urine freely, and this was highlighted by ultraviolet torch, swabbed from the paper, extracted and hazel dormouse eDNA amplified by quantitative polymerase chain reaction (qPCR). Hazel dormouse presence was confirmed in this way in three out of 50 tubes within 8 days. Detection by conventional nest survey occurred on day 63 when a hazel dormouse nest was found in a single survey tube. We calculate that amplification of eDNA left behind in tubes increased survey efficiency here at least 12‐fold. Synthesis and applications. In this study we demonstrate that eDNA swabbed from a clean substrate placed in survey apparatus can significantly hasten the detection of a rare species. This method has the potential to broaden the application of eDNA to other terrestrial vertebrates, including surveys at large spatiotemporal scales. Beyond presence/absence, the non‐invasive DNA sample could also offer insights into sex ratio, abundance, behaviour and population genetics.

Distress and Psychological Impact of Covid-19 Pandemic and Previous Outbreaks Review and Methodological Suggestions

International Journal of Behavioral Research & Psychology (IJBRP) ISSN 2332-3000 is a comprehensive, peer reviewed journal devoted to BioAnalytical Methods and BioEquivalence Studies. publishes original research, latest developments, review papers, scientific data, editorials from leading scientists and scholars around the world.IJBRP publishes following fields:Ethnicity & Cultural,Applied Anthropology,Psychoanalysis,Environmental,Industrial-Organizational,Gestalt,Cognitivism,Organizational Behavior,Inflammatory Skin Diseases,Sociology,Psychometrics,Ethical Standards,Community,Psychobiology,Social Cognition,Semantic Networks,Social Neuroscience,Clinical,Developmental,Psychobiology,Operations Research,Personality,Functionalism,Cyberpsychology,Behavior Genetics,Behaviorism,Health,Humanism,Existentialism,Anthropology

Multilevel Modeling in Classical Twin and Modern Molecular Behavior Genetics.

For more than a decade, it has been known that many common behavior genetics models for a single phenotype can be estimated as multilevel models (e.g., van den Oord 2001; Guo and Wang 2002; McArdle and Prescott 2005; Rabe-Hesketh etal. 2007). This paper extends the current knowledge to (1) multiple phenotypes such that the method is completely general to the variance structure hypothesized, and (2) both higher and lower levels of nesting. The multi-phenotype method also allows extended relationships to be considered (see also, Bard etal. 2012; Hadfield and Nakagawa 2010). The extended relationship model can then be continuously expanded to merge with the case typically seen in the molecular genetics analyses of unrelated individuals (e.g., Yang etal. 2011). We use the multilevel form of behavior genetics models to fit a multivariate three level model that allows for (1) child level variation from unique environments and additive genetics, (2) family level variation from additive genetics and common environments, and (3) neighborhood level variation from broader geographic contexts. Finally, we provide R (R Development Core Team 2020) functions and code for multilevel specification of several common behavior genetics models using OpenMx (Neale etal. 2016).

Notes on Three Decades of Methodology Workshops.

Since 1987, a group of behavior geneticists have been teaching an annual methodology workshop on how to use state-of-the-art methods to analyze genetically informative data. In the early years, the focus was on analyzing twin and family data, using information of their known genetic relatedness to infer the role of genetic and environmental factors on phenotypic variation. With the rapid evolution of genotyping and sequencing technology and availability of measured genetic data, new methods to detect genetic variants associated with human traits were developed and became the focus of workshop teaching in alternate years. Over the years, many of the methodological advances in the field of statistical genetics have been direct outgrowths of the workshop, as evidence by the software and methodological publications authored by workshop faculty. We provide data and demographics of workshop attendees and evaluate the impact of the methodology workshops on scientific output in the field by evaluating the number of papers applying specific statistical genetic methodologies authored by individuals who have attended workshops.

Shared Environmental Influences on Electronic Cigarette Use Among Adolescent and Young Adult Females.

Electronic cigarettes are now the most commonly used form of tobacco product among youth in the United States. Current evidence suggests that although e-cigarettes are perceived as less harmful and preferred over combustible cigarettes by adolescents, adolescents who try e-cigarettes are at greater risk of transitioning to combustible cigarettes. The genetic and environmental contributions to liability for e-cigarette use have not yet been examined using a behavioral genetic design. Behavioral genetic models of lifetime and current e-cigarette use and friends who use e-cigarettes were examined among female monozygotic and dizygotic twins. A total of 41 female twin pairs (65.9% monozygotic twins; age = 19.7, SD = 1.6) with complete data on the study variables were included in the present analyses. The majority of the sample (68.1%) had at least some friends who use e-cigarettes. Additive genetic effects on e-cigarette use were not present, but the shared environment explained 98.7% of the variance in lifetime e-cigarette use, 96.6% in current e-cigarette use, and 94.9% in affiliation with friends who use e-cigarettes. This first study on the behavioral genetics of e-cigarette use among adolescents and young adults suggest that environmental factors shared by twins within a family seem to play a predominant role in the initial stages of e-cigarette use, a finding that is consistent with what has been found for tobacco. The findings emphasize the importance of continuing population-based tobacco control interventions to reduce the burden of e-cigarette use among adolescents. The shared environment significantly influences the initiation and regular use of electronic cigarettes and affiliation with friends who use electronic cigarettes among adolescent and young adult females. These findings underscore the importance of formulating preventive interventions that mitigate the social effects of familial influences on e-cigarette use through social skills training, education on harms of e-cigarettes for young people, or altering social norms regarding initiation of novel tobacco products.

Personality’ orientation as a factor of mental states of secondary school students: empirical research

The research is devoted to the theoretical substantiation and empirical identification of the correlation of mental states with the orientation of the personality of secondary school students in the dynamics of age development. The influence of teachers 'professional orientation on the course of students' mental states is determined. Based on genetic psychology, a model of subject-subject space of interaction was developed: "teacher orientation-mental states-orientation of students". It is proved that the target settings of teachers are external determinants of mental states and affect the target settings of students. The mental states of school-age children during the entire period of study in primary and secondary school were studied. The equality of manifestations of mental states and target attitudes of schoolchildren is established, in particular: the affective level of target attitudes corresponds to the mental level of states when mental states and target attitudes act as experiences, emotional assessments; cognitive level of mental states and target attitudes, when mental states and one's own target attitudes at the conative level are realized. It is specified that mental states and target attitudes of the personality have similarity of directions: at positive mental states of pupil’s target attitudes are expressed by positive motives, at negative mental states - by negative motives.&#x0D; Thus, it is established that in the conditions of educational process of comprehensive school certain dynamics of mental states and target attitudes of pupils of different age groups is traced. The dynamics of target settings is confirmed, which is characterized by a tendency to increase the components of goal setting of schoolchildren from primary to senior school age. Thus, summarizing the results of the study by comparing the empirical distributions of the manifestations of mental states and target attitudes of students and it was determined that: the distribution of positive mental states of students coincides with the distribution of positive motives in the target settings of students, organization, communication, intelligence, methodological knowledge and skills, knowledge of psychology; the distribution of positive mental states of students does not coincide with the distribution of positive motives in the target attitudes of students and the professional orientation of teachers to motivate personal approval, good relations with the staff and administration; the distribution of negative mental states of students coincides with the distribution of negative motives in the target settings of students and the professional orientation of teachers to motivate personal approval; the distribution of negative mental states of students does not coincide with the distribution of negative motives in the target attitudes of students and the professional orientation of teachers on the organization and subject and the ability to engage in teaching without harm to privacy.&#x0D; In accordance with the obtained results, the main models of optimization of subject-subject interaction in the educational activities of schoolchildren are generalized from the standpoint of genetic-modelling method and genetically oriented psychotherapy.

An overview of obesity mechanisms in humans: Endocrine regulation of food intake, eating behaviour and common determinants of body weight.

Obesity is one of the biggest health challenges of the 21st century, already affecting close to 700 million people worldwide, debilitating and shortening lives and costing billions of pounds in healthcare costs and loss of workability. Body weight homeostasis relies on complex biological mechanisms and the development of obesity occurs on a background of genetic susceptibility and an environment promoting increased caloric intake and reduced physical activity. The pathophysiology of common obesity links neuro-endocrine and metabolic disturbances with behavioural changes, genetics, epigenetics and cultural habits. Also, specific causes of obesity exist, including monogenetic diseases and iatrogenic causes. In this review, we provide an overview of obesity mechanisms in humans with a focus on energy homeostasis, endocrine regulation of food intake and eating behavior, as well as the most common specific causes of obesity.

Autistic traits and individual brain differences: functional network efficiency reflects attentional and social impairments, structural nodal efficiencies index systemising and theory-of-mind skills

BackgroundAutism is characterised not only by impaired social cognitive ‘empathising’ but also by superior rule-based ‘systemising’. These cognitive domains intertwine within the categorical diagnosis of autism, yet behavioural genetics suggest largely independent heritability, and separable brain mechanisms. We sought to determine whether quantitative behavioural measures of autistic traits are dimensionally associated with structural and functional brain network integrity, and whether brain bases of autistic traits vary independently across individuals.MethodsThirty right-handed neurotypical adults (12 females) were administered psychometric (Social Responsiveness Scale, Autism Spectrum Quotient and Systemising Quotient) and behavioural (Attention Network Test and theory-of-mind reaction time) measures of autistic traits, and structurally (diffusion tensor imaging) and functionally (500 s of 2 Hz eyes-closed resting fMRI) derived graph-theoretic measures of efficiency of information integration were computed throughout the brain and within subregions.ResultsSocial impairment was positively associated with functional efficiency (r = .47, p = .006), globally and within temporo-parietal and prefrontal cortices. Delayed orienting of attention likewise was associated with greater functional efficiency (r = − .46, p = .0133). Systemising was positively associated with global structural efficiency (r = .38, p = 0.018), driven specifically by temporal pole; theory-of-mind reaction time was related to structural efficiency (r = − .40, p = 0.0153) within right supramarginal gyrus.LimitationsInterpretation of these relationships is complicated by the many senses of the term ‘connectivity’, including functional, structural and computational; by the approximation inherent in group functional anatomical parcellations when confronted with individual variation in functional anatomy; and by the validity, sensitivity and specificity of the several survey and experimental behavioural measures applied as correlates of brain structure and function.ConclusionsFunctional connectivities highlight distributed networks associated with domain-general properties such as attentional orienting and social cognition broadly, associating more impaired behaviour with more efficient brain networks that may reflect heightened feedforward information flow subserving autistic strengths and deficits alike. Structural connectivity results highlight specific anatomical nodes of convergence, reflecting cognitive and neuroanatomical independence of systemising and theory-of-mind. In addition, this work shows that individual differences in theory-of-mind related to brain structure can be measured behaviourally, and offers neuroanatomical evidence to pin down the slippery construct of ‘systemising’ as the capacity to construct invariant contextual associations.

The genetics of perinatal behaviour of Merinos in relation to lamb survival and lambs weaned per ewe mated

Data for birth weight (BW), lamb survival (LS) and neonatal behaviour, including records of between 1494 (latency of birth to first suckling or LBS) and 2705 (BW and LS) lambs were used. Additionally to the lamb data, ewe data comprising of between 1003 ewe-year records for the latency of stay on the birth site (SBS) and 2024 ewe-year records for number of lambs weaned per ewe mated (NLW) were analysed. These records were from selection lines that had been divergently selected from the same base population since 1986, either for NLW (termed the High or H line) or against NLW (termed the Low or L line). Overall, H line lambs had an improved LS compared to their L line contemporaries, while H line ewes were superior to L line ewes for NLW. Latency of parturition of H line progeny was shorter than in L line progeny while ewe lambs had shorter births than ram lambs. Lamb sex and selection line had no effect on the latency from birth to suckling, which decreased as dam age increased. The second of multiples took longest to progress to suckling from birth, with singles being the quickest. H line ewes had shorter parturitions and cooperated better with the first suckling attempts of their offspring. Single-trait direct heritability estimates (h²) in lambs were 0.15 for BW, 0.07 for LS, 0.06 for latency of parturition (LP) and 0.14 for LBS. The inclusion of the maternal genetic variance ratio (m²) resulted in an improvement in the log likelihood ratio for BW, LP and LBS, yielding estimates of respectively 0.37, 0.18 and 0.12. The maternal permanent environment variance ratio for LS amounted to 0.07. The genetic correlation of LS with LP was favourable at -0.69. Estimates of h², as ewe traits, were 0.04 for NLW, 0.17 for LP, 0.07 for ewe cooperation score (ECS) and 0.20 for SBS. Genetic correlations indicated that ewes with a high NLW had shorter parturitions while ECS was genetically correlated to SBS. Genetic trends suggested divergence between the lines for breeding values for LP, suggesting that parturitions became shorter in the H line and longer in the L line. Selection for NLW would yield desirable outcomes for ewe and lamb behavioural traits based on genetic trends and correlations. Such selection would putatively benefit animal welfare by reducing birth stress in ewes and lambs and by promoting maternal cooperation with their offspring’s first suckling attempts in ewes.

A global collaboration to study intimate partner violence-related head trauma: The ENIGMA consortium IPV working group.

Intimate partner violence includes psychological aggression, physical violence, sexual violence, and stalking from a current or former intimate partner. Past research suggests that exposure to intimate partner violence can impact cognitive and psychological functioning, as well as neurological outcomes. These seem to be compounded in those who suffer a brain injury as a result of trauma to the head, neck or body due to physical and/or sexual violence. However, our understanding of the neurobehavioral and neurobiological effects of head trauma in this population is limited due to factors including difficulty in accessing/recruiting participants, heterogeneity of samples, and premorbid and comorbid factors that impact outcomes. Thus, the goal of the Enhancing NeuroImaging Genetics through Meta-Analysis (ENIGMA) Consortium Intimate Partner Violence Working Group is to develop a global collaboration that includes researchers, clinicians, and other key community stakeholders. Participation in the working group can include collecting harmonized data, providing data for meta- and mega-analysis across sites, or stakeholder insight on key clinical research questions, promoting safety, participant recruitment and referral to support services. Further, to facilitate the mega-analysis of data across sites within the working group, we provide suggestions for behavioral surveys, cognitive tests, neuroimaging parameters, and genetics that could be used by investigators in the early stages of study design. We anticipate that the harmonization of measures across sites within the working group prior to data collection could increase the statistical power in characterizing how intimate partner violence-related head trauma impacts long-term physical, cognitive, and psychological health.

Estimation of Parental Effects Using Polygenic Scores

Offspring resemble their parents for both genetic and environmental reasons. Understanding the relative magnitude of these alternatives has long been a core interest in behavioral genetics research, but traditional designs, which compare phenotypic covariances to make inferences about unmeasured genetic and environmental factors, have struggled to disentangle them. Recently, Kong et al. (2018) showed that by correlating offspring phenotypic values with the measured polygenic score of parents’ nontransmitted alleles, one can estimate the effect of “genetic nurture”—a type of passive gene–environment covariation that arises when heritable parental traits directly influence offspring traits. Here, we instantiate this basic idea in a set of causal models that provide novel insights into the estimation of parental influences on offspring. Most importantly, we show how jointly modeling the parental polygenic scores and the offspring phenotypes can provide an unbiased estimate of the variation attributable to the environmental influence of parents on offspring, even when the polygenic score accounts for a small fraction of trait heritability. This model can be further extended to (a) account for the influence of different types of assortative mating, (b) estimate the total variation due to additive genetic effects and their covariance with the familial environment (i.e., the full genetic nurture effect), and (c) model situations where a parental trait influences a different offspring trait. By utilizing structural equation modeling techniques developed for extended twin family designs, our approach provides a general framework for modeling polygenic scores in family studies and allows for various model extensions that can be used to answer old questions about familial influences in new ways.

ОСНОВНЫЕ НАПРАВЛЕНИЯ СИБЛИНГОВЫХ ИССЛЕДОВАНИЙ

An overview of the areas of sibling research that laid the foundation for the modern understanding of sibling issues is presented. Attention is focused on the importance of sibling relationships for personal development, socialization and adaptation, and on the existing shortage of relevant work at the same time. The main stages of the development of sibling theory in their continuity are considered, starting from the first studies devoted to the search for a connection between the order of birth and achievements and dated to the end of the 19th century, to the term “individual environment” developed by the genetics of behavior in the second half of the 20th century. It emphasizes the role of A. Adler, who has made sibling a central feature of family life and personal development and has long determined the future direction of empirical family research. It shows a gradual shift in the interest of researchers from studying the influence of birth order, gender, and age intervals between siblings on personal characteristics. In this connection, an analysis of the nature of sibling relations on the basis of reciprocity and complementarity, undertaken by Dunn, is given. Early works on the jealousy and rivalry of children in the family, the study of the impact of parental differential treatment on them, as well as the influence of child characteristics on siblings in families with sick children are considered.