century largely because of the overwhelming influence of behaviourism in the field. Later behavioural genetic research focused on quantitative methods. In 1984, a research program named the Swedish Adoption/Twin Study of Aging (SATSA) was initiated in gerontological genetics. The research was executed on Twins Reared Apart (TRA) and Twins Reared Together (TRT). In this three-year interval study, the testing was carried out in two ways, Mail-Out Questionnaire and In-Person Testing (IPT). The IPT includes functional capacity, physical performance measurements, neurological state, general health, cardiovascular health, and cognitive abilities, all of which are particularly significant in ageing. The IPT had two major components for testing, Biomedical and Cognitive Assessment. The biomedical component was constructed to analyses the general health status like age changes, lungs function and capacity, physical strength. With this, the cognitive component was developed to represent and evaluate domains of crystallized and fluid intelligence and memory. The data acquired from this study allowed researchers to assess genetic contributions to age changes and continuities throughout the length of the SATSA twins' later lives, which prolonged a decade and a half. Contemporary behavioural quantitative genetics Behavioural geneticists study both psychiatric and mental disorders, such as schizophrenia, bipolar disorder, and alcoholism, as well as behavioural and social characteristics, such as personality and social attitudes. Recent trends in behavioural genetics have indicated an additional focus toward researching the inheritance of human characteristics typically studied in developmental psychology. For instance, a major focus in developmental psychology has been to characterize the influence of parenting styles on children. However, in most studies, genes are a confounding variable. Because children share half of their alleles with each parent, any observed effects of parenting styles could be effects of having many of the same alleles as a parent (e.g. harsh aggressive parenting styles have been found to correlate with similar aggressive child characteristics: is it the parenting or the genes?). Thus, behaviour genetics research is currently undertaking to distinguish the effects of the family environment from the effects of genes. This branch of behaviour genetics research is becoming more closely associated with mainstream developmental psychology and the sub-field of developmental psychopathology as it shifts its focus to the heritability of such factors as emotional self-control, attachment, social functioning, aggressiveness, etc. Several academic bodies exist to support behaviour genetic research, including the International Behavioural and Neural Genetics Society, Behavior Genetics Association, the International Society of Psychiatric Genetics, and