Behavior or behaviour is the range of actions and mannerisms made by individuals, organisms, systems or artificial entities in some environment. These systems can include other systems or organisms as well as the inanimate physical environment. It is the computed response of the system or organism to various stimuli or inputs, whether internal or external, conscious or subconscious, overt or covert, and voluntary or involuntary.
Nature versus nurture is a long-standing debate in biology and society about the relative influence on human beings of their genetic inheritance (nature) and the environmental conditions of their development (nurture). The alliterative expression "nature and nurture" in English has been in use since at least the Elizabethan period and goes back to medieval French. The complementary combination of the two concepts is an ancient concept. Nature is what people think of as pre-wiring and is influenced by genetic inheritance and other biological factors. Nurture is generally taken as the influence of external factors after conception e.g. the product of exposure, experience and learning on an individual.
Twin studies are studies conducted on identical or fraternal twins. They aim to reveal the importance of environmental and genetic influences for traits, phenotypes, and disorders. Twin research is considered a key tool in behavioral genetics and in related fields, from biology to psychology. Twin studies are part of the broader methodology used in behavior genetics, which uses all data that are genetically informative – siblings studies, adoption studies, pedigree, etc. These studies have been used to track traits ranging from personal behavior to the presentation of severe mental illnesses such as schizophrenia.
Human behaviour genetics is an interdisciplinary subfield of behaviour genetics that studies the role of genetic and environmental influences on human behaviour. Classically, human behavioural geneticists have studied the inheritance of behavioural traits. The field was originally focused on determining the importance of genetic influences on human behaviour. It has evolved to address more complex questions such as: how important are genetic and/or environmental influences on various human behavioural traits; to what extent do the same genetic and/or environmental influences impact the overlap between human behavioural traits; how do genetic and/or environmental influences on behaviour change across development; and what environmental factors moderate the importance of genetic effects on human behaviour. The field is interdisciplinary, and draws from genetics, psychology, and statistics. Most recently, the field has moved into the area of statistical genetics, with many behavioural geneticists also involved in efforts to identify the specific genes involved in human behaviour, and to understand how the effects associated with these genes changes across time, and in conjunction with the environment.
Human genetics is the study of inheritance as it occurs in human beings. Human genetics encompasses a variety of overlapping fields including: classical genetics, cytogenetics, molecular genetics, biochemical genetics, genomics, population genetics, developmental genetics, clinical genetics, and genetic counseling.
Hereditarianism is the research program according to which heredity plays a central role in determining human nature and character traits, such as intelligence and personality. Hereditarians believe in the power of genetic influences to explain human behavior and [[eugenics|solve human social-political problems.]] They stress the value of evolutionary explanations in all areas of the human sciences.
Glayde D. Whitney was an American behavioral geneticist and psychologist. He was professor at Florida State University. Beyond his work into the genetics of sensory system function in mice, in his later life he supported David Duke as well as research into race and intelligence and eugenics.
Research on the heritability of IQ inquires into the degree of variation in IQ within a population that is due to genetic variation between individuals in that population. There has been significant controversy in the academic community about the heritability of IQ since research on the issue began in the late nineteenth century. Intelligence in the normal range is a polygenic trait, meaning that it is influenced by more than one gene, and in the case of intelligence at least 500 genes. Further, explaining the similarity in IQ of closely related persons requires careful study because environmental factors may be correlated with genetic factors.
Neal Elgar Miller was an American experimental psychologist. Described as an energetic man with a variety of interests, including physics, biology and writing, Miller entered the field of psychology to pursue these. With a background training in the sciences, he was inspired by professors and leading psychologists at the time to work on various areas in behavioral psychology and physiological psychology, specifically, relating visceral responses to behavior.
Peter McGuffin was a Northern Irish psychiatrist and geneticist from Belfast.
Irving Isadore Gottesman was an American professor of psychology who devoted most of his career to the study of the genetics of schizophrenia. He wrote 17 books and more than 290 other publications, mostly on schizophrenia and behavioral genetics, and created the first academic program on behavioral genetics in the United States. He won awards such as the Hofheimer Prize for Research, the highest award from the American Psychiatric Association for psychiatric research. Lastly, Gottesman was a professor in the psychology department at the University of Minnesota, where he received his Ph.D.
Behavioural genetics, also referred to as behaviour genetics, is a field of scientific research that uses genetic methods to investigate the nature and origins of individual differences in behaviour. While the name "behavioural genetics" connotes a focus on genetic influences, the field broadly investigates the extent to which genetic and environmental factors influence individual differences, and the development of research designs that can remove the confounding of genes and environment. Behavioural genetics was founded as a scientific discipline by Francis Galton in the late 19th century, only to be discredited through association with eugenics movements before and during World War II. In the latter half of the 20th century, the field saw renewed prominence with research on inheritance of behaviour and mental illness in humans, as well as research on genetically informative model organisms through selective breeding and crosses. In the late 20th and early 21st centuries, technological advances in molecular genetics made it possible to measure and modify the genome directly. This led to major advances in model organism research and in human studies, leading to new scientific discoveries.
John C. DeFries is one of the world's leading behavior geneticists. His achievements include being President of the Behavior Genetics Association (1982–1983) and cofounder of the journal Behavior Genetics, as well as its co-editor (1970–1978). His awards include the Dobzhansky Award for Outstanding Research in Behavior Genetics, Consulting Editor of the Journal of Learning Disabilities (1987–2002) and fellowships in the International Academy for Research in Learning Disabilities, Association for Psychological Science, and the American Association for the Advancement of Science, Section J (Psychology).
There are a variety of disabilities affecting cognitive ability. This is a broad concept encompassing various intellectual or cognitive deficits, including intellectual disability, deficits too mild to properly qualify as intellectual disability, various specific conditions, and problems acquired later in life through acquired brain injuries or neurodegenerative diseases like dementia.
Gerald "Jerry" McClearn was an American behavior geneticist and professor emeritus of health and human development and biobehavioral health at the Pennsylvania State University.
In behavioural genetics, DeFries–Fulker (DF) regression, also sometimes called DeFries–Fulker extremes analysis, is a type of multiple regression analysis designed for estimating the magnitude of genetic and environmental effects in twin studies. It is named after John C. DeFries and David Fulker, who first proposed it in 1985. It was originally developed to assess heritability of reading disability in twin studies, but it has since been used to assess the heritability of other cognitive traits, and has also been applied to non-twin methodologies.
Jenae M. Neiderhiser is an American behavior geneticist who is a Distinguished Professor of Psychology and Human Development and Family Studies at Pennsylvania State University, where she is also co-director of the Gene Environment Research Initiative.
Nancy L. Pedersen is an American genetic epidemiologist. She is Professor of Genetic Epidemiology and the leader of the Swedish Adoption/Twin Study of Aging (SATSA) at the Karolinska Institutet in Stockholm, Sweden. She is known for her research on human twins, much of which is based on the Swedish Twin Registry. This has included research on the genetic basis of Alzheimer's disease and self-confidence.
In the context of the nature-nurture debate, interactionism is the view that all human behavioral traits develop from the interaction of both "nature" and "nurture", that is, from both genetic and environmental factors. This view further holds that genetic and environmental influences on organismal development are so closely interdependent that they are inseparable from one another. Historically, it has often been confused with the statistical concept of gene-environment interaction. Historically, interactionism has presented a limited view of the manner in which behavioral traits develop, and has simply demonstrated that "nature" and "nurture" are both necessary. Among the first biologists to propose an interactionist theory of development was Daniel Lehrman. Since then, numerous interactionist perspectives have been proposed, and the contradictions between many of these perspectives has led to much controversy in evolutionary psychology and behavioral genetics. Proponents of various forms of interactionist perspectives include Philip Kitcher, who refers to his view as "causal democracy", and Susan Oyama, who describes her perspective as "constructive interactionism". Critics of interactionism include major figures in behavioral genetics such as Arthur Jensen, Robert Plomin, and philosopher Neven Sesardic.
In adoption studies, selective placement refers to the practice by which adoption agencies tend to deliberately match certain characteristics of an adopted child's adopted parents with those of his or her biological parents. When this occurs, it results in a correlation between environments between biological relatives raised in different homes. It has the potential to bias the conclusions of such studies, because twins who were reared in separate environments may in fact have been reared in much more similar environments than assumed. This can result in an inflated estimate of heritability. There is evidence that selective placement was a major confound in many early studies of twins reared apart. Some adoption studies report little or no evidence of selective placement. For example, a 1979 study by Ho et al. reported a generally low level of selective placement in adopted children for either physical or behavioral traits. The authors concluded that to the extent that selective placement occurred for such traits, "our data suggest that it is based largely on characteristics of the birth father," rather than those of the adoptee. Carey (2003) concluded that selective placement was "moderate" for physical characteristics and typically "small or nonexistent" for behavioral characteristics.
