Kendler Et Al 2006 Ib Psychology
Melanie Wendelberger
Kendler was born on June 9, 1919, in New York City, New York. He studied psychology at Brooklyn College, where he worked as an assistant to Abraham Maslow and conducted a project on thinking under the supervision of Solomon Asch.[1] During this time, Kendler became interested in Gestalt psychology, which prompted him to enroll at the University of Iowa in the hopes of working with Kurt Lewin. However, Kendler later changed his mind and chose to work with Kenneth Spence, under whose supervision Kendler received his Ph.D. from the University of Iowa in 1943.[2]
After serving in the United States Army during World War II, Kendler joined the faculty of the University of Colorado as an assistant professor after the University successfully persuaded the Army to discharge him.[3] In 1948, he joined the faculty of New York University, where he became Professor of Psychology and Chair of the Department of Psychology at University College in 1951. In 1963, he joined the faculty of the University of California, Santa Barbara (UCSB). He was a fellow of the Center for Advanced Study in the Behavioral Sciences in 1969 and 1970, and served as president of the Western Psychological Association in 1971. He retired from the faculty of UCSB in 1990.[2]
Kendler was married to Tracy Kendler (born Tracy Sylvia Seedman), who was also an academic psychologist. In addition to their marriage, the two collaborated on some of their research on discrimination learning.[2] They had two sons: Kenneth and Joel.[3] Howard and Tracy Kendler named their second son Kenneth after Kenneth Spence, the Ph.D. supervisor whom they had both shared.[4] Howard Kendler died on February 17, 2011, in Santa Barbara, California.[1]
The proposed levels theory presented in this book concerns some developmental changes in the capacity to selectively encode information and provide rational solutions to problems. These changes are measured by the behavior exhibited in simple discrimination-learning problems that allow both for information to be encoded either selectively or nonselectively and for solutions to be produced by associative learning or by hypothesis-testing.
The simplicity of these problems permits comparisons between infrahuman and human performance and also between a wide range of ages among humans. Human adults presented with these problems typically encode the relevant information selectively and solve the problems in a rational mode. Infrahuman animals, however, typically process the information nonselectively and solve the problems in an automatic, associative mode. How human children encode the information and solve the problems depends on their age. The youngest children -- like the infrahuman animals -- mostly encode the information nonselectively and solve the problems in the associative mode. But between early childhood and young adulthood there is a gradual, long-term, quantifiable increase in the tendency to encode the information selectively and to solve the problem by testing plausible hypotheses.
The theory explains in some detail the structure, function, development, and operation of the psychological system that produces both the ontogenetic and phylogenetic differences. This system is assumed to be differentiated into an information-processing system and an executive system analogous to the differentiation of the nervous system into afferent and efferent systems. Each of these systems is further differentiated into structural levels, with the higher level, in part, duplicating the function of the lower level, but in a more plastic, voluntary, and efficient manner. The differentiation of the information-processing and executive systems into different functional levels is presumed to have occurred sometime during the evolution of mankind with the higher level evolving later than the lower one as the central nervous system became increasing encephalized. As for human ontogeny, the higher levels are assumed to develop later and more slowly than their lower-level counterparts.
In addition to accounting for a substantial body of empirical data, the theory resolves some recurrent controversies that have bedeviled psychology since its inception as a science. It accomplishes this by showing how information can be both nonselectively and selectively encoded, how automatic associative learning and rational problem-solving can operate in harmony, and how cognitive development can be both qualitative and quantitative.
Genetic similarity refers to the degree of genetic resemblance between individuals or populations. This can be measured by the proportion of shared genetic variants or the level of genetic relatedness between individuals. Genetic similarity can be influenced by various factors, such as genetic ancestry, kinship, and environmental exposure. Individuals who are closely related, such as siblings or parents and offspring, are likely to share a higher degree of genetic similarity than unrelated individuals. Similarly, individuals from the same population or ethnic group may share a higher degree of genetic similarity due to shared ancestry and genetic heritage.
Twin studies are a research method commonly used in psychology to investigate the relative contributions of genetic and environmental factors in human behavior and development. Twin studies involve comparing the similarities and differences between monozygotic (identical) twins, who share 100% of their genetic material, and dizygotic (fraternal) twins, who share only 50% of their genetic material on average.
By comparing the concordance rates of monozygotic and dizygotic twins on a particular trait or behavior, researchers can estimate the relative contributions of genetic and environmental factors to that trait or behavior. If monozygotic twins are more similar in a trait or behavior than dizygotic twins, this suggests a genetic influence. If the concordance rates are similar for both types of twins, this suggests an environmental influence.
Twin studies have been used to investigate a wide range of traits and behaviors, including intelligence, personality, mental health, and substance abuse. They have also been used to explore gene-environment interactions and the role of epigenetics in gene expression and behavior.
One of the key strengths of twin studies is their ability to control for genetic and environmental confounding variables. By comparing the concordance rates of monozygotic and dizygotic twins, researchers can control for genetic factors and investigate the role of environmental factors in shaping behavior. However, twin studies also have limitations, such as the assumption of equal environments for twins and the generalizability of findings to the broader population. Nonetheless, twin studies have provided important insights into the complex interplay of genetic and environmental factors in human behavior and development.
Kendler et al. (2006) conducted a large-scale twin study to investigate the heritability of lifetime major depression in a Swedish population. The study included 11,494 twin pairs born between 1926 and 1958, both monozygotic (MZ) and dizygotic (DZ), who were recruited from the Swedish Twin Registry. The twins were assessed for lifetime major depression using the Structured Interview for DSM-IV diagnoses.
The study found that the heritability of lifetime major depression was estimated to be 38%, indicating a moderate genetic contribution to the risk for major depression. The remaining variance was attributed to non-shared environmental factors (34%) and shared environmental factors (28%). The correlation for lifetime major depression was higher in MZ twins (0.42) than in DZ twins (0.20), indicating a genetic influence on the risk for lifetime major depression.
The study also examined the influence of gender on the heritability of major depression and found no significant differences between males and females. However, the study did find that the heritability of major depression increased with age, suggesting that genetic factors become more important in the development of major depression later in life.
Additionally, the study did not examine potential gene-environment interactions or epigenetic mechanisms that could mediate the relationship between genetic factors and major depression. Thus, the findings should be interpreted with caution and replicated in future studies with more comprehensive assessment methods and diverse samples.
The study by McGue, Elkins, and Iacono (2000) aimed to investigate the relative contributions of genetic and environmental factors to substance use and abuse in adolescence using a twin study design. The study utilized a population-based sample of male and female adolescents born between 1975 and 1984, including 1,389 twin pairs, to assess the heritability of alcohol, tobacco, and drug use.
The study found that genetic factors played a significant role in substance use and abuse in adolescence, with heritability estimates ranging from 44% for tobacco use to 65% for drug use. Environmental factors, including shared and non-shared environmental influences, also contributed to substance use and abuse. Additionally, the study found that genetic influences on substance use and abuse increased with age, suggesting that genetic factors become more important in shaping substance use and abuse as adolescents mature.
Overall, the use of a twin study design allowed the researchers to control for genetic and environmental confounding variables and estimate the relative contributions of genetic and environmental factors to substance use and abuse in adolescence. Twin studies provide a powerful method for investigating the complex interplay of genetic and environmental factors in human behavior and development, including substance use and abuse.
One strength of the study is its use of a large population-based sample of twin pairs. The large sample size increases the statistical power of the study and enhances the generalizability of the findings to the broader population of adolescents. Additionally, the study utilized standardized measures of substance use and abuse, which enhances the validity and reliability of the data. The use of a twin design allowed the researchers to control for genetic and environmental confounding variables and estimate the relative contributions of genetic and environmental factors to substance use and abuse.
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