Download
1 / 84
2.26k likes | 6.07k Vues
Genetics and Behavior. Formal Lecture. To what extent are you influenced by the following?. Parents and Peers Parents and Early Experiences Peer Influence Cultural Influences Variations Across Cultures Culture and the Self. To what extent are you influenced by the following?.
E N D
Genetics and Behavior Formal Lecture
To what extent are you influenced by the following? Parents and Peers • Parents and Early Experiences • Peer Influence Cultural Influences • Variations Across Cultures • Culture and the Self
To what extent are you influenced by the following? Cultural Influences • Culture and Child-Rearing • Developmental Similarities Across Groups Gender Development • Gender Similarities and Differences
To what extent are you influenced by the following? Gender Development • The Nature of Gender • The Nurture of Gender
Behavior Genetics: Predicting Individual Differences Behavior Geneticists study our differences and weigh the relative effects of heredity and environment.
Genetics Crash Course • Genetic arguments of behavior are based on the principle of inheritance ( heredity ). • Genes, the basic unit of heredity, are located on chromosomes. Humans have 23 pairs of chromosomes, with approximately 25,000 genes which were passed on from each parent. • Chromosomes are made up of DNA, and genes are just segments of DNA. • Each gene ( or segment of DNA) contains four basic chemicals –identified by the letters A,T,C and G.
Genes: Our Codes for Life Chromosomes containing DNA (deoxyribonucleic acid) are situated in the nucleus of a cell.
Genes: Our Codes for Life Segments within DNA consist of genes that make proteins to determine our development.
Genome Genome is the set of complete instructions for making an organism, containing all the genes in that organism. Thus, the human genome makes us human, and the genome for drosophila makes it a common house fly.
What is behavioral genetics? • Sir Francis Galton (1822-1911) was the first scientist to study heredity and human behavior systematically. • The term "genetics" did not even appear until 1909, only 2 years before Galton's death. With or without a formal name, the study of heredity always has been, at its core, the study of biological variation. • Human behavioral genetics, a relatively new field, seeks to understand both the genetic and environmental contributions to individual variations in human behavior. It is important to note that genetics alone could never define behavior. Our environment plays a significant role in genetic expression.
Objective 3.1 *With reference to relevant research studies, to what extent does genetic inheritance influence behavior? *Essay Question
What have we learned thus far that could help us answer this question?
Principle 4: • Genetic predispositionsmay affect behavior and or mental processes. • Our behaviors have an evolutionary explanation and have been passed from generation to generation through the process of natural selection. • These behaviors are genetically inherited and play a role in human behavior.
“Nice Genes” • Genetics is the study of how living things pass on traits from one generation to the next. • We are not clones of our parents, but some traits or characteristics appear generation after generation in predictable patterns. • Scientists named these basic units of inheritance genes.
“Nice Genes” • Genes are carried by threadlike bodies called chromosomes found in the nucleus of all cells. Humans have 23 pairs, peas have 7, monkeys have 27. • The main ingredient of chromosomes is DNA -- a complex molecule in a double helix pattern. DNA carries the directions for a particular trait.
Genetic Influence on behavior • Understanding differences in human behavior has traditionally been done from two perspectives – the nature approach that emphasized genes and inborn characteristics, and the nurture approach that emphasize learning, experience and the environment. This was the origin of the nature/nurture debate that spanned the 20th century. • The twentieth century saw a swing between these two perspectives, but current thinking emphasizes gene - environment interplay A+ info on gene expression http://www.gnxp.com/MT2/archives/003642.html
Genetic Influence on behavior • Psychologists now believe that an individual may have a genetic predisposition towards a certain behavior, but without the appropriate environmental stimuli this behavior may not be manifested ( e.g. a genetic predisposition towards depression, but a happy childhood environment ) A+ info on gene expression http://www.gnxp.com/MT2/archives/003642.html
Studying genes • The effects of genes on behaviors (such as aggression)can be seen primarily through three methods; correlational ( twin and adoption studies) linkage studies and gene-environment interplay. Evidence for the influence of genes: • Twin studies • Gene studies
Twin Studies • Twin studies are often used by psychologists to look at the influence of heredity and environment. • Identical (monozygotic - MZ) twins develop from a single fertilized ovum so any differences between them must be due to environmental factors. • Fraternal (dizydotic - DZ) twins develop from two separate fertilized eggs and are no more similar genetically than brothers and sisters
Twin Studies • Identical twins serve as excellent subjects for controlled experiments because they share prenatal environments and those reared together also share common family, social, and cultural environments. • Furthermore, studies of twins can both point to hereditary effects and also estimate heritability, a term that describes the magnitude of the genetic effect.
Twin Studies • Some of the most conclusive twin study research has analyzed identical and fraternal twins who were raised apart. • Researchers have sought to establish whether characteristics such as personality traits, aptitudes, and occupational preferences are the products of.nature or nurture
Twin Studies • Similar characteristics among identical twins reared apart might indicate that their genes played a major role in developing that trait. • Different characteristics might indicate the opposite—that environmental influences assume a much stronger role. By comparing identical and fraternal twins, investigators can investigate the extent to which genetic inheritance influences behavior.
The Minnesota Twins Studies • In the most widely publicized study of this type, launched in 1979, University of Minnesota psychologist Thomas Bouchard and his colleagues have chronicled the fates of about 60 pairs of identical twins raised separately. • Some of the pairs had scarcely met before Bouchard contacted them, and yet the behaviors and personalities and social attitudes they displayed in lengthy batteries of tests were often remarkably alike.
The Minnesota Twins Studies • The first pair Bouchard met, James Arthur Springer and James Edward Lewis, had just been reunited at age 39 after being given up by their mother and separately adopted as 1-month-olds.
The Minnesota Twins Studies • Springer and Lewis, both Ohioans, found they had each married and divorced a woman named Linda and remarried a Betty. • They shared interests in mechanical drawing and carpentry; their favorite school subject had been math, their least favorite, spelling. • This type of twin study research has consistently suggested that genes can play an important role in our behaviors. But is it the only factor?
Things to consider… • It is often difficult to separate the relative influences of heredity and environment on human characteristics. • People who have similar genetic makeup (e.g., brothers and sisters, parents and their children) typically live in similar environments as well. So when we see similarities in behavior among members of the same family, it is hard to know whether those similarities are due to the genes or to the environments that family members share. • Nevertheless, a significant body of research tells us that both heredity and environment affect behavior. A+ info on gene expression http://www.gnxp.com/MT2/archives/003642.html
Environmental Influences • Thus far it has been established through research and various studies that genetics do influence criminal or antisocial behavior. However, researchers also agree that there is an environmental component that needs to be examined. Thus, it safe to safe that environment research is just as important as genetic research.Environment enrichment research can also be used to support this idea. Social Learning theory (1965) • Bandura (1965), claims that aggressive behavior is learned through observing and imitating aggressive other people. His Bobodoll studies powerfully demonstrated the imitation of aggressive behaviors by children. We shall look at this study in more detail under the Sociocultural level of analysis.
Nature and Nurture Some human traits are fixed, such as having two eyes. However, most psychological traits are liable to change with environmental experience. Genes provide choices for the organism to change its form or traits when environmental variables change. Therefore, genes are malleable or self-regulating.
Gene-Environment Interaction Genes can influence traits which affect responses, and environment can affect gene activity. A genetic predisposition that makes a child restless and hyperactive evokes an angry response from his parents. A stressful environment can trigger genes to manufacture neurotransmitters leading to depression.
Gene-Environment Interaction Genes can influence traits which affect responses, and environment can affect gene activity. A genetic predisposition that makes a child restless and hyperactive evokes an angry response from his parents. A stressful environment can trigger genes to manufacture neurotransmitters leading to depression.
Objective 3.2 Examine one evolutionary explanation of behavior.
“ Genetics is the key to the past. Every human gene must have an ancestor….each gene is a message from our forebears and together they contain the whole story of human evolution” ( Steve Jones, 1994, British Geneticist)
What is evolution and how does it tie into psychology? “Our modern skulls houses a Stone Age mind “ (Cosmides & Tooby) • Evolutionary psychology is a combination of evolutionary biology and cognitive psychology. It sees the mind as a set of evolved mechanisms, or adaptations, that have promoted survival and reproduction. • All behavior is a result of these evolved mechanisms. Thus every behavior that we see today is the result of an evolved process.
What is evolution and how does it tie into psychology? • To understand evolutionary psychology it is necessary to have a basic understanding of genes, inheritance, and the principles of natural selection.
What is evolution and how does it tie into psychology? • Evolutionary psychology is inspired by the work of Charles Darwin and applies his ideas of natural selection to the mind. • Natural selection is the nonrandom process by which biological traits become more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution. A+ info on Darwin’s work http://embryology.med.unsw.edu.au/pdf/Origin_of_Species.pdf
Evolutionary explanations of behavior • Darwin's theory argues that all living species, including humans, arrived at their current biological form through a historical process involving random inheritable changes (genetic mutations) • Some changes are adaptive, that is, they increase an individual's chances of surviving and reproducing. • Changes of this kind are more likely to be passed on to the next generation (natural selection), while changes that hinder survival are lost.
Evolutionary explanations of behavior • Examples of adaptations which would have promoted survival and reproduction are behaviors such as aggression which might be understood as an adaptive necessity in the competition for limited resources. • Food preferences for sweet tastes might be understood as a adaptive urge to seek out scarce sweet, ripe fruits which provided energy.
Evolutionary explanations of behavior • Even mental disorders might be explained from an evolutionary perspective. • Depression may be explained as an adaptive urge to strategic ally withdrawal to conserve energy and regroup after a setback of some kind. • Anorexia may have evolved from rationing tendencies. During human evolution it would not have been adaptive to always eat everything in site, but rather it would have important to effectively ration during lean times, as well as eating up during more abundant times. Thus, the capacity to "go without food" would have been important for survival.
What is attachment and what evolutionary purposes does it serve? • Attachment is a deep and enduring emotional bond that connects one person to another across time and space (Ainsworth, 1973; Bowlby, 1969). • Attachment does not have to be reciprocal. One person may have an attachment with an individual which is not shared.
What is attachment and what evolutionary purposes does it serve? • Attachment is characterized by specific behaviors in children, such as seeking proximity with the attachment figure when upset or threatened (Bowlby, 1969). • It appears to be a behavior that ALL living creatures have encoded in their genes.
What evolutionary purpose could forming attachments after birth (both parents and children) serve?
Evolutionary explanation of attachment • If the sole purpose of a gene is to ensure survival, having parents that have the gene that influences bonding would ensure the survival of the offspring. • Having children with an innate push to form attachments will also ensure the protection of the child (along with the gene). • This is suggesting that attachments are inherited from parents and expressed regardless of the environment.
Theories of attachment • Attachment theory in psychology originates with the seminal work of John Bowlby (1958). • In the 1930’s John Bowlby worked as a psychiatrist in a Child Guidance Clinic in London, where he treated many emotionally disturbed children.
Theories of attachment • This experience led Bowlby to consider the importance of the child’s relationship with their mother in terms of their social, emotional and cognitive development. • Specifically, it shaped his belief about the link between early infant separations with the mother and later maladjustment, and led Bowlby to formulate his attachment theory.
Theories of attachment • Adaptive Behavior – According to Bowlby, infants have an innate desire to attach to their mothers as it increases their chances of survival. • If a mother does not care for her child, the child will die and therefore the mother’s genes will also die. • Due to this process, mothers now have a gene for looking after their babies.
Theories of attachment • Monotrophy: infants have an innate tendency to attach to one figure. This attachment will be qualitatively different to any other attachment the child will make. • This attachment usually forms with who or whatever the infant views at the “mother”.
Research support of an evolutionary explanation of attachment • In 1935 Konrad Lorenz supported the evolutionary attachment thesis with young ducklings and goslings. • He observed that at a certain critical stage soon after hatching, they learn to follow real or foster parents.
Research support of an evolutionary explanation of attachment • He divided goose eggs into two groups and marked each goose once hatched so he knew which geese were in which group. • One group was hatched with the mother goose and one group was hatched with Lorenz. • The geese that were hatched with Lorenz followed him and attached to him as if he were their mother and showed distress if they lost sight of him, none of the geese in this group became attached to their real mother goose.
