genetic inheritance and behavior

Genetic Inheritance and Behavior

Genetic Inheritance and Behavior

IB Psychology

from Levels of AnalysisIB Psychology

from Levels of Analysis

To what extent does genetic inheritance influence behavior?

To what extent does genetic inheritance influence behavior?

We want there to be a genetic link to behavior because it would be an easy explanation for things like homosexuality, criminality, and addiction.

We want there to be a genetic link to behavior because it would be an easy explanation for things like homosexuality, criminality, and addiction.

My Genes Made Me Do ItMy Genes Made Me Do It

Very few diseases have been linked to a single gene- Huntington’s Disease.

Very few diseases have been linked to a single gene- Huntington’s Disease.

Most researchers no longer believe a single of gene is implicated in any behavior.

Most researchers no longer believe a single of gene is implicated in any behavior.

Human behavior is so complex that simple explanations are not possible.

Human behavior is so complex that simple explanations are not possible.

My Genes Made Me Do ItMy Genes Made Me Do It Physical Traits

Purely Genetic (eye color) Some Environmental Influence (height) Combination of Genetic Disposition and

Behavior (obesity)

Physical Traits Purely Genetic (eye color) Some Environmental Influence (height) Combination of Genetic Disposition and

Behavior (obesity)

Illnesses Purely Genetic (Huntington’s Disease) Some Environmental Influence (breast

cancer, heart disease, schizophrenia, bipolar)

Illnesses Purely Genetic (Huntington’s Disease) Some Environmental Influence (breast

cancer, heart disease, schizophrenia, bipolar)

My Genes Made Me Do ItMy Genes Made Me Do It

Alcoholism Obesity

Alcoholism Obesity

Behavioral GeneticsBehavioral Genetics

Behavioral Genetics Examines the role between behavior and

genetics. Study the inheritance of behavioral traits. Use twin and adoption studies. Calculate the heritability statistic which shows

what percentage of a trait is due to genetic inheritance.

Behavioral Genetics Examines the role between behavior and

genetics. Study the inheritance of behavioral traits. Use twin and adoption studies. Calculate the heritability statistic which shows

what percentage of a trait is due to genetic inheritance.

Behavioral GeneticsBehavioral Genetics

IQ - 20% to 80% Alcoholism (men)- 30% to 98% Autism - 90% to 95% Bipolar Disorder - 60% to 80% Schizophrenia - 40% to 90% Divorce/Marital Success 55% Height (women) 92% Weight (women) 42%

IQ - 20% to 80% Alcoholism (men)- 30% to 98% Autism - 90% to 95% Bipolar Disorder - 60% to 80% Schizophrenia - 40% to 90% Divorce/Marital Success 55% Height (women) 92% Weight (women) 42%

Behavioral Genetics: CriticismsBehavioral Genetics: Criticisms

Heritability figures vary from study to study.

Problems with Adoption Studies- People tend to be adopted by relatives.

Problems with Twin Studies- Identical twins tend to be treated the same.

Power of expectations (alcoholism) “learned helplessness”

Heritability figures vary from study to study.

Problems with Adoption Studies- People tend to be adopted by relatives.

Problems with Twin Studies- Identical twins tend to be treated the same.

Power of expectations (alcoholism) “learned helplessness”

Molecular GeneticsMolecular Genetics

Studies the structure and function of genes at the molecular level.

Studies how the genes are transferred from generation to generation.

Human Genome Project - mapping the entire genome.

Studies the structure and function of genes at the molecular level.

Studies how the genes are transferred from generation to generation.

Human Genome Project - mapping the entire genome.

The important aspects of gene expression

The important aspects of gene expression

Complex Behavior is either: Oligogenic- few genes are involved in

behavior Polygenic- meaning there are a large number

of genes involved in behavior.

Complex Behavior is either: Oligogenic- few genes are involved in

behavior Polygenic- meaning there are a large number

of genes involved in behavior.

Gene ExpressionGene Expression

We do not inherit genes. We inherit DNA strands that come on chromosomes.

Chromosome contain many genes. Genes are portions of DNA sequences

that code for protein synthesis; this is how we get behavior.

An allele is a variation of a gene and can be either long or short.

We do not inherit genes. We inherit DNA strands that come on chromosomes.

Chromosome contain many genes. Genes are portions of DNA sequences

that code for protein synthesis; this is how we get behavior.

An allele is a variation of a gene and can be either long or short.

Gene ExpressionGene Expression

Why do we care? Genes do not affect behavior unless they

become templates or master patterns for proteins.

This happens through either transcription or translation.

Why do we care? Genes do not affect behavior unless they

become templates or master patterns for proteins.

This happens through either transcription or translation.

Why do we care?Why do we care?

Two kinds of cells relevant to psychology are those that make up neurons and endocrine glands.

Much of our behavior is related to neurotransmitters and hormones.

Research is showing how specific environmental experiences affect the transcription process.

Two kinds of cells relevant to psychology are those that make up neurons and endocrine glands.

Much of our behavior is related to neurotransmitters and hormones.

Research is showing how specific environmental experiences affect the transcription process.

Three ways genes and the environment become correlated

Three ways genes and the environment become correlated

Passive gene-environment correlation: Aggression in Children Parents contribute genes and provide an environment for the child. Aggressive behavior is not dependent on anything the child does, but is a result both

inherited genes and inherited environment.

Passive gene-environment correlation: Aggression in Children Parents contribute genes and provide an environment for the child. Aggressive behavior is not dependent on anything the child does, but is a result both

inherited genes and inherited environment.

Active gene-environment correlation: Child selects certain environments which are

conducive to the behavior.

Active gene-environment correlation: Child selects certain environments which are

conducive to the behavior. Evocative gene-environment correlation:

Child creates their own environment by encouraging abusive/aggressive behavior.

Evocative gene-environment correlation: Child creates their own environment by encouraging

abusive/aggressive behavior.

Why is it Challenging to Study Genetic Contributions to Behavior?

Why is it Challenging to Study Genetic Contributions to Behavior?

We cannot directly study genes and how they combine with other genes and the environment.

Most examples about genetic influence come from researching abnormal behavior.

We cannot directly study genes and how they combine with other genes and the environment.

Most examples about genetic influence come from researching abnormal behavior.

Genes, Environment, and Depression


Caspi (2003) 5-HTT gene, the serotonin transporter gene, appears

to heighten one’s reactivity to stress. Research investigated the relationship between

genetic type, having one short allele (s/l heterozygote), two short alleles (s/s homozygote), or two long alleles (l/l homozygote) of 5-HTT, with response on questionnaires about stressful life events and having depression syndromes.

Caspi (2003) 5-HTT gene, the serotonin transporter gene, appears

to heighten one’s reactivity to stress. Research investigated the relationship between

genetic type, having one short allele (s/l heterozygote), two short alleles (s/s homozygote), or two long alleles (l/l homozygote) of 5-HTT, with response on questionnaires about stressful life events and having depression syndromes.

Everyone experiences stressors. As the amount of stress rises the risk for

depression increases. People with two short alleles (s/s) have an even

greater risk. The risk goes down if a person has two long

alleles (l/l). Possessing two long alleles is correlated with

resilience to depression.

Everyone experiences stressors. As the amount of stress rises the risk for

depression increases. People with two short alleles (s/s) have an even

greater risk. The risk goes down if a person has two long

alleles (l/l). Possessing two long alleles is correlated with

resilience to depression.



5-HTT is not a direct cause of depression, but moderates the serotonergic response to stress.

Supported through: Studies on mice Studies on rhesus monkeys Human Brain Imaging Technology

5-HTT is not a direct cause of depression, but moderates the serotonergic response to stress.

Supported through: Studies on mice Studies on rhesus monkeys Human Brain Imaging Technology



Caspi (2006) Participants

847 Caucasians from New Zeland, all 26 years old Equal number of males and females

Groups (s/s) (s/l) (l/l)

Caspi (2006) Participants

847 Caucasians from New Zeland, all 26 years old Equal number of males and females

Groups (s/s) (s/l) (l/l)



Participants filled out a survey that included: Life history survey: life events, employment,

health, and relationships. No differences in amount of life stress was

found between the groups. Participants were measured on depression

levels between the ages of 25 and 26. 17% qualified for a major depression diagnosis.

Participants filled out a survey that included: Life history survey: life events, employment,

health, and relationships. No differences in amount of life stress was

found between the groups. Participants were measured on depression

levels between the ages of 25 and 26. 17% qualified for a major depression diagnosis.



Results Data were analyzed with correlations between

depression symptoms and genotype, stress events, and the interaction between the two.

Participants with (s/s) had greater self reports of depression.

Results Data were analyzed with correlations between

depression symptoms and genotype, stress events, and the interaction between the two.

Participants with (s/s) had greater self reports of depression.



Support for results across cultures: Japanese Western Europeans

Other research: Robert Sapolsky (2004) Research on

Monkeys

Support for results across cultures: Japanese Western Europeans

Other research: Robert Sapolsky (2004) Research on

Monkeys



Depression: Gender, Stress Hormones, and Genes

Depression: Gender, Stress Hormones, and Genes

Nolan-Hoeksema (2004) *refresh* Nolan-Hoeksema (2004) *refresh*

genetic inheritance and behavior

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