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Chapter 2

PSYB32H3 Chapter Notes - Chapter 2: Impulse Control Disorder, Twin Study, Panic Disorder

Course Code
Konstantine Zakzanis

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Chapter 2 Current Paradigms and the Role of Cultural Factors
- a paradigm is a set of basic assumptions, a general perspective, that defines how to conceptualize and
study a subject, how to gather and interpret relevant data, even how to think about a particular subject
The Role of Paradigms
- science is bound by the limitations imposed on scientific inquiry by the current state of knowledge
- it is also bound by whether the scientist can remain objective when trying to understand and study
abnormal behavior
paradigm a set of basic assumptions that outlines the universe of scientific inquiry, specifying both the
concepts regarded as legitimate and the methods to be used in collecting and interpreting data
- a paradigm is the conceptual framework or approach within which the scientist works
- paradigms specify what problems scientists will investigate and how they will go about the investigation
- paradigms are an intrinsic part of a science, serving the vital function of indicating the rules to be
The Biological Paradigm
biological paradigm a broad theoretical view that holds that mental disorders are caused by some
aberrant somatic process or defect
- the biological paradigm of abnormal psychology is a continuation of the somatogenic hypothesis
medical (disease) model as applied in abnormal psychology, a set of assumptions that conceptualizes
abnormal behavior as similar to physical diseases
- the study of abnormal behavior is linked historically to medicine
- for a time, the germ theory was the paradigm of medicine, but it soon became apparent that this theory
could not account for all diseases
- medical illnesses can differ widely from one another in their causes; however, they all share one
characteristic: in all of them, some biological process is disrupted or not functioning normally; that is why
we call this the biological paradigm
- the biological paradigm was the dominant paradigm in Canada and elsewhere from the late 1800’s until
at least the middle of the 20th century
Contemporary Approaches to the Biological Paradigm
- psychopathology is viewed as caused by the disturbance of some biological process
Behavior Genetics
- when the ovum, the female reproductive cell, is joined by the male’s spermatozoon, a zygote, or
fertilized egg, is produced; it has 46 chromosomes
- each chromosome is made up of thousands of genes
gene an ultramicroscopic area of the chromosome; the gene is the smallest physical unit of the DNA
molecule that carries a piece of hereditary information
- genes are the carriers of the genetic information (DNA) passed from parents to child

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behavior genetics the study of individual differences in behavior that are attributable to differences in
genetic makeup
genotype an individuals unobservable, genetic constitution; the totality of genes possessed by an
- the total genetic makeup of an individual, consisting of inherited genes, is referred to as the genotype
- the genotype is fixed at birth
- genes controlling various features of development switch off and on at specific times to control aspects
of physical development
phenotype the totality of observable, behavioral characteristics of a person; eg: level of anxiety
- the phenotype changes over time and is viewed as the product of an interaction between the genotype
and the environment; for example, an individual may be born with the capacity for high intellectual
achievement, but whether he/she develops this genetically given potential depends on such
environmental factors as upbringing and education; hence, any measure of intelligence is best viewed as
an index of the phenotype
- various clinical syndromes are disorders of the phenotype, not of the genotype
- only the genotypes for disorders can be inherited; whether these genotypes will eventually engender the
phenotypic behavior disorder will depend on environment and experience
- a predisposition, a.k.a. a diathesis, may be inherited, but not the disorder itself
- the study of behavior genetics has relied on 4 basic methods to uncover whether a predisposition for
psychopathology is inherited: comparison of members of a family, comparison of pairs of twins, the
investigation of adoptees, and linkage analysis
family method a research strategy in behavior genetics in which the frequency of a trait or of abnormal
behavior is determined in relatives who have varying percentages of shared genetic background
- children receive a random sample of half their genes from one parent and half from the other; thus, on
average, siblings as well as parents and their children are identical in 50% of their genetic background
- people who share 50% of their genes with a given individual are called 1st-degree relatives of that
- relatives not as closely related share fewer genes
- nieces and nephews shae 25% of the genetic makeup of an uncle and are called 2nd-degree relatives
- if a predisposition for a mental disorder can be inherited, a study of the family should reveal a
relationship between the number of shared genes and the prevalence of the disorder in relatives
- if a genetic predisposition to the disorder being studied is present, 1st degree relatives of the index cases
should have the disorder at a rate higher than that found in the general population
index cases (proband) the person who in a genetic investigation bears the diagnosis or trait in which
the investigator is interested
twin method research strategy in behavior genetics in which concordance rates of monozygotic and
dizygotic twins are compared
monozygotic (MZ) twins genetically identical siblings who have developed from a single-fertilized egg;
sometimes calledidentical twins”
- MZ twins are always the same sex
dizygotic (DZ) twins birth partners who have developed from separate fertilized eggs and who are only
50% alike genetically, no more so than siblings born from different pregnancies; sometimes called
fraternal twins

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- DZ twins can be either the same or the opposite sex
concordance as applied in behavior genetics, the similarity in psychiatric diagnosis or in other traits
within a pair of twins
- when the twins are similar diagnostically, they are said to be concordant
- to the extent that a predisposition for a mental disorder can be inherited, concordance for the disorder
should be greater in genetically identical MZ pairs than in DZ pairs
- when the MZ concordance rate is higher than the DZ rate, the characteristic being studied is said to be
- the concordance for many forms of psychopathology is higher in MZ twins than in DZ twins
- the ability to offer a genetic interpretation of data from twin studies hinges on what is called the equal
environment assumption
- the equal environment assumption is that the environmental factors that are partial causes of
concordance are equally influential for MZ pairs and DZ pairs; the assumption of equality applies only to
factors that are plausible environmental causes of psychopatholgy
adoptees method research method that studies children who were adopted and reared completely
apart from their abnormal parents, thereby eliminating the influence of being raised by disordered parents
- if a high frequency of panic disorder were found in children reared apart from parents who also had
panic disorder, we would have support for the theory that a genetic predisposition figures in the disorder
Molecular Genetics
- molecular genetics tries to specify the particular gene or genes involved and the precise functions of
these genes
- each cell has 46 chromosomes (23 pairs)
- the chromosomes are our genetic material and one of each pair comes from a person’s mother and
his/her father
- allele refers to any one of several DNA codings that occupy the same position or location on a
chromosome; a person’s genotype is his/her set of alleles
- genetic polymorphism refers to variability among members of the species
linkage analysis a technique in genetic research whereby occurrence of a disorder in a family is
evaluated alongside a known genetic marker
- researchers use linkage analysis to study families in which a disorder is heavily concentrated
- they study the inheritance pattern of characteristics whose genetics are fully understood, referred to as
genetic markers
- gene-environment interactions is the notion that a disorder or related symptoms are the joint product of
a genetic vulnerability and specific environmental experiences or conditions
Neuroscience and Biochemistry in the Nervous System
neuron a single nerve cell
- each neuron has 4 major parts: (1) cell body (2) several dendrites (the short and thick extensions) (3) 1
or more axons of varying lengths (usually only 1 long and thin axon extending a considerable distance
from the cell body) (4) terminal buttons on the many end branches of the axon
nerve impulse a change in the electrical potential of a neuron; a wave of depolarization spreads along
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