Chapter 2

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Published on 7 Dec 2010
School
UTSC
Department
Psychology
Course
PSYB32H3
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
followed
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
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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
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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
behavior genetics ± the study of individual differences in behavior that are attributable to differences in
genetic makeup
genotype ± DQLQGLYLGXDVXQREVHUYDEOHJHQHWLFFRQVWLtution; the totality of genes possessed by an
individual
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- 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
person
- 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;
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- 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
- 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
heritable
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- 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 SDLUFRPHVIURPDSHUVRQVPRWKHUDQG
his/her father
- allele refers to any one of several DNA codings that occupy the same position or location on a
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- 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
the neuron and causes the release of a neurotransmitter
synapse ± a small gap between 2 neurons where the nerve impulse passes from the axon of the 1st to
the dendrites, cell body, or axon of the 2nd
neurotransmitter ± a chemical substance important in transferring a nerve impulse from one neuron to
another; eg: serotonin and norepinephrine
- the terminal buttons of each axon contain synaptic vesicles, small structures that are filled with
neurotransmitters
- nerve impulses cause the synaptic vesicles to release molecules of their transmitter substances, and
these molecules flood the synapse and diffuse toward the receiving, or postsynaptic, neuron
- the cell membrane of the postsynaptic cell contains proteins, called receptor sites, that are configured so
that specific neurotransmitters can fit into them
- when a neurotransmitter fits into a receptor site, a message can be sent to the postsynaptic cell
- sometimes the messages are excitatory, leading to the creation of a nerve impulse in the postsynaptic
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