CHAPTER 2: CURRENT PARADIGMS AND THE ROLE OF CULTURAL FACTORS
PAGES 38- 82 (44 pages)
PART I: THE ROLE OF PARADIGM
- Central to any applicant of scientific principles, in Kuhns view, is the notion of para-
digm, the conceptual framework to approach within which scientist works.
- A paradigm is a set of basic assumptions that outline the particular universe of scien-
- Paradigms specify what problems scientists will investigate and how they will go about
- Paradigms are an inartistic part of a science, serving the vital function of indicating the
rules to be followed.
- A paradigm injects inevitable biases into the definition and collection of data, and may
also effect the interpretation of acts
PART II: THE BIOLOGICAL PARADIGM
- The biological paradigm: of abnormal behavior is a continuation of the somatogenic
- This broad perspective holds that mental disorders are caused by aberrant biological
- This paradigm has often been referred to as the medical model or disease model
- Medical illnesses can differ widely from one another in their cause, however they all
share one characteristic: in all of them, some biological process is disrupted or not func-
- The biological paradigm was the dominant paradigm in Canada and elsewhere from
the late 1800s until at least the middle of the 20 century.
Contemporary Approaches to the Biological Paradigm
- When the ovum, the female reproductive cell, is joined by the males spermatozoon, a
zygote, or fertilized egg, is produced.
- It has 46 chromosomes, the number characteristic of a human being.
- Each chromosomes is made up of thousands of genes-the carriers of the genetic in-
formation (DNA) passed from parents to child.
- Behavior genetics is the study of the individual differences in behavior that are attrib-
utable in part to differences in genetic makeup. - The total genetic makeup of an individual, consisting of inherited genes, is referred to
as the genotype.
- An individuals genotype is his or her unobservable genetic constitution; in contrast an
individuals phenotype is the totality of his or her observable, behavioral characteristics
(i.e. Level of anxiety)
- The genotype is fixed at birth, but it should not be viewed as a static entity.
- Genes controlling various features of development switch off and on at specific times
to control aspects of physical development.
- The phenotype changes over time and is viewed as the product of an interaction be-
tween the genotype and the environment.
- Ex. A person may be born with the capacity for high intellectual achievement, but
whether he or she develops this genetically given potential depends on such environ-
mental factors as upbringing and education
- It is critical to recognize that various clinical syndromes are disorders of the phenotype,
not the genotype.
- The study of behavior genetics has relied on 4 basic methods to uncover whether a
predisposition for psychopathology is inherited:
- 1. Comparison of members of a family
- 2. Comparison of pairs of twins
- 3. The investigation of adoptees
- 4. Linkage analysis.
- The family method can be used to study a genetic predisposition among members of
a family because the average number of genes shared by 2 blood relates is known.
- People who share 50% of their genes with a given individual are called first degree rel-
atives of that person.
- Nephews and nieces share 25% of the genetic makeup of an uncle and are called sec-
ond degree relatives.
- The starting point for these investigations is the collection of a sample of an individual
who bear the diagnosis in question-these people are referred to as index cases or
- In the twin method both monozygotic (MZ) twins and dizygotic (DZ) twins are com-
- MZ twins develop from a single fertilized egg and are genetically the same.
- DZ pairs develop from separate eggs made are on average only 50% alike genetically,
no more alike than any other 2 siblings. - MZ twins are always the same sex, but DZ twins can be either the same or the oppo-
- Twin studies begin with diagnosed cases and then search for the presence of the dis-
order in the other twin.
- 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, con-
cordance 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 be-
ing studied is said to be heritable.
- The ability to offer a genetic interpretation of data from twin studies hinge on what is
called the equal environment assumption.
- The EES is that the environmental factors that are partial causes of concor-
dance are equally influential in MZ pairs and DZ pairs.
- The assumption of equality applies only to factors that are plausible environmental
cause of psychopathy.
- The equal environment assumption would assert that MZ pairs and DZ pairs have
equivalent numbers of stressful life experiences.
- One factor can also complicate the results of twin research-in a study of post traumatic
stress disorder they identified 3 factors as biasing heritability estimates
- 1.violation of the equal environments assumption
- 2.the sex of the participant
- 3.his or her age when the assessment took place.
- When they controlled statistically for the effect s of age and sex differences, they found
that genetic and non-shared environmental factors contributed to symptoms of post-
traumatic stress disorder
- Analyses of the role of these factors in a persons exposure to traumatic events re-
vealed that only environmental factors contributed to exposure to events involving non-
assaultive traumas, but both genetic and environmental factors contributed to exposure
to assaultive traumas
- Thus, genetic factors may determine, in part the extent to which a person is likely to
experience post traumatic stress after an assaultive traumas
- However is limited because it had to rely on self report measures of trauma
- Researchers using the adoptees method study children with abnormal disorders who
were adopted and reared apart from their parents. - This situation has the benefit of eliminating the effects of being raised by disordered
- Molecular genetics is a highly advanced approach that goes beyond mere attempts to
show whether a disorder has a genetic component; it tries to specify the particular gene
or genes involved and the precise functions of these genes.
- Each cell consists of 46 chromosomes (23pairs) with thousands of genes per chromo-
- The term genetic polymorphism refers to variability among members of the species.
- It involves differences in the DNA sequence that can manifest in very different
forms among members in the same habitat.
- It entails mutations in chromosome that can be induced or naturally occurring.
- Linkage analysis: a method in molecular genetics that is used to study people. Re-
searchers using this method typically study families in which a disorder is heavily con-
- Researchers in this area often hypothesize gene-environment interactions. This 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
- Neuroscience is the study of the brain and the nervous system.
- Each neuron has 4 major parts:
- 1. The cell body
- 2.several dendrites
- 3. One or more axons of varying lengths (usually only one long and thin axon
extending a considerable distance form the cell body)
- 4. Terminal buttons on the many end branches of the axon
- Nerve impulse: which is a charge in the electric potential of Th. Cell, travels down the
axon to the terminal ending.
- Between the terminal endings of the sending axon and cell membrane of the receiving
neuron, thee is a small gap, called the synapse.
- For a nerve impulse to pass from one neuron Th. Another and for communication to
occur, the impulse must have a way of birding the synaptic gap. The terminal buttons of
each axon contain synaptic vesicles, small strict that are filled with neurotransmitters,
email substance that allow a nerve impulse to cross the synapse.