CHAPTER TWO
Causes of Abnormal Behavior: A Systems
Approach
Causes of Abnormal Behavior
• What are paradigms?
• 4 basic psychological paradigms
• Behavior genetics
• Systems theory
What is a Paradigm?
A set of shared assumptions about:
• the substance of a theory
• how scientists should collect data and
test theoretical propositions.
Causes of Abnormal Behavior
• What are paradigms?
• 4 basic psychological paradigms
• Behavior genetics
• Systems theory
4 Basic Psychological Paradigms
• Psychodynamic
• Cognitive-Behavioral
• Humanistic
• Biological
Which paradigm is correct?
The blind men and the
elephant
Which paradigm is correct?
Two answers:
• Individually, all of them
• Some or all of them together
• This approach is a Systems theory or
biopsychosocial approach
Causes of Abnormal Behavior
• What are paradigms?
• 4 basic psychological paradigms
• Systems theory
• Behavior genetics
Systems Theory: Outline
• Definition
• Causality
• Levels of Analysis
Systems Theory: Definition
• No one paradigm offers the “right” approach.
Systems theory integrates evidence from the
biological, psychological and social domains.
• The centerpiece of systems theory is:
Holism: whole=more than the sum of parts
e.g. playing in a sports team (basketball, volleyball)
The opposite of holism is:
Reductionism: whole = sum of its parts.
e.g. playing in a sports team (gymnastics, wrestling)
Systems Theory: Causality
• Diathesis-Stress Model
• Diathesis: existing vulnerability that
precedes stressor
• Stress: any event that triggers the onset of
disturbance
• A diathesis may or may not be biological,
and a stressor may or may not be
environmental.
Systems Theory: Causality
Equifinality: different causes for same
disorder
Death of parent
Loss of job
Change in brain chemistry
Depression
Depression
Depression
Systems Theory: Causality
Multifinality: same causal factor but
different outcomes
Phobia
Earthquake
PTSD
Depression
Systems Theory: Causality
Reciprocal causality: causality is
bidirectional.
Parent’s behavior
Child’s behavior
Systems Theory: Levels of
Analysis
• Systems theory integrates evidence from
biological, psychological and social
domains of behavior (not additive)
• Different paradigms operate at different
levels of analysis when explaining human
behavior:
e.g., neuron, individual, couple, family,
community, culture.
Multidimensional Model
• 50% of psychology due to biological
factors, 50% due to social factors??
Misleading…
• Because interactions between factors are
more important
Causes of Abnormal Behavior
• What are paradigms?
• 4 basic psychological paradigms
• Systems theory
• Behavior genetics
Biological Paradigm: Behavior
Genetics
• Behavior genetics
• the study of genetic contributions to the
development of normal and abnormal
behaviors
• Genotype
• total genetic make-up (genetic profile)
Biological Paradigm: Behavior
Genetics
• Phenotype
• observable expression/characteristics of
genotype (such as weight and eye color)
• Genotype is fixed at birth, but phenotype
is a result of genotype and experiences.
Genotype vs. Phenotype
Biological Paradigm: Behavior
Genetics
• There are three different approaches to
studying behavior genetics.
• Family incidence studies
• Twin studies
• Adoption studies
Biological Paradigm: Behavior
Genetics
Family Incidence Studies:
Do disorders run in families?
• Researchers identify the
index person in a family
or a proband
• Then examine the proportion of family
members that suffer from different disorders
relative to this person (the proband)
Biological Paradigm: Behavior
Genetics
Hypothetical Data Set
Proband
%family MDD
MDD
30
Schizophrenia
10
No diagnosis
10
%family Schz.
0.5
10
0.5
*Are members of my family at risk for having
a disorder given that I have the disorder?
Biological Paradigm: Behavior
Genetics
Hypothetical Data Set
Proband
%family MDD
MDD
30
Schizophrenia
10
No diagnosis
10
%family Schz.
0.5
10
0.5
Biological Paradigm: Behavior
Genetics
Hypothetical Data Set
Proband
%family MDD
MDD
30
Schizophrenia
10
No diagnosis
10
%family Schz.
0.5
10
0.5
Biological Paradigm: Behavior
Genetics
Hypothetical Data Set
Proband
%family MDD
MDD
30
Schizophrenia
10
No diagnosis
10
%family Schz.
0.5
10
0.5
Biological Paradigm: Behavior
Genetics
Hypothetical Data Set
Proband
%family MDD
MDD
30
Schizophrenia
10
No diagnosis
10
%family Schz.
0.5
10
0.5
Twin Studies: Logic
Twin studies
• Concordance, simply
means “agreement”
• Depressed Twin A = Depressed Twin B
• Example: in a study of 100 Twins, if
60% of all the twins both have
depression, then the concordance rate
is 60%
• MZ twins have 100% genetic overlap.
• On average, DZ twins have 50% genetic
overlap (like typical siblings)
Twin Studies: Shortcoming
• Assumes that pairs of MZ twins are not
treated any more alike than are pairs of
DZ twins
• But MZ twins may be treated more alike
because they look alike…
Twin Studies: Twins Raised
Apart (MZ twins)
• To account for the fact that MZ twins may be
treated more similarly than DZ
• Different adoptive families (= different environment
or different treatment)
• Differences in concordance rates cannot be
attributed to MZ twins having a more similar
environment than DZ
• Can’t assume similar treatment of MZ twins, so if
differences are found they may be attributed to
environmental factors…
Behavior Genetics: Adoption
Studies
• Compare adopted children with and
without family histories of a disorder
• Compare concordance rates with
biological and adoptive parents to see
which is higher
• Genetic and environmental factors
Adoption Study: Disorder X
Proband
(Biological Parents)
% Adopted-Away children
with Disorder
With Disorder X
20
Without Disorder X
10
Adoption Study: Disorder X
Proband
(Biological Parents)
% Adopted-Away children
with Disorder
With Disorder X
20
Without Disorder X
10
* Children of Bio Parents with Disorder X are at a higher risk, so
there is a Genetic Influence
Adoption Study: Disorder Y
Proband
(Biological Parents)
% Adopted-Away children
with Disorder
With Disorder Y
10
Without Disorder Y
10
Adoption Study: Disorder X
Proband
(Biological Parents)
% Adopted-Away children
with Disorder
With Disorder Y
10
Without Disorder Y
10
* Children of Bio Parents with Disorder Y are NOT at a higher risk,
so there’s NO Genetic Influence
Adoption Study: Disorder X
% biological
parents with
Disorder X
% adoptive
parents with
Disorder X
Adoptees with
Disorder X
20
10
Adoptees without
Disorder X
10
10
Proband
Adoption Study: Disorder X
% biological
parents with
Disorder X
% adoptive
parents with
Disorder X
Adoptees with
Disorder X
20
10
Adoptees without
Disorder X
10
10
Proband
* Bio Parents of children with Disorder X are at a higher risk compared
to Adoptive Parents, so there is a Genetic Influence
Adoption Study: Disorder Y
% biological
parents with
Disorder Y
% adoptive
parents with
Disorder Y
Adoptees with
Disorder Y
10
10
Adoptees without
Disorder Y
10
10
Proband
Adoption Study: Disorder Y
% biological
parents with
Disorder Y
% adoptive
parents with
Disorder Y
Adoptees with
Disorder Y
10
10
Adoptees without
Disorder Y
10
10
Proband
* Bio Parents of children with Disorder Y are NOT at a higher risk
compared to Adoptive Parents, so there’s NO Genetic Influence
Adoption Study: Disorder Z
% biological
parents with
Disorder Z
% adoptive
parents with
Disorder Z
Adoptees with
Disorder Z
20
10
Adoptees without
Disorder Z
20
10
Proband
Adoption Study: Disorder Z
% biological
parents with
Disorder Z
% adoptive
parents with
Disorder Z
Adoptees with
Disorder Z
20
10
Adoptees without
Disorder Z
20
10
Proband
* Bio Parents of children with Disorder Z are NOT at a higher risk compared
to Bio Parents of children without Disorder Z, so there’s NO Genetic Influence
Biological Paradigm: Behavior
Genetics
• Genes not sufficient to account for
development of any psychological disorder.
We need to study environmental factors
• Gene-environment interactions:
Reciprocal gene-environment model
• Genes might influence the environment
that people seek out. Environmental factors
may bring out a genetic predisposition. The
two are not independent.
Misinterpretation of Behavior
Genetics
INCORRECT ASSUMPTIONS
• If there is a genetic influence, a disorder is inevitable
• i.e., environmental factors are often necessary to trigger the
expression of genes
• If a behavior or characteristic is genetically influenced, it
cannot be changed
• e.g., some people have genetic predisposition to alcohol, but they
are still able to change
• If there is a genetic influence, a gene must be directly
responsible for the behavior
• polygenetic + environmental stress
Biological Perspective
• Biology can be influenced by psychology!
• Biological causes do not necessarily
require biological treatment
• Today most psychologists view disorders
as being caused by multiple factors.
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