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Chapter 2

Chapter 2.docx


Department
Psychology
Course Code
PSYCH 2310A/B
Professor
Rod Martin
Chapter
2

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Chapter 2
Theoretical Perspectives on Abnormal Behaviour
Levels of Theories
Single factor explanations one factor is said to cause the disorder such as a genetic defect or a
traumatic experience
o Usually reflects the primary focus of the researcher rather than a belief in a single cause
Interactionist explanations behaviour is the product of the interaction of a variety of factors
o Identifies risk factors rather than specific causes, more complex theories
Scientific theories are judged to be valuable because they contain three essential features:
o They integrate most of what is currently known about the phenomena in the simplest
way possible (parsimonious)
o They make testable predictions about aspects of the phenomena that were not
previously thought of
o They make it possible to specify what evidence would deny the theory
Theories are not set up to prove the worth of a theory but rather to reject or fail to reject the
null hypothesis
Null hypothesis- proposes that the prediction made from the theory is false
Theories gain strength when alternative explanations are rejected; theories are not facts they
are the best approximation we have at any moment, so as knowledge accumulates old theories
are usually replaced
Search for Causes
General aims of theories about mental disorders are to:
o Explain etiology (causes or origins) of problem or behaviour
o Identify the factors that maintain the behaviour
o Predict the course of the disorder
o Design effective treatments
Factors involved in the etiology of the problem may not be relevant to its maintenance
o Ex: get attacked by a dog so develop a phobia but maintain phobia by avoiding them
o Even if there is a clear biological cause, environmental manipulations can increase or
decrease prevalence of disorder
Biological Models
Role of the Central Nervous System
Brain is estimated to have 100 billion neurons and thousands of billions of glia cells
Cells group together in to concentrated areas which appear to have distinctive functions
Hindbrain directs functioning of the autonomic nervous system which controls primary
internal activities such as digestion, cardiovascular functioning and breathing

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Midbrain centre of the reticular activating system which controls arousal levels and thereby
attentional processes
Forebrain controls thought, speech perception, memory, learning, planning; some disorders
have been shown to be directly linked to brain damage
Dementia a deterioration in all cognitive processes particularly memory and learning
o Occurs in disorders such as Parkinson’s and Alzheimer’s, linked to the loss or ineffective
functioning of brain cells
o Irreversible in many cases and may result from various sources such as direct head
injuries, diseases, toxins
Neurotransmitters the chemical substances that carry the messages from one neuron to the
next in the complex pathways of nervous activity within the brain
o nerve cells are not directly attached to each other so one neuron does not directly
stimulate another
o there is a gap, the synapse, between the axons of one neuron and the dendrites of
neighbouring neurons
o transmission of electrical activity in the axon to the neighbouring dendrites occurs as a
result of the release of chemicals called neurotransmitters
o majority of research attention is on the dopamine, serotonin, norepinephrine and GABA
neurotransmitters; sometimes act on their own or with others
o tens of thousands of brain circuits
abnormal behaviour can result from various disturbances in neurotransmitter systems:
o there may be too little or too much of the neurotransmitter produced or released in to
the synapse
o there may be too few or too many receptors on the dendrites
o there may be an excess or a deficit in the amount of the transmitter-deactivating
substance in the synapse
o the reuptake process may be too rapid or too slow (when neurotransmitters are drawn
back in to releasing axon)
o any or all of these problems can cause too much excitation or too little inhibition in the
particular brain circuits
neurotransmitter activity affects behaviour but behaviour can also affect neurotransmitter
activity
brain plasticity capacity of the brain to reorganize its circuitry
o can be influenced by a number of experiences that occur pre- and postnatally through
hormones, diet, aging, stress, disease, and maturation
Role of the Peripheral Nervous System
includes the somatic nervous system which controls the muscles and the autonomic nervous
system
ANS has 2 parts: the sympathetic nervous system and the parasympathetic nervous system

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o Function together to produce a balanced activity in a variety of bodily functions such as
heart rate, digestion, etc. (parasympathetic)
o Function antagonistically during times of stress, fight or flight response (sympathetic)
Stress Psychology (developed by Hans Seyle)
o In some people the ANS response to threat is very weak or very strong
o This can be related to a person’s tendency to develop psychophysiological disorders
o Overactive ANS can increase likelihood to acquire phobias or other anxiety disorders
o Generalized Anxiety Disorder (GAD) is associated with decreased parasympathetic
regulation
Also show chronic muscle tension and worry (coming from somatic nervous
system and cognitive behaviour)
Role of the Endocrine System
Maintains appropriate levels of hormones circulating in the bloodstream in a feedback loop with
the CNS
Hormones are chemical messengers that maintain adequate bodily functioning and play an
important role in the development of the organism
Has many complex effects on behaviour
Cretinism a disorder involving a dwarflike appearance and mental retardation as a result of a
defective thyroid gland
Hypoglycemia pancreas fail to produce balanced levels of insulin or glycogen, produces
experiences that mimic anxiety
Thyroid disregulation has also been associated with psychiatric symptoms including anxiety and
depression
Genetics and Behaviour
Thomas Hobbes aggression and self-interest were inborn features of all humans and it was the
business of the political systems to restrain their impulses
Cesare Lombrosso criminals could be identified by the physiological features they had
inherited from their degenerate parents
Paul Broca males were born with superior brains; many other people believed that whites
were born with more superior brains than blacks
Behavioural genetics offers an insight into the biological bases of abnormal functioning
Genotype-environment interaction genes may influence behaviours that contribute to
environmental stressors which, in turn, increase the risk of psychopathology; has been found in
animal models and human studies
o Study: Caspi and Colleagues; relationship between stressful life events and depression
was stronger in adults who also exhibited the short variant of a particular gene related
to negative emotionality; those with this gene only had depression if they had SLE’s
Genetic research usually takes one of 3 forms: family studies, twin studies, adoption studies
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