In this chapter we introduce some of the different

In this chapter, we introduce some of the different models that try to explain
abnormal behaviour. You might wonder why so many different models exist. The
answer is that abnormal behaviour is very complex, and no one model appears capable
of providing a comprehensive explanation. Using a scientific approach, researchers
develop, examine, and discard models as new facts emerge. Next we examine some of
the currently accepted models of abnormal behaviour.
1.5
Describe the modern biological, psychological, sociocultural, and
biopsychosocial perspectives on the origins of abnormal behaviour.
Biological Models
The biological model assumes that abnormal behaviour results from biological processes
of the body, particularly the brain. Although long suspected to be the seat of abnormal
behaviour, only in the last 20 or 30 years have scientific advances allowed us to observe
brain mechanisms directly. One area of scientific breakthrough has been in our under-
standing of genetics. As already noted, genetic mapping is allowing us to begin to under-
stand whether psychological disorders such as schizophrenia or manic-depressive
disorder have a genetic basis, and if so, how that understanding might lead to better
intervention and prevention efforts. Technology breakthroughs such as computerized
axial tomography (CT) scans and magnetic resonance imaging (MRI) allow direct exami-
nation of brain structure and activity. With this direct observation, we now have a much
greater understanding of the role of the brain in abnormal behaviour.

abnormal psychology: historical and modern perspectives CHAPTER 1 25
Although we often refer to the brain as if it were a single entity, it is a very com-
plex organ. In fact, about 86 billion
neurons
(brain cells) make up the brain (Azevedo
et al., 2009). Between the neurons are spaces known as
synapses
. Neurons (see Figure 1.4)
communicate when
neurotransmitters
(chemical substances) are released into the
synapse (i.e., the neuron fires) and land on a receptor site of the next neuron. That neu-
ron then fires, sending an electrical impulse down the axon, releasing neurotransmitters
into the next synapse, and so the process begins again. Neurotransmitter activity is the
basis for brain activity (thinking, feeling, and motor activity) and is related to many
physical and mental disorders. Until recently, the activity of neurotransmitters in the
brain had to be assessed indirectly from their presence in other parts of the body (blood
or spinal fluid). However, it was always unclear how accurately chemicals in blood or
spinal fluid really reflected neurotransmitter activity in the brain. Through advances in
neuroscience
, we now rely less on assumptions and indirect measures to understand
the structure and function of the nervous system and its interaction with behaviour. We
can now directly observe many aspects of the brains functioning, just as we do external
behaviour.