BIOLOGICAL EXPLANATIONS OF PHOBIC DISORDERS
To read up on the biological explanations of phobic disorders, refer to pages 479–485 of Eysenck’s A2
Level Psychology.
Ask yourself
 What is the genetic hypothesis?
 Could phobias help us survive and so have an evolutionary benefit?
 What are the weaknesses of the biological approach?
What you need to know
GENETIC FACTORS
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The genetics hypothesis
Research evidence and evaluation
EVOLUTIONARY EXPLANATIONS
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Evolutionary explanations
Research evidence and evaluation
GENETIC FACTORS
Most evidence for the genetics hypothesis for phobias is based on twin studies, with some family studies.
The evidence is strongest for agoraphobia, weakest for specific phobia, and falls in the middle for social
phobia. The concordance rates can be compared with the prevalence rates for the random population given
in the Clinical Characteristics and Diagnosis section of the revision guide for this chapter.
Bienvenu et al. (2007, see A2 Level Psychology page 482) have suggested that the genetic factors
underlying social and agoraphobia are very similar and are linked to individual differences in extraversion
and neuroticism (susceptibility to negative mood states); where genetically predisposed introverts and those
high in neuroticism were found to be more susceptible to social and agoraphobia. However, the genetic
factors underlying specific phobia differ from those underlying agoraphobia and social phobia.
RESEARCH EVIDENCE FOR GENETIC FACTORS
 Specific phobias. 31% of relatives of individuals with specific phobia also
had a phobia (Fyer et al., 1990, see A2 Level Psychology page 480). Ost
(1989, see A2 Level Psychology page 480) found that 64% of blood phobics
had a relative who was also blood phobic. A study of 1708 female twins was
reported by Kendler, Karkowski, and Prescott (1999, see A2 Level Psychology
page 481), which found heritability was moderately high for blood-injury
phobia, animal phobia, and situational phobia.
 Social phobia. Fyer et al. (1993, see A2 Level Psychology page 481)
discovered that 16% of the close relatives of social phobics developed the
same disorder against only 5% of the relatives of individuals without social
phobia. Kendler et al. (1999, see A2 Level Psychology page 481) claim the role
of genetic factors in various phobias had been underestimated because the
unreliability of diagnosis of phobias (most likely due to the categorical
approach) reduces the concordance rate. Taking this issue into account, they
concluded that genetic factors are moderately important in the development
of social phobia.
 Agoraphobia. A twin study found concordance rates of 31% for MZ
compared to 0% for DZ for agoraphobia (Torgersen, 1983, see A2 Level
Psychology page 481). Close relatives of agoraphobics were more likely to be
suffering from agoraphobia than the relatives of nonagoraphobics (Harris et
al., 1983, see A2 Level Psychology page 482). In a further study, Noyes et al.
(1986, see A2 Level Psychology page 482) found the relatives of agoraphobics
were more likely to have agoraphobia and panic disorder than the general
population and so support the genetic hypothesis.
RESEARCH EVIDENCE AGAINST GENETIC FACTORS
 Skre et al. (1993, see A2 Level Psychology page 481) found that the
concordance rate for social phobia was similar in MZ and DZ twins, which
challenges the role of genetic factors.
 The psychological explanations covered below provide counterperspectives.
In particular, social learning theory provides a persuasive explanation; that
is, phobias may run in families because the phobic behaviour is imitated and
so learned, rather than because it is inherited.
EVALUATION OF RESEARCH INTO GENETIC FACTORS
 Not 100% concordance. The concordance rates are moderate apart from
the finding on blood phobics, which suggests that genetic factors may
predispose but do not cause phobias.
 Nature vs. nurture. Do concordance rates reflect nature or are they really
due to nurture? The phobia could be culturally rather than genetically
transmitted because close family members and twins may learn the same
phobia, one may imitate the other.
 Sample size. The samples in such studies are very small and so
generalisability and population validity may be limited, which means the
findings may not be representative of other populations.
 Generalisability of twin research. Twins share a special relationship,
particularly identical twins who experience a more similar environment even
than fraternal twins, and so first, this supports nurture over nature in
explaining phobias and second, research on twins lacks generalisability to
the general population.
 Biologically deterministic. The suggestion that the genes determine
phobias is deterministic as this ignores the individual’s ability to control
their own behaviour. For example, an individual may be able to prevent their
fear escalating to a phobia by changing the way they think about the
disorder.
 Methodological weaknesses of concordance studies. Family and twin
studies must be considered cautiously because they are retrospective and
diagnosis may be biased by knowledge that another family member has been
diagnosed.
 Reliability of diagnosis. As Kendler et al. (1999) pointed out, the lack of
reliability in the diagnosis of phobias has led to the role of genetic factors
being underestimated.
 General rather than specific inheritance. The genetic vulnerability may be
a general vulnerability to phobias as Bienvenu et al.’s (2007) research
suggests, at least in the cases of social and agoraphobia. In fact this general
vulnerability may be to mental disorder in general if we consider that
phobics often have comorbidity (i.e. also have another disorder). This means
we lack understanding on the exact nature of the genetic vulnerability.
EVOLUTIONARY EXPLANATIONS
The adaptive value of anxiety is indisputable as the arousal of the “fight-or-flight” response ensures that the
individual is able to face environmental threats. Also, it encourages caution and reduces risk-taking
behaviour, which clearly links to survival and so acts as an “alarm detector”. Phobias are irrational fears
that are out of proportion to the reality of the threat provided by the fear-provoking stimulus. Whilst
anxiety can be adaptive, phobias can be maladaptive.
According to the “preparedness” argument (Seligman, 1970, see A2 Level Psychology page 483), phobias
are adaptive because they are a fear of things that would have been of danger in our evolutionary past, e.g.
snakes, spiders, heights, (specific phobias), strangers (social phobia), strange territory (agoraphobia). The
“preparedness” explanation suggests that humans have an innate predisposition to acquire the fear response
through conditioning. This means humans are biologically prepared to exhibit physiological and emotional
responses as defence mechanisms to environmental demands.
RESEARCH EVIDENCE FOR EVOLUTIONARY EXPLANATIONS
 Fear conditioning research provides evidence that we more readily associate
harm with certain stimuli than with others. Tomarken, Mineka, and Cook
(1989, see A2 Level Psychology page 483) presented participants with a
situation in which various stimuli (snakes, spiders, damaged electrical outlet)
were sometimes followed by electric shock. Participants exaggerated how
often snakes and spiders had been followed by electric shock but did not do
so with the damaged electrical outlet. Thus, supporting that we associate fear
more readily with dangers of our evolutionary past than modern day
dangers.
 Cook and Mineka (1989, see A2 Level Psychology page 484) reported good
evidence for preparedness in a study on laboratory-bred monkeys that
developed snake phobia from observing another monkey’s fearful reaction to
a toy snake, whereas no fear developed in monkeys when they saw another
monkey reacting with strong fear to a rabbit. This suggests that we are
biologically prepared to learn through modelling.
 Another study on classical conditioning involved monkeys being exposed to
electric shocks and certain stimuli. They reacted fearfully to snakes and
spiders but not to flowers or leaves, supporting an innate predisposition to
fear certain stimuli.
 Non-random distribution of feared objects: We fear things that would have
existed in our evolutionary past more than modern dangers. Or the fear of
modern dangers can be linked to previous dangers, e.g. fear of flying can be
linked to fear of heights.
 Fear is negatively correlated with animals’ appearance. Those least like
humans elicit stronger phobic responses. This suggests an evolutionary basis
as we are programmed to imprint onto our own species and evade unrelated
species, thus supporting the evolutionary explanation that phobias are due to
innate predispositions.
RESEARCH EVIDENCE AGAINST EVOLUTIONARY EXPLANATIONS
 Specific phobias treated by therapists include non-prepared phobias, i.e. have
no connection to our evolutionary past. Nor are prepared phobias harder to
treat than non-prepared ones, which we would expect if innate preparedness
was valid as we would not be able to cure such a biological predisposition
(Davey, 1995, see A2 Level Psychology page 484).
We do fear modern dangers, e.g. public transport and driving. Of those with a
phobia of driving about 50% had been involved in a car accident (Barlow &
Durand, 1995, see A2 Level Psychology page 486).
 Traditional behavioural explanations alone may fully account for phobias and
so contradict an evolutionary basis because phobias may be solely learned
(i.e. through classical and operant conditioning) rather than learned
preparedness.
 Social learning theory also provides an alternative behavioural explanation.
According to this, phobias are culturally transmitted as they are learned
through observation and imitation.
 A breakdown in cognitive processing has been linked to phobias—
interpretations of the fear-provoking stimulus, bodily response, and
emotions are maladaptive given that the fear is disproportionate to the
threat. Thus, counter-perspectives provide insights that may have more
relevance to the individual’s current experience than explanations based on
our evolutionary past.
EVALUATION OF EVOLUTIONARY EXPLANATIONS
 Universality of mental disorders. Anxiety occurs in all cultures. Whilst
there may be differences in terms of anxieties they are labelled and
expressed, it can be argued that they are fundamentally the same disorder,
which supports a genetic basis. But just because behaviours are common
does not mean that they are genetic, and evidence of a genetic basis does not
necessarily validate evolutionary explanations. Also, there is some evidence
against universality as fear of spiders is more common in Europe than in
non-Western cultures.
 Face validity. The linking of phobias to our evolutionary past makes sense.
We can understand why different phobias may have developed, e.g. fear of
people may link to the fact they may have meant us harm in the highly
competitive evolutionary environment. The fear response as a survival
mechanism is valid.
 Conjecture—evolutionary stories? Deciding what was dangerous in our
evolutionary past is highly speculative. Such explanations are post hoc (made
up after the event) and so cannot be verified or falsified, and given that
falsification is a key criterion of science, according to Popper, then the theory
lacks scientific validity.
 Reductionist and deterministic. Evolutionary theories are reductionist as
they focus on one factor only (the gene) when other emotional, social,
cognitive, behavioural, and developmental factors are highly relevant to the
aetiology of mental disorders. They are oversimplified accounts at best. They
are also deterministic as they suggest that genes control behaviour, which
ignores the free will of the individual.
 Psychological explanations. The psychological models of abnormality are
counter-perspectives. Moreover, they may account for why adaptive
behaviours have become distorted. For example, the evolved “fight-or-flight”
stress response may be genetically predisposed and have adaptive value. But
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it interacts with psychological factors such as individual differences and self
perception, which may result in maladaptive anxiety responses.
 Social learning theory has great explanatory power. It accounts for how
children learn so much so quickly and so may provide a more valid
explanation of how children acquire phobias.
 Nature/nurture. The evolutionary explanations overemphasise the role of
nature and ignore nurture. It is not a question of nature or nurture, as
indisputably an interactionist perspective must be taken. However, as the
evolutionary explanations ignore nurture this is a key weakness.
 Adaptive or maladaptive? Mental disorders are often very disturbing to the
patient and may severely disrupt their everyday functioning, thus we
shouldn’t exaggerate any adaptive value they may have. It is often unclear
how some behaviour of patients with mental disorders could be classed as
adaptive (e.g. agoraphobics who are unable to leave the house). At best, the
explanations lack conviction.
 Alternative explanations. There are alternatives explanations to the
evolutionary claim that phobias are adaptive in some way. For example, it
can be argued that natural selection does not create perfect organisms in
which all behaviours are adaptive in some way, instead phobias may be
recessive and so difficult to weed out. Or alternatively one theory is that
there were “bottle-necks” in human evolution, which meant that the human
population was too small for genetic mutations to be weeded out and so
phobias are due to mutations that have persisted in our gene pool in spite of
the fact they are maladaptive.
So what does this mean?
There is moderately strong evidence for the role of genetics in phobias, however concordances are not as
high as they are for schizophrenia and depression.
Kendler et al. (1999) argued that the role of genetic factors may be underestimated due to the unreliability
of diagnosis, which reduces the concordance rates. This could be because many phobias go undiagnosed,
particularly specific phobias because patients may find avoiding the stimulus easier than dealing with the
phobia. However, the genetic concordances could be due to the shared environment and so behavioural
explanations offer a powerful alternative to the idea that phobias are inherited.
Not all family members develop the same phobia and so genes alone cannot explain why different types of
phobia develop. Therefore, genetic factors do not account for individual differences in susceptibility to
different types of phobias. Any genetic vulnerability may be general across phobias or even mental
disorders rather than specific to the different types of phobia.
Perhaps of more interest is why one family member may suffer with a phobia and others do not,
particularly in the case of identical twins that have 100% genetic similarity. The diathesis–stress model
provides a more comprehensive understanding of how nature and nurture may interact and so can better
explain such individual differences. Individuals may be predisposed (the diathesis) to phobia but this does
not necessarily result in a phobia as this depends on the interaction of the diathesis with environmental
factors. This accounts for the lack of consistency in the findings on genetics and the fact that the
abnormality differs across MZ twins who share the same genes.
The evolutionary explanations provide interesting insights into the possible origins of phobias; it seems
unquestionable that the fear response does ensure survival. However, whether phobias are innate is less
conclusive because as always evolutionary explanations are speculative and so are limited by a lack of
scientific validity.
Over to you
1. Outline and evaluate one or more biological explanation(s) of one anxiety disorder. (25 marks)