A CONTEMPORARY LEARNING THEORY PERSPECTIVE ON THE ETIOLOGY OF ANXIETY DISORDERS
The authors describe how contemporary learning theory and research provide the basis for perspectives on the
etiology and maintenance of anxiety disorders that capture the complexity associated with individual differences in the
development and course of these disorders. These insights from modern research on learning overcome the
shortcomings of earlier overly simplistic behavioral approaches, which sometimes have been justifiably criticized. The
authors show how considerations of early learning histories and temperamental vulnerabilities affect the short- and
long-term outcomes of experiences with stressful events. They also demonstrate how contextual variables during and
following stressful learning events affect the course of anxiety disorder symptoms once they develop. This range of
variables can lead to a rich and nuanced understanding of the etiology and course of anxiety disorders.
Although behavioral/learning approaches were the dominant empirical perspective on anxiety disorders from the
1920s until the 1970s, these approaches have been widely criticized since the early 1970s. Many of these criticisms
stemmed from the inability of early learning approaches to account for the diverse factors involved in the origins of
people’s anxieties. More recently, however, a resurgence of interest in learning approaches has occurred, as these
approaches have incorporated some of the complexity predicted by contemporary learning theory and research.
Early learning histories, when considered together with temperamental vulnerabilities, can serve as diatheses that
make certain individuals more susceptible to adverse and stressful experiences that sometimes lead to the
development of anxiety disorders.
Researchers believe that these new contemporary learning approaches have several advantages over the other two
approaches (cognitive/psychodynamic approaches): The learning approaches are better grounded in the theories and
methods of experimental psychology, they provide more comprehensive formulations of the etiology of anxiety
disorders, and they provide a more explicit analysis of factors promoting or inhibiting the development of different
anxiety disorders.
Specific phobia
Researchers originally argued that phobias are simply intense
classically conditioned fears that develop when a neutral stimulus is
paired with a traumatic event, such as occurred when their Little Albert
acquired an intense fear of rats after hearing a frightening gong paired
with the presence of a rat several times.
Many people with phobias can recall a traumatic conditioning event
when their phobia began.
- In a famous psychology experiment in the 1920s, John Watson
and his assistant Rosalie Rayner made a terrifyingly loud
noise whenever a baby boy named Albert began to play with
a white rat. In this way, they trained the infant to fear the
rodent.
- The original view was that there was a CS-CR
association. The contemporary view was that there
was a CS-US association.
Deconditioning = In her study, Mary Cover Jones successfully used
a process similar to what we now call "systematic desensitization" to
help "Little Peter" overcome his fear of rabbits. Jones gradually
exposed Little Peter to the feared object (a white rabbit) while he
was engaged in activities he enjoyed. Over time, Little Peter's fear
diminished, and he eventually showed no signs of fear when near the rabbit.
Two-process model
- Fear acquisition through classical conditioning
- Maintenance of fear through operant conditioning
- Avoidance feared object (CS) → decrease fear
- Decrease fear → increase avoidance behavior
- But… prevents someone to learn that fear for CS is
unfounded
- Fear persists
1
,Fear potentiated startle reflex
- Startle response is universal startle reflex to loud noise (104 dB, startle probe)
- Protective function with motor responses, e.g., eyeblink reflex
- Eye blink reflex measured with electromyography (EMG) of muscle activity under eye
- Startle reflex is strengthened when someone is tense
Differential response → Difference between the CS+ (spider and shock) and CS- response (spider). The absence of
the shock in CS- ensures that any observed responses are due to the presence of the spider alone, without the
influence of fear conditioning.
- After conditioning: US-expectancy higher for CS+ than for CS- which is indicative of fear learning
- After conditioning: Startle response stronger to CS+ than for CS-, and noise alone which is indicative of
conditioning.
Fear conditioning in the animal brain shows that the amygdala plays a crucial role. However, there is no convincing
evidence that the amygdala is involved in human fear conditioning.
Summary
• ‘Little Albert' first demonstration of fear learning in humans
• Classical conditioning: model for development of fear
• Operant conditioning: model for maintenance of fear
• Amygdala crucial for fear learning (in animals)
• Classic conditioning elegant and simple model
• Too simple? Is it clinically relevant?
Criticism learning theory
a) US not necessary
- Many phobics cannot remember a traumatic event
- Phobics fear stimuli they have never encountered
- According to contemporary learning theory there are different pathways of fear learning namely
vicarious learning (observational/modeling), information transfer (learning by instruction) and trauma
(direct learning). There is empirical evidence for this theory.
b) US not sufficient
- According to contemporary learning theory there are differences in genetic predisposition/traits and
differences in learning history (before, during or after fearful experience)
c) Selectivity phobias
- Belongingness and preparedness
- Preparedness → Fear for prepared stimuli (important for evolution) easier to learn and more
difficult to extinguish
- Belongingness → Certain CS-US combinations (between sensory modalities) more easily
associated than other combinations
- Taste (CS) and nausea (US) easier than taste and pain
- Sound (CS) and pain (US) easier than taste and pain
d) CR not equal to UR
- According to learning theory the conditioned response is often identical to the initial unconditioned
response, but this is not true. In panic disorder, CR is not always equal to initial panic reaction (UR).
Panic is the intense fear, sweating etc. however the anxiety is the anticipation anxiety of having
another panic attack.
- According to contemporary learning theory there is a CS-US association. Association between CS
and cognitive representation of US (CS-US). Feared stimulus (CS) predicts occurence of catastrophe
(US). CR (e.g., freezing) prepares the body for impending catastrophe (US). Association between
cues (CSs) and anticipated catastrophe (US: going mad, loss of control). Contemporary learning
theory suggests that there's an association between the conditioned stimulus (CS) and the cognitive
representation of the unconditioned stimulus (US) (CS-US association). In the case of panic disorder,
the CS (feared stimulus) predicts the occurrence of a catastrophe (US), such as having a panic
attack. The CR, such as freezing or anticipatory anxiety, prepares the body for the impending
catastrophe (US). Essentially, cues (CSs) become associated with the anticipation of catastrophic
events (US), like feelings of going mad or losing control, contributing to the experience of anxiety.
2
, - Anxiety disorders: feel, think and act as if feared stimulus (CS) is followed by a catastrophe
(US).
Criticism contemporary learning theory
1. Vicarious conditioning of fears and phobias
- Many people with phobias do not appear to have had any relevant history of classical conditioning.
Clinicians have long speculated that simply observing others experiencing a trauma or behaving
fearfully could be sufficient for some phobias to develop.
- In Mineka and Cook’s series of experiments on observational conditioning of snake fear,
laboratory-reared young adult rhesus monkeys who initially were not afraid of snakes served
as observers who watched unrelated wild-reared model monkeys reacting very fearfully in the
presence of live and toy snakes.
- This vicarious conditioning also occurred simply through watching videotapes of models behaving
fearfully, suggesting that humans are also susceptible to acquiring fears vicariously simply through
watching movies and TV
2. Sources of individual differences in the acquisition of fears and phobias
a. How to explain why many individuals who do undergo traumatic experiences do not develop phobias.
There seems to be a modest genetically based vulnerability for phobias. This genetic vulnerability
may well be mediated through genetic contributions to fear conditioning, which may in turn be
mediated through personality variables such as high trait anxiety that also seem to serve as
vulnerability factors, affecting the speed and strength of conditioning. Moreover, children categorized
as behaviorally inhibited (excessively timid, shy, etc.) at 21 months of age have been found to be at
higher risk for the development of multiple specific phobias.
- Individual differences in genetic predisposition and psychological traits
- High trait anxiety
- Low expression of 5-HTT gene
b. Differences in life experiences (before, during or after fear experience) among individuals can also
strongly affect the outcome of conditioning experiences. → May serve as (in)vulnerability factors
- A phenomenon known as latent inhibition demonstrates that simple prior exposure to a
conditioned stimulus (CS) before the conditioned and unconditioned stimulus (US) are ever
paired together reduces the amount of subsequent conditioning to the CS when paired with
the US
- Children who have had more previous nontraumatic encounters with a dentist are
less likely to develop dental anxiety if subsequently traumatized at the dentist’s office
than are those with fewer prior encounters when they are traumatized → Neutral
experiences at the dentist reduce risk of dental anxiety when having a subsequent
aversive dentist experience
- Most monkeys who had initially simply watched a nonfearful model monkey behaving
non- fearfully with snakes were completely immunized against acquiring a fear of
snakes when subsequently exposed to fearful monkeys behaving fearfully with
snakes.
c. A person’s history of control over important aspects of his or her environment. Children reared with a
stronger sense of mastery over their environments should be more invulnerable to developing
phobias following traumatic experiences
3. Impact of contextual variables during conditioning
- For example, having control over a traumatic event (such as being able to escape it) has a major
impact on how much fear is conditioned to CSs paired with that trauma.
4. Impact of postevent variables
- Inflation effect = A person who is exposed to a more intense traumatic experience (not paired with
the CS) after conditioning of a mild fear is likely to show an increase in fear of the CS.
- Simple mental rehearsal or reevaluation of CS–US relationships can lead to enhanced strength of the
conditioned fear response.
Selective associations in the conditioning of fears and phobias
- Primates may be evolutionarily prepared to rapidly associate certain kinds of objects (such as snakes,
spiders, water, heights) with aversive events. This is because there may have been a selective advantage in
the course of evolution for primates who rapidly acquired fears of certain objects or situations that posed
3
, threats to humans’ early ancestors. Thus, prepared fears are not seen as inborn or innate but rather as very
easily acquired and/or especially resistant to extinction. (= preparedness)
- Cook and Mineka’s experiments using videotaped model monkeys showed that naive monkeys can
easily acquire fears of such fear-relevant stimuli as a toy snake or a toy crocodile but not of such
fear-irrelevant stimuli as flowers or a toy rabbit.
- In both monkeys and humans, therefore, evolutionary fear-relevant stimuli more readily enter into selective
associations with aversive events, and these same stimuli seem more likely than others to become the
objects of human phobias. Moreover, the special characteristics of fear learning seen with fear-relevant (but
not fear-irrelevant) stimuli (e.g., its automaticity and its resistance to higher cognitive control) suggest that the
acquisition of phobias involves a primitive basic emotional level of learning that humans share with many
other mammalian species.
Interestingly, reduced differential fear learning is linked to anxiety disorders
- In studies, individuals with high levels of anxiety often exhibit similar rates of fear acquisition to the
conditioned stimulus paired with the aversive event (CS+) compared to individuals without anxiety. However,
what's particularly noteworthy is their elevated responses to the conditioned stimulus not paired with the
aversive event (CS-). This means that while they may learn to associate the CS+ with fear, they also show
heightened responses to neutral stimuli. This reduced differential fear learning, where there's less distinction
between the CS+ and CS-, has been linked to anxiety disorders 6 months later (= prospective validity).
To study fear conditioning you can model maladaptive processes in the lab. Modeling maladaptive processes can help
to better understand individual differences in fear learning and how to change these processes:
a) Generalisation
- Phase 1: Participants undergo classical fear conditioning where they learn to associate one circle
(CS+) with an aversive stimulus like an electric shock (US), while another circle (CS-) is not paired
with the shock.
- Phase 2: During the generalization test, participants are presented with circles of intermediary sizes
(generalization stimuli, GSs), as well as the original CS+ and CS-. The goal is to observe how
participants respond to stimuli that are similar but not identical to the original CS+.
- Anxious participants typically exhibit a steeper generalization slope compared to non-anxious
individuals. This means that they tend to generalize fear responses more readily to stimuli that are
similar to the CS+.
b) Avoidance
- Participants are given the choice to avoid an aversive stimulus during fear conditioning.
- They are offered a reward for not avoiding the stimulus.
- The aversive stimulus is eventually removed, regardless of avoidance behavior.
- Anxious participants are more inclined to continue avoiding the stimulus, even when offered a reward,
hindering their ability to learn that the stimulus is no longer present.
c) Resistance to extinction
- Anxious participants often exhibit higher responses to the CS+ (the conditioned stimulus paired with
the aversive US) during extinction compared to non-anxious individuals. This heightened response to
the CS+ during extinction indicates greater resistance to the extinction process among anxious
individuals. Despite the absence of the aversive US, anxious participants continue to display fear
responses to the CS+.
- Furthermore, anxious participants tend to show increased differentiation between the CS+ and CS-
(the conditioned stimulus not paired with the US) throughout the extinction process. This means that
anxious individuals maintain a clearer distinction between the feared stimulus (CS+) and the safe
stimulus (CS-) even as extinction proceeds.
In summary, the origins and maintenance of fears and phobias are considerably more complex than was assumed by
traditional conditioning models. Nevertheless, these complexities are expected from the standpoint of contemporary
research on conditioning, which reveals a large variety of vulnerability, invulnerability, and contextual variables that
have a strong impact on the outcome of direct and observational conditioning experiences. Moreover, evolutionary
pressures seem to have affected the kinds of objects and situations that humans are most prone to learn to fear.
4
The authors describe how contemporary learning theory and research provide the basis for perspectives on the
etiology and maintenance of anxiety disorders that capture the complexity associated with individual differences in the
development and course of these disorders. These insights from modern research on learning overcome the
shortcomings of earlier overly simplistic behavioral approaches, which sometimes have been justifiably criticized. The
authors show how considerations of early learning histories and temperamental vulnerabilities affect the short- and
long-term outcomes of experiences with stressful events. They also demonstrate how contextual variables during and
following stressful learning events affect the course of anxiety disorder symptoms once they develop. This range of
variables can lead to a rich and nuanced understanding of the etiology and course of anxiety disorders.
Although behavioral/learning approaches were the dominant empirical perspective on anxiety disorders from the
1920s until the 1970s, these approaches have been widely criticized since the early 1970s. Many of these criticisms
stemmed from the inability of early learning approaches to account for the diverse factors involved in the origins of
people’s anxieties. More recently, however, a resurgence of interest in learning approaches has occurred, as these
approaches have incorporated some of the complexity predicted by contemporary learning theory and research.
Early learning histories, when considered together with temperamental vulnerabilities, can serve as diatheses that
make certain individuals more susceptible to adverse and stressful experiences that sometimes lead to the
development of anxiety disorders.
Researchers believe that these new contemporary learning approaches have several advantages over the other two
approaches (cognitive/psychodynamic approaches): The learning approaches are better grounded in the theories and
methods of experimental psychology, they provide more comprehensive formulations of the etiology of anxiety
disorders, and they provide a more explicit analysis of factors promoting or inhibiting the development of different
anxiety disorders.
Specific phobia
Researchers originally argued that phobias are simply intense
classically conditioned fears that develop when a neutral stimulus is
paired with a traumatic event, such as occurred when their Little Albert
acquired an intense fear of rats after hearing a frightening gong paired
with the presence of a rat several times.
Many people with phobias can recall a traumatic conditioning event
when their phobia began.
- In a famous psychology experiment in the 1920s, John Watson
and his assistant Rosalie Rayner made a terrifyingly loud
noise whenever a baby boy named Albert began to play with
a white rat. In this way, they trained the infant to fear the
rodent.
- The original view was that there was a CS-CR
association. The contemporary view was that there
was a CS-US association.
Deconditioning = In her study, Mary Cover Jones successfully used
a process similar to what we now call "systematic desensitization" to
help "Little Peter" overcome his fear of rabbits. Jones gradually
exposed Little Peter to the feared object (a white rabbit) while he
was engaged in activities he enjoyed. Over time, Little Peter's fear
diminished, and he eventually showed no signs of fear when near the rabbit.
Two-process model
- Fear acquisition through classical conditioning
- Maintenance of fear through operant conditioning
- Avoidance feared object (CS) → decrease fear
- Decrease fear → increase avoidance behavior
- But… prevents someone to learn that fear for CS is
unfounded
- Fear persists
1
,Fear potentiated startle reflex
- Startle response is universal startle reflex to loud noise (104 dB, startle probe)
- Protective function with motor responses, e.g., eyeblink reflex
- Eye blink reflex measured with electromyography (EMG) of muscle activity under eye
- Startle reflex is strengthened when someone is tense
Differential response → Difference between the CS+ (spider and shock) and CS- response (spider). The absence of
the shock in CS- ensures that any observed responses are due to the presence of the spider alone, without the
influence of fear conditioning.
- After conditioning: US-expectancy higher for CS+ than for CS- which is indicative of fear learning
- After conditioning: Startle response stronger to CS+ than for CS-, and noise alone which is indicative of
conditioning.
Fear conditioning in the animal brain shows that the amygdala plays a crucial role. However, there is no convincing
evidence that the amygdala is involved in human fear conditioning.
Summary
• ‘Little Albert' first demonstration of fear learning in humans
• Classical conditioning: model for development of fear
• Operant conditioning: model for maintenance of fear
• Amygdala crucial for fear learning (in animals)
• Classic conditioning elegant and simple model
• Too simple? Is it clinically relevant?
Criticism learning theory
a) US not necessary
- Many phobics cannot remember a traumatic event
- Phobics fear stimuli they have never encountered
- According to contemporary learning theory there are different pathways of fear learning namely
vicarious learning (observational/modeling), information transfer (learning by instruction) and trauma
(direct learning). There is empirical evidence for this theory.
b) US not sufficient
- According to contemporary learning theory there are differences in genetic predisposition/traits and
differences in learning history (before, during or after fearful experience)
c) Selectivity phobias
- Belongingness and preparedness
- Preparedness → Fear for prepared stimuli (important for evolution) easier to learn and more
difficult to extinguish
- Belongingness → Certain CS-US combinations (between sensory modalities) more easily
associated than other combinations
- Taste (CS) and nausea (US) easier than taste and pain
- Sound (CS) and pain (US) easier than taste and pain
d) CR not equal to UR
- According to learning theory the conditioned response is often identical to the initial unconditioned
response, but this is not true. In panic disorder, CR is not always equal to initial panic reaction (UR).
Panic is the intense fear, sweating etc. however the anxiety is the anticipation anxiety of having
another panic attack.
- According to contemporary learning theory there is a CS-US association. Association between CS
and cognitive representation of US (CS-US). Feared stimulus (CS) predicts occurence of catastrophe
(US). CR (e.g., freezing) prepares the body for impending catastrophe (US). Association between
cues (CSs) and anticipated catastrophe (US: going mad, loss of control). Contemporary learning
theory suggests that there's an association between the conditioned stimulus (CS) and the cognitive
representation of the unconditioned stimulus (US) (CS-US association). In the case of panic disorder,
the CS (feared stimulus) predicts the occurrence of a catastrophe (US), such as having a panic
attack. The CR, such as freezing or anticipatory anxiety, prepares the body for the impending
catastrophe (US). Essentially, cues (CSs) become associated with the anticipation of catastrophic
events (US), like feelings of going mad or losing control, contributing to the experience of anxiety.
2
, - Anxiety disorders: feel, think and act as if feared stimulus (CS) is followed by a catastrophe
(US).
Criticism contemporary learning theory
1. Vicarious conditioning of fears and phobias
- Many people with phobias do not appear to have had any relevant history of classical conditioning.
Clinicians have long speculated that simply observing others experiencing a trauma or behaving
fearfully could be sufficient for some phobias to develop.
- In Mineka and Cook’s series of experiments on observational conditioning of snake fear,
laboratory-reared young adult rhesus monkeys who initially were not afraid of snakes served
as observers who watched unrelated wild-reared model monkeys reacting very fearfully in the
presence of live and toy snakes.
- This vicarious conditioning also occurred simply through watching videotapes of models behaving
fearfully, suggesting that humans are also susceptible to acquiring fears vicariously simply through
watching movies and TV
2. Sources of individual differences in the acquisition of fears and phobias
a. How to explain why many individuals who do undergo traumatic experiences do not develop phobias.
There seems to be a modest genetically based vulnerability for phobias. This genetic vulnerability
may well be mediated through genetic contributions to fear conditioning, which may in turn be
mediated through personality variables such as high trait anxiety that also seem to serve as
vulnerability factors, affecting the speed and strength of conditioning. Moreover, children categorized
as behaviorally inhibited (excessively timid, shy, etc.) at 21 months of age have been found to be at
higher risk for the development of multiple specific phobias.
- Individual differences in genetic predisposition and psychological traits
- High trait anxiety
- Low expression of 5-HTT gene
b. Differences in life experiences (before, during or after fear experience) among individuals can also
strongly affect the outcome of conditioning experiences. → May serve as (in)vulnerability factors
- A phenomenon known as latent inhibition demonstrates that simple prior exposure to a
conditioned stimulus (CS) before the conditioned and unconditioned stimulus (US) are ever
paired together reduces the amount of subsequent conditioning to the CS when paired with
the US
- Children who have had more previous nontraumatic encounters with a dentist are
less likely to develop dental anxiety if subsequently traumatized at the dentist’s office
than are those with fewer prior encounters when they are traumatized → Neutral
experiences at the dentist reduce risk of dental anxiety when having a subsequent
aversive dentist experience
- Most monkeys who had initially simply watched a nonfearful model monkey behaving
non- fearfully with snakes were completely immunized against acquiring a fear of
snakes when subsequently exposed to fearful monkeys behaving fearfully with
snakes.
c. A person’s history of control over important aspects of his or her environment. Children reared with a
stronger sense of mastery over their environments should be more invulnerable to developing
phobias following traumatic experiences
3. Impact of contextual variables during conditioning
- For example, having control over a traumatic event (such as being able to escape it) has a major
impact on how much fear is conditioned to CSs paired with that trauma.
4. Impact of postevent variables
- Inflation effect = A person who is exposed to a more intense traumatic experience (not paired with
the CS) after conditioning of a mild fear is likely to show an increase in fear of the CS.
- Simple mental rehearsal or reevaluation of CS–US relationships can lead to enhanced strength of the
conditioned fear response.
Selective associations in the conditioning of fears and phobias
- Primates may be evolutionarily prepared to rapidly associate certain kinds of objects (such as snakes,
spiders, water, heights) with aversive events. This is because there may have been a selective advantage in
the course of evolution for primates who rapidly acquired fears of certain objects or situations that posed
3
, threats to humans’ early ancestors. Thus, prepared fears are not seen as inborn or innate but rather as very
easily acquired and/or especially resistant to extinction. (= preparedness)
- Cook and Mineka’s experiments using videotaped model monkeys showed that naive monkeys can
easily acquire fears of such fear-relevant stimuli as a toy snake or a toy crocodile but not of such
fear-irrelevant stimuli as flowers or a toy rabbit.
- In both monkeys and humans, therefore, evolutionary fear-relevant stimuli more readily enter into selective
associations with aversive events, and these same stimuli seem more likely than others to become the
objects of human phobias. Moreover, the special characteristics of fear learning seen with fear-relevant (but
not fear-irrelevant) stimuli (e.g., its automaticity and its resistance to higher cognitive control) suggest that the
acquisition of phobias involves a primitive basic emotional level of learning that humans share with many
other mammalian species.
Interestingly, reduced differential fear learning is linked to anxiety disorders
- In studies, individuals with high levels of anxiety often exhibit similar rates of fear acquisition to the
conditioned stimulus paired with the aversive event (CS+) compared to individuals without anxiety. However,
what's particularly noteworthy is their elevated responses to the conditioned stimulus not paired with the
aversive event (CS-). This means that while they may learn to associate the CS+ with fear, they also show
heightened responses to neutral stimuli. This reduced differential fear learning, where there's less distinction
between the CS+ and CS-, has been linked to anxiety disorders 6 months later (= prospective validity).
To study fear conditioning you can model maladaptive processes in the lab. Modeling maladaptive processes can help
to better understand individual differences in fear learning and how to change these processes:
a) Generalisation
- Phase 1: Participants undergo classical fear conditioning where they learn to associate one circle
(CS+) with an aversive stimulus like an electric shock (US), while another circle (CS-) is not paired
with the shock.
- Phase 2: During the generalization test, participants are presented with circles of intermediary sizes
(generalization stimuli, GSs), as well as the original CS+ and CS-. The goal is to observe how
participants respond to stimuli that are similar but not identical to the original CS+.
- Anxious participants typically exhibit a steeper generalization slope compared to non-anxious
individuals. This means that they tend to generalize fear responses more readily to stimuli that are
similar to the CS+.
b) Avoidance
- Participants are given the choice to avoid an aversive stimulus during fear conditioning.
- They are offered a reward for not avoiding the stimulus.
- The aversive stimulus is eventually removed, regardless of avoidance behavior.
- Anxious participants are more inclined to continue avoiding the stimulus, even when offered a reward,
hindering their ability to learn that the stimulus is no longer present.
c) Resistance to extinction
- Anxious participants often exhibit higher responses to the CS+ (the conditioned stimulus paired with
the aversive US) during extinction compared to non-anxious individuals. This heightened response to
the CS+ during extinction indicates greater resistance to the extinction process among anxious
individuals. Despite the absence of the aversive US, anxious participants continue to display fear
responses to the CS+.
- Furthermore, anxious participants tend to show increased differentiation between the CS+ and CS-
(the conditioned stimulus not paired with the US) throughout the extinction process. This means that
anxious individuals maintain a clearer distinction between the feared stimulus (CS+) and the safe
stimulus (CS-) even as extinction proceeds.
In summary, the origins and maintenance of fears and phobias are considerably more complex than was assumed by
traditional conditioning models. Nevertheless, these complexities are expected from the standpoint of contemporary
research on conditioning, which reveals a large variety of vulnerability, invulnerability, and contextual variables that
have a strong impact on the outcome of direct and observational conditioning experiences. Moreover, evolutionary
pressures seem to have affected the kinds of objects and situations that humans are most prone to learn to fear.
4
