This document contains the summaries of the articles from Understanding Psychopathology Week 4 . This document is more expensive than the last ones, because this week there was more literature (8 articles). The articles summarized are:
- Classical conditioning and the acquisition of human fears...
Literature week 4
ANXIETY
Classical conditioning and the acquisition of human fears and phobias: A review and
synthesis of the literature – Graham C. L. Davey
http://proxy-ub.rug.nl/login?url=http://dx.doi.org/10.1016/0146-6402(92)90010-L
Abstract
This paper is an attempt to consider classical conditioning models of human fears and phobias in a
contemporary context, and to consider how conditioning models might be of some theoretical help
in this area. The paper covers (i) a contemporary review of the basic phenomena of human
conditioning, (ii) a comparison of conditioning processes in humans and animals, (iii) a description of
a contemporary model of human conditioning designed to accommodate recent research findings,
(iv) a re-examination of the traditional criticisms of conditioning accounts of phobias in the light of
this contemporary model, (v) a discussion of some of the features of fears and phobias that this
model can address, and (vi) a brief discussion of the scope of this model and some implications for
the treatment of clinical fears and phobias.
Introduction
The area in which the theoretical application of classical conditioning processes has received the
worst press is in the explanation of human fears and phobias.
In recent years our knowledge of conditioning processes in humans has expanded to a point where
we can now reassess the relevance of models of conditioning in humans to the etiology and
treatment of human fears and phobias. These contemporary models provide much information
about learning and performance that was unavailable just a few years ago. First, these models are
now able to specify fairly precisely the conditions under which associative learning is likely to occur,
this has important implications for preventative therapy and also enables contemporary conditioning
theory to successfully address many of the traditional criticisms of conditioning models of phobias.
Secondly, it has become clear in recent years that there are important nonassociative processes that
modulate the strength of a conditioned response. Including these nonassociative processes in a
comprehensive model of human conditioning allows the theorist to explain many of the perplexing
phenomena of fears and phobias that have hitherto proved difficult for conditioning accounts.
The paper will be structured in the following way: (i) a contemporary review of the basic phenomena
of human conditioning, (ii) a comparison of conditioning processes in humans and animals, (iii) a
description of a contemporary model of human conditioning designed to accommodate recent
research findings, (iv) a re-examination of the traditional criticisms of conditioning accounts of
phobias in the light of this contemporary model, (v) a discussion of some of the features of fears and
phobias that this model can address, and (vi) a brief discussion of the scope of this model and some
implications for the treatment of clinical fears and phobias.
Conditioning Processes in Humans
Most traditional conditioning theories of phobias have based their accounts on conditioning
processes found in nonhuman animals, and, indeed, critics of conditioning theories have based some
,of their criticisms on the fact that human phobias do not obey rules derived from animal learning.
We can only begin to compare human and animal conditioning when we have developed a model of
human conditioning based primarily on studies of humans. This requires an understanding of the
associative substructure that underlies conditioning and of the associative and nonassociative
variables that modulate conditioned responding. This should allow the construction of a model of
human conditioning which can either be contrasted or integrated with our knowledge of animal
conditioning.
Contemporary Classical Conditioning in Animals
The two most important developments have concerned (i) the kinds of associations that are formed
during different types of classical conditioning, and (ii) the nature of the cognitive representations
that mediate the CR.
In most first-order conditioning studies which have used postconditioning UCS revaluation
procedures (both appetitive and aversive) the results have suggested that the animal learns a CS-UCS
association, and that the CR is mediated by the animal’s evaluation of the UCS. While implying that
animals generally learn CS-UCS associations in simple first-order conditioning procedures (some
second-order conditioning procedures may, however, produce more reflexive S-R learning, these
results also have implications for our conception of Pavlovian responding. First, they imply that the
CS activates some kind of internal representation of the UCS and it is this representation that
mediates the CR. Secondly, they imply that the strength or even the nature of the CR will depend on
how that UCS representation is evaluated when it is activated. Thirdly, they imply that the strength of
the CR can be modulated by procedures which lead to the revaluation of the UCS representation
independently of any experiences with the CS-UCS contingency; that is, CR strength can be
modulated relatively independently by both CS-UCS associative processes and UCS revaluation
processes.
Associations in Human Conditioning
Two lines of evidence suggest that humans also learn CS-UCS associations in first-order Pavlovian
conditioning. First, a large number of studies have suggested that human subjects only exhibit a
differential CR when they are able to verbalize the CS-UCS contingency. According to many theorists
this implies some kind of “cognitive relational learning” involving the processing of the relationship
between CS and UCS.
Secondly, those studies which have used the postconditioning UCS devaluation method with human
subjects have all demonstrated that postconditioning revaluation of the UCS affects the strength of
the CR in both first- and second-order aversive conditioning.
UCS Revaluation Processes in Human Conditioning
Davey (1987, 1989b) has pointed out that the sensitivity of humans to UCS revaluation procedures
suggests that processes of UCS revaluation may have considerable importance in the modulation of
human CR strength. Furthermore, in human subjects there are a variety of ways in which UCS
revaluation might be achieved. The first is by direct experience with the UCS alone, and is one which
has been generally used with animals. ‘
A second method involves socially or verbally transmitted information about the UCS. For example, in
a laboratory experiment subjects can simply be told that on future presentations the UCS will be less
intense or less likely to occur. If they believe this, then the UCS is rated as less aversive and a weaker
CR elicited on future CS presentations.
,A third important source of information on which the subject can attempt to evaluate the UCS is their
reaction to either the CS or UCS itself. If, during an aversive conditioning procedure, they emit a
strong discriminable fear reaction to either the CS or UCS, this may lead them to attribute aversive
characteristics to the UCS which results either in the inflated aversiveness of the UCS or a firmly-
established UCS representation that is resistant to extinction.
Associative Phenomena in Human Conditioning
Most contemporary models of animal conditioning are contingencyrather than contiguity-based.
That is, they stress that simple contiguity between CS and UCS is not sufficient to generate
conditioning. What is more important is the predictive significance of the CS in heralding the UCS.
This implies that there will be certain conditions under which simple pairing of a CS with a UCS does
not generate a CR of the kind predicted by traditional contiguity-based conditioning theories. The
following sections examine associative learning in humans, and, in particular, discuss the existence of
various associative phenomena in humans.
Covariation assessment and covariation bias
imals is mediated by CS-UCS associations, the CR will be determined by factors which influence the
perception of the CS-UCS relationship. While animal theorists have emphasized that the predictive
contingency between CS and UCS is of prime importance in this perception, human studies of
covariation assessment have pointed out that assessing the relationship or covariation between
events appears to be influenced by both situational information (i.e., current information about the
contingency) and prior expectations or beliefs about the covariation.
In a thorough review of covariation assessment in both humans and animals, Alloy and Tabachnik
(1984) drew a number of conclusions: (i) in circumstances where situational information is
unambiguous and prior expectations are low, human subjects can detect event contingencies very
accurately, (ii) however, there are a variety of circumstances in which the combination of situational
information and prior expectancies give rise to what is called a covariution bias which generates a
distorted perception of the covariation - usually in the direction of the prior expectation, and (iii)
when the evidence from animal conditioning studies is considered, this too can be interpreted in
terms of the animal’s covariation assessment being determined by both situational information and
prior expectancies (the latter resulting primarily from prior conditioning experiences).
An important consequence of these conclusions is that perception of the relationship between CS
and UCS need not depend solely on the situational information contained in the actual CS-UCS
contingency, but can also depend critically on any prior expectations that the subject holds about the
stimuli in the episode. In this respect, covariation bias may help to explain some important occasions
when human conditioning does not comply with predictions based solely on contingency assessment.
Prior expectancies can influence the strength or course of conditioning in human subjects -
presumably by generating a covariation bias which influences perception of the CS-UCS relationship.
The sources of such expectancy biases remain unclear, although they may be pre-wired as a result of
natural selection processes, formed during the organism’s developmental history, or – less excitingly
from a theoretical viewpoint – an artefact of the demand characteristics of the experimental
procedure.
Latent inhibition
When a CS is presented alone on a number of trials prior to conditioning, it is much more difficult to
condition an association between CS and UCS than if there were no CS-alone trials prior to
, conditioning. This process is known as latent inhibition. From the point of view of contemporary
human conditioning theory, latent inhibition is important since it demonstrates another way in which
pairings of a CS and UCS may be relatively ineffective. Furthermore, this ineffectiveness appears to
derive from the normal operation of associative processes.
Blocking
If a UCS is already reliably predicted by a CS (call it A), then subsequently signalling that UCS with a
compound CS consisting of the original CS, A, plus a new component (call it B), results in little or no
learning about the new component B. This is known as blocking, and it is a robust phenomenon in
animal conditioning. Blocking is normally considered to be an associative phenomenon, in that
organisms do not appear to learn about the new component B because the UCS is already reliably
signalled by component A. Thus, blocking is yet another example of CS-UCS pairings failing to
generate a CR.
Demonstrations of blocking in humans have been less reliable than in animals, although this appears
to be in part a result of the kind of CR used. Blocking can be detected in human subjects, but use of
the electrodermal response as the CR may obscure it.
Sensory preconditioning
If an animal is exposed to pairings of two neutral stimuli such as a brief light (CSl) followed by a tone
(CS2), there appear to be no obvious behavioral changes. However, if the animal is then given
pairings of CS2 with a UCS, subsequent presentation of CSl alone will elicit CRs appropriate to the
UCS. This phenomenon is known as sensory preconditioning and is considered an example of
“behaviorally silent” learning, because it is only subsequent tests that reveal that learning did occur
in the initial phase of the procedure.
Sensory preconditioning has also been detected in humans using inferential methods.
Sensory preconditioning is important in that it demonstrates that associative learning can take place
in the absence of differential CRs, and, more importantly from the point of view of later discussions,
in the absence of an obviously aversive UCS.
Higher-order conditioning
A final associative phenomenon that is of some relevance in this context is higher-order conditioning.
Once a CS has been associated with a UCS and is capable of eliciting a reliable CR, that CS can then be
used to reinforce other potential CSs. Once established, the second-order CR is much more
“reflexive” and not mediated by a representation of the UCS.
Second-order conditioning can also be established fairly readily in human subjects, although
revaluation studies have suggested that secondorder responding in these procedures is mediated by
a representation of the UCS.
A Model of Human Conditioning
First, the preceding sections have demonstrated that conditioning in humans displays most of the
important associative phenomena known to be characteristic of animal conditioning. Establishing this
fact is important when we come to consider how associative factors might modulate the learning of
fears and phobias, and, in particular, when it comes to developing a conditioning model of phobias
which is able to predict the conditions under which fear learning will and will not occur.
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