Return of fear in a human differential conditioning paradigm caused by a return to the original acquistion context

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Abstract

In a differential human fear conditioning paradigm evidence for ABA-renewal was obtained manipulating the lighting in the experimental room. During acquisition in either a dark or illuminated room, one neutral slide was sometimes paired with a loud aversive noise whereas another slide was not. Subsequently, extinction took place in the opposite lighting context. When afterwards the participants were tested again in the original acquisition context, measurements revealed a recovery of the conditioned electrodermal response and an increase in the retrospective verbal US-expectancy ratings. No response recovery was obtained in an AAA-group that received acquisition, extinction and test trials in one and the same context. Several theoretical explanations for this type of return of fear as well as implications for clinical practice are discussed.

Introduction

Powerful therapeutic tools exist for the treatment of specific phobias. Most often the behavioural treatment involves repeated and systematic exposure to the fear-provoking stimulus (e.g. Öst, 1997). Although such exposure-based treatment is highly effective, there is substantial evidence in the clinical literature that fear may return with the passage of time. Rachman and colleagues (e.g. Rachman, 1989) have studied the phenomenon of return of fear extensively and explored (post)treatment and individual difference variables that predispose individuals to the return of fear. Although findings across various studies are rather mixed and it is too early to make any firm predictions, several suggestions have been made in literature. Research indicates that individual difference variables such as mood during exposure (Salkovskis & Mills, 1994) and initial level of heart rate (Wood & McGlynn, 2000; Grey, Rachman, & Sartory, 1980) may correlate with levels of return of fear. There are also indications that for example the strength of covariation bias immediately after treatment (De Jong, Vandenhout, & Merckelbach, 1995), the incompleteness of fear reduction at the end of exposure (Rachman, Robinson, & Lopatka, 1987) and the speed of fear reduction can be predictive for a return of fear. Furthermore, research indicates that distraction during exposure can have a facilitative effect on return of fear (Kamphuis & Telch, 2000). Treatment variables that might reduce the return of fear are the use of varied stimuli instead of the same stimulus during exposure (Rowe & Craske, 1998a) and the use of an expanding-spaced instead of massed exposure schedule (Rowe & Craske (1998b) though see Lang & Craske (2000), for a lack of replication).

The post-treatment variable of interest for the research presented in this manuscript is context-change after exposure. There is good evidence from clinical studies that return of fear may be facilitated by entering a new context. Mineka, Mystkowski, Hladek, and Rodriguez (1999) showed a return of self-reported fear one week after a one-session exposure-based treatment when treated spider-phobics were tested in a different room. Rodriguez, Craske, Mineka, and Hladek (1999) showed a return in the level of heart rate responding for one specific stimulus two weeks after exposure treatment when the incidental (room) and meaningful (therapist) context were changed. Finally, Mystkowski, Craske, and Echiverri (2002) manipulated the contexts in a more naturalistic way and used an inside and an outside context. They showed a clear return of fear in self-report data one week after a one-session exposure-based therapy when participants were tested in the other context.

The results of these clinical studies show a striking resemblance to the substantial experimental evidence from the animal conditioning literature that conditioned responses return after a context change. These studies demonstrate a context-dependency of extinction, analogous to the context-dependency of exposure treatment. It is assumed that exposure therapy involves processes analogous to extinction: repeatedly presenting the conditioned stimulus (CS) without the unconditioned stimulus (US) after acquisition most often leads to a decrease in conditioned responding. The most frequently observation reported is ABA-renewal. Bouton and colleagues (e.g. Bouton & King, 1983; Rosas & Bouton, 1997; Bouton & Swartzentruber, 1986) demonstrated that conditioned responding is renewed when after extinction in a context different from the acquisition context, animals are again tested in the original acquisition context. The effect was not only demonstrated in traditional animal fear conditioning paradigms such as conditioned suppression (Bouton & King, 1983), but also in appetitive conditioning (Bouton & Peck, 1989) and in a taste aversion paradigm (Rosas & Bouton, 1996). Similar effects are obtained when after extinction in a different context, transfer of extinction is tested in a third context (ABC-renewal, Bouton & Brooks, 1993; Bouton & Swartzentruber, 1986). The clinical studies described above can best be compared with the latter type of renewal: exposure therapy most often takes place in a context different from the original acquisition context, and return of fear is then observed in a new, third context. Finally, AAB-renewal was also demonstrated in animals (Bouton & Ricker, 1994). In such a procedure acquisition and extinction take place in an identical context but testing is executed in a new context.

Classical conditioning theory and the findings from animal conditioning studies might be very helpful in clarifying the context-specificity effect of exposure. They may provide insight in the learning mechanisms that are responsible for return of fear. Recent conditioning theories about extinction (for a review see Rescorla, 2001) suggest that extinction should not be equated with unlearning. Instead extinction would involve learning about additional context-specific information (Bouton, 1988, Bouton, 1994, Bouton, 2000). As a result the extinction context acquires a modulatory role and helps to disambiguate between the old (acquisition) and the new (extinction) information. Translating this idea to a clinical context, this would suggest that during exposure the original association of the fearful object with fear is not subjected to change. Rather, one learns that sometimes the fearful object is not to be feared. This additional information will only come to expression when the therapy context is present. According to this approach, expectations with regard to the generality and permanence of the effect of exposure are rather pessimistic.

In the animal conditioning literature, this contextual theory of extinction has received a lot of attention. Nonetheless, there are two other mechanisms that were traditionally used to explain the context-specificity of extinction. The first mechanism is the formation of a direct inhibitory association between the extinction context and the US. In the clinical literature this inhibitory context is called a safety signal. It predicts the non-occurrence of the US and as such protects the CS from extinction (Lovibond, Davis, & O’Flaherty, 2000). When leaving the therapy context, the inhibitory power of the context/therapist is no longer present and fear will return. The second mechanism received less attention in the literature. It is possible that the fearful object is perceived differently in the exposure context than in the acquisition context. In this respect, exposure might have involved a (partially) wrong stimulus and fear will return when the original acquisition stimulus is presented. In the animal conditioning literature, this mechanism is called generalisation decrement. From an a priori point of view, these mechanisms can be at work in ABA- and ABC-renewal demonstrations in animals as well as in the clinical studies. However, Bouton and his colleagues showed that in their animal conditioning preparations the context did not become inhibitory during extinction and excluded this explanation for their renewal effects (e.g. Bouton & King, 1983, Bouton & Swartzentruber, 1986). Moreover, they also showed no generalisation decrement between acquisition and extinction, excluding the second alternative mechanism. Hence they made a very strong case in favour of the modulatory mechanism in their conditioning preparations.

Because contexts and stimuli in different conditioning preparations might serve different functions due to differences in salience, meaning, distance, etc., these animal conditioning findings cannot immediately be generalised to human fear conditioning studies. All three mechanisms can in principle play a role in human ABA-renewal demonstrations. A replication of the renewal-effect in a human conditioning study with experimentally induced fear might be a first step towards unravelling these mechanisms. Additionally, it might complement the existing evidence from clinical studies. Despite the loss of some ecological validity, the strength of such a human study with experimentally induced fear is that it brings the theoretical assumptions to their essence and allows studying the phenomenon under strictly controlled circumstances. First of all, in a clinical context one does not have control over the acquisition of fear. Therefore, studying the equivalent of an ABA-renewal effect for instance, is rather difficult. Often the original acquisition context is not known and even if it was known, recreating this context is often practically/ethically impossible. Moreover, in clinical studies it is very difficult to know what the differences are between the acquisition and the extinction context, information that might be useful when one wants to differentiate between different mechanisms. Secondly, not only acquisition but also, and importantly, extinction is strictly under control of the experimenter. This might be important if one wants to make an analysis of the underlying mechanisms. When studying return of fear after exposure-based treatment, this treatment involves often more than what is included in a simple extinction-procedure, such as modelling, counterconditioning, social reinforcement, etc.

In sum, it might be worthwhile to fill the gap between clinical experiments and animal conditioning studies. This was the main intention of our research. As a first step in disentangling the possible underlying mechanisms, we wanted to demonstrate the ABA-renewal effect in a human differential fear-conditioning paradigm with visual stimuli as CSs and a loud aversive noise as US (Vansteenwegen, Crombez, Baeyens, & Eelen, 1998). Contexts were manipulated by switching the central lighting in the experimental room on or off. One group (ABA) either received acquisition and test in the dark context and extinction in the illuminated context or vice versa. For the other group (AAA) acquisition, extinction and test were conducted in the same context (all dark or all illuminated). In the first place, we aimed to demonstrate the ABA-renewal effect using a psychophysiological index namely electrodermal responding. The evidence for renewal in clinical studies is mainly based on verbal self-reports. If one wants to study the phenomenon of the return of a real emotional response such as fear, it can be important not to rely solely on verbal indices of fear, as bodily responses are an integrative part of emotional responding. Moreover, correlations between verbal, physiological and behavioural indices are often low (Ohman, 1987). In this respect, demonstrating ABA renewal with skin conductance is not without relevance. The psychophysiological index was complemented with US-expectancy ratings in order to see whether we could replicate the already existing clinical evidence for a return in verbal indices under the more strictly controlled conditions of this human fear conditioning study. However, we took the option to formulate these ratings in a retrospective in order not to interfere with the natural development of the electrodermal responses.

Section snippets

Participants

Forty first-year psychology students participated in order to fulfil course requirements. Twenty participants were assigned to the ABA-group and twenty to the AAA-group. They all gave informed consent and were informed that they could decline to participate at any time.

Apparatus

Two clearly distinct line drawings of pictorial faces served as conditioned stimuli. For half of the participants, one picture was sometimes followed by the US (CS+) and the other stimulus was not (CS−), for the other half of the

US-ratings

The mean pleasantness rating for the US was −6.44 (SD=2.66), and the mean intensity score lay near the third label, namely intense (M=3.00, SD=0.59). Previous research by the authors (Vansteenwegen et al., 1998) that used this US independently of a conditioning procedure2 revealed similar ratings for the loud noise. The mean pleasantness rating

Discussion

It was the intention of this study to demonstrate a return of conditioned electrodermal responding after extinction when returning to the original acquisition context. The experimental as well as the control group showed clear acquisition. Acquisition developed somewhat slower in the AAA-group as on the last acquisition trial no significant CS+/CS− differentiation was observed yet. However, the data from the first extinction trial clearly show that these participants have learned the

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    Debora Vansteenwegen and Tom Beckers are postdoctoral researchers of the Fund for Scientific Research FWO-Vlaanderen.

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