Effects of an Acceptance/Defusion Intervention on Experimentally Induced Generalized Avoidance: A Laboratory Demonstration

Full reference: Luciano, C., Valdivia-Salas, S., Ruiz, F. J., Rodríguez-Valverde, M., Barnes-Holmes, D., Dougher, M. J., López-López, J. C., Barnes-Holmes, Y., & Gutiérrez-Martínez, O. (2014). Effects of an acceptance/defusion intervention on experimentally induced generalized avoidance: A laboratory demonstration. Journal of the Experimental Analysis of Behavior, 101, 94-111.

Study type: Laboratory experiment / Analogue study / Translational research on basic behavioral processes

Background and objectives

This study examined how anxiety disorders, among the most prevalent psychiatric conditions in Western societies, are maintained by avoidance patterns and how they may be modified through psychological interventions. Although exposure therapy is considered the gold-standard empirically supported treatment, fundamental uncertainties persist regarding the basic processes that produce therapeutic change. Prior research has demonstrated that avoidance—rather than the history of fear conditioning itself—is the critical factor maintaining anxiety disorders. Analogue studies have shown that it is possible to learn to fear and avoid stimuli that are arbitrarily related to an unconditioned aversive stimulus through the transfer of derived aversive functions within stimulus equivalence classes.

The present study was designed to evaluate the impact of an acceptance/defusion protocol (DEF) on experimentally induced avoidance, contrasting it with general motivational protocols (MOT) and a post-hoc control condition (CMOT). The primary aim was to establish and test the transfer of respondent and avoidance/approach functions within a relational network of stimuli, and to demonstrate that a brief acceptance/defusion protocol could be effective in modifying previously established avoidance behavior through the presentation of personally relevant examples and discrimination training. The authors sought to understand how acceptance/defusion procedures could alter the stimulus control exerted by private events (such as thoughts and uncertainty) over avoidance responses.

Method

Participants / Subjects / Models

The study included 23 young adult participants (17 females; age range 18-27 years) attending undergraduate courses at different universities. None of the participants had previous experience with the procedures employed in the study. Participants were recruited through in-class announcements and convenience sampling, and each received 10 euros for participation. Upon completion of the tasks, participants were fully debriefed about the procedure and received the promised compensation. Additionally, 16 control participants (ages 8-24) were recruited and subjected to procedures identical to the experimental group, with the exception that they received none of the three experimental protocols during Phase 4.

Experimental design

The study employed a multi-phase design with six sequential phases. All procedures were reviewed and approved by the Ethics Committee for Research with Human Participants at the university. The independent variables were: (1) conditional discrimination training with the formation of two 6-member stimulus equivalence classes; (2) Pavlovian and avoidance/approach conditioning; (3) implementation of three different protocols (MOT, DEF, CMOT). The primary dependent variables were: (1) avoidance/approach responses measured throughout the experimental session; (2) skin conductance responses (SCRs) as a measure of aversive physiological activation; (3) relational responses during equivalence tests.

The study included experimental conditions (MOT and DEF) and a post-hoc control condition (CMOT). Clear group assignments were made: 7 and 8 participants were randomly assigned to the MOT and DEF conditions respectively during Phase 4, while 8 participants were assigned to the CMOT condition. The 16 control participants received identical treatment except for the absence of the experimental protocol.

Materials and apparatus

The experiment was conducted in a laboratory consisting of two adjacent rooms (an experimental room and an observation room) with a computer and monitor for stimulus presentation. A computerized physiological recording system (BioPAC Instruments MP100 with GSR100C module) was employed to measure and record skin conductance responses (SCRs). Visual stimuli consisted of 18 black shapes presented on a white general background on a 15-inch computer monitor. For identification of each stimulus, an alphanumeric label was used (e.g., A1, A2).

The stimulation system included an isolated square-wave stimulator (Lafayette 84815-85) that delivered constant electrical pulses (duration 450 ms, maximum output voltage 100V) through disposable round electrodes (15 mm diameter with 0.95% NaCl foam adhesive) applied to the inner surface of the participant's forearm. Skin conductance electrodes (AgCl with round contact area of 6 mm diameter) were attached to the palmar side of the index and middle fingers of the participant's nondominant hand. The experiment tasks were presented by a laptop computer connected to the physiological system through a custom parallel port cable that provided markers for physiological recordings.

Procedure

All procedures were reviewed and approved by the Ethics Committee, and participants were escorted to the experimental room completing informed consent procedures. Participants completed the individual experimental session in six phases, conducted in a single session lasting 150-180 minutes.

Phase 1: Conditional discrimination training. A matching-to-sample (MTS) procedure was employed to train the conditional discriminations necessary for the formation of two 6-member stimulus equivalence classes (classes: A-B, B-C, C-D, D-E, E-F; A-B, B-C, C-D, D-E, E-F). Training was conducted in blocks of 16 trials. Two Pavlovian contaminated conditioning trials were presented at the beginning of each block of mixed trials (four trials presented the A1-B1 contingency without escape opportunity; 12 trials were operant). The learning criterion was emission of avoidance responses on all A1/B1 trials (and not on any A2/B2 trials) as well as when participants produced responses on all two maximum A2/B2 trials (and never on A1/B1 trials). After one block, participants advanced to the next phase; participants not meeting criterion were excluded from further participation.

Phase 2: Pavlovian and avoidance/approach conditioning. Phase 2 began with presentation of brief shocks in a 10V intermittent sequence until a voltage was identified that the participant described as "uncomfortable but not painful" in previous shock presentations. This voltage was used as the unconditioned stimulus (US). A delayed Pavlovian conditioning procedure was employed. In early trials, the circle (125 cm diameter) was presented with a shock (after A1 and B1) or with gain points (after A2 and B2). In subsequent operant trials, participants were instructed to press an avoidance key (Q) to cancel an imminent shock, and to press a different approach key (P) to earn points when the stimulus was presented with the other member of the B class. Responses during the color transition interval did not satisfy the operant contingency. After the circle was completely colored green (but not during the color transition), participants should rapidly press either the Q key to avoid shock or the P key to earn points.

Phase 3: Test for the transfer of Pavlovian and avoidance/approach functions. Phase 3 began immediately after Phase 2 and included only operant trials (SCRs and avoidance responses were measured concurrently). The trials were identical to the operant trials in Phase 2, with the exception that instead of A1 and B1, stimuli D1 and D2 were used (two trials per stimulus in random order). If the participant failed to press the avoidance key on D1 trials, then no shock was delivered. If the participant failed to press the approach key on D2 trials, then zero-point written feedback was displayed. A fourth test block was presented with F1 and F2 trials (two trials per stimulus). The criterion for transfer of avoidance was that participants produced avoidance responses on all F1 trials and approach responses on all F2 trials. Participants who met the transfer criterion proceeded to the next phase; participants who did not were excluded from further participation.

Phase 4: Protocol administration. The 20 participants remaining in the study after Phase 3 were randomly assigned to the MOT and DEF conditions (7/3 and 8/2 female/male respectively, in that order). The assignments were:

General Motivational Protocol (MOT): This protocol conveyed a general motivational or values component for non-avoidance responding. The experimenter entered the room where the participant was seated, sat facing the participant, and read the following instructions: "From now on, the computer task will work in a slightly different way in relation to the conditioned shock. Until now, if you did not press the Q key, you were shocked. From now on, if you do not press the Q key, you may not get shocked. This is programmed at random across participants, and the chance to win the gift is little."

General Motivational Protocol plus Defusion Training (DEF): The acceptance/defusion protocol consisted of two components in addition to the MOT protocol: (1) personally relevant examples of acting in the face of fear, uncertainty or worries; (2) discrimination/defusion training to notice and step back from thoughts and sensations as a detached observer. The defusion procedure was as follows (experimenter part in italics): "E: Now, could I ask you to do something that might seem a bit odd? Are you willing to do it if it's for the sake of research? Well, that was the only way of finding out (...). That was a real opportunity. The situation you are going to be in now is pretty similar to the examples you mentioned. At some point you might feel uncertain or almost unbearable anxiety about the possibility of getting shocked, and you might choose whether it is worth the risk in the long run." The procedure continued with the request that the participant provide two personal examples in which he or she might have felt uncertain or anxious, despite the feelings. The experimenter used acceptance/defusion questions to help the participant notice and step back from their thoughts and sensations. The dialogue proceeded as follows (experimenter part in italics):

"P: Yes, I recall something. E: What's the ink color? P: It is black. E: And where is it? P: It is in the upper left of the screen. E: It is a handwritten note, is it? P: Yes, E: What's the ink color? P: It is black. E: And where is it? P: It is in the upper left of the screen."

The MOT protocol lasted 5 minutes and consisted of a general motivational/values component. The DEF protocol lasted 15-20 minutes and consisted of the general motivational/values component plus two additional components (personally relevant examples of acting in the face of fear, uncertainty or worries; second, discrimination/defusion training to notice and distance from thoughts and sensations as a detached observer). Both protocols were synthesized in written form (a complete transcript of both protocols is available upon request from the authors).

Post-hoc Control Condition (CMOT): After the experiment was completed, to compare the MOT and DEF protocols, a post-hoc control condition was conducted where participants underwent a different protocol in Phase 4 (identical to DEF but without active acceptance/defusion training components). The CMOT condition was where participants underwent a different protocol during Phase 4 (identical to DEF protocol) but without active acceptance/defusion components. The 16 control participants received identical treatment to the main experiment, with the exception of the protocol administered in Phase 4.

Phase 5: Critical Test. After protocol administration, the experimenter left the room and the participant was presented with a sequence of trials containing directly conditioned stimuli (A1 and B1) and non-directly conditioned stimuli (D, E, and F) from both Class 1 and Class 2. Non-avoidance to Class 1 members was followed by shock on three occasions to present extinction of avoidance-evoking functions (shock presentations are marked with an asterisk in the stimulus sequence presented next). Participants who had shown complete transfer of functions during Phase 3 (i.e., class-consistent avoidance/approach responses with D and F stimuli) were exposed to this sequence.

Phase 6: Equivalence Test. The mutual (symmetry) and combinatorial (transitivity/equivalence) relations of derived relations were tested using the same format as in conditional discrimination training (Phase 1), with the difference that no verbal feedback was provided. Twenty possible combinatorial relations among eighteen possible class members were tested. The completion criterion was production of a minimum of 34 correct symmetry responses. A block finished if the criterion was achieved or if the second combinatorial block was not reached.

Data analysis

Individual and group analyses of the data were conducted to examine the effects of each protocol on avoidance responding, both directly conditioned and derived by means. The primary datum for individual analyses was the percentage of participants who met the specified avoidance/approach criteria in each phase. Our primary focus was on avoidance responding and its suppression or lack thereof as a result of protocol administration.

For group data analysis, the average number of avoidance responses (pressing Q) and average SCRs were calculated. The elements of Class 1 and Class 2 in each phase were analyzed separately for Phases 2, 3, 4, and 5. Kolmogorov-Smirnov tests were conducted on all pertinent SCR and avoidance response datasets to determine if the data met the assumption of normality. Where the normality assumption was not met, the nonparametric Wilcoxon Signed-Rank test was employed. Analyses were conducted to compare between classes within the same phase. Otherwise, one-way ANOVAs (with protocol condition as a factor) were conducted for each phase on the percentage of avoidance responses to Class 1 stimuli and the difference in average SCRs between Class 1 and Class 2 stimuli. Where the normality assumption was not met, a nonparametric counterpart (Kruskal-Wallis) was employed.

Results

All 23 participants met the conditional discrimination training criterion in Phase 1 within a range of 124 (P2) to 366 (P21) trials. In Phase 2, all 23 participants showed avoidance responses to A1 and B1 stimuli (solid bars, Fig. 2). For all 23 participants, larger SCRs were elicited by A1 and B1 (M = 99.37, SD = 1.53) than to Class 2 stimuli (M = 0.21, SD = 0.95). Likewise, significantly larger SCRs were elicited by A1 (M = 0.29; SD = 0.34) than by A2 and B2 (M = 0.08; SD = 0.16); t(19) = 3.27, p = 0.004.

For Phase 3 (transfer test), significantly more avoidance responses were emitted to Class 1 stimuli (M = 90.00, SD = 20.52) than to Class 2 stimuli (M = 3.00, SD = 15.39); Z = 4.065, p < 0.01. However, SCRs were undifferentiated between Class 1 (M = 0.31, SD = 0.33) and Class 2 (M = 0.24, SD = 0.33); t(19) = 0.68, p > 0.05. This is consistent with the aforementioned reduction in the proportion of participants who reached SCR criterion in Phase 3.

For the post-hoc control condition (CMOT), see Figure 2 and Table 2. All 16 participants passed conditional discrimination training within a range of 122 (P15) to 221 (P2) trials. In Phase 2, all produced avoidance responses to A1, B1 and approach responses to A2, B2. In Phase 3, six participants failed to show transfer of avoidance-evoking functions (i.e., failed to press the avoidance key on F1 trials) and were excluded from further participation. Of the 10 remaining participants, avoidance responses were differentiated between F1 and F2 (see Table 1 and solid bars in Fig. 2, Phase 3) in that avoidance responses occurred only on F1 trials and never on F2 trials. Thirteen of these 20 also showed the same pattern of differentiated avoidance between D1 and D2. Only seven participants (35%) showed larger SCRs to D1 and F1 than to D2 and F2.

Critical Test: Effect of Protocols on Avoidance Functions (Phase 5). As shown in the Phase 5 portion of Figure 2, six of ten participants who completed the MOT protocol pressed the avoidance key when Class 1 stimuli were presented. Table 1 (Phase 5 columns) shows the percentage of directly conditioned trials (A1 and B1), derived stimuli (D1, E1, F1), and the three novel stimuli (X, Y, and Z) on which avoidance responses were emitted. In contrast, participants who received the DEF protocol showed complete suppression of avoidance responding in the critical phase trials. For participants assigned to the CMOT condition, all ten emitted avoidance responses on directly conditioned, derived, and novel stimulus trials; this within-group difference was statistically significant, χ²(2) = 14.73; p = 0.001. Avoidance responses (SCRs) were undifferentiated across groups, F(2, 27) = 1.884; p = 0.171.

Mann-Whitney comparisons. Mann-Whitney tests were performed for pairwise comparisons among all conditions. The Bonferroni correction for repeated comparisons was applied, α = 0.017. Two-tailed significance was computed for each comparison. Participants in the MOT condition produced significantly more avoidance responses (U = 20.0, p = 0.011) than those in the DEF condition (U = 5-10.0, p = 0.001). Finally, there were no statistically significant differences between CMOT and MOT once Bonferroni correction was applied (U = 22.0, p = 0.026).

Additional analyses were conducted to compare differences between conditions in the number of shocks received during Phase 5. Participants in the DEF condition (M = 4, SD = 0) received more shocks than those in MOT (M = 3, SD = 1.05), and these, in turn, received more shocks than those in CMOT (M = 1.3, SD = 1.7). These differences were significant, χ²(2) = 14.722; p = 0.001. Pairwise comparisons (Bonferroni-corrected) indicated that DEF participants received significantly a higher number of shocks than those in MOT (U = 20, p = 0.011) and CMOT (U = 10, p = 0.001).

Discussion and conclusions

In the present study, two stimuli within a 6-member stimulus equivalence class reliably evoked operant avoidance responses and aversive respondent functions measured as SCRs. When other members of the equivalence class were presented, they also evoked avoidance responses, thus demonstrating transfer of operant function. In a subsequent phase, when participants were instructed that they could withhold avoidance responses to earn a probabilistic reward, participants exposed to motivational protocols (MOT and CMOT) made avoidance responses when they encountered shock-preceded stimuli. In contrast, most participants exposed to the acceptance/defusion protocol (DEF condition) reliably withheld avoidance responding when they encountered shock-preceded stimuli.

The clear suppressive effect of the acceptance/defusion protocol (DEF) on avoidance responses was due to its content and not to a longer interaction with the experimenter. The fact that participants in all three conditions showed similar levels of aversive physiological responses (SCRs) across all phases suggests that the effectiveness of the DEF protocol in avoidance responding was not due to a reduction in conditioned fear responses. Concurrently measuring avoidance responding and a correlated physiological measure (SCR) revealed that many participants emitted avoidance responses when they encountered stimuli that did not elicit significant physiological activation. This is consistent with findings in the clinical literature showing that for patients with anxiety disorders, the availability of opportunities to engage in avoidance behaviors (in the case of safety behaviors in the context of exposure therapy) may have a "fear suppression" effect (e.g., Rachman, Radomsky, & Shafran, 2008). Analogously, for some of our participants, avoidance responding was apparently to seek relief from uncertainty when the participant could reliably avoid shock.

The avoidance-suppressing effect of the DEF protocol contrasts sharply with the effects of exposure protocols (Luciano et al., 2013) when participants were instructed to avoid shock. The acceptance/defusion protocol in this study disrupted avoidance responding in the absence of extinction of conditioned/derived aversive functions or any direct manipulation of avoidance contingencies. The results from a brief applied acceptance/defusion protocol, consistent with findings from other analogue studies (Luciano et al., 2013), suggest that when the goal is to reduce avoidance responding, it is possible to eliminate avoidance of stimuli with directly and derivatively acquired aversive functions using an acceptance/defusion protocol.

Results were obtained using the same experimental avoidance induction procedures as in Luciano et al. (2013) for establishing and testing the transfer of respondent and avoidance-evoking functions. An important consideration is that the DEF protocol in this study had two separate components: (a) connecting relevant parts of the experimental task to examples of the participant's personal experience, and (b) using defusion or discrimination training to notice and distance from private events as a detached observer to alter the participant's perspective of private events and their functions in subsequent actions. The results of the present study demonstrate that the DEF protocol was effective in suppressing avoidance. Although all participants were matched on experimental demand in terms of interaction with the experimenter (post-hoc control condition), this may have reduced demand compared to the MOT protocol. The data suggest a higher rate of avoidance responding in the CMOT condition than in the MOT condition. There were no significant differences between CMOT and MOT after Bonferroni correction. An additional limitation is that neither participants' expectations about shock nor any other type of verbal report was measured. Consequently, there is no information obtained about whether there was a cessation of avoidance (DEF condition) or whether it continued (MOT and CMOT conditions) under similar levels of perceived fear.

Although extrapolation of these findings to the clinical arena should be taken with caution, the present results align with those derived from studies conducted to establish derived aversion (e.g., Dougher et al., 1994; Rodriguez-Valverde et al., 2009) and avoidance responding (e.g., Augustson & Dougher, 1997; Dymond et al., 2007; Luciano et al., 2013) and more specifically those from Luciano et al. (2013), suggesting a promising avenue for experimental psychology and intervention components that bridge experimental research areas and applied clinical areas.

Significance and contribution

This study demonstrates that a brief acceptance/defusion protocol can be effective in suppressing experimentally induced persistent avoidance without requiring extinction of conditioned fear responses, opening new avenues for understanding the basic processes underlying clinical behavioral disturbances. The results suggest that acceptance/defusion procedures that teach acceptance/defusion increase tolerance for experimentally induced discomfort and enable participants to develop the ability to discriminate between private events (thoughts and emotions) and actions, providing important ground for translational research applied to reducing experimentally induced avoidance responding.

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