Avoidance and its bi-directional relationship with conditioned fear: Mechanisms, moderators, and clinical implications

The Good, the Bad, and the Ugly-Chances, Challenges, and Clinical Implications of Avoidance Research in Psychosomatic Medicine

Avoidance behaviors are shaped by associative learning processes in response to fear of impending threats, particularly physical harm. As part of a defensive repertoire, avoidance is highly adaptive in case of acute danger, serving a potent protective function. However, persistent or excessive fear and maladaptive avoidance are considered key factors in the etiology and pathophysiology of anxiety- and stress-related psychosomatic disorders. In these overlapping conditions, avoidance can increase the risk of mental comorbidities and interfere with the efficacy of cognitive behavioral treatment approaches built on fear extinction. Despite resurging interest in avoidance research also in the context of psychosomatic medicine, especially in conditions associated with pain, disturbed interoception, and disorders of the gut-brain axis, current study designs and their translation into the clinical context face significant challenges limiting both, the investigation of mechanisms involved in avoidance and the development of novel targeted treatment options. We herein selectively review the conceptual framework of learning and memory processes, emphasizing how classical and operant conditioning, fear extinction, and return of fear shape avoidance behaviors. We further discuss pathological avoidance and safety behaviors as hallmark features in psychosomatic diseases, with a focus on anxiety- and stress-related disorders. Aiming to emphasize chances of improved translational knowledge across clinical conditions, we further point out limitations in current experimental avoidance research. Based on these considerations, we propose means to improve existing avoidance paradigms to broaden our understanding of underlying mechanisms, moderators and mediators of avoidance, and to inspire tailored treatments for patients suffering from psychosomatic disorders.

Avoiding a feared stimulus: Modelling costly avoidance of learnt fear in a sensory preconditioning paradigm

Avoidance of learnt fear prevents the onset of a feared stimulus and the threat that follows. In anxiety-related disorders, it turns pathological given its cost and persistence in the absence of realistic threat. The current study examined the acquisition of costly avoidance of learnt fear in healthy individuals (n = 45), via a sensory preconditioning paradigm. Two neutral preconditioning stimuli (PSs) were paired with two neutral conditioned stimuli (CSs). One CS then came to predict an aversive outcome whereas the other CS came to predict safety. In test, participants engaged in stronger avoidance to the PS associated with the fear-related CS than the PS associated with the safety-related CS. Of note, executing behavioral avoidance led to missing out a competing reward, thus rendering avoidance costly. The results also provide preliminary evidence that threat anticipation and a negative change in valence play a role in driving costly avoidance of learnt fear. Future studies should examine how avoidance of learnt fear maintains pathological anxiety.

Generalization of conditioned disgust and the attendant maladaptive avoidance: Validation of a novel paradigm and effects of trait disgust-proneness

Overgeneralization of conditioned fear to safe stimuli that resemble a previously-learned threat-cue is a well-studied correlate of clinical anxiety, yet whether conditioned disgust generalizes remains unknown, as does the extent to which such generalization is associated with disgust-related traits and maladaptive outcomes. The present study addresses this gap by adapting a validated fear-generalization paradigm to assess conditioned disgust and behavioral avoidance to a disgust-cue (CS+) paired with a disgusting video clip, and safe generalization stimuli parametrically varying in perceptual similarity to CS+. For comparison, levels of fear generalization were also assessed using the original fear-generalization paradigm. In both paradigms, costly and unnecessary avoidance to safe threat-cue approximations analogues maladaptive outcomes of generalization. In the disgust paradigm only, disgust-proneness was associated with elevated perceived risk to safe stimuli and increases in the extent to which such elevations were accompanied by maladaptive avoidance. Comparable levels of generalization, and positive associations between generalization and maladaptive avoidance, were found across disgust and fear paradigms. Results confirm that conditioned disgust is subject to generalization, implicate generalized disgust as a source of maladaptive avoidance particularly among those prone to disgust, and suggest a potential role for these processes in the etiology and maintenance of disgust-related disorders.

Costly habitual avoidance is reduced by concurrent goal-directed approach in a modified devaluation paradigm

Avoidance habits potentially contribute to maintaining maladaptive, costly avoidance behaviors that persist in the absence of threat. However, experimental evidence about costly habitual avoidance is scarce. In two experiments, we tested whether extensively trained avoidance impairs the subsequent goal-directed approach of rewards. Healthy participants were extensively trained to avoid an aversive outcome by performing simple responses to distinct full-screen color stimuli. After the subsequent devaluation of the aversive outcome, participants received monetary rewards for correct responses to neutral object pictures, which were presented on top of the same full-screen colors. These approach responses were either compatible or incompatible with habitual avoidance responses. Notably, the full-screen colors were not relevant to inform approach responses. In Experiment 1, participants were not instructed about post-devaluation stimulus-response-reward contingencies. Accuracy was lower in habit-incompatible than in habit-compatible trials, indicating costly avoidance, whereas reaction times did not differ. In Experiment 2, contingencies were explicitly instructed. Accuracy differences disappeared, but reaction times were slower in habit-incompatible than in habit-compatible trials, indicating low-cost habitual avoidance tendencies. These findings suggest a small but consistent impact of habitual avoidance tendencies on subsequent goal-directed approach. Costly habitual responding could, however, be inhibited when competing goal-directed approach was easily realizable.

The (shared) features of fear: Toward the source of human fear responding

Little is known about why people behave the way they do in threatening situations. Some theories invoke a transfer of responses from unconditioned stimuli (US) to conditioned stimuli (CS), but this principle goes astray because responses to the US and CS can differ substantially. The idea that we introduce here is that the pattern of responses to a newly established CS does not come from the US but (at least partly) transfers from how one (learned to) respond(s) to previously encountered stimuli with threat value. So, we conceptualize threat value as a stimulus feature that allows responses to transfer between stimuli that share this feature (in the same way as, for example, overlap in color or shape can support transfer). In contrast to prevailing views, this new perspective focuses on the relation between the CS and already established threat signals rather than on the relation between the CS and the US. We discuss how this shared features perspective on human fear responding can inspire future directions in both the laboratory and clinical practice.

Increased anxiety of public situations during the COVID-19 pandemic: Evidence from a community and a patient sample

Background

Increases in emotional distress in response to the global outbreak of the SARS-CoV-2 (COVID-19) pandemic have been reported. So far, little is known about how anxiety responses in specific everyday public life situations have been affected.

Method

Self-reported anxiety in selected public situations, which are relevant in the COVID-19 pandemic, was investigated in non-representative samples from the community (n = 352) and patients undergoing psychotherapy (n = 228). Situational anxiety in each situation was rated on a 5-point Likert scale (0 = no anxiety at all to 4 = very strong anxiety). Situational anxiety during the pandemic was compared with retrospectively reported situational anxiety before the pandemic (direct change) and with anxiety levels in a matched sample assessed before the pandemic (n = 100; indirect change).

Results

In the community and patient sample, indirect and direct change analyses demonstrated an increase in anxiety in relevant public situations but not in control situations. Average anxiety levels during the pandemic were moderate, but 5-28% of participants reported high to very high levels of anxiety in specific situations. Interestingly, the direct increase in anxiety levels was higher in the community sample: patients reported higher anxiety levels than the community sample before, but not during the pandemic. Finally, a higher increase in situational anxiety was associated with a higher perceived danger of COVID-19, a higher perceived likelihood of contracting COVID-19, and stronger symptoms of general anxiety and stress.

Conclusions

Preliminary findings demonstrate an increase in anxiety in public situations during the COVID-19 pandemic in a community and a patient sample. Moderate anxiety may facilitate compliance with public safety measures. However, high anxiety levels may result in persistent impairments and should be monitored during the pandemic.

Avoidance in Anorexia Nervosa: Towards a research agenda

Anorexia Nervosa is a severe and disabling mental disorder and a huge challenge to treat. Intense fears of e.g., food, eating, weight gain and social evaluation are core features of anorexia nervosa and obstacles during treatment. The perceived threats trigger avoidance and safety behaviors like highly restrictive eating, strict eating rules, vomiting and body checking, to minimize feared outcomes. The role of avoidance in anorexia nervosa is however hardly studied experimentally. In the present article, the focus is on a new transdiagnostic research agenda featuring both basic and clinical experimental research into avoidance as a most important mechanism maintaining the eating disorder. Avoidance learning and the generalization of learned avoidance behaviors are discussed, as well as safety behaviors and the need for inhibitory learning as a treatment target during exposure therapy.

Optimizing Long-term Outcomes of Exposure for Chronic Primary Pain from the Lens of Learning Theory

Exposure in vivo is a theory-driven and widely used treatment to tackle functional disability in people with chronic primary pain. Exposure is quite effective; yet, in line with exposure outcomes for anxiety disorders, a number of patients may not profit from it, or relapse. In this focus article, we critically reflect on the current exposure protocols in chronic primary pain, and provide recommendations on how to optimize them. We propose several adaptations that are expected to strengthen inhibitory learning and/or retrieval of the extinction memory, thus likely decreasing relapse. We summarize the limited, but emerging experimental data in the pain domain, and draw parallels with experimental evidence in the anxiety literature. Our reflections and suggestions pertain to the use of the fear hierarchy, reassurance, positive psychology interventions, exposure with a range of stimuli and within different contexts, and the use of safety behaviors during treatment, as well as associating the fear-inducing stimuli with novel outcomes. In addition, we reflect on the importance of specifically tackling (the return of) pain-related avoidance behavior with techniques such as disentangling fear from avoidance and reinforcing approach behaviors. Finally, we discuss challenges in the clinical application of exposure to improve functioning in chronic primary pain and possible avenues for future research. Perspectives: Inspired by recent advances in learning theory and its applications on the treatment of anxiety disorders, we reflect on the delivery of exposure treatment for chronic primary pain and propose strategies to improve its long-term outcomes.

Safety learning and the Pavlovian conditioned inhibition of fear in humans: Current state and future directions

Safety learning occurs when an otherwise neutral stimulus comes to signal the absence of threat, allowing organisms to use safety information to inhibit fear and anxiety in nonthreatening environments. Although it continues to emerge as a topic of relevance in biological and clinical psychology, safety learning remains inconsistently defined and under-researched. Here, we analyse the Pavlovian conditioned inhibition paradigm and its application to the study of safety learning in humans. We discuss existing studies; address outstanding theoretical considerations; and identify prospects for its further application. Though Pavlovian conditioned inhibition presents a theoretically sound model of safety learning, it has been investigated infrequently, with decade-long interims between some studies, and notable methodological variability. Consequently, we argue that the full potential of conditioned inhibition as a model for human safety learning remains untapped, and propose that it could be revisited as a framework for addressing timely questions in the behavioural and clinical sciences.

Avoidance behaviour performed in the context of a novel, ambiguous movement increases threat and pain-related fear

ABSTRACT

The fear-avoidance model of chronic pain predicts that catastrophic (mis)interpretation of pain elicits pain-related fear that in turn may spur avoidance behaviour leading to chronic pain disability. Here, we investigated whether performing a movement to avoid a painful stimulus in the context of a novel movement increases threat and pain-related fear towards this novel movement and whether avoidance behaviour persisted when given the choice between performing the acquired movement to avoid a painful stimulus or an alternative, novel movement. Applying a robotic arm-reaching task, participants could choose between 2 movements to reach a target location: a short, but painful movement trajectory, or a longer nonpainful movement trajectory. After avoidance acquisition, the option to choose the painful trajectory was removed. The experimental group (N = 50) could choose between the longest trajectory or a novel intermediate trajectory, whereas the control group (N = 50) was allowed to only perform the novel trajectory. In a final test, participants of both groups were allowed to choose any of the 3 trajectories. After acquisition, experimental group participants showed elevated pain expectancy and pain-related fear towards the novel trajectory, compared with the control group. During test, the experimental group participants persisted in performing the longest pain-free (avoidance) trajectory and were less likely to choose the novel trajectory. In addition, these participants maintained higher levels of pain-related fear for the novel trajectory compared with the control group. These findings suggest that avoidance in the context of other neutral activities/movements may lead to the development and maintenance of threat appraisals and irrational fears.

Ventral hippocampus mediates the context-dependence of two-way signaled avoidance in male rats

Considerable work indicates that instrumental responding is context-dependent, but the neural mechanisms underlying this phenomenon are poorly understood. Given the important role for the hippocampal formation in contextual processing, we hypothesized that reversible inactivation of the hippocampus would impair the context-dependence of active avoidance. To test this hypothesis, we used a two-way signaled active avoidance (SAA) task that requires rats to shuttle across a divided chamber during a tone CS in order to avoid a footshock US. After training, avoidance responding was assessed in an extinction test in both the training context and a novel context in a counterbalanced order. Rats performed significantly more avoidance responses in the training context than in the novel context, demonstrating the context-dependence of shuttle avoidance behavior. To examine the role of the hippocampus in the context-dependence of SAA, we reversibly inactivated either the dorsal (DH) or ventral hippocampus (VH) prior to testing. Inactivation of the VH eliminated the context-dependence of SAA and elevated avoidance responding in the novel context to levels similar to that expressed in the training context. In contrast, DH inactivation had no effect on avoidance in either context, and neither manipulation affected freezing behavior. Therefore, the integrity of the VH, but not DH, is required for the expression of the context-dependence of avoidance behavior.

Latent cause inference during extinction learning in trauma-exposed individuals with and without PTSD

BACKGROUND

Problems in learning that sights, sounds, or situations that were once associated with danger have become safe (extinction learning) may explain why some individuals suffer prolonged psychological distress following traumatic experiences. Although simple learning models have been unable to provide a convincing account of why this learning fails, it has recently been proposed that this may be explained by individual differences in beliefs about the causal structure of the environment.

METHODS

Here, we tested two competing hypotheses as to how differences in causal inference might be related to trauma-related psychopathology, using extinction learning data collected from clinically well-characterised individuals with varying degrees of post-traumatic stress (N = 56). Model parameters describing individual differences in causal inference were related to multiple post-traumatic stress disorder (PTSD) and depression symptom dimensions via network analysis.

RESULTS

Individuals with more severe PTSD were more likely to assign observations from conditioning and extinction stages to a single underlying cause. Specifically, greater re-experiencing symptom severity was associated with a lower likelihood of inferring that multiple causes were active in the environment.

CONCLUSIONS

We interpret these results as providing evidence of a primary deficit in discriminative learning in participants with more severe PTSD. Specifically, a tendency to attribute a greater diversity of stimulus configurations to the same underlying cause resulted in greater uncertainty about stimulus-outcome associations, impeding learning both that certain stimuli were safe, and that certain stimuli were no longer dangerous. In the future, better understanding of the role of causal inference in trauma-related psychopathology may help refine cognitive therapies for these disorders.

A dimensional measure of safety behavior: A non-dichotomous assessment of costly avoidance in human fear conditioning

Safety behavior prevents the occurrence of threat, thus it is typically considered adaptive. However, safety behavior in anxiety-related disorders is often costly, and persists even the situation does not entail realistic threat. Individuals can engage in safety behavior to varying extents, however, these behaviors are typically measured dichotomously (i.e., to execute or not). To better understand the nuances of safety behavior, this study developed a dimensional measure of safety behavior that had a negative linear relationship with the admission of an aversive outcome. In two experiments, a Reward group receiving fixed or individually calibrated incentives competing with safety behavior showed reduced safety behavior than a Control group receiving no incentives. This allowed extinction learning to a previously learnt warning signal in the Reward group (i.e., updating the belief that this stimulus no longer signals threat). Despite the Reward group exhibited extinction learning, both groups showed a similar increase in fear to the warning signal once safety behavior was no longer available. This null group difference was due to some participants in the Reward group not incentivized enough to disengage from safety behavior. Dimensional assessment revealed a dissociation between low fear but substantial safety behavior to a safety signal in the Control group. This suggests that low-cost safety behavior does not accurately reflect the fear-driven processes, but also other non-fear-driven processes, such as cost (i.e., engage in safety behavior merely because it bears little to no cost). Pinpointing both processes is important for furthering the understanding of safety behavior.

Elevated costly avoidance in anxiety disorders: Patients show little downregulation of acquired avoidance in face of competing rewards for approach

BACKGROUND

Pathological avoidance is a transdiagnostic characteristic of anxiety disorders. Avoidance conditioning re-emerged as a translational model to examine mechanisms and treatment of avoidance. However, its validity for anxiety disorders remains unclear.

METHODS

This study tested for altered avoidance in patients with anxiety disorders compared to matched controls (n = 40/group) using instrumental conditioning assessing low-cost avoidance (avoiding a single aversive outcome) and costly avoidance (avoidance conflicted with gaining rewards). Autonomic arousal and threat expectancy were assessed as indicators of conditioned fear. Associations with dimensional symptom severity were examined.

RESULTS

Patients and controls showed frequent low-cost avoidance without group differences. Controls subsequently inhibited avoidance to gain rewards, which was amplified when aversive outcomes discontinued. In contrast, patients failed to reduce avoidance when aversive and positive outcomes competed (elevated costly avoidance) and showed limited reduction when aversive outcomes discontinued (persistent costly avoidance). Interestingly, elevated costly avoidance was not linked to higher conditioned fear in patients. Moreover, individual data revealed a bimodal distribution of costly avoidance: Some patients showed persistent avoidance, others showed little to no avoidance. Persistent versus low avoiders did not differ in other task-related variables, response to gains and losses in absence of threat, sociodemographic data, or clinical characteristics.

CONCLUSIONS

Findings suggest that anxious psychopathology is associated with a deficit to inhibit avoidance in presence of competing positive outcomes. This offers novel perspectives for research on mechanisms and treatment of anxiety disorders.

Incentive-based, instructed, and social observational extinction of avoidance: Fear-opposite actions and their influence on fear extinction

Avoidance is a transdiagnostic symptom of clinical anxiety and its reduction a major focus of cognitive-behavioral treatments. This study examined the instrumental extinction of goal-directed avoidance by means of incentives, verbal instruction, and social observation and their influence on fear extinction. Participants acquired conditioned fear and instrumental avoidance responses (N = 160). In four randomized groups, the reduction of avoidance by incentives for non-avoidance, instructions to refrain from avoidance, and social observation of non-avoidance was compared to no intervention before removing the aversive outcome. Conditioned fear when avoidance became unavailable subsequently was tested. Incentives, instruction, and observation all reduced avoidance better than no intervention, however, with different degrees and influence on conditioned fear. Incentives and instructions strongly reduced avoidance despite high levels of fear (i.e., fear-opposite actions). This initiated fear extinction, thereby reducing conditioned fear when avoidance became unavailable. Social observation directly reduced conditioned fear, presumably because it conveyed additional information about the absence of the aversive outcome. However, observation only moderately reduced avoidance and resulted in higher fear when avoidance became unavailable. The effects of social observation may depend on the nuances of the demonstrator's behavior. The clear effects of incentive and instructions provide support for clinical interventions to reduce avoidance during exposure therapy and can serve as experimental models for their controlled investigation.

The Role of Disgust in Eating Disorders

PURPOSE OF REVIEW

In current review, we evaluate the current literature examining the role of disgust in eating disorders (EDs), and provide a theoretical model designed to inform the study and treatment of disgust-based symptoms in EDs.

RECENT FINDINGS

Findings from this review suggest that aberrant disgust-conditioning processes represent promising but understudied mechanisms that may contribute to the risk and maintenance of core eating disorder (ED) psychopathology. In addition, preliminary evidence supports the use of interventions designed to target aversive disgust cues and disrupt maladaptive disgust-based conditioning that may maintain eating pathology. However, experimental studies designed to elucidate the role of disgust and aversive learning processes remain limited. Disgust is a promising risk and maintenance factor in EDs. Future systematic investigation is needed to examine disgust-based processes at a mechanistic level in order to better understand the links between disgust, avoidance behaviors, and EDs. Further investigation of the mechanistic role of disgust in EDs is warranted.

Generalization of extinction with a generalization stimulus is determined by learnt threat beliefs

Expectancy violation refers to the mismatch between an expected and the actual outcome. Maximizing expectancy violation is crucial for exposure-based treatment. Since the original stimulus of fear acquisition (CS+) is rarely available, stimuli that resemble the CS+ (generalization stimuli; GSs) are presented during treatment. A given GS may evoke either strong or weak generalized fear depending on an individual's threat beliefs. Presenting this GS in extinction would then evoke different levels of expectancy violation, which determines the strength of the subsequent generalization of extinction to other stimuli, including the CS+. After differential fear conditioning, participants exhibited discrete generalization gradients depending on their inferred relational rules (Linear vs Similarity). Crucially, the Linear group showed strong generalized fear to the GS used in extinction. This strong expectancy violation led to enhanced extinction learning and subsequently to strong generalization of extinction as characterized by a flat generalization gradient, and reduced conditioned fear to the CS+. In contrast, the Similarity group showed weak generalized fear to the same GS in extinction, and limited generalization of extinction. These results corroborate the importance of expectancy violation in exposure-based treatment, and suggest that exposure sessions designed to evoke strong threat beliefs may lead to better treatment outcome.

High avoidance despite low fear of a second-order conditional stimulus

This study examined avoidance learning using a second-order threat conditioning paradigm. Participants completed fear acquisition wherein a second-order threat cue (preCS+) was paired with a threat cue (CS+) followed by an aversive sound (US); another stimulus was never associated with the US (CS-). During avoidance conditioning, participants could press a button when the preCS + or the CS- was presented, preventing upcoming events. During response prevention and extinction, the avoidance button was removed. Avoidance persistence was then examined in the absence of the actual threat. Results revealed that although the preCS+ and CS- elicited low levels of fear following Pavlovian fear acquisition, during avoidance conditioning, participants showed more avoidance of the preCS+ than the CS-. They also reported the preCS+ as more dangerous than the CS-. Following extinction, participants returned to actively avoid the preCS+ and rated it as more dangerous than the CS-. Finally, the association between avoidance learning and persistence of avoidance was mediated by self-reported threat expectancy during extinction. Our findings suggest avoidance behavior can be triggered by low levels of experienced fear, and this avoidance may play a role in the development and maintenance of threat beliefs.

Quantifying Human Avoidance Behavior in Immersive Virtual Reality

Avoidance behavior is a key symptom of most anxiety disorders and a central readout in animal research. However, the quantification of real-life avoidance behavior in humans is typically restricted to clinical populations, who show actual avoidance of phobic objects. In experimental approaches for healthy participants, many avoidance tasks utilize button responses or a joystick navigation on the screen as indicators of avoidance behavior. To allow the ecologically valid assessment of avoidance behavior in healthy participants, we developed a new automated immersive Virtual Reality paradigm, where participants could freely navigate in virtual 3-dimensional, 360-degrees scenes by real naturalistic body movements. A differential fear conditioning procedure was followed by three newly developed behavioral tasks to assess participants’ avoidance behavior of the conditioned stimuli: an approach, a forced-choice, and a search task. They varied in instructions, degrees of freedom, and high or low task-related relevance of the stimuli. We initially examined the tasks in a quasi-experiment (N = 55), with four consecutive runs and various experimental adaptations. Here, although we observed avoidance behavior in all three tasks after additional reinforcement, we only detected fear-conditioned avoidance behavior in the behavioral forced-choice and search tasks. These findings were largely replicated in a confirmatory experiment (N = 72) with randomized group allocation, except that fear-conditioned avoidance behavior was only manifest in the behavioral search task. This supports the notion that the behavioral search task is sensitive to detect avoidance behavior after fear conditioning only, whereas the behavioral approach and forced-choice tasks are still able to detect “strong” avoidance behavior after fear conditioning and additional reinforcement.

Decomposing conditioned avoidance performance with computational models

Avoidance towards innocuous stimuli is a key characteristic across anxiety-related disorders and chronic pain. Insights into the relevant learning processes of avoidance are often gained via laboratory procedures, where individuals learn to avoid stimuli or movements that have been previously associated with an aversive stimulus. Typically, statistical analyses of data gathered with conditioned avoidance procedures include frequency data, for example, the number of times a participant has avoided an aversive stimulus. Here, we argue that further insights into the underlying processes of avoidance behavior could be unraveled using computational models of behavior. We then demonstrate how computational models could be used by reanalysing a previously published avoidance data set and interpreting the key findings. We conclude our article by listing some challenges in the direct application of computational modeling to avoidance data sets.

Negative reinforcement rate and persistent avoidance following response-prevention extinction

Persistent avoidance may be influenced by prior negative reinforcement rate (i.e., how effective the response is at controlling threat). In clinical settings, the effectiveness of extinction-based methods for treating anxiety-related avoidance may be impacted by prior reinforcement rate. Here, we conducted a laboratory-based treatment study to investigate the persistence of avoidance following response-prevention extinction (RPE) when prior avoidance had been differentially effective at cancelling shock. Participants in three negative reinforcement rate groups (100%, 50%, and 0%) completed a validated avoidance conditioning paradigm involving Pavlovian fear extinction, RPE, and re-extinction phases. It was hypothesised that partially reinforced avoidance would lead to diminished resistance to fear extinction following response prevention, compared to continuously- or never-reinforced avoidance. Persistent avoidance was related to prior negative reinforcement rate, with higher rates more resistant to extinction. These findings illustrate the role of reinforcement rate in the persistence of avoidance and may aid understanding of treatment relapse.

Costly avoidance triggered by categorical fear generalization

Fear generalization refers to the spread of acquired fear to novel stimuli that resemble the original fear-related stimulus. Preliminary evidence suggests that excessive fear generalization is a pathogenic feature of anxiety disorders, however, it remains unclear how fear generalization affects pathological avoidance. The current study thus aimed to examine the link between categorical fear generalization and costly avoidance. By combining a fear acquisition training phase and an avoidance test, the current findings showed that acquired fear spreads to novel stimuli that belonged to the same category of the original fear-related stimuli, but not to those that belonged to the fear-irrelevant categories. Importantly, participants avoided these fear-related novel stimuli despite costs. The current findings indicate that categorical fear generalization triggers costly avoidance. In terms of clinical implication, a decrease in costly avoidance aligned with a decrease in US expectancies. This emphasizes that behavioral approach may initiate extinction learning.