Working hard to avoid: Fixed-ratio response effort and maladaptive avoidance in humans.

Maladaptive avoidance of safe stimuli is a defining feature of anxiety and related disorders. Avoidance may involve physical effort or the completion of a fixed series of responses to prevent occurrence of, or cues associated with, the aversive event. Understanding the role of response effort in the acquisition and extinction of avoidance may facilitate the development of new clinical treatments for maladaptive avoidance. Despite this, little is known about the impact of response effort on extinction-resistant avoidance in humans. Here, we describe findings from two laboratory-based treatment studies designed to investigate the impact of high and low response effort on the extinction (Experiment 1) and return (Experiment 2) of avoidance. Response effort was operationalised as completion of fixed-ratio (FR) reinforcement schedules for both danger and safety cues in a multi-cue avoidance paradigm with behavioural, self-report, and physiology measures. Completion of the FR response requirements cancelled upcoming shock presentations following danger cues and had no impact on the consequences that followed safety cues. Both experiments found persistence of high response-effort avoidance across danger and safety cues and sustained (Experiment 1) and reinstated (Experiment 2) levels of fear and threat expectancy. Skin conductance responses evoked by all cues were similar across experiments. The present findings and paradigm have implications for translational research on maladaptive anxious coping and treatment development.

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.

Living in fear: Low-cost avoidance maintains low-level threat.

BACKGROUND AND OBJECTIVES: Excessive avoidance of potential threat is a hallmark of anxiety and is thought to maintain fear by preserving the perceived high-threat value of avoided situations. Previous research has shown that the availability of avoidance maintains low-level threat. Here, we investigated whether an opportunity to engage in avoidance in the presence of a low-threat value safety cue would maintain its perceived threat value when avoidance was unavailable. METHODS: In a threat conditioning procedure, one conditional danger stimulus (CS+; A+) was followed by an aversive unconditioned stimulus (US; electric shock), and two safety stimuli (CS-; B- and C-) were never followed by the US. Next, clicking a button present during A+ avoided the scheduled US. Avoidance was then made available during C- for participants in the Experimental group but not in the Control group. In the test, all stimuli were presented without the opportunity to avoid. Threat expectancy, eyeblink startle electromyography (EMG), and skin conductance responses (SCRs) were measured. RESULTS: Findings showed an increase in threat expectancy for only C- in the Experimental group during the test phase following avoidance learning to similar levels as during threat conditioning. Compared to the Control group, threat expectancy for both B- and C- remained higher in Experimental group. SCR and startle EMG data did not corroborate these findings. LIMITATIONS: Further research is needed to test the commonly held clinical assumption that avoidance can increase threat value. CONCLUSIONS: Low-cost avoidance maintains low-threat value of safety cues.

Partial reinforcement of avoidance and resistance to extinction in humans.

In anxiety, maladaptive avoidance behavior provides for near-perfect controllability of potential threat. There has been little laboratory-based treatment research conducted on controllability as a contributing factor in the transition from adaptive to maladaptive avoidance. Here, we investigated for the first time whether partial reinforcement rate, or the reliability of avoidance at controlling or preventing contact with an aversive event, influences subsequent extinction of avoidance in humans. Five groups of participants were exposed to different partial reinforcement rates where avoidance cancelled upcoming shock on 100%, 75%, 50%, 25% or 0% of trials. During extinction, all shocks were withheld. Avoidance behavior, online shock expectancy ratings and skin conductance responses (SCRs) were measured throughout. We found that avoidance was a function of relative controllability: higher reinforcement rate groups engaged in significantly more extinction-resistant avoidance than lower reinforcement groups, and shock expectancy was inversely related with reinforcement rate during avoidance acquisition. Partial reinforcement effects were not evident in SCRs. Overall, the current study highlights the clinical relevance of laboratory-based treatment research on partial reinforcement or controllability effects on extinction of avoidance.