Generalisation of fear and avoidance along a semantic continuum

Directly conditioned fear and avoidance readily generalises to dissimilar but conceptually related stimuli. Here, for the first time, we examined the conceptual/semantic generalisation of both fear and avoidance using real words (synonyms). Participants were first exposed to a differential fear conditioning procedure in which one word (e.g., “broth”; CS+) was followed with brief electric shock [unconditioned stimulus (US)] and another was not (e.g., “assist”; CS–). Next, an instrumental conditioning phase taught avoidance in the presence the CS+ but not the CS–. During generalisation testing, synonyms of the CS+ (e.g., “soup”; GCS+) and CS– (e.g., “help”; GCS–) were presented in the absence of shock. Conditioned fear and avoidance, measured via skin conductance responses, behavioural avoidance and US expectancy ratings, generalised to the semantically related, but not to the semantically unrelated, synonyms. Findings have implications for how natural language categories and concepts mediate the expansion of fear and avoidance repertoires in clinical contexts.     

状态焦虑对条件性恐惧泛化的影响

恐惧的过度泛化是焦虑障碍患者重要的潜在病因,探索焦虑对恐惧泛化的影响具有重要意义。本研究在恐惧习得后,通过恐惧创伤电影范式诱发状态焦虑组被试的焦虑水平,采用主观预期值和皮电反应值作为指标,考察状态焦虑对条件性恐惧泛化的影响。结果表明,恐惧创伤电影范式显著提高了状态焦虑组被试的焦虑水平。在泛化阶段,状态焦虑组被试表现出更强的恐惧泛化,对与条件刺激相似的泛化刺激表现出更强烈的恐惧以及更高的预期。状态焦虑使得被试恐惧泛化的消退更慢,持续时间更长。研究同时发现,在状态焦虑下,被试对条件刺激的辨识出现增强趋势。研究结果提示在对经历负性事件个体进行临床干预时,可通过降低其焦虑水平来减少过度泛化。     

条件性恐惧泛化的性别差异

恐惧的过度泛化是焦虑障碍的核心症状之一, 表现为患者对与原危险刺激极不相似的中性刺激也有着较高强度的恐惧反应。临床上, 女性比男性更有可能患焦虑障碍, 因而对恐惧泛化进行性别差异研究可以为解释女性有着更高焦虑障碍发病率提供新的角度, 同时为临床治疗提供参考。本研究采用辨别性条件恐惧范式, 以主观预期值和皮电反应值作为测量指标, 从行为和生理两个层面对条件性恐惧泛化程度和恐惧泛化消退的性别差异进行研究。结果发现, 在恐惧泛化程度上, 未出现显著性别差异。在恐惧泛化消退上, 在主观预期值和皮电反应值两个层面均有着显著性别差异, 具体表现为相较于男性, 女性恐惧泛化的消退更慢, 持续时间更长。研究结果表明, 女性焦虑障碍高发病率的潜在影响因素之一可能在于女性对于恐惧泛化刺激的难以消除。     

Pavlovian Disgust Conditioning and Generalization: Specificity and Associations With Individual Differences

Although studies have identified differences between fear and disgust conditioning, much less is known about the generalization of conditioned disgust. This is an important gap in the literature given that overgeneralization of conditioned disgust to neutral stimuli may have clinical implications. To address this knowledge gap, female participants (n = 80) completed a Pavlovian conditioning procedure in which one neutral food item (conditioned stimulus; CS+) was followed by disgusting videos of individuals vomiting (unconditioned stimulus; US) and another neutral food item (CS–) was not reinforced with the disgusting video. Following this acquisition phase, there was an extinction phase in which both CSs were presented unreinforced. Importantly, participants also evaluated generalization stimuli (GS+, GS?) that resembled, but were distinct from, the CS after each conditioning phase. As predicted, the CS+ was rated as significantly more disgusting and fear inducing than the CS? after acquisition and this pattern persisted after extinction. However, disgust ratings of the CS+ after acquisition were significantly larger than fear ratings. Participants also rated the GS+ as significantly more disgusting, but not fear inducing, than the GS? after acquisition. However, this effect was not observed after extinction. Disgust proneness did predict a greater increase in disgust and fear ratings of the CS+ relative to the CS? after acquisition and extinction. In contrast, trait anxiety predicted only higher fear ratings to the CS+ relative to the CS? after acquisition and extinction. Disgust proneness nor trait anxiety predicted the greater increase in disgust to the GS+ relative to the GS? after acquisition. These findings suggest that while conditioned disgust can generalize, individual difference variables that predict generalization remain unclear. The implications of these findings for disorders of disgust are discussed.     

Reinstatement of fear in humans: autonomic and experiential responses in a differential conditioning paradigm

The present study investigated reinstatement of fear in humans using an aversive differential conditioning paradigm. Two neutral human face pictures were presented during habituation, acquisition, extinction, and postreinstatement phases. One picture served as a conditioned stimulus (CS) reinforced by an unconditioned stimulus (US) in the form of electrical stimulation (CS+) and the second picture as a control stimulus that was never reinforced (CS-). The prediction that in a reinstatement manipulation a previously extinguished fear response in humans can be reinstated in a reinstatement group by the mere presentation of three unpredicted electrical stimulations (USs) was tested. Participants in the control group were not exposed to unpredicted USs and no reinstatement effect was expected. Outcome measures included subjective US expectancy ratings and skin conductance responses. Results showed non-selective return of the fear response due to fear recovery associated with both CSs (CS+/CS-) in the reinstatement group. Unexpected fear recovery was observed for both CSs (CS+/CS-) in control participants. Results are discussed with respect to context conditioning, fear generalisation, and anxiety-related cognitive mechanisms underlying fear recovery after extinction.     

From bad to worse: Symbolic equivalence and opposition in fear generalisation

The present study compared the impact of symbolic equivalence and opposition relations on fear generalisation. In a procedure using nonsense words, some stimuli became symbolically equivalent to an aversively conditioned stimulus while others were symbolically opposite. The generalisation of fear to symbolically related stimuli was then measured using behavioural avoidance, retrospective unconditioned stimulus expectancy and stimulus valence ratings. Equivalence relations facilitated fear generalisation while opposition relations constrained generalisation. The potential clinical implications of symbolic generalisation are discussed.     

状态焦虑对条件恐惧习得和消退的影响

采用44名正常女性大学生作为被试, 通过心理社会压力暴露的方法诱发焦虑组被试的状态焦虑, 采用主观预期值作为指标, 考察焦虑对条件恐惧习得和消退的直接影响, 并探讨这种影响是否也表现在评价性条件作用上。结果表明：心理社会压力暴露显著提高了焦虑组被试的状态焦虑。在习得阶段, 状态焦虑降低了被试对条件刺激的辨别条件恐惧反应, 具体而言, 状态焦虑降低了被试对CS+的主观预期值, 但是却提高了对CS?的主观预期值; 在消退阶段, 状态焦虑抑制了被试对条件刺激的消退。状态焦虑的影响也表现在评价性条件作用上, 和控制组相比, 焦虑组在习惯化和消退阶段对条件刺激表现出了更为负性的效价评定。     

Safety behaviours preserve threat beliefs: Protection from extinction of human fear conditioning by an avoidance response

A laboratory autonomic conditioning procedure was used to establish fear conditioning in human participants by pairing neutral stimuli with electric shock. Participants were also trained to make a button-press response to avoid shock. A target fear stimulus was then extinguished by presenting it without shock. The experimental group was given the opportunity to make the avoidance response during extinction whereas the control group was not. When the fear stimulus was tested without the response available, the control group showed normal extinction of both shock expectancy ratings and skin conductance responses, but the experimental group showed “protection from extinction”: they continued to give high expectancy ratings and strong skin conductance responses. We interpret this effect as analogous to the role of within-situation safety behaviours in preserving threat beliefs during exposure therapy for anxiety disorders. The results support a cognitive account of learning and anxiety. The procedure provides a potential laboratory model for further examination of the cognitive and neural mechanisms underlying anxiety and its reduction.     

Contextual control of human fear associations in a renewal paradigm

The original model of behavior change suggests that extinction is context dependent whereas fear acquisition is context independent [Bouton, M. E. & Ricker, S. T. (1994). Renewal of extinguished responding in a second context. Animal Learning and Behavior, 22, 317-324]. Supportive evidence stems mainly from animal studies, showing that after acquisition (conditioned stimulus-unconditioned stimulus (CS-US)) in Context A and extinction in Context B, fear is renewed by presenting the CS in acquisition Context A (ABA renewal) or in a novel Context C (ABC renewal). By implication, the model predicts equal ABA and ABC renewal. However, there is also evidence to suggest that the context dependency of extinction and the context independency of acquisition may be less stringent than originally proposed. The present study investigated renewal in humans using a differential fear conditioning paradigm with a shock US and online shock expectancy ratings and electrodermal responses as dependent variables. Experiment 1 compared an ABA condition with an AAA condition. Experiment 2 compared three conditions: ABA, ABC, and AAA. Both experiments demonstrated ABA renewal. Most importantly, Experiment 2 showed larger ABA than ABC renewal. Overall, results for expectancy ratings were more convincing than for electrodermal responses. In line with the extinction model, the present findings support the context dependency of extinction in humans. In contrast to the model, the findings suggest that in humans not only extinction learning, but also fear acquisition is controlled by its current context.     

Shaking That Icky Feeling: Effects of Extinction and Counterconditioning on Disgust-Related Evaluative Learning

Learned disgust appears to play an important role in certain anxiety disorders, and can be explained by the process of evaluative conditioning, in which an affective evaluative reaction evoked by an unconditional stimulus (US) is transferred to a conditional stimulus (CS). Much remains unknown about how disgust-related evaluative learning can be effectively eliminated. Study 1 of the present investigation examined the effects of extinction on reducing the negative evaluation of a CS that was acquired during disgust conditioning. Participants completed acquisition trials, with a disgusting picture as US and two neutral pictures as CS (CS + was paired with the US; CS- was unpaired), followed by extinction trials ("CS only"; experimental condition) or a filler task (control condition). Extinction trials reduced acquired US expectancy to the CS +, but did not extinguish negative evaluations of the CS +. Study 2 examined the effects of counterconditioning on evaluative learned disgust. After disgust acquisition trials, counterconditioning trials followed in which the CS + was paired with a pleasant US (experimental condition) or a filler task (control condition). Counterconditioning trials reduced acquired US expectancy to the CS + and reduced evaluative conditioned disgust. Implications of the potential differential effects of extinction and counterconditioning on evaluative learning for exposure-based treatment of specific anxiety disorders are discussed.     

US habituation,like CS extinction,produces a decrement in conditioned fear responding that is NMDA dependent and subject to renewal and reinstatement

Just as fear can be learned, it can also be inhibited. The most common way of reducing learned fear is through extinction, where the conditioned stimulus (CS) previously paired with an aversive unconditioned stimulus (US) is repeatedly presented on its own. Another, much less commonly studied, way to inhibit learned fear is by habituating, or devaluing, the US. In this procedure, fear responding to a CS is reduced by repeatedly presenting the US in the absence of the CS following the conditioning phase. The purpose of the present study was to directly compare the effects of US habituation and CS extinction on a learned fear response (freezing). Experiment 1 demonstrated that US habituation given either after (Experiment 1A) or before (Experiment 1B) fear conditioning reduced freezing to the CS at test. We then showed that the reduction in freezing resulting from either US habituation or CS extinction was context-specific (i.e., a change in context led to a renewal of the learned fear response; Experiment 2) and, furthermore, was attenuated when a pre-test shock was given (i.e., reinstatement of fear was observed in both cases; Experiment 3). Finally, Experiment 4 demonstrated that an injection of the NMDA antagonist MK-801 prior to US habituation impaired long-term retention of the learning that takes place during this procedure. Together, these results suggest that the decrement in conditioned fear responses produced by US habituation and CS extinction could rely on overlapping processes.     

When two paradigms meet: Does evaluative learning extinguish in differential fear conditioning?

Contemporary theories of Pavlovian conditioning propose a distinction between signal learning (SL), in which a conditioned stimulus (CS) becomes a predictor for a biologically significant unconditioned stimulus (US), and evaluative learning (EL), in which the valence of the US is transferred to the CS. This distinction is based largely on the different susceptibilities of EL and SL to extinction. This study compared the extinction of indices of EL (online valence ratings) and SL (US-expectancy ratings and skin conductance responses, SCRs) in a differential fear conditioning design using complex CSs. Only half of the participants gave online valence ratings, allowing us to confirm that online valence measurement did not influence SCRs. In line with the distinction between EL and SL, SCRs extinguished rapidly while valence ratings showed resistance to extinction. US-expectancy ratings, however, were not distinguishable from valence ratings indicating that verbal indicators of EL and SL share a similar time course.     

Associative learning versus fear habituation as predictors of long-term extinction retention

Violation of unconditioned stimulus (US) expectancy during extinction training may enhance associative learning and result in improved long-term extinction retention compared to within-session habituation. This experiment examines variation in US expectancy (i.e., expectancy violation) as a predictor of long-term extinction retention. It also examines within-session habituation of fear-potentiated startle (electromyography, EMG) and fear of conditioned stimuli (CS) throughout extinction training as predictors of extinction retention. Participants (n?=?63) underwent fear conditioning, extinction and retention and provided continuous ratings of US expectancy and EMG, as well as CS fear ratings before and after each phase. Variation in US expectancy throughout extinction and habituation of EMG and fear was entered into a regression as predictors of retention and reinstatement of levels of expectancy and fear. Greater variation in US expectancy throughout extinction training was significantly predictive of enhanced extinction performance measured at retention test, although not after reinstatement test. Slope of EMG and CS fear during extinction did not predict retention of extinction. Within-session habituation of EMG and self-reported fear is not sufficient for long-term retention of extinction learning, and models emphasizing expectation violation may result in enhanced outcomes.     

The impact of arbitrarily applicable relational responding on evaluative learning about hypothetical money and shock outcomes

Evaluative learning comprises changes in preferences after co-occurrences between conditioned stimuli (CSs) and an unconditioned stimulus (US) of affective value. Co-occurrences may involve relational responding. Two experiments examined the impact of arbitrary relational responding on evaluative preferences for hypothetical money and shock outcomes. In Experiment 1, participants were trained to make arbitrary relational responses by placing CSs of the same size but different colours into boxes and were then instructed that these CSs represented different intensities of hypothetical USs (money or shock). Liking ratings of the CSs were altered in accordance with the underlying bigger/smaller than relations. A reversal of preference was also observed: the CS associated with the smallest hypothetical shock was rated more positively than the CS associated with the smallest amount of hypothetical money. In Experiment 2, procedures from Relational Frame Theory (RFT) established a relational network of more than/less than relations consisting of five CSs (A-B-C-D-E). Overall, evaluative preferences were altered, but not reversed, depending on (a) how stimuli had been related to one another during the learning phase and (b) whether those stimuli referred to money or shocks. The contribution of RFT to evaluative learning research is discussed.     

Electrometric Studies of Sleep

The authors provided a differential test between stimulus-stimulus (S-S) and stimulus-response (S-R) theory predictions in regard to the roles that the constructs of expectancy and of fear play in maintaining classically conditioned fear responding within the context of a human conditioned-avoidance paradigm. After the participants had developed sustained avoidance responding, their shock electrodes and avoidance response apparatus were removed to enhance the cognitive expectancy that the conditioned stimulus (CS) would not be followed by the unconditioned stimulus (UCS). This manipulation of expectancy was successful in 96% of the participants. The study was conducted over a 2-day period and involved 1 experimental group and 3 control groups. During the test trials, the authors used autonomic and self-report indices of fear to assess the presence or absence of fear to the CS. The data disconfirmed the prediction of the S-S theory that fear to the CS would be extinguished. The authors discuss the implications of this finding for S-S theories and for approaches in cognitive behavior therapy.     

Fear conditioning and extinction in anxiety- and depression-prone persons

Anxiety and depression frequently co-occur and may share similar deficits in the processing of emotional stimuli. High anxiety is associated with a failure in the acquisition and extinction of fear conditioning. Despite the supposed common deficits, no research has been conducted on fear acquisition and extinction in depression. The main aim of the present study was to investigate and compare fear acquisition and extinction in anxiety- and depression-prone participants. Non-clinical anxious, depressive, anxious-depressive and control participants performed a fear discrimination task. During acquisition, the CS+ predicted an aversive event (unconditioned stimulus, US) and the CS? safety (no US). During extinction, the CS+ was no longer followed by the US, rendering it (temporarily) into a safety signal. On each CS participants rated their US expectancy; skin conductance responses (SCRs) were measured throughout. The expectancy scores indicated that high anxiety resulted in less safety learning during acquisition and extinction; no effect of depression was observed. SCRs showed that high-anxiety persons displayed less discrimination learning (CS+ minus CS?) during acquisition than low-anxiety persons. During extinction, high-depression persons demonstrated more discriminative SCR than low-depression persons. The observed discrepancies in response patterns of high-anxiety and -depression persons seem to indicate distinctive information processing of emotional stimuli.     

The S-S construct of expectancy versus the S-R construct of fear: which motivates the acquisition of avoidance behavior?

The authors provided a differential test between stimulus-stimulus (S-S) and stimulus-response (S-R) theory predictions in regard to the roles that the constructs of expectancy and of fear play in maintaining classically conditioned fear responding within the context of a human conditioned-avoidance paradigm. After the participants had developed sustained avoidance responding, their shock electrodes and avoidance response apparatus were removed to enhance the cognitive expectancy that the conditioned stimulus (CS) would not be followed by the unconditioned stimulus (UCS). This manipulation of expectancy was successful in 96% of the participants. The study was conducted over a 2-day period and involved 1 experimental group and 3 control groups. During the test trials, the authors used autonomic and self-report indices of fear to assess the presence or absence of fear to the CS. The data disconfirmed the prediction of the S-S theory that fear to the CS would be extinguished. The authors discuss the implications of this finding for S-S theories and for approaches in cognitive behavior therapy.     

Verbal instructions targeting valence alter negative conditional stimulus evaluations (but do not affect reinstatement rates)

Negative conditional stimulus (CS) valence acquired during fear conditioning may enhance fear relapse and is difficult to remove as it extinguishes slowly and does not respond to the instruction that unconditional stimulus (US) presentations will cease. We examined whether instructions targeting CS valence would be more effective. In Experiment 1, an image of one person (CS+) was paired with an aversive US, while another (CS?) was presented alone. After acquisition, participants were given positive information about the CS+ poser and negative information about the CS? poser. Instructions reversed the pattern of differential CS valence present during acquisition and eliminated differential electrodermal responding. In Experiment 2, we compared positive and negative CS revaluation by providing positive/negative information about the CS+ and neutral information about CS?. After positive revaluation, differential valence was removed and differential electrodermal responding remained intact. After negative revaluation, differential valence was strengthened and differential electrodermal responding was eliminated. Unexpectedly, the instructions did not affect the reinstatement of differential electrodermal responding.     

On the intentional control of conditioned evaluative responses

The evaluative conditioning (EC) effect is defined as a change in the evaluation of a conditioned stimulus (CS) due to its pairing with a valenced unconditioned stimulus (US). The current research investigated the controllability of EC effects by asking participants to either promote or prevent the influence of CS–US pairings before they provided evaluative ratings of the CS. Experiment 1 showed that instructions to maximize or minimize the influence of CS–US pairings moderated EC effects in line with task instructions. However, this moderation was observed only when participants were able to recall the valence of the US that had been paired with a given CS. When participants failed to remember the valence of the US, significant EC effects emerged regardless of control instructions. Experiment 2 tested whether the influence of CS–US pairings on CS evaluations can be intentionally reversed. The results showed that reversal instructions led to a reverse EC effect when participants were able to recall the valence of the US that had been paired with a given CS, but not when they were unable to recall the valence of the US. Taken together, these results suggest that US valence memory is a necessary precondition for controlling the expression of a conditioned evaluative response, but it is not a necessary precondition for the emergence of EC effects per se.     

Eye movements during recall of aversive memory decreases conditioned fear

Cognitive-behavioral therapy for anxiety disorders typically involves exposure to the conditioned stimulus (CS). Despite its status as an effective and primary treatment, many patients do not show clinical improvement or relapse. Contemporary learning theory suggests that treatment may be optimized by adding techniques that aim at revaluating the aversive consequence (US) of the feared stimulus. This study tested whether US devaluation via a dual task – imagining the US while making eye movements – decreases conditioned fear. Following fear acquisition one group recalled the US while making eye movements (EM) and one group merely recalled the US (RO). Next, during a test phase, all participants were re-presented the CSs. Dual tasking, relative to the control condition, decreased memory vividness and emotionality. Moreover, only in the dual task condition reductions were observed in self-reported fear, US expectancy, and CS unpleasantness, but not in skin conductance responses. Findings provide the first evidence that the dual task decreases conditioned fear and suggest it may be a valuable addition to exposure therapy.