The influence of instructions on reversing the generalization of valence, US expectancy, and electrodermal responding in fear conditioning

Pairing a conditional stimulus (CS) with an aversive unconditional stimulus (US) causes negative valence and US expectancy to generalize to stimuli that are perceptually and/or conceptually similar to the CS. Past research has shown that instructing participants that the US is more likely to follow stimuli that are dissimilar to the CS reversed the generalization of US expectancy but left generalized valence unchanged. Here, we examined whether instructions about the relationship between stimuli that are perceptually similar would affect the generalization of valence. A picture of an alien (CS+) was paired with an electric stimulus, while a perceptually different alien stimulus (CS-) was presented alone. After conditioning, valence, US expectancy, and electrodermal responses generalized to different aliens that were perceptually similar (by color and shape) to the CS+ and CS-. Participants were then instructed that aliens perceptually similar to the CS+ belonged to the same group as the CS- and that aliens perceptually similar to the CS- belonged to the same group as the CS+. The instructions caused an elimination (but not a reversal) of generalized expectancy and valence but did not affect generalized electrodermal responses. This suggests that evaluations of generalization stimuli are sensitive to instructions about their relationship to the CS and that dissociations reported in the literature between valence and expectancy after instructions may occur due to the type of instruction used.

Approximating exposure therapy in the lab: Replacing the CS+ with a similar versus a different stimulus and including additional stimuli resembling the CS+ during extinction

Recent studies have shown that extinction training including the conditional stimulus (CS+) and stimuli that are similar to the CS + enhances extinction retention and generalisation to novel stimuli. However, in a clinical setting, the CS+ is rarely available for use during exposure therapy. The aim of the present study was to determine if replacing the CS+ with a similar versus different stimulus, and including other similar stimuli during extinction, could reduce fear at test on par with extinction using the original CS+ with and without other similar stimuli. In an experiment conducted in a single session, participants completed a habituation phase followed by an acquisition phase using two dog images presented with (CS+) and without (CS-) an acoustic unconditional stimulus (US). Participants were randomly allocated to four extinction conditions: similar CS + dog with novel dog images (Similar replacement extinction condition); different CS + dog with novel dog images (Different replacement extinction condition); original CS + dog with novel dog images (Multiple extinction control condition); and original CS + without novel dog images (Standard extinction control condition). All participants completed a test phase with the original CSs followed by a generalisation test with another two novel dog images. All groups acquired, and then extinguished differential skin conductance responses (SCRs) with no differences observed between groups. Whereas the Similar replacement extinction group and the Multiple and Standard extinction control groups did not exhibit significant differential SCRs when re-exposed to the original CS + relative to the CS- at test, differential responding to the CSs was significant at test in the Different replacement extinction group. There were no significant differences between groups in SCRs to the two novel dog images during the generalisation phase and in between-phase subjective ratings. Findings suggest that replacement stimuli used during extinction should be as similar as possible to the CS + to reduce physiological arousal to the original CS+.

The influence of instructions on generalised valence - conditional stimulus instructions after evaluative conditioning update the explicit and implicit evaluations of generalisation stimuli

Generalisation in evaluative conditioning occurs when the valence acquired by a conditional stimulus (CS), after repeated pairing with an unconditional stimulus (US), spreads to stimuli that are similar to the CS (generalisation stimuli, GS). CS evaluations can be updated via CS instructions that conflict with prior conditioning (negative conditioning + positive instruction). We examined whether CS instructions can update GS evaluations after conditioning. We used alien stimuli where one alien (CSp) from a fictional group was paired with pleasant US images and another alien (CSu) from a different group was paired with unpleasant US images. The other members from the two groups were used as GSs. After conditioning, participants received negative CSp instructions and positive CSu instructions. In Experiment 1, explicit and implicit GS evaluations were measured before and after the instructions. In Experiment 2, we used a between-participants design where one group received positive/negative CS instructions while a control group received neutral instructions. In both experiments, the positive/negative CS instructions caused a reversal of explicit GS evaluations and an elimination of implicit GS evaluations. The findings suggest that generalised evaluations can change after CS instructions which may have implications for interventions aimed at reducing negative group attitudes.

The influence of cross unconditional stimulus reinstatement on electrodermal responding and conditional stimulus valence in differential fear conditioning

We examined whether the inhibitory Conditional Stimulus (CS)-no Unconditional Stimulus (US) association formed during extinction can be triggered by a novel US during the reinstatement of conditional electrodermal responding and self-reported CS valence in human differential fear conditioning. Participants were trained with either a shock or an aversive scream US before undergoing extinction. Participants then received either the same (i.e., shock_shock or scream_scream) or a different US during reinstatement (i.e., shock_scream, scream_shock). Differential conditioning across all indices was stronger when a shock US was used during acquisition. After reinstatement, electrodermal responding to both the CS+ and the CS- increased regardless of the type of US used during reinstatement (non-differential reinstatement). Differential CS valence evaluations were larger after reinstatement in the groups that received the same US during acquisition and reinstatement (differential reinstatement), but differential evaluations did not increase in the groups receiving a different US at reinstatement. This dissociation suggests that the reinstatement of negative stimulus valence and the reinstatement of expectancy learning may differ.

Intolerance of uncertainty affects electrodermal responses during fear acquisition: Evidence from electrodermal responses to unconditional stimulus omission

Past research has shown that Intolerance of Uncertainty (IU) affects Pavlovian fear conditioning processes. In particular, extinction of learned fear is delayed in those reporting high IU. Reports of differences during acquisition are less consistent with most of the studies reporting no evidence for effects of IU. This may be due to past studies' focus on first interval electrodermal responses or fear potentiated startle, rather than on indices that may better capture uncertainty - like the response to the absence of a probabilistic unconditional stimulus. The current analysis combined data across three experiments that employed a 50 % reinforcement schedule and assessed electrodermal responses and (in two experiments) ratings of conditional stimulus pleasantness. Participants scoring high on IU showed overall larger electrodermal first interval responses during habituation and acquisition but did not differ from those scoring low on IU in differential conditioning (the difference between CS+ and CS-), as indicated by electrodermal first or second interval responses or ratings of CS pleasantness. However, participants high in IU showed larger differential third interval electrodermal responses to the omission of the electro-tactile unconditional stimulus during acquisition. Some evidence for this difference emerged in each experiment, supporting the reliability of the result. The current results suggest that effects of IU emerge in conditions of high uncertainty in Pavlovian fear learning tasks, such as during the omission of probabilistic unconditional stimuli.

Conceptual generalisation in fear conditioning using single and multiple category exemplars as conditional stimuli - electrodermal responses and valence evaluations generalise to the broader category

Conceptual generalisation occurs when conditional responses generalise to novel stimuli from the same category. Past research demonstrates that physiological fear responses generalise across categories, however, conceptual generalisation of stimulus valence evaluations during fear conditioning has not been examined. We investigated whether conceptual generalisation, as indexed by electrodermal responses and stimulus evaluations, would occur, and differ after training with single or multiple conditional stimuli (CSs). Stimuli from two of four categories (vegetables, farm animals, clothing, and office supplies) were used as the CS+ (followed by an electric stimulus) or CS- (presented alone). Generalisation was assessed by presenting novel stimuli from the CS categories after acquisition, extinction, and reinstatement. One category exemplar was used as the CS+ and CS- in the single group, whereas three exemplars were used as the CS+ and CS- in the multiple group. Electrodermal responses generalised in acquisition and extinction but did not differ between groups. In the multiple group, CS evaluations generalised in acquisition and extinction, whereas generalisation was not evident in the single group. Training with multiple CSs also resulted in the extinction of stimulus valence. The current findings have implications for future research examining the generalisation of valence and for exposure-based treatments of anxiety.

Conditional stimulus choices affect fear learning: Comparing fear conditioning with neutral faces and shapes or angry faces

Past fear conditioning studies have used different types of conditional stimuli (CSs). Whether this choice affects learning outcomes in particular when neutral stimuli (e.g., neutral faces vs. shapes) are used is unclear. Data were aggregated across nine studies using an electric shock unconditional stimulus to test for differences in acquisition and extinction of electrodermal responses and self‐reported CS pleasantness when CSs were neutral faces or shapes (Experiment 1, N = 594) and when CSs were angry or neutral faces (Experiment 2, N = 157). Reliable electrodermal conditioning was observed in all stimulus conditions. We found stronger differential conditioning in electrodermal second interval responses and CS pleasantness and more pronounced extinction in CS pleasantness for neutral shape than neutral face CSs, but no differences in electrodermal first interval responses, the most frequently reported index of fear conditioning. For angry and neutral face CSs, there were no differences during acquisition, but the extinction of first and second interval electrodermal conditioning to angry faces was retarded relative to neutral faces. Acquisition of differential CS pleasantness, which was reliably observed for neutral face CSs, was absent for angry face CSs. The current results suggest that fear conditioning with a neutral face and shape CSs yields broadly similar results with differences limited to second interval electrodermal responses and CS pleasantness ratings. Using angry face CSs resulted in impaired extinction of electrodermal indices and no differential CS pleasantness ratings and should only be considered in studies designed to address questions about these specific CS materials.

Methodological choices like the nature of the conditional stimulus (CS) may affect fear learning. Here, we document in a very well powered analysis, that differences in fear conditioned to neutral face or shape CSs are limited to anticipatory electrodermal responses and self‐reported CS pleasantness but are not apparent in the more frequently reported electrodermal responses to CS onset. In contrast, differences in fear conditioned to angry and neutral face CSs emerge across indices of fear, in particular during extinction.

The absence of differential electrodermal responding in the second half of acquisition does not indicate the absence of fear learning

Many contemporary studies of human fear conditioning exclude participants who fail to show differential electrodermal responding during late stages of acquisition training, deeming them to be non-Learners. The current study examined whether non-Learners, defined as those who fail to show larger electrodermal first interval responses to CS+ than to CS- in the second half of acquisition, show differential electrodermal responding early during acquisition or during extinction or evidence of fear-learning on other measures, including rated CS valence and contingency report. In a sample of 351 participants who completed a standard differential fear-conditioning paradigm that employed electrodermal first and second interval responses (FIR, SIR), continuous CS evaluations, and post-experimental contingency reports to assess fear-learning, 74 participants were identified as non-Learners. These non-Learners displayed overall smaller electrodermal responses but showed evidence for differential conditioning during acquisition in electrodermal FIR (block1) and SIR (blocks 2-3) and in CS evaluations during acquisition (blocks 2-4) and extinction (blocks 1-4). Fifty-nine non-Learners correctly reported the contingencies. A lack of differential electrodermal first interval responding during the second half of acquisition does not indicate the absence of fear-learning. Rather, this criterion appears to capture participants who exhibit low physiological arousal and performance decrements toward the end of acquisition. Applying criteria based on "end of acquisition" electrodermal responding to determine "non-learning" results in the exclusion of participants who display fear-learning at other experimental stages or in other measures.

Presentation of unpaired unconditional stimuli during extinction reduces renewal of conditional fear and slows re-acquisition

Past research has shown that presenting unconditional stimuli (US) during extinction training, either paired with the conditional stimulus (CS) or explicitly unpaired, can reduce spontaneous recovery and slow the re-acquisition of conditional fear. Whether contextual renewal of conditioned fear as indexed by electrodermal responses and self-report measures of anxiety and CS evaluations is also reduced after presentation of paired or unpaired USs during extinction training is currently unclear. Three groups of participants (Paired, Unpaired, Standard Extinction) completed a sequence of habituation, acquisition, extinction, renewal, and re-acquisition phases. During extinction, five CS-US pairings were presented in group Paired, whereas five US were presented alone in group Unpaired. No US were presented during standard extinction. For all groups, extinction was conducted in a context that was different from that of the other phases. Extinction of differential electrodermal responding was evident in groups Unpaired and Standard, but not in group Paired. Contextual renewal and fast re-acquisition, as indexed by differential electrodermal responding, were evident in group Standard, but not in group Unpaired and differential electrodermal responding persisted in group Paired. After extinction, self-reported anxiety was higher in groups Paired and Unpaired, but differential CS evaluations were evident in group Paired only. The current results suggest that presenting additional unpaired USs during extinction training strengthens extinction and protects against the renewal of differential electrodermal responding.

The effects of presenting additional stimuli resembling the CS+ during extinction on extinction retention and generalisation to novel stimuli

Recent studies have shown that extinction training including the conditional stimulus (CS+) and stimuli similar to the CS + enhances extinction retention and generalisation to novel stimuli. The aim of the present study was to confirm that these effects are specific to presenting stimuli similar to the CS+ during extinction and not merely an effect of additional trials or additional stimuli unrelated to the CS+. In an experiment conducted in a single session on the same day, participants (134 adults; 70.7% female; 17-40 years of age, M = 20.04, SD = 4.36) completed a habituation phase followed by an acquisition phase using dog images presented with (CS+) and without (CS-) a dog growl paired with a scream unconditional stimulus (US). Participants were randomly allocated to four extinction conditions: Multiple exemplar extinction comprising the CSs and two novel dog images similar to the CS+; Standard extinction control matched for the number of CS+ and CS- presentations; Extended extinction control matched for the total number extinction trials, and Other stimuli extinction control comprising the CSs and two novel stimuli unrelated to the CS+. All participants completed an extinction test with the original CSs followed by a generalisation test with two novel dog images. Multiple, Standard and Other stimuli extinction groups exhibited larger skin conductance responses (SCRs) during extinction to the CSs compared to the Extended extinction group. SCRs to the additional dog images in the Multiple group were larger than SCRs to the additional CSs in the Extended group and the novel images in the Other stimuli group. There were no group differences in responses to the CSs during extinction test. Unlike the other groups, SCRs to the first presentation of the novel generalisation dogs did not differ from those to the last CS trials in extinction in the Multiple group. However, this group difference did not persist beyond the initial generalisation trial. Finally, the Multiple, Extended, and Other stimuli groups exhibited more negative CS evaluations after extinction, extinction test, and generalisation test than the Standard extinction group. The results suggest that extinction with the original CSs and additional stimuli resembling the CS + elevated physiological responses during extinction and reduced physiological responses to novel stimuli similar to the CSs. Further studies are needed including clinical samples and trial-by-trial evaluations of the stimuli presented.

Measuring unconditional stimulus expectancy during evaluative conditioning strengthens explicit conditional stimulus valence

During evaluative conditioning, a neutral conditional stimulus (CS) becomes pleasant or unpleasant after pairings with a positive/negative unconditional stimulus (US). Measures of US expectancy are commonly assessed during conditioning but it is unclear whether this affects evaluative learning. In Experiment 1, we examined whether the concurrent assessment of US expectancy alongside measures of CS valence would influence the acquisition, extinction, and reinstatement of explicit CS valence. Participants rated both valence and expectancy during conditioning (valence/expectancy group) or only CS valence (valence only group). Evaluative conditioning was acquired in both groups during acquisition, but its magnitude was enhanced in the valence/expectancy group. Measuring US expectancy did not influence the extinction or reinstatement of conditional valence. In Experiment 2, we confirmed the enhancement of evaluative conditioning due to concurrent measurement of US expectancy in an explicit measure, but did not find corresponding evidence in an implicit measure of conditional valence. In Experiment 3, we replicated the results using a different US expectancy scale and demonstrated that measuring CS valence multiple times throughout conditioning also strengthens conditional valence. Overall, the results suggest that the measurement of US expectancy and CS valence throughout conditioning draws attention to the contingencies and strengthens explicit evaluative learning.

"Prepared" fear or socio-cultural learning? Fear conditioned to guns, snakes, and spiders is eliminated by instructed extinction in a within-participant differential fear conditioning paradigm

Across three experiments, we investigated whether electrodermal responses conditioned to ontogenetic fear-relevant (pointed guns) and phylogenetic fear-relevant stimuli (snakes and spiders) would resist instructed extinction in a within-participant differential fear conditioning paradigm. Instructed extinction involves informing participants before extinction that the unconditional stimulus (US) will no longer be presented. This manipulation has been shown to abolish fear conditioned to fear-irrelevant conditional stimuli, but is said to leave fear conditioned to images of snakes and spiders intact. The latter finding, however, has only been demonstrated when fear-relevance is manipulated between-groups. It is also not known whether instructed extinction affects fear conditioned to ontogenetic fear-relevant stimuli, such as pointed guns. In Experiment 1, we demonstrated that fear conditioned to images of pointed guns does not resist instructed extinction. In Experiment 2, we detected some evidence to suggest that fear conditioned to images of snakes and spiders survives instructed extinction but this evidence was not conclusive. In Experiment 3, we directly compared the effects of instructed extinction on fear conditioned to snakes and spiders and to guns and provide strong evidence that fear conditioned to both classes of stimuli is reduced after instructed extinction with no differences between ontogenetic and phylogenetic stimuli. The current results suggest that when fear relevance is manipulated within-participants fear conditioned to both phylogenetic and ontogenetic, fear-relevant stimuli responds to instructed extinction providing evidence in favor of a socio-cultural explanation for "preparedness" effects.

Evaluative conditioning affects the subsequent acquisition of differential fear conditioning as indexed by electrodermal responding and stimulus evaluations

It is currently unclear whether the acquisition of negative stimulus valence in evaluative and fear conditioning paradigms is interrelated or independent. The present study used a transfer paradigm to address this question. Three groups of participants were trained in a picture-picture evaluative conditioning paradigm before completing acquisition of differential fear conditioning using graphical shapes as conditional stimuli (CSs). In group congruent, the shape used as CS+ (paired with the US during fear conditioning) was paired with negative pictures, whereas the shape used as CS- (presented alone during fear conditioning) was paired with positive pictures. In group incongruent, the shape used as CS+ was paired with positive pictures, whereas the shape used as CS- was paired with negative pictures. In group different, different shapes were employed in evaluative and fear conditioning. Acquisition of differential electrodermal responses emerged within fewer acquisition trials in groups congruent and different than in group incongruent. Transfer of evaluative learning across paradigms was evident only after removal of participants who failed to display evaluative conditioning. The current research indicates that stimulus valence acquired during evaluative conditioning transfers to fear conditioning and will differentially affect the acquisition of fear learning as indexed by subjective evaluations and electrodermal responses. The findings suggest that evaluative and fear conditioning are not independent.

Temporal context cues in human fear conditioning: Unreinforced conditional stimuli can segment learning into distinct temporal contexts and drive fear responding

In associative learning, if stimulus A is presented in the same temporal context as the conditional stimulus (CS) - outcome association (but not in a way that allows an A-CS association to form) it becomes a temporal context cue, acquiring the ability to activate this context and retrieve the CS-outcome association. We examined whether a CS- presented during acquisition or extinction that predicted the absence of the unconditional stimulus (US) could act as a temporal context cue, reducing or enhancing responding, in differential fear conditioning. Two groups received acquisition (CSx-US, CSa-noUS) in phase 1 and extinction (CSx-noUS; CSe-noUS) in phase 2 (AE groups), and two groups received extinction in phase 1 and acquisition in phase 2 (EA groups). After a delay, participants were presented with either CSa (AEa and EAa groups) or CSe (AEe and EAe groups). Responding to CSx was enhanced after presentation of CSa but reduced after presentation of CSe, suggesting that training was segmented into two learning episodes and that the unreinforced CS present during an episode retrieved the CSx-US or CSx-noUS association. These findings suggest that temporal context cues may enhance or reduce fear responding, providing an exciting new avenue for relapse prevention research.

Is the devil in the detail? Evidence for S-S learning after unconditional stimulus revaluation in human evaluative conditioning under a broader set of experimental conditions

Whether valence change during evaluative conditioning is mediated by a link between the conditional stimulus (CS) and the unconditional stimulus (US; S-S learning) or between the CS and the unconditional response (S-R learning) is a matter of continued debate. Changing the valence of the US after conditioning, known as US revaluation, can be used to dissociate these accounts. Changes in CS valence after US revaluation provide evidence for S-S learning but if CS valence does not change, evidence for S-R learning is found. Support for S-S learning has been provided by most past revaluation studies, but typically the CS and US have been from the same stimulus category, the task instructions have suggested that judgements of the CS should be based on the US, and USs have been mildly valenced stimuli. These factors may bias the results in favour of S-S learning. We examined whether S-R learning would be evident when CSs and USs were taken from different categories, the task instructions were removed, and more salient USs were used. US revaluation was found to influence explicit US evaluations and explicit and implicit CS evaluations, supporting an S-S learning account and suggesting that past results are stable across procedural changes.

Enhanced sensitization to animal, interpersonal, and intergroup fear-relevant stimuli (but no evidence for selective one-trial fear learning)

Selective sensitization has been proposed as an alternative explanation for enhanced responding to animal fear-relevant stimuli--snakes and spiders--during extinction of Pavlovian fear conditioning. The current study sought to replicate the phenomenon using a shock workup procedure as the sensitizing manipulation and to extend it to interpersonal and intergroup fear-relevant stimuli--angry faces and other-race faces. Assessment of selective sensitization was followed by a one-trial fear learning procedure. Selective sensitization, larger electrodermal responses to fear-relevant than to control stimuli after sensitization, or a larger increase in electrodermal responding to fear-relevant than to control stimuli after sensitization was observed across stimulus domains. However, the one-trial fear learning procedure failed to provide evidence for enhanced fear conditioning to fear-relevant stimuli. One-trial fear learning was either absent or present for fear-relevant and nonfear-relevant stimuli. The current study confirms that electrodermal responses to fear-relevant stimuli across stimulus domains are subject to selective sensitization.