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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.

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.

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.

Past studies of backward evaluative conditioning (EC) have found an assimilation effect, in that neutral conditional stimuli (conditional stimulus [CS]) were found to acquire the valence of co-occurring unconditional stimuli (US). Recent studies employing a concurrent forward and backward conditioning paradigm with instructions suggesting a contrastive relation between the US and the backward CS have resulted in contrast effects, in that backward CSs acquired valence opposite to the US. The current research investigated whether these effects were in fact due to the instructions highlighting the contrastive relation between the US and CS, or whether affective relief/disappointment experienced at US offset could account for this result. Consistent with the hypothesized role of instructions, backward CS contrast effects occurred only when instructions highlighted the valence of the US and attributed control of that US to the CSs. In contrast to the affective relief/disappointment hypothesis, no backward CS contrast effects were found without such instructions. (PsycInfo Database Record (c) 2021 APA, all rights reserved)

In evaluative conditioning, a conditional stimulus (CS; e.g. a neutral picture) acquires positive/negative valence if it is paired with a pleasant/unpleasant unconditional stimulus (US; e.g. a positive/negative picture). This valence generalises to other stimuli similar to the CS and to the wider CS category. Being informed that the CS will be paired with the US induces a similar change in valence (instructional learning), but it is not clear whether instructional learning would also generalise. In Experiment 1, participants were informed that one shape would be paired with pleasant and another with unpleasant images. These instructions instilled conditional valence to the CSs which generalised to different shapes from the same category (generalisation stimuli). In Experiment 2, we replicated this finding in an implicit measure using stimuli varying in perceptual features. Participants were informed that three CSs from one category (e.g. vegetables) would be paired with pleasant images and three CSs from a second category (e.g. office supplies) would be paired with unpleasant images. This instruction instilled conditional valence to the CSs which generalised to novel exemplars from the same categories. This suggests that conditional valence instilled via instructions generalises to other stimuli–a finding with implications for prejudice and racism.

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.

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.

Instructions highlighting that backward conditional stimuli (CSs) stop unconditional stimuli (USs) result in their acquiring valence opposite to that of the US on explicit measures of valence. We assessed whether such instructions would influence startle blink modulation in the same way. Two groups were presented with concurrent forward and backward evaluative conditioning (CS-US-CS) using cartoon aliens as CSs, and pleasant, neutral, and unpleasant sounds as USs. Startle magnitude was measured during conditioning and valence ratings were assessed after conditioning. Participants in the “start-stop” instructions group (n = 41) were instructed to learn whether CSs started or stopped US presentations, while participants in the “observe” instructions group (n = 41) were told to pay attention to the stimuli as they would be asked questions about them after the experiment. In the start-stop instructions group backward CSs paired with positive USs were rated as less pleasant than backward CSs paired with neutral and negative USs (contrast effect), whereas ratings of backward CSs did not differ in the observe instructions group. Startle magnitude was larger during backward CSs paired with positive USs in comparison to CSs paired with neutral or negative USs in both instruction groups. Startle blink modulation was unaffected by instructions, suggesting that startle indexes the emotional state at the time of probe presentation rather than CS valence based on propositional information about the function of the CS.

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.

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.

Past research on backward conditioning in evaluative and fear conditioning yielded inconsistent results in that self-report measures suggest that the conditional stimulus (CS) acquired the valence of the unconditional stimulus (US) in fear conditioning (assimilation effects), but the opposite valence in evaluative conditioning (contrast effects). Conversely, implicit measures of CS valence suggest assimilation effects in evaluative backward conditioning, whereas startle modulation indicates contrast effects in backward fear conditioning. The current study investigated whether US intensity could account for the dissociation on implicit measures between fear and evaluative conditioning. Self-report measures of evaluative learning indicated assimilation effects for forward conditioning, whereas backward contrast effects were observed with intense USs only. Blink startle modulation indicated assimilation effects in forward conditioning and contrast effects in backward conditioning, regardless of US intensity. Experiment 2 included a neutral US in order to assess whether the offset of the positive US elicits an opponent emotional response that mirrors relief (disappointment), which is thought to mediate the reduction in startle seen during backward CSs in fear conditioning. This opponent emotional response was evident as startle magnitude during backward CSs increased linearly with increasing US pleasantness. Omission of the forward CSs led to an assimilation effect in self-report measures. The current results extend our understanding of emotional learning to stimuli encountered after salient emotional events. Startle reflects the emotion prevailing after US offset, relief or disappointment, whereas self-report measures seem more attuned to factors such as US predictability and intensity.

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.

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.

Blink startle magnitude is linearly modulated by affect such that, relative to neutral stimuli, startle magnitude is inhibited during pleasant stimuli and potentiated during unpleasant stimuli. Andreatta, Mühlberger, Yarali, Gerber, and Pauli (2010), however, report a dissociation between startle modulation and explicit valence evaluations during backward conditioning, a procedure in which the unconditional stimulus precedes the conditional stimulus (CS). Relative to controls, startles elicited during the CS were inhibited, suggesting that the CS had acquired positive valence, but participants still evaluated the CS as unpleasant after the experiment. In Experiment 1, we aimed to replicate this dissociation using a trial-by-trial measure of CS valence to measure startle modulation and CS valence simultaneously during forward and backward differential fear conditioning. In Experiment 2, we examined whether early and late portions of the CS could acquire differential valence by presenting startle probes at early and late probe positions during the CS. In both experiments, the dissociation between startle modulation and explicit valence evaluations in backward conditioning replicated, with CS+ evaluated as less pleasant than CS-, but startles elicited during CS+ inhibited relative to CS-. In Experiment 2, we provide preliminary evidence that this inhibition was present early, but not late, during the CS+. The results replicate the dissociation between implicit and explicit CS valence reported by Andreatta et al. (2010) using a trial-by-trial measure of valence. We also provide preliminary evidence that this dissociation may occur because the implicit and explicit measures are recorded at different times during the CS presentation.

Instructed extinction is an experimental manipulation that involves informing participants after the acquisition of fear learning that the unconditional stimulus (US) will no longer be presented. It has been used as a laboratory analogue to assess the capacity of cognitive interventions to reduce experimentally induced fear. In this review, we examine and integrate research on instructed extinction and discuss its implications for clinical practice. Overall, the results suggest that instructed extinction reduces conditional fear responding and facilitates extinction learning, except when conditional stimulus valence is assessed as an index of fear or when fear is conditioned to images of animal fear-relevant stimuli (snakes and spiders) or with a very intense US. These exceptions highlight potential boundary conditions for the reliance on cognitive interventions when treating fear in clinical settings.

Following differential fear conditioning, the instruction that the unconditional stimulus will no longer be presented (instructed extinction) reduces differential electrodermal responding to CS+ and CS-, but does not affect differential conditional stimulus valence evaluations. Reductions in differential electrodermal responding have been attributed to the provision of verbal instructions; however, during instructed extinction the unconditional stimulus electrode is often removed as well. This removal could reduce the participants' general arousal levels rendering the detection of differential electrodermal responding difficult. The current study examined this alternative interpretation by comparing the electrodermal responses and conditional stimulus valence evaluations of an instruction/electrode-on group, an instruction/electrode-off group, and a control group who were not instructed. Following instructed extinction, differential electrodermal responding was eliminated in both instruction groups, an effect that was not influenced by the attachment/removal of the electrode. Replicating previous findings, conditional stimulus valence was not affected by instructed extinction. The results suggest that verbal instructions, not unconditional stimulus electrode removal, reduce differential electrodermal responding during instructed extinction manipulations.

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.