Contingency awareness in evaluative conditioning: A case for unaware affective-evaluative learning

Attribution Impacts Implicit (And Explicit) Evaluations

Two studies examined whether the attributional framing of negative events affected explicit evaluations, as measured by differences in liking, and implicit evaluations, as measured by the Implicit Association Test (Greenwald et al., 1998). In Study 1, participants read negative information about a novel target ordered to elicit internal or external attributions. Participants in the internal attribution condition evaluated the target more negatively than did those in the external attribution condition on both implicit and explicit measures. Study 2 replicated these results and tested the effects of attribution on recently formed negative evaluations. Participants who evaluated targets before and after receiving additional negative information about them demonstrated implicit and explicit evaluative change consistent with the attributional framing of that information. This research provides clear evidence that attribution influences the formation and change of implicit evaluations; however, these effects were weaker than those on explicit measures of evaluation.

Scaling preferences using probabilistic choice models: is there a ratio-scale representation of subjective liking?

In two online experiments, we tested whether preference judgments can be used to derive a valid ratio-scale representation of subjective liking across different stimulus sets. Therefore, participants were asked to indicate their preferences for all possible pairwise comparisons of 20 paintings (Experiment 1) and 20 faces (Experiment 2). Probabilistic choice models were fit to the resulting preference probabilities (requiring different degrees of stochastic transitivity), demonstrating that a ratio-scale representation of the liking of both paintings and faces can be derived consistently from the preference judgments. While the preference judgments of paintings were consistent with the highly restrictive Bradley–Terry–Luce model (Bradley and Terry, Biometrika 39:324–345, 1952; Luce, 1959), the liking of faces could be represented on a ratio scale only when accounting for face gender as an additional aspect in an elimination-by-aspects model. These ratio-scaled liking scores were then related to direct evaluative ratings of the same stimuli on a 21-point Likert scale, given both before and after the pairwise comparisons. It was found in both studies that evaluative ratings can be described accurately as a logarithmic function of the indirectly derived liking scores for both types of stimuli. The results indicate that participants are able (a) to consistently judge preferences across two heterogeneous stimulus sets, and (b) to validly report their liking in direct evaluative ratings, although the numeric labels derived from direct evaluative ratings cannot be interpreted at face value for ratio-scaled liking scores.

Transfer of negative valence in an episodic memory task

Emotion can color what we perceive and subsequently remember in myriad ways. Indeed, it is well established that emotion enhances some aspects of memory, while impairing others. For example, a number of recent episodic memory studies show that emotion-particularly negative emotion-weakens associative memory, including item-item associations. Other literature shows that emotion biases our later attitudes and preferences. That is, the coincident pairing of a negative stimulus with a neutral one can reduce one's preference for that neutral stimulus upon subsequent encounter-a 'transfer of valence' effect. In an effort to connect these two phenomena, here we ask if and under what circumstances they co-occur. Across multiple experiments, we show that negative emotion impairs associative memory for item-item pairings, in accordance with prior work. We also show a transfer of valence effect in this paradigm, such that items paired with negative versus neutral stimuli are subsequently rated as less pleasant. Our data further show that transfer of valence is contingent on episodic memory. These findings highlight the complexity and multifaceted nature of emotional effects on memory.

The timing-dependent effects of stress-induced cortisol release on evaluative conditioning

The neuro-physiological response to stress has far-reaching implications for learning and memory processes. Here, we examined whether and how the stress-induced release of cortisol, following the socially-evaluated cold pressor test, influenced the acquisition of preferences in an evaluative conditioning (EC) procedure. We found that when the stressor preceded the evaluation phase, cortisol responders showed decreased evaluative conditioning effects. By contrast, impairing effects of a stressor-induced cortisol release before encoding were not found. Moreover, explicit memory was not found to be affected by the stressor or its timing. Implications of the timing-dependent effects of stress-induced cortisol release on EC and the relation between stress and associative memory are discussed.

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.

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.

Dissociations between Learning Phenomena do Not Necessitate Multiple Learning Processes: Mere Instructions about Upcoming Stimulus Presentations Differentially Influence Liking and Expectancy

Prior research showed that the degree of statistical contingency between the presence of stimuli moderates changes in expectancies about the presence of those stimuli (i.e., expectancy learning) but not changes in the liking of those stimuli (i.e., evaluative conditioning). This dissociation is typically interpreted as evidence for dual process models of associative learning. We tested an alternative account according to which both types of learning rely on a single process propositional learning mechanism but reflect different kinds of propositional beliefs. In line with the idea that changes in liking reflect beliefs about stimulus co-occurrences whereas changes in expectancy reflect beliefs about stimulus contingency, we found that evaluative ratings depended only on instructions about whether a stimulus would co-occur with a positive or negative stimulus whereas expectancy ratings were influenced also by instructions about individual stimulus presentations.

The influence of misinformation manipulations on evaluative conditioning

We tested the influence of misinformation on evaluative conditioning (EC) by giving false information about the contingencies between CS and US stimuli after a conditioning procedure. This was done by asking participants questions about the USs while inaccurately suggesting that some CSs had been paired with a US that had the opposite valence than the US it had actually been paired with. For CS-US pairs from other conditions, accurate suggestions or no suggestions at all were given to participants. This manipulation significantly moderated EC effects. For pairs that were combined with inaccurate information we found a reversed EC effect, while we found a standard EC effect for both pairs combined with no suggestions and pairs combined with accurate suggestions. Additional analyses showed that the misinformation manipulation also moderated memory for the pairs. These results show that misinformation manipulations cannot only influence explicit memory but also attitudes. Furthermore, and in line with some theories of EC, they support the relevance of explicit memory for EC effects.

A Declarative Memory Model of Evaluative Conditioning

I propose a Declarative Memory Model (DMM) of evaluative conditioning (EC). EC effects are changes in the valence of a conditioned stimulus (CS) due to previous pairings with a positive or negative unconditioned stimulus (US; e.g., De Houwer, 2007, https://doi.org/10.1017/S1138741600006491). According to the DMM, EC effects are found if (1) a memory trace is formed in the learning phase that links the CS to evaluative information from the US, if (2) this trace survives the retention interval, if (3) the trace or part of it is consciously retrieved when the CS is being evaluated, and if (4) the retrieved trace is used in the CS evaluation. For each of these stages, I make separate predictions about EC effects, many of which are based on empirical research on declarative memory. Where available, I report and discuss empirical evidence on EC that speaks to these hypotheses. The available empirical evidence is largely in line with the predictions of the DMM. Several predictions, however, have yet to be tested and some findings are ambiguous. While the DMM specifies conditions under which CS-US pairings should lead to a valence change, it does not deny the possibility that other processes might lead to a change in attitude as well. Advantages of the DMM are its foundation on declarative memory research, its applicability for attitude change effects in general, and its suitability for predictions of EC effects in the real world.

Positive, negative, or all relative? Evaluative conditioning of ambivalence

In evaluative conditioning (EC), the pairing of a positively or negatively valenced stimulus (US) with a neutral stimulus (CS) leads to a corresponding change in liking of the CS. EC research so far has concentrated on using unambiguously positive or negative USs. However, attitude objects are often ambivalent, i.e., can simultaneously possess positive and negative features. The present research investigated whether ambivalence can be evaluatively conditioned and whether contingency awareness moderates this effect. In two studies, positive, negative, neutral, and ambivalent USs were paired with affectively neutral CSs. Results showed standard EC effects that were moderated by contingency awareness. Most interestingly, EC effects were also obtained for the ambivalent USs, indicating that ambivalence can indeed be conditioned. However, contingency awareness seemed to play a lesser role in ambivalence conditioning. Ambivalence EC effects were obtained on subjective and objective direct measures of ambivalence as well as on a more indirect measure.

Successful differential evaluative conditioning using simultaneous and trace conditioning procedures in the picture–picture paradigm

This paper describes a study designed to investigate the efficacy of two traditional classical conditioning procedures in generating evaluative conditioning (EC) in the picture–picture paradigm in human participants. Differential EC was found using both simultaneous and trace conditioning procedures. In addition, the use of a block–subblock (BSB) nonpaired control condition and full counterbalancing of conditioned stimulus–unconditioned stimulus (CS–UCS) pairings across participants indicated that the observed EC effects were the result of associative learning. Examination of whether successful conditioning could take place with or without conscious awareness of CS–UCS contingencies was inconclusive. The results provide evidence for EC as an associative process and also provide some insight into the possible conditioning parameters that might successfully generate EC.

The effects of cognitive reappraisal on conditioned disgust in contamination-based OCD: An analogue study

Experimental research has shown that conditioned disgust is resistant to extinction, which may account for the slower habituation to disgust relative to fear in contamination-based obsessive-compulsive disorder (OCD). However, few studies have examined the efficacy of interventions that may attenuate conditioned disgust responses. Studies of cognitive reappraisal have demonstrated that reinterpreting a stimulus can alter emotional responding. This technique is based on cognitive theories which suggest that anxiety disorders arise from biased cognitions; therefore, changing a person's thoughts will elicit durable changes in emotional responses. Given the demonstrated effectiveness of cognitive reappraisal, the present study examined whether cognitive reappraisal would attenuate conditioned disgust responses. We conditioned participants high in contamination fear (n=55) using images of neutral food items (conditioned stimuli; CS) paired with videos of individuals vomiting (unconditioned stimuli; US) while we obtained subjective disgust reports. After conditioning, half of the participants were randomly assigned to cognitive reappraisal training aimed at decreasing their emotional response to the US and CS, while the other half received no such training. The findings showed that cognitive reappraisal participants demonstrated a reduction in learned disgust across sessions and further benefited from extinction. These findings suggest that cognitive reappraisal may be an effective strategy for attenuating learned disgust.

Don't fear 'fear conditioning': Methodological considerations for the design and analysis of studies on human fear acquisition, extinction, and return of fear

The so-called 'replicability crisis' has sparked methodological discussions in many areas of science in general, and in psychology in particular. This has led to recent endeavours to promote the transparency, rigour, and ultimately, replicability of research. Originating from this zeitgeist, the challenge to discuss critical issues on terminology, design, methods, and analysis considerations in fear conditioning research is taken up by this work, which involved representatives from fourteen of the major human fear conditioning laboratories in Europe. This compendium is intended to provide a basis for the development of a common procedural and terminology framework for the field of human fear conditioning. Whenever possible, we give general recommendations. When this is not feasible, we provide evidence-based guidance for methodological decisions on study design, outcome measures, and analyses. Importantly, this work is also intended to raise awareness and initiate discussions on crucial questions with respect to data collection, processing, statistical analyses, the impact of subtle procedural changes, and data reporting specifically tailored to the research on fear conditioning.

Evaluative conditioning increases with temporal contiguity. The influence of stimulus order and stimulus interval on evaluative conditioning

Evaluative conditioning (EC) is a change in valence that is due to pairing a conditioned stimulus (CS) with another, typically valent, unconditioned stimulus (US). This paper investigates how basic presentation parameters moderate EC effects. In two studies we tested the effectiveness of different temporal relations of the CS and the US, that is, the order in which the stimuli were presented and the temporal distance between them. Both studies showed that the size of EC effects was independent of the presentation order of CS and US within a stimulus pair. Contrary to classical conditioning effects, EC effects are thus not most pronounced after CS-first presentations. Furthermore, as shown in Experiment 2, EC effects increased in magnitude as the temporal interval between CS and US presentations decreased. Experiment 1 showed largest EC effects in the condition with simultaneous presentations - which can be seen as the condition with the temporally closest presentation. In this Experiment stimuli were presented in two different modalities, which might have facilitated simultaneous processing. In Experiment 2, in which all stimuli were presented visually, this advantage of simultaneous presentation was not found. We discuss practical and theoretical implications of our findings.

Eyeblink Classical Conditioning and Awareness Revisited

Dual-task performance was assessed in 140 adults during eyeblink classical conditioning (EBCC) and one of several secondary tasks (timed-interval tapping, recognition memory choice reaction time, video viewing) Four groups received paired-EBCC stimulus presentation and three groups received explicitly unpaired EBCC stimuli Although the subjects were not told about the conditioning task, they acquired conditioned responses (CRs) at normal levels Postsession interviews probed participants' awareness of EBCC stimulus contingencies and production of CRs Reported awareness of paired-EBCC stimulus contingencies and CR production was not related to actual EBCC performance Twenty-seven percent of the participants receiving explicitly unpaired stimuli reported a stimulus contingency when none existed The dissociation between awareness and performance provides additional support for the categorization of simple EBCC as a form of nondeclarative learning

Approach–Avoidance Training Effects Are Moderated by Awareness of Stimulus–Action Contingencies

Prior research suggests that repeatedly approaching or avoiding a stimulus changes the liking of that stimulus. In two experiments, we investigated the relationship between, on one hand, effects of approach–avoidance (AA) training on implicit and explicit evaluations of novel faces and, on the other hand, contingency awareness as indexed by participants’ memory for the relation between stimulus and action. We observed stronger effects for faces that were classified as contingency aware and found no evidence that AA training caused changes in stimulus evaluations in the absence of contingency awareness. These findings challenge the standard view that AA training effects are (exclusively) the product of implicit learning processes, such as the automatic formation of associations in memory.

Dual-task interference in evaluative conditioning: Similarity matters!

Evaluative conditioning (EC) refers to changes in liking that are due to the pairing of stimuli. Although the question of whether a secondary task can interfere with the occurrence of EC is of great theoretical relevance, previous research has not obtained a consistent pattern of results. Whereas in some studies EC remains intact under dual-task conditions, in others a secondary task resulted in reduced or diminished EC. In order to reconcile these inconsistent findings, we hypothesized that dual-task interference in EC depends on the similarity of demands incurred by processing the stimuli used in the conditioning procedure and the secondary task. Specifically, we assumed that interference only occurs when similar verbal or visuospatial demands are imposed. In order to test this hypothesis, we investigated the occurrence of EC under conditions of a demanding 3-back working memory task while using either orthographic or pictorial stimuli to manipulate verbal and visuospatial processing demands, respectively. Relative to conditions using dissimilar types of stimuli, we found that the 3-back task interfered with the occurrence of EC only when the same types of stimuli were used. The implications for the underlying processes of EC are discussed.

Reappraisal facilitates extinction in healthy and socially anxious individuals

BACKGROUND AND OBJECTIVES

Cognitive behavioral therapy (CBT) combines cognitive restructuring with exposure to feared stimuli in the treatment of anxiety disorders. Due to the complexities of cognition–emotion interactions during ongoing CBT, the underlying mechanisms remain unclear, which hinders treatment optimization.

METHODS

We created a laboratory analogue by combining reappraisal, a key ingredient of cognitive restructuring, with Pavlovian conditioning, a key ingredient in behavioral treatments. The novel differential Pavlovian acquisition and extinction task featured social stimuli as conditioned and unconditioned stimuli under unregulated and reappraisal instructions.

RESULTS

Findings indicated that reappraising the conditioned stimuli attenuated acquisition (Study 1) and facilitated extinction (Study 2) of conditioned negative valence. In Study 3, highly socially anxious individuals showed deficient extinction learning relative to low socially anxious individuals but compensated for this by using reappraisal.

LIMITATIONS

Diagnostic status of participants was not assessed in structured clinical interviews.

CONCLUSIONS

Reappraisal of feared stimuli could be useful in prevention and treatment of social anxiety.

All in its proper time: monitoring the emergence of a memory bias for novel, arousing-negative words in individuals with high and low trait anxiety

The well-established memory bias for arousing-negative stimuli seems to be enhanced in high trait-anxious persons and persons suffering from anxiety disorders. We monitored the emergence and development of such a bias during and after learning, in high and low trait anxious participants. A word-learning paradigm was applied, consisting of spoken pseudowords paired either with arousing-negative or neutral pictures. Learning performance during training evidenced a short-lived advantage for arousing-negative associated words, which was not present at the end of training. Cued recall and valence ratings revealed a memory bias for pseudowords that had been paired with arousing-negative pictures, immediately after learning and two weeks later. This held even for items that were not explicitly remembered. High anxious individuals evidenced a stronger memory bias in the cued-recall test, and their ratings were also more negative overall compared to low anxious persons. Both effects were evident, even when explicit recall was controlled for. Regarding the memory bias in anxiety prone persons, explicit memory seems to play a more crucial role than implicit memory. The study stresses the need for several time points of bias measurement during the course of learning and retrieval, as well as the employment of different measures for learning success.

The role of awareness in attitude formation through evaluative conditioning

This article provides a review of past and contemporary debates regarding the role of awareness in attitude formation through evaluative conditioning (EC), that is, by repeatedly pairing a stimulus with other stimuli of positive or negative valence. Because EC is considered the most prototypical method to form and change the network of evaluative associations in memory, the role of awareness in this effect is critical to the question of whether attitudes may be formed and changed through dual processes. We analyze the reasons why there has been so much discussion and disagreement regarding the role of awareness, review past and contemporary methodologies and their limitations, discuss the role of mental processes and conditioning procedures, and identify promising directions for future research in this area.

Co-activation of NR2A and NR2B subunits induces resistance to fear extinction

Unpredictable stress is known to profoundly enhance susceptibility to fear and anxiety while reducing the ability to extinguish fear when threat is no longer present. Accordingly, partial aversive reinforcement, via random exposure to footshocks, induces fear that is resistant to extinction. Here we sought to determine the hippocampal mechanisms underlying susceptibility versus resistance to context fear extinction as a result of continuous (CR) and partial (PR) reinforcement, respectively. We focused on N-methyl-D-aspartate receptor (NMDAR) subunits 2A and B (NR2A and NR2B) as well as their downstream signaling effector, extracellular signal-regulated kinase (ERK), based on their critical role in the acquisition and extinction of fear. Pharmacological inactivation of NR2A, but not NR2B, blocked extinction after CR, whereas inactivation of NR2A, NR2B, or both subunits facilitated extinction after PR. The latter finding suggests that co-activation of NR2A and NR2B contributes to persistent fear following PR. In contrast to CR, PR increased membrane levels of ERK and NR2 subunits after the conditioning and extinction sessions, respectively. In parallel, nuclear activation of ERK was significantly reduced after the extinction session. Thus, co-activation and increased surface expression of NR2A and NR2B, possibly mediated by ERK, may cause persistent fear. These findings suggest that patients with post-traumatic stress disorder (PTSD) may benefit from antagonism of specific NR2 subunits.

Overcoming Correlational Pitfalls

Do people need to explicitly encode conditioned stimuli–unconditioned stimuli (CS–US) pairings for evaluative conditioning (EC) effects to emerge? Despite the large number of studies that addressed this issue, no simple answer has emerged yet. In part, this is due to the relative lack of experimental evidence for the role of awareness of the CS–US contingency at encoding in EC. In the present experiment, participants’ encoding of the CS–US pairings was experimentally manipulated by relying on foveal and parafoveal presentations of the CSs. More specifically, spatial locations (i.e., foveal vs. parafoveal) of the CSs and US valence (i.e., positive vs. negative) were manipulated within participants, and CS–US pairings were counterbalanced across participants. Results reveal explicit encoding of the CSs and EC effects for the foveal CS presentations only. We discuss the implications of these experimental findings for the associative and propositional approach to EC.

Evaluative Conditioning with Facial Stimuli in Dementia Patients

We present results of a study investigating evaluative learning in dementia patients with a classic evaluative conditioning paradigm. Picture pairs of three unfamiliar faces with liked, disliked, or neutral faces, that were rated prior to the presentation, were presented 10 times each to a group of dementia patients (N = 15) and healthy controls (N = 14) in random order. Valence ratings of all faces were assessed before and after presentation. In contrast to controls, dementia patients changed their valence ratings of unfamiliar faces according to their pairing with either a liked or disliked face, although they were not able to explicitly assign the picture pairs after the presentation. Our finding suggests preserved evaluative conditioning in dementia patients. However, the result has to be considered preliminary, as it is unclear which factors prevented the predicted rating changes in the expected direction in the control group.

Learning, awareness, and instruction: subjective contingency awareness does matter in the colour-word contingency learning paradigm

In three experiments, each of a set colour-unrelated distracting words was presented most often in a particular target print colour (e.g., "month" most often in red). In Experiment 1, half of the participants were told the word-colour contingencies in advance (instructed) and half were not (control). The instructed group showed a larger learning effect. This instruction effect was fully explained by increases in subjective awareness with instruction. In Experiment 2, contingency instructions were again given, but no contingencies were actually present. Although many participants claimed to be aware of these (non-existent) contingencies, they did not produce an instructed contingency effect. In Experiment 3, half of the participants were given contingency instructions that did not correspond to the correct contingencies. Participants with these false instructions learned the actual contingencies worse than controls. Collectively, our results suggest that conscious contingency knowledge might play a moderating role in the strength of implicit learning.

Associative learning of likes and dislikes: Some current controversies and possible ways forward

Evaluative conditioning (EC) is one of the terms that is used to refer to associatively induced changes in liking. Many controversies have arisen in the literature on EC. Do associatively induced changes in liking actually exist? Does EC depend on awareness of the fact that stimuli are associated? Is EC resistant to extinction? Does attention help or hinder EC? As an introduction to this special issue, we will discuss the extent to which the papers that are published in this issue help to resolve some of the controversies that surround EC. We also speculate about possible boundary conditions of EC and attempt to reconcile conflicting results on the functional properties of EC.

Contingency Learning With Evaluative Stimuli

In two experiments, we tested the generality of the learning effects in the recently-introduced color-word contingency learning paradigm. Participants made speeded evaluative judgments to valenced target words. Each of a set of distracting nonwords was presented most often with either positive or negative target words. We observed that participants responded faster on trials that respected these contingencies than on trials that contradicted the contingencies. The contingencies also produced changes in liking: in a subsequent explicit evaluative rating task, participants rated positively-conditioned nonwords more positively than negatively-conditioned nonwords. Interestingly, contingency effects in the performance task correlated with this explicit rating effect in both experiments. In Experiment 2, all effects reported were independent of subjective and objective contingency awareness (which was completely lacking), even when awareness was measured at the item level. Our results reveal that learning in this type of performance task extends to nonword-valence contingencies and to responses different from those emitted during the performance task. We discuss the implications of these findings for theories about the processes that underlie contingency learning in performance tasks and for research on evaluative conditioning.

Stimulation of the noradrenergic system during memory formation impairs extinction learning but not the disruption of reconsolidation

The noradrenergic system plays a critical role in the 'consolidation' of emotional memory. If we are to target 'reconsolidation' in patients with anxiety disorders, the noradrenergic strengthening of fear memory should not impair the disruption of reconsolidation. In Experiment I, we addressed this issue using a differential fear conditioning procedure allowing selective reactivation of one of two fear associations. First, we strengthened fear memory by administering an α(2)-adrenergic receptor antagonist (ie, yohimbine HCl; double-blind placebo-controlled study) 30 min before acquisition (time for peak value yohimbine HCl <1 h). Next, the reconsolidation of one of the fear associations was manipulated by administering a β-adrenergic receptor antagonist (ie, propranolol HCl) 90 min before its selective reactivation (time for peak value propranolol HCl <2 h). In Experiment II, we administered propranolol HCl after reactivation of the memory to rule out a possible effect of the pharmacological manipulation on the memory retrieval itself. The excessive release of noradrenaline during memory formation not only delayed the process of extinction 48 h later, but also triggered broader fear generalization. Yet, the β-adrenergic receptor blocker during reconsolidation selectively 'neutralized' the fear-arousing aspects of the noradrenergic-strengthened memory and undermined the generalization of fear. We observed a similar reduction in fear responding when propranolol HCl was administered after reactivation of the memory. The present findings demonstrate the involvement of noradrenergic modulation in the formation as well as generalization of human fear memory. Given that the noradrenergic strengthening of fear memory impaired extinction learning but not the disruption of reconsolidation, our findings may have implications for the treatment of anxiety disorders.

Making implicit measures of associations with snack foods more negative through evaluative conditioning

The present study examined whether implicit measures of associations with snack foods and food consumer behaviour could be changed through a picture-picture evaluative conditioning procedure. In the experimental condition (n=41), female participants completed a conditioning procedure in which pictures of snack foods were paired with images of negatively valenced female body shapes, and pictures of fruits were paired with images of positively valenced body shapes. In a control condition (n=44), snack and fruit stimuli were randomly paired with positively and negatively valenced body shapes. Implicit measures of associations with high-fat snack foods were obtained by using a positive and a negative unipolar single category Implicit Association Test (sc-IAT). A virtual supermarket task was used to assess food consumer behaviour. Results indicated that participants in the experimental condition held a less positive association with high-fat foods on the positive sc-IAT and a more negative association with these foods on the negative sc-IAT as compared to control participants. Opposed to our hypothesis, no behavioural differences were found between the groups. These results imply that this form of associative learning can produce shifts in implicit measures of food evaluations, though behavioural effects were absent.