It has been proposed that memory retrieval can destabilize consolidated memories, after which they need to be reconsolidated in order to be retained. The presentation of relevant information during memory reconsolidation could then result in the modification of a destabilized memory trace, by allowing the memory trace to be updated before being reconsolidated. In line with this idea, Schiller et al. (2010) have demonstrated that memory retrieval shortly before extinction training can prevent the later recovery of conditioned fear responding that is observed after regular extinction training. Those findings have been the subject of considerable controversy, due in part to theoretical reasons but also due to a number of failures to obtain similar results in conceptual replication attempts. Here, we report the results of a highly powered, direct, independent replication of the critical conditions of Schiller et al. (2010, Experiment 1). Due to misrepresentation of the exclusion criteria in the original Schiller et al. (2010) report, data collection was considerably delayed. When we eventually managed to attain our pre-registered sample size, we found that we could not observe any benefit of reactivation-extinction over regular extinction training in preventing recovery of conditioned fear. The results of the present study, along with the mixed findings in the literature and the misreporting in Schiller et al. (2010), give cause to question whether there is robust evidence that reactivation-extinction prevents the return of fear in humans.

The generalization of learned behavior has been extensively investigated, but accounting for variance in generalized responding remains a challenge. Based on recent advances, we demonstrate that the inclusion of perceptual measures in generalization research may lead to a better understanding of both intra-and interindividual differences in generalization. We explore various ways through which perceptual variability can influence generalized responding. We investigate its impact on the ability to discriminate between stimuli and how similarity between stimuli may be variable, rather than fixed, because of it. Subsequently, we argue that perceptual variations can yield different learning experiences and that interindividual differences in generalized responding may be understood from this perspective. Finally, we point to the role of memory and decision-making within this context. Throughout this paper, we argue that accounting for perception in current generalization protocols will improve the precision of obtained generalization gradients and the ability to infer latent mechanisms. This can inspire future attempts to use generalization gradients as a (clinical) predictor or to relate them to individual traits and neural correlates and, ultimately, may lead to new theoretical and clinical insights.

Summary Sleep disturbances and anxiety disorders exhibit high comorbidity levels, but it remains unclear whether sleep problems are causes or consequences of increased anxiety. To experimentally probe the aetiological role of sleep disturbances in anxiety, we investigated in healthy participants how total sleep deprivation influences fear expression in a conditioning paradigm. In a fear conditioning procedure, one face stimulus (conditioned stimulus [CS+]) was paired with electric shock, whereas another face stimulus was not (unpaired stimulus [CS−]). Fear expression was tested the next morning using the two face stimuli from the training phase and a generalization stimulus (i.e. a morph between the CS+ and CS− stimuli). Between fear conditioning and test, participants were either kept awake in the laboratory for 12 hr (n = 20) or had a night of sleep at home (n = 20). Irrespective of stimulus type, subjective threat expectancies, but not skin conductance responses, were enhanced after sleep deprivation, relative to regular sleep. These results suggest that sleep disturbances may play a role in anxiety disorders by increasing perceived threat.

Although memory of past experiences is crucial for the ability to transfer knowledge to new situations, surprisingly little research has directly investigated the relationship between memory and generalization. The present study sought to investigate how the perceptual memory of a trained stimulus influences generalization to similar stimuli. Forty participants underwent a fear conditioning procedure on Day 1, and separate memory recall and generalization tests on Day 2. We focused on two aspects of perceptual memory: namely memory bias (i.e., over-or underestimating stimulus features) and uncertainty. We found that memory bias influenced the pattern of generalized selfreported (expectancy ratings) and psychophysiological responses (fear-potentiated startle responses). Memory uncertainty was measured in two ways: self-reported uncertainty ratings and variability in stimulus recall. We demonstrated that higher levels of self-reported memory uncertainty led to a broadening of the US expectancy generalization gradient, whereas an effect of variability in memory recall on generalization was only found for fear-potentiated startle responses. Taken together, our findings suggest that memory is an important determinant of generalized behavior and illustrate the need to account for these interindividual differences in perceptual memory when examining the generalization of learned responses.

The human fear-conditioning paradigm is a widely used procedure to study anxiety. However, merely thinking about the aversive outcome is typically not measured in this procedure. This is surprising because thinking of an aversive event is of clinical relevance (e.g., in the form of intrusions) and theoretical interest. We present two preregistered studies that (a) included thinking of an aversive outcome as an additional dependent variable and (b) compared several interventions to reduce it. We found that mere thinking of an aversive outcome could be successfully conditioned. Among the participants who showed successful acquisition, extinction training was less successful in reducing it than counterconditioning. Presenting new additional outcomes also proved effective to reduce thoughts about the initial outcome when the new outcomes were positive stimuli. Including thinking of the aversive outcome as an additional dependent variable may serve to enhance the understanding of anxiety-related disorders and inform their treatment.