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Concept: Replicate


The articular release of the metacarpophalangeal joint produces a typical cracking sound, resulting in what is commonly referred to as the cracking of knuckles. Despite over sixty years of research, the source of the knuckle cracking sound continues to be debated due to inconclusive experimental evidence as a result of limitations in the temporal resolution of non-invasive physiological imaging techniques. To support the available experimental data and shed light onto the source of the cracking sound, we have developed a mathematical model of the events leading to the generation of the sound. The model resolves the dynamics of a collapsing cavitation bubble in the synovial fluid inside a metacarpophalangeal joint during an articular release. The acoustic signature from the resulting bubble dynamics is shown to be consistent in both magnitude and dominant frequency with experimental measurements in the literature and with our own experiments, thus lending support for cavitation bubble collapse as the source of the cracking sound. Finally, the model also shows that only a partial collapse of the bubble is needed to replicate the experimentally observed acoustic spectra, thus allowing for bubbles to persist following the generation of sound as has been reported in recent experiments.

Concepts: Replicate, Science, Causality, Sound, Sonar, Cavitation, Experiment, Joints


Bargh et al. (2001) reported two experiments in which people were exposed to words related to achievement (e.g., strive, attain) or to neutral words, and then performed a demanding cognitive task. Performance on the task was enhanced after exposure to the achievement related words. Bargh and colleagues concluded that better performance was due to the achievement words having activated a “high-performance goal”. Because the paper has been cited well over 1100 times, an attempt to replicate its findings would seem warranted. Two direct replication attempts were performed. Results from the first experiment (n = 98) found no effect of priming, and the means were in the opposite direction from those reported by Bargh and colleagues. The second experiment followed up on the observation by Bargh et al. (2001) that high-performance-goal priming was enhanced by a 5-minute delay between priming and test. Adding such a delay, we still found no evidence for high-performance-goal priming (n = 66). These failures to replicate, along with other recent results, suggest that the literature on goal priming requires some skeptical scrutiny.

Concepts: Cognition, Design of experiments, Hypothesis, Scientific method, Replicate, Effects unit, Experiment, Test method


Zebrafish is fast becoming a species of choice in biomedical research for the investigation of functional and dysfunctional processes coupled with their genetic and pharmacological modulation. As with mammals, experimentation with zebrafish constitutes a complicated ethical issue that calls for the exploration of alternative testing methods to reduce the number of subjects, refine experimental designs, and replace live animals. Inspired by the demonstrated advantages of computational studies in other life science domains, we establish an authentic data-driven modelling framework to simulate zebrafish swimming in three dimensions. The model encapsulates burst-and-coast swimming style, speed modulation, and wall interaction, laying the foundations for in-silico experiments of zebrafish behaviour. Through computational studies, we demonstrate the ability of the model to replicate common ethological observables such as speed and spatial preference, and anticipate experimental observations on the correlation between tank dimensions on zebrafish behaviour. Reaching to other experimental paradigms, our framework is expected to contribute to a reduction in animal use and suffering.

Concepts: Test method, Replicate, Biology, Model, Design of experiments, Experimental physics, Science, Experiment


Recent advances in the field of fear learning have demonstrated that a single reminder exposure prior to extinction training can prevent the return of extinguished fear by disrupting the process of reconsolidation. These findings have however proven hard to replicate in humans. Given the significant implications of preventing the return of fear, the purpose of the present study was to further study the putative effects of disrupting reconsolidation. In two experiments, we assessed whether extinction training initiated within the reconsolidation time window could abolish the return of fear using fear-relevant (Experiment 1) or fear-irrelevant (Experiment 2) conditioned stimuli (CS). In both experiments, participants went through conditioning, extinction, and reinstatement testing on three consecutive days, with one of two reinforced CS being reactivated 10 min prior to extinction. We found that a single reminder exposure prior to extinction training did not prevent the return of extinguished fear responding using either fear-relevant or fear-irrelevant CSs. Our findings point to the need to further study the specific parameters that enable disruption of reconsolidation.

Concepts: Science, Present, Time, Operant conditioning, Classical conditioning, Learning, Replicate, Experiment


There has been considerable controversy around the limits and reproducibility of so-called “behavior” priming effects. Payne, Brown-Iannuzzi, and Loersch (2016) reported a series of 6 experiments on the effects of primes on participants' bets in a simulated blackjack game, and claimed that their findings not only establish the reality of behavior priming beyond dispute, but also demonstrate that this form of priming has the crucial hallmark of occurring outside participants' awareness and control. I describe a statistical model that does not distinguish automatic and controlled processes, but which nonetheless reproduces Payne et al.’s (2016) results and hence shows that their conclusions are unwarranted. Payne et al.’s (2016) experimental task and within-subjects design provide little insight into why some behavior priming studies have proven difficult to replicate. (PsycINFO Database Record

Concepts: Statistics, Replicate, Relational database, Control, Controversy, Legal terms, Experiment


A core feature of intractable conflicts is the tendency to cognitively freeze on existing, pro-ingroup beliefs. In three experiments, conducted in the context of the Palestinian-Israeli conflict, we tested the idea that an external incentive for negotiating peace helps unfreeze cognitions. In Experiment 1, making salient that peace with the Palestinians would reduce the Iranian nuclear threat (an external incentive) led to a process of unfreezing. In Experiment 2, we examined whether collective angst as an emotional sentiment (i.e., concern for the ingroup’s future vitality as a temporally stable emotional disposition) moderated the aforementioned external incentive-cognitive unfreezing link. As predicted, external incentive salience promoted cognitive unfreezing, but only among people low in collective angst (i.e., people who are not concerned for the ingroup’s future). In Experiment 3, we sought to replicate the results of Experiment 2. However, socio-political forces (i.e., a significant upswing in tensions between Palestinians and Israelis) likely served to freeze cognitions to such an extent that thawing was not possible by the means demonstrated in Experiments 1 and 2. The importance of confidence in a peace process is discussed in the context of efforts to unfreeze cognitions during an intractable conflict.

Concepts: Psychology, Fatah, Cognitive psychology, Replicate, Arab citizens of Israel, Experiment, Cognition, Israel


Research on perceptual learning shows that the way stimuli are presented leads to different outcomes. The intermixed/blocked (I/B) effect is one of these outcomes, and different mechanisms have been proposed to explain it. In human research, it seems that comparison between stimuli is important, and the placement of a distractor between the pre-exposed stimuli interferes with the effect. Results from animal research are usually interpreted in different terms because the type of procedure normally used in animal perceptual learning does not favour comparison. In our experiments, we explore the possibility that a distractor placed between the to-be-discriminated stimuli may interfere with the perceptual learning process in rats. In Experiment 1, two flavoured solutions are presented in an I/B fashion, with a short time lapse between them to favour comparison, showing the typical I/B effect. In Experiment 2, we introduced a distractor in between the solutions, abolishing this effect. Experiment 3 further replicates this by comparing two intermixed groups with or without distractor. The results replicate the findings from human research, suggesting that comparison also plays an important role in animal perceptual learning.

Concepts: Developmental psychology, Replicate, Theory, Play, Science, Learning, Experiment, Psychology


Background : Vivid trauma-related intrusions are a hallmark symptom of posttraumatic stress disorder (PTSD), and may be involved in its onset. Effective interventions to reduce intrusions and to potentially prevent the onset of subsequent PTSD are scarce. Studies suggest that playing the videogame Tetris, shortly after watching aversive film clips, reduces subsequent intrusions. Other studies have shown that taxing working memory (WM) while retrieving an emotional memory reduces the memory’s vividness and emotionality.Objective: We developed TraumaGameplay (TGP), a gaming app designed to reduce intrusions. This paper describes two successive experiments to determine whether playing TGP without memory retrieval (regular TGP) or TGP with memory retrieval (dual-task TGP) reduces intrusion frequency at one week compared to a no-game control.Method: For both experiments, healthy university students were recruited. Experiment 1: 92 participants were exposed to a trauma film and randomized to (1)regular TGP1(n = 31), (2)dual-task TGP1(n = 31) or (3) control (n = 30). In experiment 2, 120 healthy students were exposed to a trauma film and randomized to (1) regular TGP2 (n = 30), (2) dual-task TGP2 (n = 29), (3) recall only (n = 31) or (4) control (n = 30).Results: We found no significant difference between conditions on the number of intrusions for either playing regular TGP or dual-task TGP in both experiment 1 and experiment 2.Conclusion: Our results could not replicate earlier promising findings from preceding experimental research. Several reasons may underpin this difference ranging from the visuospatial videogame used in our experiments to the method of the experiment to the difficulties of replicability in general.

Concepts: Posttraumatic stress disorder, Chemistry, Science, Replicate, Psychological trauma, Experiment


Current models of word-meaning access typically assume that lexical-semantic representations of ambiguous words (e.g., ‘bark of the dog/tree’) reach a relatively stable state in adulthood, with only the relative frequencies of meanings and immediate sentence context determining meaning preference. However, recent experience also affects interpretation: recently encountered word-meanings become more readily available (Rodd et al., 2016, 2013). Here, 3 experiments investigated how multiple encounters with word-meanings influence the subsequent interpretation of these ambiguous words. Participants heard ambiguous words contextually-disambiguated towards a particular meaning and, after a 20- to 30-min delay, interpretations of the words were tested in isolation. We replicate the finding that 1 encounter with an ambiguous word biased the later interpretation of this word towards the primed meaning for both subordinate (Experiments 1, 2, 3) and dominant meanings (Experiment 1). In addition, for the first time, we show cumulative effects of multiple repetitions of both the same and different meanings. The effect of a single subordinate exposure persisted after a subsequent encounter with the dominant meaning, compared to a dominant exposure alone (Experiment 1). Furthermore, 3 subordinate word-meaning repetitions provided an additional boost to priming compared to 1, although only when their presentation was spaced (Experiments 2, 3); massed repetitions provided no such boost (Experiments 1, 3). These findings indicate that comprehension is guided by the collective effect of multiple recently activated meanings and that the spacing of these activations is key to producing lasting updates to the lexical-semantic network. (PsycINFO Database Record

Concepts: Replicate, Tonality, Effects unit, Word, Linguistics, Affect, Effect, Experiment


A key component in many RNA-Seq based studies is contrasting multiple replicates from different experimental conditions. In this setup, replicates play a key role as they allow to capture underlying biological variability inherent to the compared conditions, as well as experimental variability. However, what constitutes a “bad” replicate is not necessarily well defined. Consequently, researchers might discard valuable data or downstream analysis may be hampered by failed experiments.

Concepts: Mathematical terminology, Research, Paleontology, Science, Replicate, Empiricism, Philosophical logic, Experiment