Think/no-think Research Articles

Everything you ever wanted to know about the Think/No-Think task, but forgot to ask

The Think/No-Think (TNT) task has just celebrated 20 years since its inception, and its use has been growing as a tool to investigate the mechanisms underlying memory control and its neural underpinnings. Here, we present a theoretical and practical guide for designing, implementing, and running TNT studies. For this purpose, we provide a step-by-step description of the structure of the TNT task, methodological choices that can be made, parameters that can be chosen, instruments available, aspects to be aware of, systematic information about how to run a study and analyze the data. Importantly, we provide a TNT training package (as Supplementary Material), that is, a series of multimedia materials (e.g., tutorial videos, informative HTML pages, MATLAB code to run experiments, questionnaires, scoring sheets, etc.) to complement this method paper and facilitate a deeper understanding of the TNT task, its rationale, and how to set it up in practice. Given the recent discussion about the replication crisis in the behavioral sciences, we hope that this contribution will increase standardization, reliability, and replicability across laboratories.

Intentional forgetting in excessive behavior: direct suppression and thought substitution

Excessive behavior refers to certain conduct or activities that exceed normal or healthy levels in terms of degree or frequency and may result in negative consequences for individuals. The present study suggests that negative memories underlie the recurrence and maintenance of excessive behaviors, and investigates whether individuals with excessive behavior might benefit from strategies of intentional forgetting to forget negative memories. In a modified think/no-think (TNT) task, 36 excessive gaming individuals and 36 controls were randomly assigned to two forgetting strategies: direct suppression and thought substitution. Direct suppression involved trying not to recall paired targets in no-think trials, while thought substitution involved participants being given substitutes to recall. The results indicate that thought substitution exhibited significant below-baseline forgetting and produced larger forgetting effects than direct suppression in both the excessive gaming group and the control group. These findings suggest that thought substitution may be a more effective approach to counteract unwanted memories among individuals with excessive behavior. The idea of substitution in this study could also provide enlightenment on interventions for excessive behavior.

Attentional capture mediates the emergence and suppression of intrusive memories.

Intrusive memories hijack consciousness and their control may lead to forgetting. However, the contribution of reflexive attention to qualifying a memory signal as interfering is unknown. We used machine learning to decode the brain's electrical activity and pinpoint the otherwise hidden emergence of intrusive memories reported during a memory suppression task. Importantly, the algorithm was trained on an independent attentional model of visual activity, mimicking either the abrupt and interfering appearance of visual scenes into conscious awareness or their deliberate exploration. Intrusion of memories into conscious awareness were decoded above chance. The decoding accuracy increased when the algorithm was trained using a model of reflexive attention. Conscious detection of intrusive activity decoded from the brain signal was central to the future silencing of suppressed memories and laterforgetting. Unwanted memories require the reflexive orienting of attention and access to consciousness to be suppressed effectively by inhibitory control.

No-think, No drink? Assessing the ability of reconsolidation interference by intentional forgetting to suppress alcohol memories in hazardous drinkers

Memory reconsolidation offers an opportunity to modify previously consolidated memories by first reactivating them. The process is triggered by the presentation of retrieval cues (reminders of the memory to be reactivated). However, reconsolidation is not universally triggered upon retrieval. Here we investigate one boundary condition thought to constrain memory reactivation: retrieval length. We also investigate the effects of a novel post-retrieval manipulation: intentional suppression. We assessed this with the think/no-think (TNT) task, in a clinically relevant sample of hazardous drinkers, using alcohol-related paired associate learning. 73 participants took part in four online sessions. On the first session participants were required to learn 36 image-word pairs. On the second session participants received 0, 4, 18 or 36 retrieval cues followed by the TNT task. The recall of the pairs was assessed 2 and 7 days after the retrieval + TNT procedure. The 4-trial retrieval procedure was the most consistent with triggering memory reconsolidation. This group showed greater practice effects and was the only group in which suppression-induced forgetting was observed at test. However, suppression-induced forgetting of alcohol cues was lower than in normative samples, indicating that intentional forgetting effects may depend upon population, salience of material and time between suppression and retrieval.

Task compliance predicts suppression-induced forgetting in a large sample

Suppression-induced forgetting (SIF) refers to a memory impairment resulting from repeated attempts to stop the retrieval of unwanted memory associates. SIF has become established in the literature through a growing number of reports built upon the Think/No-Think (TNT) paradigm. Not all individuals and not all reported experiments yield reliable forgetting, however. Given the reliance on task instructions to motivate participants to suppress target memories, such inconsistencies in SIF may reasonably owe to differences in compliance or expectations as to whether they will again need to retrieve those items (on, say, a final test). We tested these possibilities on a large (N = 497) sample of TNT participants. In addition to successfully replicating SIF, we found that the magnitude of the effect was significantly and negatively correlated with participants’ reported compliance during the No-Think trials. This pattern held true on both same- and independent-probe measures of forgetting, as well as when the analysis was conditionalized on initial learning. In contrast, test expectancy was not associated with SIF. Supporting previous intuition and more limited post-hoc examinations, this study provides robust evidence that a lack of compliance with No-Think instructions significantly compromises SIF. As such, it suggests that diminished effects in some studies may owe, at least in part, to non-compliance—a factor that should be carefully tracked and/or controlled. Motivated forgetting is possible, provided that one is sufficiently motivated and capable of following the task instructions.

Suppressing negative materials for remitted depressed individuals: Substitution forgetting and incidental forgetting strategies

Intentional forgetting is significantly effective for forgetting unwanted non-emotional material. However, whether the suppressive effect of unaided suppression differs from that of substitution forgetting when applied to negative materials by remitted depressed individuals is unclear. A modified think/no-think (TNT) emotional paradigm including specific strategies (unaided suppression, positive-word substitution, and positive-picture substitution) was used with 84 remitted depressed individuals and 80 controls. The participants in both groups forgot more negative words in the substitution condition than in the unaided condition. The remitted participants forgot more with positive-picture substitution than with positive-word substitution, while the controls showed no difference. Moreover, the participants in both groups forgot more with 0 cue presentations (incidental forgetting) than under any other experimental condition. These results indicate that unaided suppression of negative material in the TNT paradigm shows little suppressive effect. Incidental forgetting and positive-picture substitution forgetting may be better strategies for remitted depressed individuals to forget negative materials.

A multiverse analysis of early attempts to replicate memory suppression with the Think/No-think Task

ABSTRACT In 2001, Anderson and Green [2001. Suppressing unwanted memories by executive control. Nature, 410(6826), 366–369] showed memory suppression using a novel Think/No-think (TNT) task. When participants attempted to prevent studied words from entering awareness, they reported fewer of those words than baseline words in subsequent cued recall (i.e., suppression effect). The TNT literature contains predominantly positive findings and few null-results. Therefore we report unpublished replications conducted in the 2000s (N = 49; N = 36). As the features of the data obtained with the TNT task call for a variety of plausible solutions, we report parallel “universes” of data-analyses (i.e., multiverse analysis) testing the suppression effect. Two published studies (Wessel et al., 2005. Dissociation and memory suppression: A comparison of high and low dissociative individuals’ performance on the Think–No think Task. Personality and Individual Differences, 39(8), 1461–1470, N = 68; Wessel et al., 2010. Cognitive control and suppression of memories of an emotional film. Journal of Behavior Therapy and Experimental Psychiatry, 41(2), 83–89. https://doi.org/10.1016/j.jbtep.2009.10.005, N = 80) were reanalysed in a similar fashion. For recall probed with studied cues (Same Probes, SP), some tests (sample 3) or all (samples 2 and 4) showed statistically significant suppression effects, whereas in sample 1, only one test showed significance. Recall probed with novel cues (Independent Probes, IP) predominantly rendered non-significant results. The absence of statistically significant IP suppression effects raises problems for inhibition theory and its implication that repression is a viable mechanism of forgetting. The pre-registration, materials, data, and code are publicly available (https://osf.io/qgcy5/).

Investigating the mediating effect of working memory on intentional forgetting in dysphoria

Our aim was to determine if deficits in intentional forgetting that are associated with depression and dysphoria (subclinical depression) could be explained, at least in part, by variations in working memory function. Sixty dysphoric and 61 non-dysphoric participants completed a modified version of the think/no-think (TNT) task and a measure of complex working memory (the operation span task). The TNT task involved participants learning a series of emotional cue–target word pairs, before being presented with a subset of the cues and asked to either recall the associated target (think) or to prevent it from coming to mind (no think) by thinking about a substitute target word. Participants were subsequently asked to recall the targets to all cues (regardless of previous recall instructions). As expected, after controlling for anxiety, we found that dysphoric individuals exhibited impaired forgetting relative to the non-dysphoric participants. Also as expected, we found that superior working memory function was associated with more successful forgetting. Critically, in the dysphoric group, we found that working memory mediated the effect of depression on intentional forgetting. That is, depression influenced forgetting indirectly via its effect on working memory. However, under conditions of repeated suppression, there was also a direct effect of depression on forgetting. These findings represent an important development in the understanding of impaired forgetting in depression and also suggest that working memory training might be a viable intervention for improving the ability of depressed individuals to prevent unwanted memories from coming to mind.

The Think/No-Think Alcohol Task: A New Paradigm for Assessing Memory Suppression in Alcohol-Related Contexts.

Research with the Think/No-Think (TNT) task has shown that voluntary suppression of an unwanted memory may lead to its later forgetting. To date, however, no study has assessed the memory suppression abilities in alcohol-related contexts despite the potential implications that it might have for alcohol research. With this aim, we developed a new version of the TNT paradigm, the TNT Alcohol (TNTA) task, which consists of 36 neutral pictures paired with 36 alcohol/no-alcohol images that are instructed to be suppressed or recollected. Electroencephalographic activity was recorded from 64 electrodes while 20 young healthy females performed the TNTA task. The event-related potentials (ERPs) typically involved in memory suppression/recollection were analyzed, namely the fronto-central N2, the late parietal positivity (LPP), and the frontal slow wave (FSW). Findings revealed reduced recall for previously learned images that were subsequently instructed to be suppressed (No-Think) relative to those instructed to be retrieved (Think) and those not cued to be suppressed or retrieved (Baseline). This reduction seemed to be more prominent for alcohol-related memories. In addition, ERP analysis showed that compared to attempts of recollection, attempts of memory suppression were associated with attenuated LPP amplitude-more pronounced for alcohol-related memories-(indicating reduced conscious recollection for No-Think images) as well as with increased FSW (suggesting strategic control aiming at decrease accessibility of unwanted memories). These results replicate and extend previously reported behavioral and ERP findings in the TNT paradigm and suggest that the TNTA task may be a useful instrument to measure the ability to suppress alcohol-related memories.

Ruminators (Unlike Others) Fail to Show Suppression-Induced Forgetting on Indirect Measures of Memory

Suppression is a useful everyday skill leading to the clinically important outcome of forgetting. Suppression-induced forgetting, investigated with the think/no-think (TNT) paradigm, is typically demonstrated on direct tests of memory, even though indirect tests are often more ecologically valid. We report results from two TNT experiments terminating in indirect tests—tests that seem not to measure memory. For a subset of the participants in Experiment 1, latencies to rate word valence were delayed by flankers previously learned but not by flankers previously learned and then suppressed on 16 occasions. For a similar subset in Experiment 2, cue meaning denoted by free associations reflected the meaning established during learning, but less so when targets had been suppressed. These subsets showing suppression effects were students who did not describe themselves as ruminators. That ruminators failed to show “forgetting” on either test suggests that ruminative habits cannot be easily overcome by practicing suppression.

Intentional forgetting in dysphoria: Investigating the inhibitory effects of thought substitution using independent cues

BackgroundIndividuals with clinical and subclinical depression (dysphoria) exhibit problems intentionally forgetting unwanted memories on the think/no-think (TNT) paradigm (Anderson & Green, 2001). However, providing substitute words to think about instead of the to-be-forgotten targets can improve forgetting in depressed patients. ObjectivesTo determine if thought substitution can enhance forgetting in dysphoric participants and to examine the potential mechanisms (blocking or inhibition) that might underpin successful forgetting. MethodsThirty-six dysphoric and 36 non-dysphoric participants learned neutral word-pairs and then practiced responding with the targets to some cues (think trials) and suppressing responses to others (no think trials). Half the participants were provided with substitute words to recall instead of the original targets (aided suppression) and half were simply told to avoid thinking about the targets (unaided suppression). Finally, participants completed two recall tests for the targets; one cued with the original probes and one with independent probes. ResultsRegardless of suppression condition (aided or unaided), dysphoric participants exhibited impaired forgetting, relative to their non-dysphoric counterparts, but only when cued with the original probes. Furthermore, higher depression scores were associated with poorer forgetting. In the aided condition, successful forgetting was observed on both the original and independent probe tasks, which supports the inhibitory account of thought substitution. LimitationsNon-clinical status of the dysphoric participants was not confirmed using a validated measure. ConclusionsFindings do not support the utility of thought substitution as a method of improving the forgetting in depressed participants, but do support the inhibition account of thought substitution.

Behavioral and EEG Evidence for Auditory Memory Suppression.

The neural basis of motivated forgetting using the Think/No-Think (TNT) paradigm is receiving increased attention with a particular focus on the mechanisms that enable memory suppression. However, most TNT studies have been limited to the visual domain. To assess whether and to what extent direct memory suppression extends across sensory modalities, we examined behavioral and electroencephalographic (EEG) effects of auditory TNT in healthy young adults by adapting the TNT paradigm to the auditory modality. Behaviorally, suppression of memory strength was indexed by prolonged response time (RTs) during the retrieval of subsequently remembered No-Think words. We examined task-related EEG activity of both attempted memory retrieval and inhibition of a previously learned target word during the presentation of its paired associate. Event-related EEG responses revealed two main findings: (1) a centralized Think > No-Think positivity during auditory word presentation (from approximately 0–500 ms); and (2) a sustained Think positivity over parietal electrodes beginning at approximately 600 ms reflecting the memory retrieval effect which was significantly reduced for No-Think words. In addition, word-locked theta (4–8 Hz) power was initially greater for No-Think compared to Think during auditory word presentation over fronto-central electrodes. This was followed by a posterior theta increase indexing successful memory retrieval in the Think condition. The observed event-related potential pattern and theta power analysis are similar to that reported in visual TNT studies and support a modality non-specific mechanism for memory inhibition. The EEG data also provide evidence supporting differing roles and time courses of frontal and parietal regions in the flexible control of auditory memory.

Cue-independent forgetting by intentional suppression – Evidence for inhibition as the mechanism of intentional forgetting

People are able to intentionally forget unwanted memories through voluntary suppression, as revealed by the Think/No-think (TNT) paradigm. However, the nature of intentional forgetting is controversial. Findings that forgetting is independent of retrieval cues suggest that inhibitory control underlies intentional forgetting, but this result is also in line with an interference account. To resolve this controversy, we have directly contrasted the cue-independent characteristic of suppression versus interference. A double-cue paradigm was used, in which two different cues were associated with the same target during initial memory formation. Only one cue-target association received further interference/suppression training. In the test phase, when both cues were used to retrieve the target, we found that interference caused memory impairment that was restricted to the trained cue-target association, while suppression induced forgetting that generalized to the independent cue-target association. Therefore, the effect of suppression differs from that of interference. The cue-independent forgetting by voluntary suppression indicates that the target memory itself is inhibited, providing evidence that the underlying mechanism of suppression-induced forgetting is inhibitory control.

The impact of intermediate-term alcohol abstinence on memory retrieval and suppression

Background: The nature of episodic memory deficit in intermediate-term abstinence from alcohol in alcohol dependence (AD) is not yet clarified. Deficits in inhibitory control are commonly reported in substance use disorders. However, much less is known about cognitive control suppressing interference from memory. The Think/No-think (TNT) paradigm is a well established method to investigate inhibition of associative memory retrieval.Methods: Thirty-six unmedicated patients with AD and 36 healthy controls (HCs) performed the TNT task. Thirty image–word pairs were trained up to a predefined accuracy level. Cued recall was examined in three conditions: Think (T) for items instructed to-be-remembered, No-think (NT) assessing the ability to suppress retrieval and Baseline (B) for general relational memory. Premorbid IQ, clinical variables and impulsivity measures were quantified.Results: AD patients had a significantly increased demand for training. Baseline memory abilities and effect of practice on retrieval were not markedly different between the groups. We found a significant main effect of group (HC vs. AD) × condition (B, T, and NT) and a significant difference in mean NT–B scores for the two groups.Discussion: AD and HC groups did not differ essentially in their baseline memory abilities. Also, the instruction to focus on retrieval improved episodic memory performance in both groups. Crucially, control participants were able to suppress relational words in the NT condition supporting the critical effect of cognitive control processes over inhibition of retrieval. In contrast to this, the ability of AD patients to suppress retrieval was found to be impaired.

Inhibitory effects of thought substitution in the think/no-think task: Evidence from independent cues

When people try not to think about a certain item, they can accomplish this goal by using a thought substitution strategy and think about something else. Research conducted with the think/no-think (TNT) paradigm indicates that such strategy leads subsequently to forgetting the information participants tried not to think about. The present study pursued two goals. First, it investigated the mechanism of forgetting due to thought substitution, contrasting the hypothesis by which forgetting is due to blocking caused by substitutes with the hypothesis that forgetting is due to inhibition (using an independent cue methodology). Second, a boundary condition for forgetting due to thought substitution was examined by creating conditions under which the generation of appropriate substitutes would be impaired. In two experiments, participants completed a TNT task under thought substitution instructions in which either words or pseudo-words were used as original cues and memory was assessed with original and independent cues. The results revealed forgetting in both original and independent cue tests, supporting the inhibitory account of thought substitution, but only when cues were words, and not when they were non-words, pointing to the ineffectiveness of a thought substitution strategy when original cues lack semantic content.

ERPs and Neural Oscillations during Volitional Suppression of Memory Retrieval

Although investigations of memory and the dynamics of ERP components and neural oscillations as assessed through EEG have been well utilized, little research into the volitional nature of suppression over memory retrieval have used these methods. Oscillation analyses conducted on the Think/No-Think (TNT) task and volitional suppression of retrieval are of interest to broaden our knowledge of neural oscillations associated not only during successful memory retrieval but also when retrieval is unwanted or suppressed. In the current study, we measured EEG during a TNT task and performed ERP and EEG spectral power band analyses. ERP results replicated other researchers' observations of increases in 500-800 msec parietal effects for items where retrieval was instructed to be elaborated compared with being suppressed. Furthermore, EEG analyses indicated increased alpha (8-12 Hz) and theta (3-8 Hz) oscillations across parietal electrodes for items that were instructed to be suppressed versus those to be elaborated. Additionally, during the second half of the experiment (after repeated attempts at control), increases in theta oscillations were found across both frontal and parietal electrodes for items that were instructed to be suppressed and that were ultimately forgotten versus those ultimately remembered. Increased alpha power for items that were instructed to be suppressed versus elaborated may indicate reductions of retrieval attempts or lack of retrieval success. Increased theta power for items that were instructed to be suppressed versus elaborated may indicate increased or prolonged cognitive control to monitor retrieval events.

Classification aided analysis of oscillatory signatures in controlled retrieval

Control processes are critical for both facilitating and suppressing memory retrieval, but these processes are not well understood. The current work, inspired by a similar fMRI design (Detre et al., in press), used a modified Think/No-Think(TNT) paradigm to investigate the neural signatures of volition over enhancing and suppressing memory retrieval. Previous studies have shown memory enhancement when well-learned stimulus pairs are restudied in cued recall (“Recall or think of studied pair item”), and degradation when restudied with cued suppression (“Avoid thinking of studied pair item”). We used category-based (faces vs. scenes) multivariate classification of electroencephalography signals to determine if individual target items were successfully retrieved or suppressed. A logistic regression based on classifier output determined that retrieval activation during the cued recall/suppression period was a predictor for subsequent memory. Labeling trials with this internal measure, as opposed to their nominal Think vs. No-Think condition, revealed the classic TNT pattern of enhanced memory for successful cued-retrieval and degraded memory for cued-suppression. This classification process enabled a more selective investigation into the time-frequency signatures of control over retrieval. Comparing controlled retrieval vs. controlled suppression, results showed more prominent Theta oscillations (3 to 8Hz) in controlled retrieval. Beta oscillations (12 to 30Hz) were involved in high levels of both controlled retrieval and suppression, suggesting it may have a more general control-related role. These results suggest unique roles for these frequency bands in retrieval processes.

Effects of Intentional Suppression of Recall of Unwanted Images in Repressors and Nonrepressors

We investigated the ability to suppress recall of visual images, using the think/no-think (TNT) paradigm. Participants were 27 male undergraduates (13 repressors, 14 nonrepressors) who watched video clips of a motorbike accident as we recorded their galvanic skin response (GSR). We then conducted the TNT paradigm using motorbike accident images. Both repressors and nonrepressors recorded higher GSR when watching the video clips than at baseline. Both groups showed greater suppression of imaginary memories in the no-think condition than they did in either the think or the baseline conditions. We found repeated attempts at no-think might be an effective strategy for suppressing imaginary memories and that there were no differences in the ability of repressors and nonrepressors to suppress memory in the imaginary memory condition.

Suppression-Induced Reduction in the Specificity of Autobiographical Memories.

To extend its relevance to everyday forgetting, we applied the think/no-think (TNT) suppression method devised by Anderson and Green (2001) to autobiographical memories. Dysphoric and nondysphoric participants first generated autobiographical memories and corresponding titles to neutral and emotionally positive or negative cues. During the TNT phase, participants repeatedly practiced responding to some cues with their associated titles and avoiding thoughts about titles and memories associated with other cues. Later, they were asked to report memories associated with all cues, including baseline cues not presented during the TNT phase. Results revealed impaired recall, as measured by reductions in specificity, for suppressed memories relative to baseline memories. Also, regardless of TNT instructions, memories of dysphoric students who had received negative cues became less specific and less negative than they were at the outset.

Suppression of novel stimuli: Changes in accessibility of suppressed nonverbalizable shapes

Recently, a new method of considering successful intentional thought suppression has emerged. This method, the think/no-think (TNT) paradigm has been utilized over a multitude of settings and has fairly robustly demonstrated the ability to interfere with memory recall. The following experiment examined the effect of intentional thought suppression on recognition memory of nonverbalizeable shapes. In this experiment, participants learned word-shape targets. For some of the pairs, they rehearsed the shape when presented with the word; for others, they suppressed the shape when presented with the word. Finally, participants were shown multiple shapes, one at a time, and asked to identify which they had previously seen as paired with a word. Results of the experiment indicated that, similar to results involving words, participants were less accurate in identifying suppressed shapes, as compared to rehearsed shapes. Implications of these findings are discussed.