How We Lost 90% of Participants on a Bad Bet: Results from a Pilot Randomized Controlled Trial on Cognitive Bias Modification in Problem Gamblers.

Whilst opportunities to participate in gambling have increased, access to support for problem gamblers is lacking behind. This lack of balance calls for improved and accessible intervention methods. The present double-blind randomized controlled trial (RCT) explored the effectiveness of two interventions targeting automatic cognitive processes, known as Attentional Bias Modification (AtBM) and Approach Bias Modification (ApBM). It was hypothesized these interventions would reduce gambling behavior and reduce or reverse targeted biases. Participants (N = 331) were community-recruited Flemish (35%) and Dutch (65%) adult problem gamblers motivated to reduce or stop their gambling who received either six sessions of active training (AtBM or ApBM) or of the corresponding sham-training (sham-AtBM or sham-ApBM). Due to high attrition rates (90.1% up to the intervention phase) the study was terminated before completion, since it would greatly limit the validity of any results. A post hoc qualitative study was performed on a subset of participants to gain insight into contributing factors for the high attrition rate. Issues negatively impacting participants' motivation to complete the program were identified, as well as elements of the program that received approval. The results from this study provide a first insight into the potential of the use of online cognitive bias modification (CBM) interventions in problem gambling (PG). Suggestions and directions for future studies are discussed.

Losing sight of Luck: Automatic approach tendencies toward gambling cues in Canadian moderate- to high-risk gamblers - A replication study.

Evidence for approach bias tendencies to underly automatic behavioural impulses towards seeking out gambling activities in the presence of appetitive salient cues was first shown by Boffo et al. (2018) in a Dutch sample. Relative to non-problem gamblers, moderate-to-high-risk gamblers demonstrated stronger approach tendencies towards gambling-related stimuli compared with neutral ones. Moreover, gambling approach bias was associated with past-month gambling behaviour and predictive of gambling activity persistence over time. The current study aimed to replicate these findings within a Canadian sample evaluating the concurrent and longitudinal correlates of gambling approach bias. The study was conducted online, available throughout Canada. Twenty-seven non-treatment-seeking moderate-to-high-risk gamblers and 26 non-problem gamblers community-recruited via multiple channels (i.e., internet and newspaper advertisements, land-based flyers, and university recruitment portals). Participants completed two online assessment sessions 6-months apart. Each session included (1) self-report measures of gambling behaviour (frequency, duration, and expenditure), (2) self-report assessment of problem gambling severity (PGSI), and (3) a gambling approach-avoidance task, utilising culturally relevant stimuli tailored to individual gambling habits. However, our study failed to replicate Boffo et al. (2018) findings in a Canadian sample. Relative to non-problem gamblers, moderate-to-high-risk gamblers did not exhibit greater approach bias tendencies towards gambling-related stimuli compared to neutral stimuli. Moreover, gambling approach bias was not predictive of prospective gambling behaviour (frequency, duration, or expenditure) or severity of gambling problems. Reported results do not provide evidence for approach tendencies contributing to problematic gambling behaviour in a Canadian sample of moderate-to-high-risk gamblers compared to non-problematic gambler controls. Further replications on the topic are needed. Future research should evaluate approach tendencies within the gambling context, considering the potential impact of task reliability to assess approach bias in light of individual gambling modality preferences.

Can we measure individual differences in cognitive measures reliably via smartphones? A comparison of the flanker effect across device types and samples.

Research deployed via the internet and administered via smartphones could have access to more diverse samples than lab-based research. Diverse samples could have relatively high variation in their traits and so yield relatively reliable measurements of individual differences in these traits. Several cognitive tasks that originated from the experimental research tradition have been reported to yield relatively low reliabilities (Hedge et al., 2018) in samples with restricted variance (students). This issue could potentially be addressed by smartphone-mediated administration in diverse samples. We formulate several criteria to determine whether a cognitive task is suitable for individual differences research on commodity smartphones: no very brief or precise stimulus timing, relative response times (RTs), a maximum of two response options, and a small number of graphical stimuli. The flanker task meets these criteria. We compared the reliability of individual differences in the flanker effect across samples and devices in a preregistered study. We found no evidence that a more diverse sample yields higher reliabilities. We also found no evidence that commodity smartphones yield lower reliabilities than commodity laptops. Hence, diverse samples might not improve reliability above student samples, but smartphones may well measure individual differences with cognitive tasks reliably. Exploratively, we examined different reliability coefficients, split-half reliabilities, and the development of reliability estimates as a function of task length.

jsQuestPlus: A JavaScript implementation of the QUEST+ method for estimating psychometric function parameters in online experiments.

The two Bayesian adaptive psychometric methods named QUEST (Watson & Pelli, 1983) and QUEST+ (Watson, 2017) are widely used to estimate psychometric parameters, especially the threshold, in laboratory-based psychophysical experiments. Considering the increase of online psychophysical experiments in recent years, there is a growing need to have the QUEST and QUEST+ methods available online as well. We developed JavaScript libraries for both, with this article introducing one of them: jsQuestPlus. We offer integrations with online experimental tools such as jsPsych (de Leeuw, 2015), PsychoPy/JS (Peirce et al., 2019), and lab.js (Henninger et al., 2021). We measured the computation time required by jsQuestPlus under four conditions. Our simulations on 37 browser-computer combinations showed that the mean initialization time was 461.08 ms, 95% CI [328.29, 593.87], the mean computation time required to determine the stimulus parameters for the next trial was less than 1 ms, and the mean update time was 79.39 ms, 95% CI [46.22, 112.55] even in extremely demanding conditions. Additionally, psychometric parameters were estimated as accurately as the original QUEST+ method did. We conclude that jsQuestPlus is fast and accurate enough to conduct online psychophysical experiments despite the complexity of the matrix calculations. The latest version of jsQuestPlus can be downloaded freely from https://github.com/kurokida/jsQuestPlus under the MIT license.

Methods to split cognitive task data for estimating split-half reliability: A comprehensive review and systematic assessment.

Estimating the reliability of cognitive task datasets is commonly done via split-half methods. We review four methods that differ in how the trials are split into parts: a first-second half split, an odd-even trial split, a permutated split, and a Monte Carlo-based split. Additionally, each splitting method could be combined with stratification by task design. These methods are reviewed in terms of the degree to which they are confounded with four effects that may occur in cognitive tasks: effects of time, task design, trial sampling, and non-linear scoring. Based on the theoretical review, we recommend Monte Carlo splitting (possibly in combination with stratification by task design) as being the most robust method with respect to the four confounds considered. Next, we estimated the reliabilities of the main outcome variables from four cognitive task datasets, each (typically) scored with a different non-linear algorithm, by systematically applying each splitting method. Differences between methods were interpreted in terms of confounding effects inflating or attenuating reliability estimates. For three task datasets, our findings were consistent with our model of confounding effects. Evidence for confounding effects was strong for time and task design and weak for non-linear scoring. When confounding effects occurred, they attenuated reliability estimates. For one task dataset, findings were inconsistent with our model but they may offer indicators for assessing whether a split-half reliability estimate is appropriate. Additionally, we make suggestions on further research of reliability estimation, supported by a compendium R package that implements each of the splitting methods reviewed here.

Subtypes of smokers in a randomized controlled trial of a web-based smoking cessation program and their role in predicting intervention non-usage attrition: Implications for the development of tailored interventions.

INTRODUCTION: Web-based smoking interventions hold potential for smoking cessation; however, many of them report low intervention usage (i.e., high levels of non-usage attrition). One strategy to counter this issue is to tailor such interventions to user subtypes if these can be identified and related to non-usage attrition outcomes. The aim of this study was two-fold: (1) to identify and describe a smoker typology in participants of a web-based smoking cessation program and (2) to explore subtypes of smokers who are at a higher risk for non-usage attrition (i.e., early dropout times). METHODS: We conducted secondary analyses of data from a large randomized controlled trial (RCT) that investigated effects of a web-based Cognitive Bias Modification intervention in adult smokers. First, we conducted a two-step cluster analysis to identify subtypes of smokers based on participants' baseline characteristics (including demographics, psychological and smoking-related variables, N = 749). Next, we conducted a discrete-time survival analysis to investigate the predictive value of the subtypes on time until dropout. RESULTS: We found three distinct clusters of smokers: Cluster 1 (25.2%, n = 189) was characterized by participants being relatively young, highly educated, unmarried, light-to-moderate smokers, poly-substance users, and relatively high scores on sensation seeking and impulsivity; Cluster 2 (41.0%, n = 307) was characterized by participants being older, with a relatively high socio-economic status (SES), moderate-to-heavy smokers and regular drinkers; Cluster 3 (33.8%, n = 253) contained mostly females of older age, and participants were further characterized by a relatively low SES, heavy smoking, and relatively high scores on hopelessness, anxiety sensitivity, impulsivity, depression, and alcohol use. Additionally, Cluster 1 was more likely to drop out at the early stage of the intervention compared to Cluster 2 (adjusted Hazard Ratio (HR adjusted) = 1.51, 95% CI = [1.25, 1.83]) and Cluster 3 (HR adjusted = 1.52, 95% CI = [1.25, 1.86]). CONCLUSIONS: We identified three clusters of smokers that differed on a broad range of characteristics and on intervention non-usage attrition patterns. This highlights the heterogeneity of participants in a web-based smoking cessation program. Also, it supports the idea that such interventions could be tailored to these subtypes to prevent non-usage attrition. The subtypes of smokers identified in this study need to be replicated in the field of e-health outside the context of RCT; based on the smoker subtypes identified in this study, we provided suggestions for developing tailored web-based smoking cessation intervention programs in future research.

Combining Web-Based Attentional Bias Modification and Approach Bias Modification as a Self-Help Smoking Intervention for Adult Smokers Seeking Online Help: Double-Blind Randomized Controlled Trial.

BACKGROUND: Automatically activated cognitive motivational processes such as the tendency to attend to or approach smoking-related stimuli (ie, attentional and approach bias) have been related to smoking behaviors. Therefore, these cognitive biases are thought to play a role in maintaining smoking behaviors. Cognitive biases can be modified with cognitive bias modification (CBM), which holds promise as an easy-access and low-cost online intervention. However, little is known about the effectiveness of online interventions combining two varieties of CBM. Targeting multiple cognitive biases may improve treatment outcomes because these biases have been shown to be relatively independent. OBJECTIVE: This study aimed to test the individual and combined effects of two web-based CBM varieties-attentional bias modification (AtBM) and approach bias modification (ApBM)-in a double-blind randomized controlled trial (RCT) with a 2 (AtBM: active versus sham) × 2 (ApBM: active versus sham) factorial design. METHODS: A total of 504 adult smokers seeking online help to quit smoking were randomly assigned to 1 of 4 experimental conditions to receive 11 fully automated CBM training sessions. To increase participants' intrinsic motivation to change their smoking behaviors, all participants first received brief, automated, tailored feedback. The primary outcome was point prevalence abstinence during the study period. Secondary outcomes included daily cigarette use and attentional and approach bias. All outcomes were repeatedly self-assessed online from baseline to the 3-month follow-up. For the examination of training effects on outcome changes, an intention-to-treat analysis with a multilevel modeling (MLM) approach was adopted. RESULTS: Only 10.7% (54/504) of the participants completed all 11 training sessions, and 8.3% (42/504) of the participants reached the 3-month follow-up assessment. MLM showed that over time, neither AtBM or ApBM nor a combination of both differed from their respective sham training in point prevalence abstinence rates (P=.17, P=.56, and P=.14, respectively), and in changes in daily cigarette use (P=.26, P=.08, and P=.13, respectively), attentional bias (P=.07, P=.81, and P=.15, respectively), and approach bias (P=.57, P=.22, and P=.40, respectively), while daily cigarette use decreased over time across conditions for all participants (P<.001). CONCLUSIONS: This RCT provides no support for the effectiveness of combining AtBM and ApBM in a self-help web-based smoking cessation intervention. However, this study had a very high dropout rate and a very low frequency of training usage, indicating an overall low acceptability of the intervention, which precludes any definite conclusion on its efficacy. We discuss how this study can inform future designs and settings of online CBM interventions. TRIAL REGISTRATION: Netherlands Trial Register NTR4678; https://www.trialregister.nl/trial/4678.

Mental chronometry in the pocket? Timing accuracy of web applications on touchscreen and keyboard devices.

Web applications can implement procedures for studying the speed of mental processes (mental chronometry) and can be administered via web browsers on most commodity desktops, laptops, smartphones, and tablets. This approach to conducting mental chronometry offers various opportunities, such as increased scale, ease of data collection, and access to specific samples. However, validity and reliability may be threatened by less accurate timing than specialized software and hardware can offer. We examined how accurately web applications time stimuli and register response times (RTs) on commodity touchscreen and keyboard devices running a range of popular web browsers. Additionally, we explored the accuracy of a range of technical innovations for timing stimuli, presenting stimuli, and estimating stimulus duration. The results offer some guidelines as to what methods may be most accurate and what mental chronometry paradigms may suitably be administered via web applications. In controlled circumstances, as can be realized in a lab setting, very accurate stimulus timing and moderately accurate RT measurements could be achieved on both touchscreen and keyboard devices, though RTs were consistently overestimated. In uncontrolled circumstances, such as researchers may encounter online, stimulus presentation may be less accurate, especially when brief durations are requested (of up to 100 ms). Differences in RT overestimation between devices might not substantially affect the reliability with which group differences can be found, but they may affect reliability for individual differences. In the latter case, measurement via absolute RTs can be more affected than measurement via relative RTs (i.e., differences in a participant's RTs between conditions).

Effectiveness of two web-based cognitive bias modification interventions targeting approach and attentional bias in gambling problems: study protocol for a pilot randomised controlled trial.

BACKGROUND: Disordered gamblers have phenotypical and pathological similarities to those with substance use disorders (SUD), including exaggerated automatic cognitive processing of motivationally salient gambling cues in the environment (i.e., attentional and approach bias). Cognitive bias modification (CBM) is a family of computerised interventions that have proved effective in successfully re-training these automatic cognitive biases in SUD. CBM interventions can, in principle, be administered online, thus showing potential of being a low-cost, low-threshold addition to conventional treatments. This paper presents the design of a pilot randomised controlled trial exploring the effectiveness of two web-based CBM interventions targeting attentional and approach bias towards gambling cues in a sample of Dutch and Belgian problematic and pathological gamblers. METHODS/DESIGN: Participants (N = 182) are community-recruited adults experiencing gambling problems, who have gambled at least twice in the past 6 months and are motivated to change their gambling behaviour. After a baseline assessment session, participants are randomly assigned to one of four experimental conditions (attentional or approach bias training, or the placebo version of the two trainings) and complete six sessions of training. At baseline and before each training session, participants receive automated personalised feedback on their gambling motives and reasons to quit or reduce gambling. The post-intervention, 1-month, and 3-month follow-up assessments will examine changes in gambling behaviour, with frequency and expenditure as primary outcomes, and depressive symptoms and gambling-related attentional and approach biases as secondary outcomes. Secondary analyses will explore possible moderators (interference control capacity and trait impulsivity) and mediators (change in cognitive bias) of training effects on the primary outcomes. DISCUSSION: This study is the first to explore the effectiveness of an online CBM intervention for gambling problems. The results of this study can be extremely valuable for developing e-health interventions for gambling problems and further understanding the role of motivational implicit cognitive processes underlying problematic gambling behaviour. TRIAL REGISTRATION: Netherlands Trial Register, NTR5096 . Registered on 11 March 2015.

A randomized controlled trial of Web-based Attentional Bias Modification to help smokers quit.

OBJECTIVE: To assess the efficacy of a multiple-sessions Web-based Attentional Bias Modification (ABM) self-help intervention in 434 smokers who made a quit-attempt. METHOD: Respondents were randomized to receive 6 sessions of ABM- or placebo-training in a period of 2 weeks. Smoking-related cognitions (e.g., self-efficacy and intention to quit) and cognitive biases (i.e., attentional and approach bias) for smoking-cues were assessed before training (pretest). Primary outcome-variable was continued abstinence, 6 months after baseline. Bias reduction at the posttraining assessment was the secondary outcome. A 2 × 2 mixed analysis of variance (ANOVA) and logistic regression analyses were conducted using the whole sample (N = 434) as well as subsamples of light to moderate smokers (<15 cigarettes, N = 115) and heavy smokers (15 or more cigarettes, N = 319). Conservative analyses (coding drop-outs as smokers) as well as complete case analyses were conducted. RESULTS: The ABM training had no significant effect regarding bias reduction and no behavioral effects in the whole sample of smokers. Subsample analyses revealed a significant positive effect on continued abstinence in heavy smokers only (complete case analyses: odds ratio [OR] = 3.15; p = .02; confidence interval [CI] = 1.24-7.99; conservative analyses: OR = 2.49; p = .02; CI = 1.13-5.48). CONCLUSION: Web-based ABM training is ineffective in fostering cognitive bias reduction and continued smoking abstinence. However, the positive effects in heavy smokers-as indicated by exploratory subsample analyses-warrant further research into the potential of multiple sessions ABM training to foster continued smoking abstinence in heavy smokers who make a quit-attempt. (PsycINFO Database Record

Validation of the Amsterdam Beverage Picture Set: A Controlled Picture Set for Cognitive Bias Measurement and Modification Paradigms.

BACKGROUND: Alcohol research may benefit from controlled and validated picture sets. We have constructed the Amsterdam Beverage Picture Set (ABPS), which was designed for alcohol research in general and cognitive bias measurement and modification in particular. Here, we first formulate a position on alcohol stimulus validity that prescribes that alcohol-containing pictures, compared to nonalcohol-containing pictures, should induce a stronger urge to drink in heavy drinkers than in light drinkers. Because a perceptually simple picture might induce stronger cognitive biases but the presence of a drinking context might induce a stronger urge to drink, the ABPS contains pictures with and without drinking context. By limiting drinking contexts to simple consumption scenes instead of real-life scenes, complexity was minimized. A validation study was conducted to establish validity, to examine ABPS drinking contexts, and to explore the role of familiarity, valence, arousal, and control. METHODS: Two hundred ninety-one psychology students completed the Alcohol Use Disorders Identification Test, as well as rating and recognition tasks for a subset of the ABPS pictures. RESULTS: The ABPS was well-recognized, familiar, and heavy drinkers reported a greater urge to drink in response to the alcohol-containing pictures only. Alcohol presented in drinking context did not elicit a stronger urge to drink but was recognized more slowly than alcohol presented without context. CONCLUSIONS: The ABPS was found to be valid, although pictures without context might be preferable for measuring cognitive biases than pictures with context. We discuss how an explicit approach to picture construction may aid in creating variations of the ABPS. Finally, we describe how ABPS adoption across studies may allow more reproducible and comparable results across paradigms, while allowing researchers to apply picture selection criteria that correspond to a wide range of theoretical positions. The latter is exemplified by ABPS derivatives and adoptions that are currently under way.

Executive Functions and Motivation as Moderators of the Relationship Between Automatic Associations and Alcohol Use in Problem Drinkers Seeking Online Help.

BACKGROUND: Dual process models posit that problem drinking is maintained by an imbalance between relatively strong automatic processes and weak controlled processes, a combination of executive functions and motivation. Few studies have examined how the interplay between automatic processes and executive functions is affected by motivation to change. This study examined this relationship in problem drinkers seeking online help to change their alcohol use. It was expected that executive functions (i.e., working memory, response inhibition) would moderate the relationship between automatic (valence and approach) associations and alcohol use and that this effect would be stronger in individuals with strong motivation to change. METHODS: A sample of 302 problem drinkers (mean age: 51.7 years) participated in this study as part of the baseline assessment before an Internet intervention. Participants completed an online version of the brief Implicit Association Test (valence and approach associations), the self-ordered pointing task (working memory), the Stroop task (response inhibition), the Readiness to Change Questionnaire (motivation to change), and the Timeline Follow-Back Questionnaire (alcohol use). Hierarchical moderated regression analysis was used to test the 4 hypothesized 3-way interactions. RESULTS: As expected, the interaction between valence associations and working memory only predicted alcohol use among individuals with strong motivation. This pattern was neither found for response inhibition nor for approach associations. CONCLUSIONS: Results provide partial support for the moderating role of motivation in the interplay between automatic processes and executive functions. Future studies should investigate this relationship in participants with the full range of motivation and alcohol use.

Weaknesses in executive functioning predict the initiating of adolescents' alcohol use.

Recently, it has been suggested that impairments in executive functioning might be risk factors for the onset of alcohol use rather than a result of heavy alcohol use. In the present study, we examined whether two aspects of executive functioning, working memory and response inhibition, predicted the first alcoholic drink and first binge drinking episode in young adolescents using discrete survival analyses. Adolescents were selected from several Dutch secondary schools including both mainstream and special education (externalizing behavioral problems). Participants were 534 adolescents between 12 and 14 years at baseline. Executive functioning and alcohol use were assessed four times over a period of two years. Working memory uniquely predicted the onset of first drink (p=.01) and first binge drinking episode (p=.04) while response inhibition only uniquely predicted the initiating of the first drink (p=.01). These results suggest that the association of executive functioning and alcohol consumption found in former studies cannot simply be interpreted as an effect of alcohol consumption, as weaknesses in executive functioning, found in alcohol naïve adolescents, predict the initiating of (binge) drinking. Though, prolonged and heavy alcohol use might further weaken already existing deficiencies.

Combining cognitive bias modification training with motivational support in alcohol dependent outpatients: study protocol for a randomised controlled trial.

BACKGROUND: Addiction research has hypothesised that automatic and reflective cognitive processes play an important role in the onset and maintenance of alcohol (ab)use, wherein automatic reactions to drug-related cues steer the drug user towards consuming before reflective processes can get over and steer towards a different behavioural response. These automatic processes include the tendency to attend and approach alcohol cues. These biases may be trained away from alcohol via computerised cognitive bias modification (CBM). The present protocol describes the design of a double-blind randomised controlled trial (RCT) testing the effectiveness of attentional bias and approach bias re-training with a 2×2 factorial design, alongside a brief motivational support (MS) program. METHODS/DESIGN: Participants (n = 120) are adult alcohol dependent outpatients, recruited from a public health service for addiction in Italy, who have been abstinent for at least two months, and with a main diagnosis of alcohol dependence disorder. Participants are randomly assigned to one of four experimental conditions and complete 11 sessions of training after a baseline assessment. The MS takes place before each training session. Post-intervention and three-month follow-up assessments examine the change in clinical outcome variables and attentional and approach biases (measured with the Visual Probe Task and the Approach-Avoidance Task, respectively). Alcohol approach-avoidance implicit memory associations (measured with the Brief Implicit Association Test) are also evaluated at pre- and post-intervention to explore generalisation effects. Primary outcome measure is relapse rate at follow-up. Secondary outcome measures include change in cognitive biases, in alcohol-related implicit memory associations, and in the clinical variables assessed. An exploratory analysis is also planned to detect interaction effects between the CBM modules and possible moderators (interference control capacity, gender, age, number of previous detoxifications) and mediators (change in cognitive bias) of the primary outcome measure. DISCUSSION: This RCT is the first to test the effectiveness of a combined CBM intervention alongside motivational support in alcohol-dependent outpatients. The results of this study can be extremely valuable for future research in the optimisation of CBM treatment for alcohol addiction. TRIAL REGISTRATION: Current Controlled Trials ISRCTN01005959 (registration date: 24 October 2013).

Interactions between parental alcohol-specific rules and risk personalities in the prediction of adolescent alcohol use.

AIMS: To examine the impact of an important context variable (alcohol-specific parental rules) and an important person variable (risky personality traits) and their interaction on prospective adolescent drinking. METHODS: Participants were 252 adolescents, 67.9% female, between 13 and 16 years old. Data were collected via online assessments during 2 years with four time points of assessments. We examined membership of alcohol use trajectories as a function of parental alcohol-specific rules, moderated by risk-associated personality traits. RESULTS: Permissive parental rules predicted early onset and trajectories of heavy drinking. High scores on Sensation Seeking and Hopelessness also predicted early onset and heavy drinking, but there was no evidence for moderation. CONCLUSION: The influence of parental rule setting and risk personality was confirmed, but no evidence was found that the impact of risk personality on adolescent drinking is moderated by parental rules. Implications of these findings, and limitations of the study, are discussed.

The role of reversal frequency in learning noisy second order conditional sequences.

The hallmark of implicit learning is that complex knowledge can be acquired unconsciously. The second order conditionals (SOCs) of Reed and Johnson (1994) were developed to be complex, and they are popular materials for implicit learning research. Recently, it was demonstrated that in a sequence made noisy (by combining two SOCs), shared features of the SOCs may be learned explicitly (Fu, Fu, & Dienes, 2008). What are these shared features? We hypothesized that low reversal frequency may play a significant role. We have varied reversal frequency, and discovered that reversal frequency affected response times, inclusion exclusion behavior, and recognition ratings. Not only does it appear to be important to distinguish implicit and explicit knowledge, but also to distinguish what the knowledge is of.