Effects of attention training on self-reported, implicit, physiological and behavioural measures of spider fear

Attention and interpretation cognitive bias change: A systematic review and meta-analysis of bias modification paradigms

This systematic review and meta-analysis examines the effect of Cognitive Bias Modification for attention (CBM-A) and interpretation (CBM-I) on reducing the targeted biases and investigates moderators of each approach. PsycINFO, PsychArticles, and PubMED databases were searched for randomized-controlled studies published before March 2020 with pre- and post-CBM cognitive bias outcome measures, resulting in 91 CBM-A (n = 5914 individuals) and 70 CBM-I samples (n = 4802 individuals). Random-effects models and Hedge's g calculation showed significant medium overall effects of bias reduction with moderate to high heterogeneity (CBM-A g = 0.49 [0.36, 0.64], I² = 85.19%; CBM-I g = 0.58 [0.48, 0.68], I² = 70.92%). Effect sizes did not differ between approaches and remained significant after trim-and-fill adjustment for possible publication bias. Moderator variables were investigated with meta-regression and subgroup analyses. Participant age, symptom type, control condition and number of trials moderated CBM-A; student and clinical status moderated CBM-I effect size. Results support attention and interpretation modification in controlled laboratory and variable (online) training settings for non-clinical and clinical samples across various symptom types (anxiety, depression, substance use, eating disorders). Further empirical evidence is necessary to determine optimal sample and methodological combinations most strongly associated with adaptive behavioral outcomes.

Capturing the dynamics of peripersonal space by integrating expectancy effects and sound propagation properties

BACKGROUND

Humans perceive near space and far space differently. Peripersonal space (PPS), i.e. the space directly surrounding the body, is often studied using paradigms based on audiotactile integration. In these paradigms, reaction time (RT) to a tactile stimulus is measured in the presence of a concurrent auditory looming stimulus.

NEW METHOD

We propose here to refine the experimental procedure by disentangling behavioral contributions of the targeted audiotactile integration mechanisms from expectancy effects. To this aim, we added to the protocol a baseline with a fixed sound distance. Furthermore, in order to improve the relevance of the audiotactile integration measures, we took into account sound propagation properties and assessed RTs for logarithmically spaced auditory distances.

RESULTS

Expectation contributed significantly to overall behavioral responses. Subtracting it isolated the audiotactile effect due to the stimulus proximity. This revealed that audiotactile integration effects have to be tested on a logarithmic scale of distances, and that they follow a linear variation on this scale.

COMPARISON WITH EXISTING METHOD(S)

The current method allows cleaner and more pertinent sampling measures for evaluating audiotactile integration phenomena linked to PPS. Furthermore, most of the existing methods propose a sigmoid fitting, which rests on the intuitive framework that PPS is an in-or-out zone. Our results suggest that behavioral effects follow a logarithmic decrease, thus a response graduated in space.

CONCLUSIONS

The proposed protocol design and method of analysis contribute to sharpen the experimental investigation of the factors influencing and modifying multisensory integration phenomena in the space surrounding the body.

Anxiety-Linked Attentional Bias: Is It Reliable?

There is substantial evidence that heightened anxiety vulnerability is characterized by increased selective attention to threatening information. The reliability of this anxiety-linked attentional bias has become the focus of considerable recent interest. We distinguish between the potential inconsistency of anxiety-linked attentional bias and inconsistency potentially reflecting the psychometric properties of the assessment approaches used to measure it. Though groups with heightened anxiety vulnerability often exhibit, on average, elevated attention to threat, the evidence suggests that individuals are unlikely to each display a stable, invariant attentional bias to threat. Moreover, although existing assessment approaches can differentiate between groups, they do not exhibit the internal consistency or test-retest reliability necessary to classify individuals in terms of their characteristic pattern of attentional responding to threat. We discuss the appropriate uses of existing attentional bias assessment tasks and propose strategies for enhancing classification of individuals in terms of their tendency to display an attentional bias to threat.

The effects of attentional bias modification on emotion regulation

BACKGROUND AND OBJECTIVES

In two experiments, we investigated the effects of Attentional Bias Modification (ABM) on emotion regulation, i.e. the manner in which people influence emotional experiences. We hypothesized that decreases in attentional bias to threat would impair upregulation and improve downregulation of negative emotions, while increases in attentional bias to threat would improve upregulation and impair downregulation of negative emotions.

METHODS

Using the emotion-in-motion paradigm (Experiment 1, N = 60) and the visual search task (Experiment 2, N = 58), we trained participants to attend to either threatening or positive stimuli and we assessed emotion intensity while observing, upregulating, and downregulating emotions in response to grids of mixed emotional pictures.

RESULTS

In Experiment 1, the attend positive group reported more positive emotions while merely watching grids of training pictures and the attend threat group showed impaired upregulation of negative affect. In Experiment 2, the attend threat group reported intensified negative emotions for all three instructions, while the attend positive group remained largely stable over time.

LIMITATIONS

We cannot unequivocally attribute these changes in emotion regulation to changes in attentional bias, as neither of the experiments yielded significant changes in attentional bias to threat.

CONCLUSIONS

By showing that attentional bias modification procedures affect the manner in which people deal with emotions, we add empirical weight to the conceptual overlap between attentional bias modification and emotion regulation.

What is so frightening about spiders? Self-rated and self-disclosed impact of different characteristics and associations with phobia symptoms

Spider phobia is a common and impairing mental disorder, yet little is known about what characteristics of spiders that spider phobic individuals find frightening. Using screening data from a clinical trial, we explored which characteristics that spider-fearful individuals (n = 194) rated as having the greatest impact on fear, used factor analysis to group specific characteristics, and explored linear associations with self-reported phobia symptoms. Second, a guided text-mining approach was used to extract the most common words in free-text responses to the question: "What is it about spiders that you find frightening?" Both analysis types suggested that movement-related characteristics of spiders were the most important, followed by appearance characteristics. There were, however, no linear associations with degree of phobia symptoms. Our findings reveal the importance of targeting movement-related fears in in-vivo exposure therapy for spider phobia and using realistically animated spider stimuli in computer-based experimental paradigms and clinical interventions such as Virtual Reality exposure therapy.

Habituation of self-reported anxiety and cortical hyper-vigilance during image-based exposure to spiders

BACKGROUND AND OBJECTIVES

The aim of the study was to examine habituation of subjective anxiety and electrophysiological correlates of cortical hyper-vigilance during exposure to spider images among high (n = 12) and low (n = 11) spider fear groups.

METHODS

Participants viewed a six-stage hierarchy of spider images. The images used at stage 1 and stage 6 were the same. Subjective anxiety was rated at four intervals during each three-minute exposure stage (0, 60, 120, and 180 s) and event-related potentials (ERPs) were averaged across these epochs (0-60, 60-120, 120-180).

RESULTS

High spider fearfuls demonstrated greater habituation of self-reported anxiety within and between exposure stages compared to low fearfuls. Consistent with attentional hyper-vigilance, the high-fear group also demonstrated greater P1 amplitude in response to spider images. In both groups, habituation of P1 amplitude was found at later relative to earlier stages, but increased at stage six when the stage 1 image was re-presented, despite low subjective anxiety.

LIMITATIONS

While the passive viewing paradigm mirrored image-based exposure, it was not possible to determine whether participants engaged in avoidance strategies. In addition, further research is needed to assess the relevance of habituation and reinstatement of P1 amplitude to therapeutic outcome.

CONCLUSIONS

Habituation of subjective anxiety during image-based exposure is not necessarily accompanied by a reduction in measures of cortical hyper-vigilance. The reinstatement of the P1 response may indicate either re-activation of previous associations, less avoidance, or a more generalised dishabituation mechanism.

Attentional bias modification based on visual probe task: methodological issues, results and clinical relevance

INTRODUCTION

Attentional bias, the tendency that a person has to drive or maintain attention to a specific class of stimuli, may play an important role in the etiology and persistence of mental disorders. Attentional bias modification has been studied as a form of additional treatment related to automatic processing.

OBJECTIVES

This systematic literature review compared and discussed methods, evidence of success and potential clinical applications of studies about attentional bias modification (ABM) using a visual probe task.

METHODS

The Web of Knowledge, PubMed and PsycInfo were searched using the keywords attentional bias modification, attentional bias manipulation and attentional bias training. We selected empirical studies about ABM training using a visual probe task written in English and published between 2002 and 2014.

RESULTS

Fifty-seven studies met inclusion criteria. Most (78%) succeeded in training attention in the predicted direction, and in 71% results were generalized to other measures correlated with the symptoms.

CONCLUSIONS

ABM has potential clinical utility, but to standardize methods and maximize applicability, future studies should include clinical samples and be based on findings of studies about its effectiveness.

Attention bias modification via single-session dot-probe training: Failures to replicate

BACKGROUND AND OBJECTIVES

Across three experiments we investigated transfer effects of single-session attention bias modification via dot-probe training.

METHODS

In experiment 1, participants received training either toward or away from negative images or no-training, and transfer to an affective task-switching task was examined. In two other experiments, participants were trained to orient attention toward either positive or negative words (experiment 2a) or facial expressions (experiment 2b), and transfer to an interpretation bias task was examined.

RESULTS

In all experiments, the dot-probe training procedure did not effectively modify biases in attention allocation at the training condition level, but produced a large variability in individual attention bias acquisition within and across conditions. Individual differences in pre-training attention bias and attention bias acquisition were not related to performance on the affective task-switching task or the interpretation tasks.

LIMITATIONS

The present investigations are limited by the lack of effectiveness of ABM at the condition level, the order in which transfer tasks were administered, and the restricted range of affective symptoms that could moderate training and transfer effects.

CONCLUSIONS

The findings from three experiments provided no evidence for single-session dot-probe ABM procedures to effectively manipulate attention bias toward negative, away from negative, or toward positive stimuli at a training condition level. At the individual differences level of analysis, again no evidence was found for transfer of attention training. The observations invite further empirical scrutiny into factors that moderate attentional plasticity in response to dot-probe ABM procedures to optimize the conditions for effective implementation and transfer of training.

Investigating the efficacy of attention bias modification in reducing high spider fear: The role of individual differences in initial bias

BACKGROUND AND OBJECTIVES

Attention Bias Modification (ABM) targets attention bias (AB) towards threat and is a potential therapeutic intervention for anxiety. The current study investigated whether initial AB (towards or away from spider images) influenced the effectiveness of ABM in spider fear.

METHODS

AB was assessed with an attentional probe task consisting of spider and neutral images presented simultaneously followed by a probe in spider congruent or spider incongruent locations. Response time (RT) differences between spider and neutral trials > 25 ms was considered 'Bias Toward' threat. RT difference < - 25 ms was considered 'Bias Away' from threat, and a difference between -25 ms and +25 ms was considered 'No Bias'. Participants were categorized into Initial Bias groups using pre-ABM AB scores calculated at the end of the study. 66 participants' (Bias Toward n = 27, Bias Away n = 18, No Bias n = 21) were randomly assigned to ABM-active training designed to reduce or eliminate a bias toward threat and 61 (Bias Toward n = 17, Bias Away n = 18, No Bias n = 26) to ABM-control.

RESULTS

ABM-active had the largest impact on those demonstrating an initial Bias Towards spider images in terms of changing AB and reducing Spider Fear Vulnerability, with the Bias Away group experiencing least benefit from ABM. However, all Initial Bias groups benefited equally from active ABM in a Stress Task.

LIMITATIONS

Participants were high spider fearful but not formally diagnosed with a specific phobia. Therefore, results should be confirmed within a clinical population.

CONCLUSIONS

Individual differences in Initial Bias may be an important determinant of ABM efficacy.

Attention bias modification in specific fears: Spiders versus snakes

BACKGROUND AND OBJECTIVES

Attention Bias Modification (ABM) is used to manipulate attention biases in anxiety disorders. It has been successful in reducing attention biases and anxious symptoms in social anxiety and generalized anxiety, but not yet in specific fears and phobias.

METHODS

We designed a new version of the dot-probe training task, aiming to train fearful participants' attention away from or towards pictures of threatening stimuli. Moreover, we studied whether the training also affected participants' avoidance behavior and their physical arousal upon being confronted with a real threat object.

RESULTS

In Experiment 1, students with fear of spiders were trained. We found that the attention manipulation was successful, but the training failed to affect behavior or arousal. In Experiment 2, the same procedure was used on snake-fearful students. Again, attention was trained in the expected directions. Moreover, participants whose attention had been trained away from snakes showed lower physiological arousal upon being confronted with a real snake.

LIMITATIONS

The study involved healthy students with normal distribution of the fear of spider/snake. Future research with clinical sample could help with determining the generalizability of the current findings.

CONCLUSIONS

The effect of ABM on specific phobia is still in question. The finding in the present study suggested the possibility to alter attentional bias with a dot-probe task with general positive stimuli and this training could even affect the behavior while encountering a real threat.

An integrative review of attention biases and their contribution to treatment for anxiety disorders

Models of exposure therapy, one of the key components of cognitive behavioral therapy for anxiety disorders, suggest that attention may play an important role in the extinction of fear and anxiety. Evidence from cognitive research suggests that individual differences may play a causal role in the onset and maintenance of anxiety disorders and so it is also likely to influence treatment. We review the evidence concerning attention and treatment outcomes in anxiety disorders. The evidence reviewed here suggests that that attention biases assessed at pre-treatment might actually predict improved response to treatment, and in particular that prolonged engagement with threat as measured in tasks such as the dot probe is associated with greater reductions in anxious symptoms following treatment. We examine this research within a fear learning framework, considering the possible role of individual differences in attention in the extinction of fear during exposure. Theoretical, experimental and clinical implications are discussed, particularly with reference to the potential for attention bias modification programs in augmenting treatment, and also with reference to how existing research in this area might inform best practice for clinicians.

Impact of Anodal and Cathodal Transcranial Direct Current Stimulation over the Left Dorsolateral Prefrontal Cortex during Attention Bias Modification: An Eye-Tracking Study

People with anxiety disorders show an attentional bias for threat (AB), and Attention Bias Modification (ABM) procedures have been found to reduce this bias. However, the underlying processes accounting for this effect remain poorly understood. One explanation suggests that ABM requires the modification of attention control, driven by the recruitment of the dorsolateral prefrontal cortex (DLPFC). In the present double-blind study, we examined whether modifying left DLPFC activation influences the effect of ABM on AB. We used transcranial direct current stimulation (tDCS) to directly modulate cortical excitability of the left DLPFC during an ABM procedure designed to reduce AB to threat. Anodal tDCS increases excitability, whereas cathodal tDCS decreases it. We randomly assigned highly trait-anxious individuals to one of three conditions: 1) ABM combined with cathodal tDCS, 2) ABM combined with anodal tDCS, or 3) ABM combined with sham tDCS. We assessed the effects of these manipulations on both reaction times and eye-movements on a task indexing AB. Results indicate that combining ABM and anodal tDCS over the left DLPFC reduces the total duration that participants' gaze remains fixated on threat, as assessed using eye-tracking measurement. However, in contrast to previous studies, there were no changes in AB from baseline to post-training for participants that received ABM without tDCS. As the tendency to maintain attention to threat is known to play an important role in the maintenance of anxiety, the present findings suggest that anodal tDCS over the left DLPFC may be considered as a promising tool to reduce the maintenance of gaze to threat. Implications for future translational research combining ABM and tDCS are discussed.

Computerized attention retraining for individuals with elevated health anxiety

BACKGROUND AND OBJECTIVES

Current cognitive-behavioral theorists conceptualize hypochondriasis as excessive health anxiety (HA). Growing evidence suggests that elevated HA is associated with attentional bias (AB) toward potential health-threat information.

DESIGN

This study aimed to examine the effects of attention retraining among individuals with elevated HA, using the established attention modification programs (AMP) designed to train participants to disengage attention from ideographically chosen health-threat words.

METHODS

Thirty-six randomly assigned individuals with elevated HA completed eight twice-weekly sessions of the AMP (n = 18) or the attention control condition (ACC; n = 18).

RESULTS

Despite using the well-established AMP protocol widely used within the field of anxiety disorders, we did not find evidence for change in AB following training. Further, AMP did not outperform ACC in reducing HA and other relevant emotional symptoms. However, both AMP and ACC evidenced overall significant symptom reduction in most of the outcome measures, including overall HA, anxiety sensitivity, general depression and anxiety, and somatic complaints.

CONCLUSIONS

Further research is needed to better understand the effects and mechanisms of AMP as a possible cognitive intervention for HA.

Absence of evidence or evidence of absence: reflecting on therapeutic implementations of attentional bias modification

Attentional bias modification (ABM) represents one of a number of cognitive bias modification techniques which are beginning to show promise as therapeutic interventions for emotional pathology. Numerous studies with both clinical and non-clinical populations have now demonstrated that ABM can reduce emotional vulnerability. However, some recent studies have failed to achieve change in either selective attention or emotional vulnerability using ABM methodologies, including a recent randomised controlled trial by Carlbring et al. Some have sought to represent such absence of evidence as a sound basis not to further pursue ABM as an online intervention. While these findings obviously raise questions about the specific conditions under which ABM procedures will produce therapeutic benefits, we suggest that the failure of some studies to modify selective attention does not challenge the theoretical and empirical basis of ABM. The present paper seeks to put these ABM failures in perspective within the broader context of attentional bias modification research. In doing so it is apparent that the current findings and future prospects of ABM are in fact very promising, suggesting that more research in this area is warranted, not less.

Attentional bias in injection phobia: overt components, time course, and relation to behavior

Blood-injection-injury (BII) phobia is an anxiety disorder that can cause serious health consequences by interfering with medical treatment. Although attentional bias for threat appears to be a core feature of many anxiety disorders and a potential target of treatment, very little is known about attentional bias in BII phobia. In the present study, eye movements were recorded in individuals high and low in injection fear (HIF, LIF) during 18-s exposures to stimulus arrays containing injection, attack, appetitive, and neutral images. Evidence for attentional vigilance was mixed, as HIF individuals oriented to injection images more often than LIF individuals, but did not orient to injection images more often than other emotional images. In contrast, evidence of attentional avoidance was highly robust. HIF individuals rapidly disengaged from injection images on initial viewing and viewed these images less overall compared to other image types, a pattern not observed in the LIF group. Furthermore, attentional avoidance of injection threat was found to uniquely predict behavioral avoidance on an injection behavioral avoidance task (BAT), and group differences on the BAT were mediated by group differences in attentional avoidance. The implications of these findings for further delineating the nature and function of attentional biases in BII phobia are discussed.

Efficacy of attention bias modification using threat and appetitive stimuli: a meta-analytic review

Attention bias modification (ABM) protocols aim to modify attentional biases underlying many forms of pathology. Our objective was to conduct an effect size analysis of ABM across a wide range of samples and psychological problems. We conducted a literature search using PubMed, PsycInfo, and author searches to identify randomized studies that examined the effects of ABM on attention and subjective experiences. We identified 37 studies (41 experiments) totaling 2,135 participants who were randomized to training toward neutral, positive, threat, or appetitive stimuli or to a control condition. The effect size estimate for changes in attentional bias was large for the neutral versus threat comparisons (g=1.06), neutral versus appetitive (g=1.41), and neutral versus control comparisons (g=0.80), and small for positive versus control (g=0.24). The effects of ABM on attention bias were moderated by stimulus type (words vs. pictures) and sample characteristics (healthy vs. high symptomatology). Effect sizes of ABM on subjective experiences ranged from 0.03 to 0.60 for postchallenge outcomes, -0.31 to 0.51 for posttreatment, and were moderated by number of training sessions, stimulus type, and stimulus orientation (top/bottom vs. left/right). Fail-safe N calculations suggested that the effect size estimates were robust for the training effects on attentional biases, but not for the effect on subjective experiences. ABM studies using threat stimuli produced significant effects on attention bias across comparison conditions, whereas appetitive stimuli produced changes in attention only when comparing appetitive versus neutral conditions. ABM has a moderate and robust effect on attention bias when using threat stimuli. Further studies are needed to determine whether these effects are also robust when using appetitive stimuli and for affecting subjective experiences.

Eye tracking of attention in the affective disorders: a meta-analytic review and synthesis

A large body of research has demonstrated that affective disorders are characterized by attentional biases for emotional stimuli. However, this research relies heavily on manual reaction time (RT) measures that cannot fully delineate the time course and components of attentional bias. Eye tracking technology, which allows relatively direct and continuous measurement of overt visual attention, may provide an important supplement to RT measures. This article reviews eye tracking research on anxiety and depression, evaluating the experimental paradigms and eye movement indicators used to study attentional biases. Also included is a meta-analysis of extant eye tracking research (33 experiments; N=1579) on both anxiety and depression. Relative to controls, anxious individuals showed increased vigilance for threat during free viewing and visual search, and showed difficulty disengaging from threat in visual search tasks, but not during free viewing. In contrast, depressed individuals were not characterized by vigilance for threat during free viewing, but were characterized by reduced orienting to positive stimuli, as well as reduced maintenance of gaze on positive stimuli and increased maintenance of gaze on dysphoric stimuli. Implications of these findings for theoretical accounts of attentional bias in anxiety and depression are discussed, and avenues for future research using eye-tracking technology are outlined.

Interrelationships between spider fear associations, attentional disengagement and self-reported fear: a preliminary test of a dual-systems model

Recent conceptualisations of anxiety posit that equivocal findings related to the time-course of disengaging from threat-relevant stimuli may be attributable to individual differences in associative and rule-based processing. The current study was designed to test the hypothesis that strength of spider-fear associations would indirectly predict reported spider fear via impaired disengagement. One hundred and thirty-one undergraduate volunteer participants completed the Go/No-go Association Task, a visual search task, and self-report spider fear questionnaires. Stronger spider-fear associations were associated with reduced disengagement accuracy, whereas higher levels of reported spider fear were related to faster engagement with and disengagement from spiders. Bootstrapping multiple mediation analyses demonstrated that stronger-spider fear associations evidenced an indirect relationship with reported spider fear via reduced disengagement accuracy, highlighting the importance of fine-grained analyses of different aspects of cognitive bias. Results are discussed in terms of cognitive models of anxiety.

Limited transfer of threat bias following attentional retraining

BACKGROUND AND OBJECTIVES

Anxiety-related attentional bias for threat is considered an important risk factor for the development and maintenance of anxiety disorders. In line with this idea, recent studies have illustrated that experimentally induced changes in attentional bias have an impact on both non-clinical and clinical levels of anxiety. Still, little is known about the potential transfer of computerized training of attention to different components of attentional processing of threat.

METHODS

In the present study, we trained participants to either avoid or attend towards threatening pictures in a dot probe task, and we examined whether this attentional training transferred to a measure of emotional interference.

RESULTS

Despite our successful manipulation of attentional bias in the dot probe task, we found no generalization of the attentional training to the interference task.

LIMITATIONS

It is possible that our study lacked statistical power to reveal possible group differences in the interference task.

CONCLUSIONS

Our study shows that attentional training using the dot probe task may influence the amount of attention that is given to the spatial location of threat, but not necessarily the amount of attention that is given to the semantic content of stimuli.

Cognitive bias modification procedures in the management of mental disorders

PURPOSE OF REVIEW

To review recent research on the therapeutic impact of cognitive bias modification (CBM) procedures, designed to train direct change in the patterns of attentional and interpretive bias known to characterize particular forms of psychopathology.

RECENT FINDINGS

CBM designed to change attentional selectivity has proven capable of modifying attentional biases associated with emotional dysfunction, pain disorders, eating disorders and addictions. CBM designed to change interpretive selectivity has proven capable of modifying the tendency to resolve ambiguity in a negative manner that is characteristic of emotional dysfunction. Recent research confirms that both forms of CBM can alter the severity of symptoms associated with psychopathology. Extended delivery of such CBM approaches now has been shown to yield therapeutic benefits for a range of anxiety disorders, and in the case of CBM-A has augmented the efficacy of treatment for alcohol dependence.

SUMMARY

CBM approaches have passed the proof-of-concept stage, and recent small-scale trials attest to their likely clinical value. There is a pressing need for large-scale randomized controlled trials, to compare the efficacy of CBM with that of alternative approaches, and to identify how CBM can most effectively be integrated into multimodal treatment programs.

Cognitive bias modification approaches to anxiety

Clinical anxiety disorders and elevated levels of anxiety vulnerability are characterized by cognitive biases, and this processing selectivity has been implicated in theoretical accounts of these conditions. We review research that has sought to evaluate the causal contributions such biases make to anxiety dysfunction and to therapeutically alleviate anxiety using cognitive-bias modification (CBM) procedures. After considering the purpose and nature of CBM methodologies, we show that variants designed to modify selective attention (CBM-A) or interpretation (CBM-I) have proven capable of reducing anxiety vulnerability and ameliorating dysfunctional anxiety. In addition to supporting the causal role of cognitive bias in anxiety vulnerability and dysfunction and illuminating the mechanisms that underpin such bias, the findings suggest that CBM procedures may have therapeutic promise within clinical settings. We discuss key issues within this burgeoning field of research and suggest future directions CBM research should take to maximize its theoretical and applied value.