Researchers have used a wide range of methods borrowed from cognitive psychology to examine attention bias to threat in individuals with Generalized Anxiety Disorder (GAD;Mathews & MacLeod, 1985
; MacLeod, Mathews, & Tata, 1986
; Mogg, Millar, & Bradley, 2000
). Research using these methods has consistently produced evidence that patients with GAD preferentially attend to threat relevant stimuli over neutral stimuli when the two compete for processing priority.
In a seminal study, MacLeod, Mathews, and Tata (1986)
developed the probe detection paradigm to measure attention bias to threat in GAD. In this paradigm, participants see two words, one above the other, on a computer screen. One word is neutral (e.g., table), and the other word has a threatening meaning (e.g., disease). Participants are asked to read the upper word and ignore the lower word. On critical trials (25%), either the upper or the lower word is replaced with a dot probe (·) and participants are asked to signal the presence of the probe by pressing a button. MacLeod et al. (1986)
found that individuals with Generalized Anxiety Disorder detect probes that replace threat words, either in the upper or the lower portion of the screen, faster than probes that replace neutral words. Thus, clinically anxious individuals with GAD consistently showed an attention bias toward threat. On the other hand, non-anxious controls tended to demonstrate an attention bias away from threat in this paradigm. In a later replication of this study, MacLeod and Mathews (1988)
calculated an attention bias score in this paradigm by subtracting the mean response latency for trials where the probe replaced the threat stimuli from the mean response latency for trials where the probe replaced the neutral stimuli, such that larger numbers revealed greater bias for threat. Using this index, these authors again found that individuals with GAD show an attention bias toward threat.
Two recent reviews of attention bias in anxiety provide clear evidence for an attention bias for threat in GAD. Mogg and Bradley (2005)
reviewed 10 studies using the probe detection task and concluded that individuals with GAD show an attention bias for threat that is absent in non-anxious controls. A second meta-analysis conducted by Bar-Haim, Lamy, Pergamin, Bakermans-Kraneberg, and van IJzendoorn (2007)
examined attention bias across 172 studies (N = 2263 anxious, N = 1768 non-anxious), concluding that this bias is a consistent and reliable finding using a variety of paradigms. In summary, there is reason to believe that individuals with GAD have an attention bias toward threat relevant information that is absent or less pronounced in non-anxious individuals.
However, most existing research has not allowed the examination of the causal relationship between attention and generalized anxiety disorder because these studies have used correlational designs. Conclusions regarding the causal role of attention bias in maintaining anxiety can only be gleaned from research designs where participants are randomly assigned to conditions and their attention is experimentally manipulated. We now turn to studies using this design.
Macleod, Rutherford, Campbell, Ebsworthy, & Holker (2002)
selected 64 undergraduate students from a large participant pool who scored in the middle third of the distribution of a self-report measure of trait anxiety. These participants were then randomly assigned to one of two probe detection tasks that were designed to train attention. Each task comprised 672 trials in which pairs of words (one threat, one neutral) were presented, one above the other, on a computer screen. In the Attend Threat condition
, probes appeared in the position of the threat word on 576 training trials. The remaining 96 trials were designed to provide a measure of attention bias to threat words. In these test trials, threat word position and probe position were fully crossed as in a typical probe detection task, thus permitting measurement of a participant's tendency to attend preferentially to threat-relevant or neutral words. In the Attend Neutral condition
, probes appeared in the position of the neutral word on 576 of the trials, with the remaining 96 trials again providing a measure of attention bias. Participants were asked to indicate which type of probe (i.e., single dot or a double dot) had appeared in each trial by pressing a corresponding button as rapidly and accurately as they could. Following the training task and a brief (4 min) rest, the authors manipulated the participants' level of stress by presenting them with a series of unsolvable anagrams and telling them that video recordings of participants who performed particularly well or poorly would be shown to other students. Results indicated that after training participants in the Attend Threat condition showed faster response latencies for detecting probes that replaced threat words than probes that replaced neutral words. Participants in the Attend Neutral condition showed the opposite pattern of results. Moreover, this training extended to word pairs containing novel threat-relevant words and was not confined to specifically trained word pairs. More importantly, participants in the Attend Threat condition reported a greater elevation of negative emotion in response to an experimental stressor.
In their second study, MacLeod et al. (2002)
successfully replicated the findings of their first study. During this second study participants' levels of negative affect were measured prior to attention training as well as subsequent to training. This modification provided a baseline against which the effects of attention training could be compared. Results again showed that participants in the Attend Threat condition reported greater elevation of negative emotion in response to the experimental stressor than did those in the Attend Neutral condition. Groups did not differ in their levels of negative affect before the training procedure or after training prior to the stressor. Thus, the difference between the two groups appears to reflect the creation of differing affective vulnerability to stress that is manifested only after the presentation of the stressor. MacLeod et al. (2002)
suggested that their findings have potentially important theoretical and practical implications. At the theoretical level, their results provide the strongest support to date for the hypothesis that individual differences in the allocation of attention to threat-relevant information are causally important in mediating vulnerability to negative affectivity. At the practical level, it may be possible to utilize such attention training procedures clinically to ameliorate anxiety symptoms.
Although the results for the above study are consistent with the hypothesis that change in attention bias can lead to change in anxiety vulnerability, several issues need further examination. First, because the two conditions in the above studies both actively trained attention (i.e., either toward threat or away from threat), it is not possible to determine the effect of each training session compared to a baseline condition without training contingencies. Thus, in the current study we compared the effects of an Attention Modification Program (AMP) to a baseline condition where there was no contingency between the location of the probe and the location of the threat or neutral information. We predicted that the AMP would lead to decreased attention to threat and anxiety symptoms compared to the Attention Control Condition (ACC).
Second, although prior research has demonstrated effective attention training procedures in non-patient samples, researchers have not examined the role of attention training in clinical populations. Therefore, we sought to extend attention training procedures to populations with clinical levels of anxiety (i.e., GAD). Application of information processing bias modification to alleviating anxiety symptoms is important because a substantial portion of individuals with GAD presenting for treatment do not respond to current therapies (psychotherapy: 52%, Fisher & Durham 1999
; medication: 43%, Gorman, 2003
), and for many, the most effective treatments are unavailable or difficult to access. Although researchers have established a relationship between GAD and attention bias to threatening information, this knowledge has yet to be translated into effective treatments for this disorder, thus making examination of such training procedures informative for advancing available treatment options.
Finally, no study has examined attention training procedures with materials specific to each individual's perception of threat. Due to the varied nature of concerns for individuals with GAD, we asked each participant to select the words most relevant to his or her own concern. In summary, the current study examined the effect of a multiple-session attention training program similar to that described by Macleod et al. (2002)
on anxiety in individuals with GAD.