The Emotional Stroop Effect in Anxiety Disorders General Emotionality Or Disorder Specificity?

Anxiety Disorders 15 Q2001) 147±159

The emotional Stroop effect in anxiety disorders General emotionality or disorder specificity?

Eni S. Beckera,*, Mike Rincka, JuÈrgen Margraf a, Walton T. Rothb

aTU, Dresden, Germany bVA Palo Alto Health Care System, Palo Alto, CA, USA Received 8 January 1999; received in revised form 22 April 1999; accepted 15 October 1999

Abstract

Selective attentional biases, often documented with a modified Stroop task, are considered to play an important role in the etiology and maintenance of anxiety. Two competing explanations for these effects are selectivity for highly emotional words in general vs. selectivity for disorder-specific words. We tested these explanations in 32 patients with generalized anxiety disorder QGAD), 29 patients with social phobia QSP), and 31 non-anxious controls. Stimuli were of four kinds: GAD-related words, SP-related words, words with a neutral valence, and words with a positive valence. Different attentional biases were observed: GAD patients were slowed by all types of emotional words, while SP patients were distracted specifically by speech-related words. D 2001 Elsevier Science Inc. All rights reserved.

Keywords: Attention; Generalized anxiety disorder; Social phobia; Stroop task

1. Introduction

Cognitive models of anxiety have received increasing empirical support over the past decade Qe.g., Barlow 1988; Beck, Emery, & Greenberg, 1985; 1992).

* Corresponding author. Department of Clinical Psychology, Dresden University of Technology, D-01062 Dresden, Germany. E-mail address: [email protected] QE.S. Becker).

These models focus on attentional processes because one function of anxiety is the detection of threat, enabling the individual to react quickly. According to cognitive theories Qe.g., Bower, 1981, 1987; Williams, Watts, MacLeod, & Mathews, 1988, 1997), anxiety patients' attention should be biased selectively towards threatening stimuli. To understand cognitive biases of attention, psychological theories and clinical research have increasingly turned to information processing paradigms derived from experimental cognitive psychology. A classical paradigm adapted to this purpose was originally introduced by Stroop Q1935). The modified version of the Stroop task is the paradigm most frequently used to show attentional biases in anxiety patients. The general approach of this task is to demonstrate selectively biased attention by showing diminished performance in a task condition where threatening stimuli could cause distraction. Specifically, participants are asked to name the ink color of words, disregarding their content. The basic finding is that, compared to other words and other participants, patients with anxiety disorders take longer to name the color of threatening words. The modified Stroop task has been used successfully with a variety of anxiety patients, among them patients with panic disorder QEhlers, Margraf, Davies, & Roth, 1988; McNally, Riemann, & Kim, 1990; McNally, Riemann, Louro, Lukach, & Kim, 1992), obsessive±compulsive disorder QIlai, Shoyer, & Foa, 1991), specific phobia QLavy, van den Hout, & Arntz, 1993), social phobia QSP, Hope, Rapee, Heimberg, & Dombeck, 1990), and posttraumatic stress disorder QFoa, Feske, Murdock, Kozak, & McCarthy, 1991; Kaspi, McNally, & Amir, 1995). Furthermore, there are several studies of patients with generalized anxiety QMartin, Williams, & Clark, 1991; Mathews & MacLeod, 1985; Mogg, Mathews, & Weinman, 1989). Most of these studies found the expected specific distraction effect, i.e., patients were specifically slowed in naming the print color of threat- related words. This effect occurs both with word-by-word and card-by-card presentation of the words, although it seems to be stronger with the blocked card- by-card format QHolle, Heimberg, & Neely, 1997; McNally, Amir, & Lipke, 1996). The color-naming interference does not seem to be due to inter-item priming, repetition of the items, or even more critically, on conscious attention. Four studies QMacLeod & Hagan, 1992; MacLeod & Rutherford, 1992; Mogg, Bradley, Williams, & Mathews, 1993; Mogg, Kentish, & Bradley, 1993) could demonstrate distraction by threatening stimuli presented subliminally. Hence, the interference seems to be a genuine bias of anxiety patients. Mathews and MacLeod Q1985) conducted one of the first studies using the modified Stroop task with anxiety patients. They found highly specific effects: patients who worried mostly about physical harm were particularly slow in naming the color of physical threat words, whereas patients worrying about social threat were especially slow in naming social threat words. Similarly, Hope et al. Q1990) reported that panic patients were slowed by physical threat cues, but not social threat cues, whereas the opposite held for social phobics. Specific, albeit slightly different, effects were also reported by Mogg et al. Q1989). Martin et al. E.S. Becker et al. / Anxiety Disorders 15 F2001) 147±159 149

Q1991), however, criticized earlier studies for confounding emotionality and threat. They presented evidence that anxiety patients were distracted by emotional words generally, regardless of their specific content. Thus, there are two competing explanations for the attentional biases observed in the emotional Stroop task: general emotionality Qpositive or negative) vs. schema congruency or specificity. If emotionality is responsible for the interference, then the schema theories proposing that anxious patients have increased accessibility only to threat information are wrong. However, Mathews and Klug Q1993), using threat-related negative and threat-related positive words Qantonyms of the threat-related negative ones, e.g., safe), and negative and positive words unrelated to threat, found evidence against the emotionality hypothesis: In their experiment, patients were slowed by all words related to their fears, regardless of the valence of the words. Furthermore, a study by MacLeod and Rutherford Q1992) found that specificity of effects depended on the level of processing. In their review, Williams, Mathews, and MacLeod Q1996) conclude that the Stroop effect is not due to emotionality per se, but rather to the degree to which words are semantically related to the schema. Furthermore, comparing interference indices over a variety of studies, they find that although ``current concern'' accounts for much Stroop interference, it does not explain all the interference in patient groups. Besides relatedness, the negativity of the material is important in determining how much color naming will be disrupted. The present study employed the modified emotional Stroop task to further clarify the role of current concerns, emotionality, and specificity in color-naming interference. In addition to a group of non-anxious control participants, two different groups of anxiety patients participated in the studies, namely patients with generalized anxiety disorder QGAD) and patients with SP, most of whom were afraid of giving speeches. These anxiety disorders were chosen for two reasons: First, they involve anxiety schemata of differing widths, i.e., a rather broad schema QGAD) vs. a very narrow one QSP). GAD patients typically worry about a wide range of topics, while fears of SP patients in this study concentrated on giving speeches. Thus, GAD patients could be expected to have an attentional bias towards a broader range of stimuli Qmaybe even emotional stimuli in general) than SP patients. The GAD-related words chosen as stimuli were either connected to worry topics or to anxiety symptoms. The SP-related words were connected with giving a speech.

2. Method

2.1. Participants

A total of 32 GAD patients, 29 SP patients, and 31 control participants without a history of any psychiatric disorder participated. GAD patients were invited to 150 E.S. Becker et al. / Anxiety Disorders 15 F2001) 147±159 participate in a drug-treatment study conducted by the fourth author at a VA Palo Alto Health Care System Hospital, Palo Alto, CA; patients with SP volunteered for a behavior therapy study at the same place. All patients completed the experiments reported here before receiving treatment. Control participants were paid a modest fee for their participation. All participants were recruited by advertisements in local newspapers. After an initial telephone screening, potential participants were given the ``Structural Clinical Interview for DSM-III-R, UpJohn Version'' QSCID-UP, Spitzer, Williams, & Gibbon, 1987) by trained interviewers. Several potential participants were excluded due to medical illness, substance abuse, and past or current psychotic episodes. Patients with both GAD and SP were excluded, as were patients with both GAD and panic disorder. Comorbidity was low in all participant groups: Four GAD patients, eight SP patients, and three control participants suffered from specific phobia, and one SP patient from panic disorder. The three groups were equated with regard to age, gender, and level of education Qsee Table 2).

2.2. Stroop cards

A modified Stroop color-naming task similar to that of Mathews and MacLeod Q1985) was used. Participants were asked to name the ink color of the words on five cards. One card contained only GAD-related words, one contained only speech-related words, one neutral words, and one positive words. The words were selected in the following way: seven experts on anxiety disorder contributed words relevant to either SP or GAD. The authors then created lists of words relevant and specific to each diagnosis from the words most frequently suggested. Lists of positively valenced words and of neutral words were created from the norms of Francis and Kucera Q1982). Table 1 shows the words selected. A fifth control card contained color words Q``black,'' ``brown,'' ``green,'' ``red,'' ``blue,'' and ``orange''), as in the original Stroop task. The words on the cards were

Table 1 Experimental stimulus words used in the modified Stroop task GAD-related Speech-related Neutral Positive illness talk chair baby injury stutter umbrella dreaming debts embarrassment solid flower nervous blush sitting gift death watched walk marry heartbeat audience hammer sunset unemployed silence forehead christmas failure criticize locker diamond abandoned dislike pencil friendly trembling clumsy rock graduation crazy ridicule potato kiss stroke shy wheat victory E.S. Becker et al. / Anxiety Disorders 15 F2001) 147±159 151 handwritten in capital letters in black, brown, green, red, blue, or orange ink. Each card contained only one group of words, arranged in six columns. Each word was repeated six times, once per column. The words in each column were ordered randomly. The order of the colors was random as well, with the restrictions that the same color could not occur twice in a row and that each word was written once in each color.

2.3. Procedure

The Symptom Check List 90 QSCL-90, Derogatis, Lipman, & Covi, 1977), the STAI-Trait questionnaire QSpielberger, Gorsuch, & Lushene, 1970), and Beck's Depression Inventory QBDI, Beck, Ward, Mendelsohn, Mock, & Erbaugh, 1961) were completed at the time of the diagnostic interview, about a week before the day of the experiment. Upon arrival for the experiment, participants completed the state form of the STAI and then received instructions for the modified Stroop task. They were asked to name aloud the colors of the 72 words printed on each card, reading down the columns as quickly as possible. Participants were told the names of the colors, shown examples, and given a practice card containing 12 words in 3 columns. As soon as the participant started to name the colors on a given experimental card, the experimenter started a timer that was stopped when the participant finished naming the colors on the card. The experimenter counted and recorded the number of errors the participant had made on that card. The first card was always the practice card, which was always followed by the color word card. Next came the four cards with the different word types, presented in random order. After finishing the Stroop task, participants gave retrospective ratings of their emotional state during the task on scales from 0 Qlabeled ``not at all'') to 10 Qlabeled ``extremely''). They rated their levels of excitement, tension, and anxiety during the study, and how much they would have liked to leave the experimental situation Qavoidance). Then, they filled out the STAI-State once more. Finally, they rated all words on three dimensions: personal relevance, excitement, and valence.

2.4. Design

The central dependent variable was card reading time QRT), which was analyzed using a mixed-factor 3 4 ANOVA, where the three-level ``participant group'' QGAD patients, SP patients,Â control participants) constituted a between- subjects factor and the four-level ``word type'' QGAD-related words, speech- related words, positive, and neutral words) a within-subjects factor. The color±word card was analyzed separately. The participants' error rates were analyzed in a manner parallel to RT. Effect sizes were computed according to Cohen Q1988) and are given as f values. As mentioned below, ANCOVAs were computed to assess potential effects of the participants' level of general psychopathology or state anxiety. 152 E.S. Becker et al. / Anxiety Disorders 15 F2001) 147±159

3. Results

3.1. Participant characteristics

Table 2 shows several demographic data of the three participant groups as well as their mean scores for the SCL-90 QDerogatis et al., 1977), the STAI-Trait questionnaire QSpielberger et al., 1970), and BDI QBeck et al., 1961). As can be seen in Table 2, the three groups were equivalent for age, gender, level of education, first language, and ethnicity. As Table 2 also indicates, the three groups differed on several of the questionnaires Qall P < .05, according to the ScheffeÂ test). GAD patients scored significantly higher than SP patients and control participants on all three trait measures, i.e., the SCL-90, the BDI, and the STAI-Trait. The SCL-90 scores indicated a significantly higher level of general psychopathology in the GAD patients, although their score of .92 was still quite low. The BDI scores reflect mild depression in the GAD group, but more than in the other two groups. As expected, GAD patients' scores in the Trait form of the STAI indicated substantial levels of anxiety, while SP patients and control participants scored significantly lower. The same was true for the STAI-State form: GAD patients reported significantly more anxiety in the STAI-State questionnaire than the two other groups, both before and after the experiment. After the experiment, the difference between SP patients and control was significant as well. In all three groups, STAI-State scores changed very little during the course of the experiment. Accordingly, a two-way ANOVA of the

Table 2 Demographic data and mean questionnaire scores for the three groups GAD GAD SP Speech vs. vs. vs. GAD phobia Control SP control control Age 44.3 46.2 45.2 ns ns ns Gender: % male 56.6 60.0 56.7 ns ns ns Years of education 16.4 16.5 16.5 ns ns ns First language: % English 87.5 85.7 96.9 ns ns ns Ethnicity ns ns ns % Black 3.2 0 9.4 % Hispanic 12.9 6.7 6.3 % White 71.0 90.0 78.1 % American Indian 0 0 3.1 % Asian 12.9 3.3 3.1 SCL-90 total score .92 .39 .24 * * BDI score 9.8 4.0 2.7 * * STAI-Trait score 51.6 39.8 34.3 * * STAI-State before 49.6 34.5 28.8 * * * STAI-State after 46.0 36.0 28.3 * * * Asterisks indicate differences significant at the .05 level determined by ScheffeÂ tests. E.S. Becker et al. / Anxiety Disorders 15 F2001) 147±159 153

STAI-State scores yielded a strong effect of group [ FQ2,78) = 35.71, P < .001, f = 0.82], whereas the time of measurement Qbefore vs. after the experiment) did not reach significance [ FQ1,78) = 1.35, ns, f = 0.06]. The interaction was margin- ally significant [ FQ2,78) = 2.99, P < .06, f = 0.12]. The fact that the GAD patients had significantly higher scores than SP patients and control participants on all questionnaires raises problems for interpretation of the results reported here, since any differences could be caused by different levels of psychopathology Qe.g., depression), rather than specific characteristics of GAD. To test this alternative explanation, two analyses of covariance QANCO- VAs) were computed for each study, using questionnaire scores as covariates. In the first type of ANCOVA, the SCL-90 total score was the single covariate because it was our best indicator of general psychopathology, and because the other questionnaires were highly correlated with it Qe.g., r =.82 for the BDI). In the other type of ANCOVA, the two STAI-State scores as well as their difference were used as covariates in order to assess the effect of state anxiety and its change over the course of the experimental tasks. Both these ANCOVAs yielded results that were almost identical to those of the simple ANOVAs reported later. Thus, it seems unlikely that the pattern of results reported below can be explained by the GAD patients' higher level of general psychopathology or state anxiety.

3.2. Emotional state during the task

Table 3 shows how participants rated their emotional state during the Stroop task, using the four subjective rating scales. Significant differences between the three groups were observed for tension, anxiety, and avoidance Qsee Table 3). As expected, both GAD and SP patients rated themselves as significantly more tense and anxious than control participants, but did not differ significantly from each other. With regard to avoidance Qthe wish to leave the situation), only GAD patients gave higher ratings than the controls. Excitement ratings of the three participant groups did not differ significantly from one another. Thus, these

Table 3 Emotional state ratings of the participants Qwith standard deviations) during the modified Stroop task GAD GAD SP Speech Significance vs. vs. vs. GAD phobia Control FQ2,89) level SP control control Excitement 3.96 Q2.44) 3.58 Q2.77) 3.46 Q2.86) < 1 ns Tension 5.25 Q2.01) 4.75 Q2.87) 2.37 Q1.82) 14.55 P < .001 * * Anxiety 5.29 Q2.66) 5.24 Q3.07) 2.28 Q1.78) 9.02 P < .001 * * Avoidance 3.87 Q3.29) 3.72 Q3.96) 1.75 Q2.14) 4.31 P < .05 * Each rating scale ranged from 0 Q``not at all'') to 10 Q``extremely''). Asterisks indicate differences significant at the .05 level determined by ScheffeÂ tests. 154 E.S. Becker et al. / Anxiety Disorders 15 F2001) 147±159 results indicate that the emotional state of the two patient groups during the Stroop task was comparable.

3.3. Stimulus characteristics

All words were rated by all participants on three dimensions: personal relevance, excitement, and valence. Analyses of these ratings indicated that appropriate words had been selected. For all participants groups, the emotional words QGAD-related, speech-related, and positive) were more relevant and more exciting than the neutral words. For positive and neutral words, the ratings of the three groups did not differ with regard to relevance, excitement, or emotional valence. GAD-related words were as relevant to the GAD patients as they were to the SP patients, although their mean relevance was slightly higher in the GAD patients Q4.26 vs. 3.81). These words were more relevant to both patient groups than to controls. The same was true for the speech-related words, which were more relevant to both patient groups without significant differences between the two. The relevance ratings of these words were slightly higher for SP than GAD patients Q4.59 vs. 4.29). All three groups judged the GAD-related words as comparably unpleasant, while the speech-related words were rated as more unpleasant by the patient groups than by the controls. Moreover, the disorder-related words were judged to be as unpleasant as the positive words were pleasant.

3.4. Color-naming times

Mean naming times for all cards and participant groups are shown in Table 4. Color-naming times for the card containing the color words were analyzed separately by means of a one-way analysis of variance because this card provides a control condition with minimal interference from attentional biases. This ANOVA revealed no statistically reliable differences among the three groups [ FQ2,89) = 1.43, ns]. Remaining color-naming times of the four

Table 4 Mean color naming times in seconds Qwith standard deviations) by word type and group in the modified Stroop task GAD GAD SP Word Speech Significance vs. vs. vs. type GAD phobia Control FQ2,89) level SP control control GAD-related 78.2 Q15.1) 69.9 Q14.9) 64.2 Q13.2) 7.50 P < .001 * * Speech-related 75.1 Q13.2) 72.5 Q17.3) 64.8 Q13.4) 4.18 P < .05 * * Neutral 71.4 Q13.1) 67.5 Q14.5) 63.1 Q14.6) 2.74 ns Positive 74.7 Q13.4) 68.8 Q15.0) 64.8 Q12.6) 4.16 P < .05 * Color words 96.5 Q23.1) 96.1 Q24.8) 88.1 Q18.0) 1.43 ns Asterisks indicate differences significant at the .05 level determined by ScheffeÂ tests. E.S. Becker et al. / Anxiety Disorders 15 F2001) 147±159 155 experimental cards were subjected to an ANOVA, which yielded a significant effect of participant group [ FQ2,89) = 4.98, P < .01, f = 0.30]. ScheffeÂ tests showed that GAD patients were slower than SP patients, who in turn were slower than controls Qsee Table 4). The main effect of word type [ FQ3,267) = 7.71, P < .001, f = 0.10] and the interaction of group and word type [ FQ6,267) = 2.39, P < .05, f = 0.08] were also significant. The ANCOVAs described above Qone using the SCL-90 sum score as a covariate, the other using the STAI-State scores before and after the study as well as their difference) yielded the same pattern of significances. Most importantly, the interaction of group and word type was significant in both ANCOVAs, just as in the ANOVA. The covariates showed only weak correlations with the color- naming times, with the STAI-State score before the experiment giving the highest correlation of r =.22. Additional analyses compared the three groups' color-naming times separately for each word type Qsee Table 4). These analyses indicated that GAD patients took longer than SP patients and control participants to name the print color of GAD-related words. For speech-related words, both GAD patients and SP patients were slower than the control participants. For positive words, GAD patients were slower than the control participants. No significant differences between groups were observed for neutral words. Further analyses compared color-naming times separately for each group. For GAD patients, the ANOVA revealed a main effect of word type [ FQ3,93) = 6.74, P < .01]. Follow-up t tests showed that the GAD patients were slower to name the color of GAD words than of both neutral words [tQ31) = 4.53, P < .01] and positive words [tQ31) = 2.07, P < .05]. GAD-related words and speech-related words did not differ [tQ31) = 1.95, ns]. The GAD patients were also slower to name the color of positive words [tQ31) = 2.64, P < .01] and speech-related words [tQ31) = 2.55, P < .05] compared to Àneutral words. Positive and speech- related words didÀ not differ. The ANOVA for social phobics also showed a main effect for word type [ FQ3,84) = 4.45, P < .01]. Social phobics were slower to name the color of speech-related words than of GAD-related words [tQ28) = 2.08, P < .05], neutral words [tQ28) = 2.69, P < .05], or positive words [tQ28) = À 3.1, P < .01]. The other t tests were notÀsignificant. The ANOVA for the controlÀparticipants revealed no significant main effect for word type [ FQ3,90) = 0.70, ns]. Participants made very few errors on the Stroop task Qon the average, less than one error per card); none of the analyses of the error rates yielded any significant effect. To summarize, color-naming times observed here indicate that all emotional words, GAD-related as well as speech-related, and even positive words, caused more interference with GAD patients than with control participants. This result accords with the emotionality hypothesis QMartin et al., 1991). For SP patients, however, only speech-related words caused increased interference. This result accords with the schema congruency hypothesis QBeck et al., 1985; Bower, 1981, 1987). 156 E.S. Becker et al. / Anxiety Disorders 15 F2001) 147±159

3.5. Influence of anxiety and depression on the attentional bias

As mentioned before, GAD patients had higher scores than social phobics and control participants on both the anxiety questionnaires and the depression questionnaire QBDI). In order to determine the effects of depression and anxiety independently, questionnaire scores were correlated with attentional bias scores. In a first analysis, three bias scores were created by subtracting each subject's color-naming time of neutral words from his or her naming time of GAD-related words, speech-related words, and positive words. Correlations and partial correlations between the bias scores and the scores of the BDI, STAI-T, and the STAI-S before and after the experiment were computed. In these analyses, only the attentional bias score for GAD-related words yielded significant correlations with the questionnaires. The BDI, the STAI-S before the experiment, and the STAI-T correlated to a similarly low degree with the bias score: r =.23 Q P < .05) for the STAI-T, r =.35 Q P < .01) for the STAI-S before the experiment, and r =.24 Q P < .05) for the BDI. The BDI score, however, did not correlate with the bias score after STAI scores were partialled out Qr =.09, ns). The STAI-S score before the experiment, on the other hand, showed a significant correlation with the bias score, even after the BDI score was partialled out Qr = .24, P < .05). Thus, state anxiety seemed to have an independent, albeit weakÀ relation to memory bias.

4. Discussion

Results of the Stroop task show that patients suffering from GAD displayed an attentional bias. They took longer to name the print color of GAD-related words than SP patients and controls. However, GAD patients also took longer than controls to name the color of positive words and speech-related words. A similar pattern emerged when color-naming times of GAD patients alone were compared. GAD patients took as long to name the color of GAD-related words as speech-related ones, with no difference between speech-related words and positive words. Thus, they were slower naming most words with affective connotations. This pattern of results cannot be explained in terms of a general increase in naming times for the GAD patients, because they were as fast as the other participants when asked to name the print color of neutral words and color words. Consequently, the GAD patients' results of the Stroop task favor the emotionality hypothesis proposed by Martin et al. Q1991). Color-naming times of the SP patients followed a different pattern. This group exhibited a highly selective attentional bias. They showed longer naming times than controls only for the color of speech-related words. There was no difference between SP patients and controls for the color-naming times of GAD-related, neutral, or positive words. The comparison of word latencies for social phobics alone showed the same pattern. They were slower naming the color of speech- E.S. Becker et al. / Anxiety Disorders 15 F2001) 147±159 157 related words than GAD-related words, neutral words, and positive words. Thus, the bias observed with SP patients was highly specific, favoring the schema congruency hypothesis QBeck et al., 1985; Bower, 1981, 1987). The group difference in width of the attentional bias cannot be accounted for by different moods during the experiment, as both patient groups felt comparably anxious, nervous, and excited. One possible explanation is that the GAD patients exhibited a higher level of general psychopathology than the SP patients, which in turn broadened the attentional bias. However, the analyses of covariance reported above did not support this hypothesis. Alternatively, the broader effect observed for GAD patients might be due to a greater array of stimuli able to trigger the anxiety schema of these patients. Another critical factor is the selection of the word material presented to the participants. Since we were interested in effects of anxiety schemata on selective information processing, the words chosen were strongly related to these schemata. A major difficulty in this study was to find words relevant to GAD patients but not to SP patients, and vice versa. We believe that we succeeded reasonably well because the ratings given by the participants show that the words selected were highly relevant to their specific disorders. Nevertheless, magnitude of the attentional biases investigated here may have been reduced by having selected stimulus words prior to the study and by using identical words for all participants. This is a potential problem, particularly for GAD-related words. Even though the selected words reflect the topics GAD patients worry about most often, each individual GAD patient must have encountered some words that were not very relevant to him or her. In future studies, the effect size of the attentional bias might be enhanced by using individualized sets of GAD- related words. We are still left with the two competing explanations for attentional biases in anxiety, namely general emotionality vs. schema congruency. Our study shows that the most appropriate explanation may depend on the anxiety disorder. If we had studied solely GAD patients, the emotionality hypothesis would have been favored. The results observed with social phobics, however, revealed a highly specific attentional bias in accord with the schema congruency hypothesis. The latter result also shows that the modified Stroop task does not always show general emotionality effects. A number of questions remain to be answered by future experiments. For example, are the effects shown by GAD patients in this experiment due to a wider anxiety schema? What kind of material is most specific for individual anxiety disorders? What patterns of attentional biases are exhibited by anxiety disorders other than GAD and SP? Whatever the answers to these questions will be, experimental paradigms derived from cognitive psychology such as the Stroop task will be helpful in investigating selective attentional processes in emotional disorders. In particular, it seems important and worthwhile to assess the diagnostic value of the Stroop task for determining the severity of anxiety disorders QHope et al., 1990) and its value for predicting therapy outcome QButler, 1993). In addition, it will have to be 158 E.S. Becker et al. / Anxiety Disorders 15 F2001) 147±159 determined if the modification of attentional biases as part of therapy adds to successful treatment of anxiety disorders.

Acknowledgments

Preparation of this paper was supported by a fellowship from the German Academic Exchange Service QDAAD) to Eni S. Becker, a fellowship from the German Research Foundation QDFG) to Mike Rinck, and the support of the Veterans Administration and the National Institute of Health to Walton T. Roth. We would like to thank Cassandra Lehmann for recruiting and diagnosing the GAD patients and Cheryl Post for her help in conducting the experiment. Furthermore, we would like to thank Gordon Bower, Michael Mangold, and two anonymous reviewers for helpful comments on earlier versions of the paper, as well as Ulrich Glowalla, Joachim Hasebrook, and Gilbert Fezzardi for supplying the software used to conduct the experiment.

References

Barlow, D. H. Q1988). Anxiety and its disorders: the nature and treatment of anxiety and panic. New York: Guilford Press. Beck, A. T., Emery, G., & Greenberg, R. L. Q1985). Anxiety disorders and phobias. New York: Basic Books. Beck, A. T., Ward, C. H., Mendelsohn, M., Mock, J., & Erbaugh, J. Q1961). An inventory for measuring depression. Archives of General Psychiatry, 41, 561±571. Bower, G. H. Q1981). Mood and memory. American Psychologist, 36, 129±148. Bower, G. H. Q1987). Commentary on mood and memory. Behaviour Research and Therapy, 25, 443±455. Butler, G. Q1993). Predicting outcome after treatment for generalised anxiety disorder. Behaviour Research and Therapy, 31, 211±213. Cohen, J. Q1988). Statistical power analysis for the behavioral sciences. Hillsdale, NJ: Lawrence Erlbaum Associates. Derogatis, L. R., Lipman, R. S., & Covi, L. Q1977). The SCL-90: an outpatient psychiatric rating scale. Psychopharmacological Bulletin, 9, 13±28. Ehlers, A., Margraf, J., Davies, S., & Roth, W. T. Q1988). Selective processing of threat cues in subjects with panic attacks. Cognition and Emotion, 2, 201±219. Eysenck, M. W. Q1992). Anxiety: the cognitive perspective. Hove: Lawrence Erlbaum Associates. Foa, E. B., Feske, U., Murdock, T. B., Kozak, M. J., & McCarthy, P. R. Q1991). Processing of threat- related information in rape victims. Journal of Abnormal Psychology, 100, 156±162. Francis, W. N., & Kucera, H. Q1982). Frequency analysis of English usage. Boston, MA: Houghton-Miffin. Holle, C., Heimberg, R. G., & Neely, J. H. Q1997). The effects of blocked versus random presentation of and semantic relatedness of stimulus words on response to a modified Stroop task among social phobics. Cognitive Therapy and Research, 21, 681±696. Hope, D. A., Rapee, R. M., Heimberg, R. G., & Dombeck, M. J. Q1990). Representations of the self in social phobia: vulnerability to social threat. Cognitive Therapy and Research, 14, 177±189. Ilai D., Shoyer B. G., & Foa E. B. Q1991). The effects of stimuli specificity and clinical severity on E.S. Becker et al. / Anxiety Disorders 15 F2001) 147±159 159

information processing in obsessive±compulsive patients. Poster presented at the 25th Annual AABT Convention, New York, NY. Kaspi, S. P., McNally, R. J., & Amir, N. Q1995). Cognitive processing of emotional information in post-traumatic stress disorder. Cognitive Therapy and Research, 19, 433±444. Lavy, E., van den Hout, M., & Arntz, A. Q1993). Attentional bias and spider phobia: conceptual and clinical issues. Behaviour Research and Therapy, 31, 17±24. MacLeod, C., & Hagan, R. Q1992). Individual differences in the selective processing of threatening information, and emotional responses to a stressful life event. Behaviour Research and Therapy, 30, 151±161. MacLeod, C., & Rutherford, E. M. Q1992). Anxiety and the selective processing of emotional information: mediating roles of awareness, trait and state variables, and personal relevance of stimulus materials. Behaviour Research and Therapy, 30, 479±491. Martin, M., Williams, R. M., & Clark, D. M. Q1991). Does anxiety lead to selective processing of threat-related information? Behaviour Research and Therapy, 29, 147±160. Mathews, A., & Klug, F. Q1993). Emotionality and interference with color-naming in anxiety. Beha- viour Research and Therapy, 31, 57±62. Mathews, A., & MacLeod, C. Q1985). Selective processing of threat cues in anxiety states. Behaviour Research and Therapy, 23, 563±569. McNally, R. J., Amir, N., & Lipke, H. J. Q1996). Subliminal processing of threat cues in post-traumatic stress disorder? Journal of Anxiety Disorders, 10, 115±128. McNally, R. J., Riemann, B. C., & Kim, E. Q1990). Selective processing of threat cues in panic disorder. Behaviour Research and Therapy, 28, 407±412. McNally, R. J., Riemann, B. C., Louro, C. E., Lukach, B. M., & Kim, E. Q1992). Cognitive processing of emotional information in panic disorder. Behaviour Research and Therapy, 30, 143±149. Mogg, K., Bradley, B. P., Williams, R., & Mathews, A. Q1993). Subliminal processing of emotional information in anxiety and depression. Journal of Abnormal Psychology, 102, 304±311. Mogg, K., Kentish, J., & Bradley, B. P. Q1993). Effects of anxiety and awareness on colour-identifica- tion latencies for emotional words. Behaviour Research and Therapy, 31, 559±567. Mogg, K., Mathews, A., & Weinman, J. Q1989). Selective processing of threat cues in anxiety states: a replication. Behaviour Research and Therapy, 27, 317±323. Spielberger, C. D., Gorsuch, R. L., & Lushene, R. E. Q1970). Manual for the State±Trait Anxiety Inventory. Palo Alto: Consulting Psychologists Press. Spitzer, R. L., Williams, J. B., & Gibbon, M. Q1987). Structured clinical interview for DSM-III-R. New York: New York State Psychiatric Institute. Stroop, J. Q1935). Studies of interference in serial verbal reactions. Journal of Psychology, 18, 643±661. Williams, J. M. G., Mathews, A., & MacLeod, C. Q1996). The emotional Stroop task and psychopathology. Psychological Bulletin, 120, 3±24. Williams, J. M. G., Watts, F. N., MacLeod, C., & Mathews, A. Q1988). Cognitive psychology and emotional disorders. Chichester: Wiley. Williams, J. M. G., Watts, F. N., MacLeod, C., & Mathews, A. Q1997). Cognitive psychology and emotional disorders. Chichester: Wiley.