Repressors vs. low- and high-anxious coping styles: EEG differences during a modified version of the emotional Stroop task

International Journal of Psychophysiology 78 (2010) 284–294

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International Journal of Psychophysiology j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / i j p s yc h o

Repressors vs. low- and high-anxious coping styles: EEG differences during a modified version of the emotional Stroop task Jennifer M.C. Vendemia a, P. Dennis Rodriguez b,⁎ a b

Department of Psychology, University of South Carolina, Columbia, SC, United States of America Department of Psychology, Indiana University South Bend, South Bend, IN 46634, United States of America

a r t i c l e

i n f o

Article history: Received 23 February 2010 Received in revised form 30 August 2010 Accepted 3 September 2010 Available online 17 September 2010 Keywords: Repressors Repressive coping Emotional Stroop task EEG Negative valence Attention bias theory Emotion Personality

a b s t r a c t In this study of 49 undergraduate university women, those exhibiting a repressive coping style – characterized by defensiveness against negative emotions – were compared to women with low-anxious and high-anxious coping styles during neutral and negative versions of a computerized emotional Stroop task (EST). Using Weinberger, Schwartz, and Davidson's (1979) approach, the present study implemented the Marlowe–Crowne Social Desirability and the Spielberger Trait Anxiety scales for selection. Participants viewed neutral or negative words during the EST but responded to the color of the word. Analysis of continuous EEG recordings for the negative vs. neutral words revealed that the repressor group differed significantly from the other two groups in many aspects but that low- vs. high-anxious groups differed in fewer aspects. Based upon Eysenck and Derakshan's (1997) model, repressor women appear to differ from low- and high-anxious women by utilizing an inhibitory process to avoid perceiving low-intensity threatening stimuli. © 2010 Elsevier B.V. All rights reserved.

1. Introduction Repression combines high defensiveness with low sell-reported anxiety (Weinberger et al., 1979). The default coping mechanism for repressors – characterized by defensiveness against negative emotions – entails shifting attention away from negative or threatening stimuli when the intensity level of threat is low but to implement a more active reinterpretation strategy when the intensity level of threat is high (Kline et al., 1993; Langens and Mörth, 2003). While some might view the repressive coping style as maladaptive, recent studies indicate an adaptive benefit to this coping style (e.g., Coifman et al., 2007), which encourages more research in this area. Contemporary repressor research evolved with Byrne's repressionsensitization model (Byrne et al., 1963), and was psychometrically refined throughout the 1970's (Kahn and Schill, 1971; Weinberger et al., 1979). Especially relevant to the repressive coping research is the theoretical conceptualization of “repressors” by Weinberger and his colleagues (Weinberger and Davidson, 1994; Weinberger and Schwartz, 1990) along with the electroencephalographic (EEG) findings of Kline et al. (1998b). Repressors differ from low- and high-anxious individuals in how they process and react to negative stimuli (Weinberger et al., 1979).

⁎ Corresponding author. Tel.: +1 574 520 4396(office); fax: +1 574 520 4538. E-mail address: [email protected] (P.D. Rodriguez). 0167-8760/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.ijpsycho.2010.09.002

When exposed to cognitive and physiological stressors, low-anxious individuals report a low level of anxiety and demonstrate low autonomic arousal, while high-anxious individuals report high levels of anxiety and demonstrate high autonomic arousal. By contrast, repressors appear to dissociate from their perceptions of negative information and report low anxiety while showing enhanced autonomic arousal typically associated with high anxiety. Thus, repressors exhibit a combination of (perceived) low-anxiety and high defensiveness (Bonanno et al., 1991). Repressors cope with external and internal stimuli by increased unconscious processing of emotion in the service of inhibition of threatening material (Kline et al., 1998b; Langens and Mörth, 2003). Weinberger et al. (1979) suggested that repressors have a “heighted recognition threshold” for anxiety provoking stimuli. In highdefensive individuals the increase in unconscious processing may facilitate active inhibition during high levels of threat (Kline et al., 1993). In instances of low levels of threat, repressors may instead rely on their default strategy of avoiding negative information in order to perform the task at hand. Eysenck and Derakshan (1997) proposed a four factor theory of cognitive processing for threatening information in low-anxious, highanxious, and repressor personality types. According to this theory, lowanxious individuals process threatening information without altering their perception of its nature, while high-anxious individuals engage in attentional bias by shifting their attention towards the threatening stimuli. By contrast, repressors shift their attention away from negative stimuli.

J.M.C. Vendemia, P.D. Rodriguez / International Journal of Psychophysiology 78 (2010) 284–294

According to Krohne (1989), cognitive avoidance and vigilance are general cognitive strategies applied to the environment by repressors and high-anxious individuals. Derakshan and Eysenck (1997) reinterpreted cognitive avoidance as opposite attentional bias or the tendency to shift attention away from negative stimuli and towards positive or neutral stimuli in the environment. They considered vigilance an attentional bias towards negative environmental stimuli. If Krohne's theory were accurate, then the reaction times of highanxious and repressor individuals should be consistent across all conditions of an emotional Stroop task (hereafter referred to as EST). Repressors would respond slower to task related stimuli in neutral and negative versions of an EST, while high-anxious participants would respond more quickly. In contrast, if Eysenck and Derakshan's (1997) four factor theory were correct, then differences between repressors and high-anxious individuals should only be apparent during the negative condition of an EST. Low-anxious individuals who utilize neither bias should have no differences across tasks according to either theory. Not only does the type of stimuli elicit different responses between the coping styles but the requirements of the task may also moderate cognitive task performance (Brosschot et al., 1999). When threatening information is presented separately, either spatially or temporally, repressors seem to exhibit an attentional bias away from a probe or may inhibit negative information, thus facilitating task performance (E. Fox, 1993, 1994; N. Fox, 1994). If, however, threatening information is presented simultaneously with the probe, forcing attention toward the threatening information, repressors may have difficulty inhibiting the negative information (Dawkins and Furnham, 1989; Derakshan and Eysenck, 1998). Other researchers, however, have not been able to replicate these results (e.g., Myers and McKenna, 1996). A potential reason is that the cognitive task must actively engage the participants in order to detect the ongoing processes associated with the coping style (Houtveen et al., 2001). While behavioral studies provide one method of investigating coping style differences, electrophysiological studies provide another. EEG studies have reported different patterns of cortical activity, usually in alpha or theta frequency bands, between coping styles during rest and task performance (Lorig et al., 1994–95; Wexler et al., 1992). Assuming that increased alpha power is associated with decreased cortical activity in that cortical region (Shagass, 1972), emotion research has often reported that less relative alpha power in the right (compared to left) frontal region – and sometimes anterior temporal area – is correlated with greater dysphoric affect and greater withdrawal motivation, while an opposite relation is observed in happy affect (e.g., Sobotka et al., 1992; Tomarken et al., 1990). However, there are important caveats to this conceptualization. Harmon-Jones et al. (in press) argue that motivation provides a better explanation for hemispheric asymmetries in cortical activity than affective valence. Individuals experiencing mania have been shown to have greater left frontal activation (Kano et al., 1992), and individuals with a proneness to hypomania/mania symptoms demonstrated leftfrontal activation when stimuli evoked anger (Harmon-Jones et al., 2002). Harmon-Jones and Gable (2009) have also found that in the experimental environment, increased motivational factor such as the amount of time since a previous meal significantly impacted cortical asymmetry when viewing positive food stimuli, but not other positive images. Their findings suggest that a motivation to perform well in the experimental environment may create conditions that facilitate of left frontal activation in repressors, because they are motivated to be perceived positively. Crawford et al. (1996) demonstrated differences in low (7.5– 9.45 Hz), mid (9.5–11.45 Hz), and high (11.5–13.45 Hz) alpha – as opposed to just “general” alpha – during self-recall of positive and negative memories. The type of memory impacted low alpha but did not affect mid nor high alpha recordings. While sustained attentional abilities and alertness influence low alpha readings, general mental

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workload may play into high alpha frequencies (Sterman et al., 1994). Increased low alpha frequencies are also thought to indicate poor cognitive performance (Bosel, 1992), while fluctuations in attentional resources seem to desynchronize mid alpha (Crawford et al.). If differences in coping styles impact transient attentional processing we would expect to see differences within the mid alpha band. Theta power, on the other hand, is oftentimes associated with focused attention (Schacter, 1977), particularly if it is higher theta (Crawford et al.). Specifically, low theta (3.5–5.45 Hz) may be affected by drowsiness and inactivity whereas high theta (5.5–7.45 Hz) may be affected by efficient or attentive performance (Schacter). With respect to coping styles, Stenberg (1992) found stronger frontal theta in high-anxious individuals than low-anxious. The theta rhythm has also been implicated in emotional and cognitive processes (for reviews, see Crawford et al. and Schacter). If the task impacts emotional processing and attentional processing than greater theta power should occur during the neutral task. However, if the task only impacts the transient aspects of attention processing, high theta may occur. While the repressor literature has largely overlooked beta power, the present study investigated this band because of the effects that negative emotions (Cole and Ray, 1985), vigilance (Makeig and Inlow, 1993), and recall of negative emotional stories (Crawford et al.) all increase beta activity. As the EST requires ongoing vigilant attention, it is anticipated that the EST will be correlated with increases in beta activity. At rest, repressor women showed a significant anterior asymmetry – left greater than right – in broad band alpha power (7.5–13.45 Hz) in the midfrontal and lateral frontal sites that differed from non-repressor women (Tomarken and Davidson, 1994). Interestingly, Kline et al. (1998a) found this replicated for women but not men. Greater left frontal activation was correlated with positive affect across many paradigms (Tomarken et al., 1992). Based upon Davidson's model for differential hemispheric activation for positive emotional approach (right N left alpha power) and negative emotional avoidance (left N right alpha power), these findings suggest that repressors' EEG activation patterns may reflect underlying anxiety (Johanson et al., 1992). Repressors appear to have a unique EEG activation pattern when engaged in tasks that produce cognitive and physical stress. During recall of positive and negative memories, broad band theta power (4.5–7.45 Hz) across all measured regions was reduced in repressors when compared to non-repressors (Lorig et al., 1994–95). Most importantly, theta asymmetry differences were observed in the posterior region: repressors exhibited reduced theta power in the right hemisphere, while low-anxious and high-anxious participants exhibited the opposite. Lorig et al. proposed that reduced right hemisphere theta power in repressors indicated less emotional arousal to negative memories than exhibited in low- and highanxious individuals. This suggests repressors may possess an underactivated right posterior region, an area that Heller's model (1993) associates with emotional arousal. When repressors are not given the opportunity to use the ongoing avoidant, attention switching strategy, such as during a word recognition task, they showed decreased posterior alpha power following registration of emotional words in comparison to neutral words (Kline et al., 1998b). When word trials contained sexually taboo words, which most significantly affected repressor task performance, alpha power (7.5–13.45 Hz) markedly decreased in the right hemisphere (Kline, Schwartz, et al.). Increase in behavioral measures combined with decrease in broad band alpha power suggests that the task with sexually taboo words demanded the greatest cognitive involvement and thus activated the right hemisphere. It follows that active cognitive processing suppresses alpha waves (which are usually associated with a relaxed and alert state). The studies reviewed here required repressors to direct their attention toward the meaning of the word and process the emotional

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aspect of it in order to complete the task. This directing-of-attention requirement presumably prevented repressors from engaging in the avoidance-of-threatening-stimuli strategy typically employed by them (Eysenck and Derakshan, 1997; Langens and Mörth, 2003), and thus decreased their alpha and theta activity, which are inversely related to active cognitive processing. The task for the present study, however, did not require participants to process or respond to the meaning of the word. While the stimuli certainly consisted of neutral and negative words, participants simply responded to a color and word vs. nonword combination (see Methods section). This would most likely enable repressor participants to avoid processing the meaning of the words if they initially detected them as negative and focus instead on a more superficial “is this the target combination or not” strategy. If this is indeed the case, alpha and theta rhythms should remain relatively higher for repressors, indicating decreased cortical activity in that area as proposed by Shagass (1972). After all, studies suggest that repressors generate their coping behaviors automatically and outside conscious awareness by not focusing on negative or threatening information (Boden and Baumeister, 1997; Coifman et al., 2007) especially when the level of threat is low (Langens and Mörth, 2003). The present study examined EEG frequency bands that are involved in specific types of attentional modulation. Because previous research indicated that repressors may inhibit threatening information (Coifman et al., 2007; Dawkins and Furnham, 1989; Derakshan and Eysenck, 1998; Langens and Mörth, 2003), we anticipated that a negatively valenced form of the EST would impair the performance of repressors as compared to the other two groups but that the waveforms associated with attention (theta and alpha) would be increased in repressors. By separating the frequency bands into subcategories, i.e., low and high theta, low, mid, and high alpha, and beta 13 and 16 (as outlined by Crawford et al., 1996), we aimed to explore the interplay between them and the emotional valence of words (negative vs. neutral) and coping style (low-anxious, highanxious, and repressor) in women. Because of the exploratory nature of this study, and because previous studies did not research beta waves, we did not formulate specific hypotheses for each band.

Table 1 Means and standard deviations for participants. Questionnaires

Coping style Low-anxious (n = 19)

SDS M SD Trait STAI M SD State STAI M SD BDI M SD AHS M SD a

High-anxious (n = 15)

Repressor (n = 15)

9.47….. 1.39…..

≅ 8.52….. 2.56…..

ba23.60….. 1.92…..

32.74….. 5.42…..

b58.13. 4.91…..

N30.60….. 6.68…..

31.21….. 6.94…..

b49.14….. 7.73…..

b30.27….. 6.35…..

6.84….. 5.51…..

b13.43….. 6.11…..

N3.67….. 4.16…..

18.42….. 3.66…..

≅ 19.14….. 3.53…..

≅ 20.27….. 4.03…..

Significant at the p b .01 level.

characteristics and present oneself in a positive light. It has good internal consistency and test–retest reliabilities (Crowne & Marlowe). For classification purposes, participants were placed in one of three coping style conditions (low-anxious, high-anxious, or repressor) based on the outcome of two measures. As Table 1 shows, lowanxious individuals (n = 19) scored in the lowest third (b45) of the trait STAI as well as in the lowest third (b11) of the SDS, high-anxious individuals (n = 15) scored in the top third (N55) of the trait STAI and the bottom third (b11) of the SDS, and repressors (n = 15) scored in the lowest third (b45) of the trait STAI and the top third (N22) of the SDS. All participants were right-hand dominant based on the Annett Handedness Scale (AHS; Annett, 1970), medication free (except for birth control pills), with no known medical problem, and low to moderate scores on the (M = 7.98, SD = 5.28) on the Beck Depression Inventory (BDI; Beck et al., 1961). 2.3. Tasks

2. Method 2.1. Participants Forty-nine undergraduates (age M = 19.28 years, SD = 1.62) who met the criteria for a repressor, low-, or high-anxious coping style were chosen from a sample of 470 women screened earlier. In the original sample of 470 participants two participants met the criteria for high defensive/high-anxious, therefore we were not able to include this group in the analysis. We excluded men from this study in order to stay within the framework of Tomarken and Davidson's (1994) study and because prior findings by Kline et al. (1998b) suggest hemispheric asymmetries between men and women. In addition, due to recent evidence that the sex of the experimenter can also contribute to hemispheric differences between the sexes when defensive coping– a characteristic of repressors – is utilized (Kline et al., 2002), we decided to only recruit women and have female experimenters in order to minimize the already complex data analysis for this study. 2.2. Measures The Spielberger State-Trait Anxiety Inventory (STAI; Spielberger et al., 1970) is a 20-item self-report measure of cognitive and affective components of anxiety. It has high internal consistency (.86–.92) and test–retest (.73–.86) reliabilities. The Marlowe–Crowne Social Desirability Scale (SDS; Crowne and Marlowe, 1964) is a 33-item selfreport measure that assesses the tendency to deny negative

The neutrally/negatively valenced forms of the computerized EST were presented on a 13-inch monitor. Stimuli presented in blue or red on a gray background consisted of 1) neutral words such as "chalk” or 2) negative words such as “scream” amongst nonsense letter-strings such as “klahc” taken from the neutral and negative word lists (e.g., “klahc” unscrambles into “chalk;” see Table 2). Nonsense letterstrings were screened to eliminate possible secondary associations. Positive words were not included due to inconsistent results reported in earlier research with the EST (Dawkins and Furnham, 1989) but should be examined in a future study. An equal number of 3-, 4-, 5-, and 6-letter words and letter strings (Times New Roman 72 pt font)

Table 2 Word stimuli for the emotional Stroop task. Neutral condition

Negative condition

Letter count

Words

Letter-strings

Words

Letter-strings

3 3 3 4 5 5 5 5 5 6

cap dot tie barn chalk brass bench purse round starch

pca otd iet rnab klahc srabs cenbh surep nrodu hrtasc

sob beg cry kick shout blush plead punch tense scream

bso gbe yrc ckik tosuh huslb delap nupch entes resamc

Note: Stimuli were presented in red or blue.

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2.4. Apparatus A Neurosearch-24 system (Lexicor Technologies, Boulder, CO) recorded EEG from anterior frontal (Fp1, Fp2), medial frontal (F3, F4), lateral frontal (F7, F8), central, (C3, C4), anterior temporal (T3, T4), posterior temporal (T5, T6), parietal (P3, P4), occipital (O1, O2), and midline (Fz, Cz, Pz) sites according to the international 10–20 system (Jasper, 1958). All scalp leads were referred to linked ear lobes (A1–A2), and the ground was in front of Fz. An EOG recording was obtained from electrodes placed at the outer canthus and sub-orbital region of the right eye. Resistance was kept below 5000 Ω with a maximum of 500 Ω variation between sites. EEG signals between 2 and 64 Hz were amplified with a gain setting of 32 K. The sampling rate was 256 samples per second. A 60 Hz notch filter was used to reduce electrical noise. The task was programmed using C+ and presented on an IBM 486 with a 13-inch CRT monitor. Stimuli were time synced with EEG through the auxiliary channel of the Neurosearch-24. 2.5. Procedure Participants arrived at the lab within two weeks of initial screening. They were to avoid alcohol for 24 h and caffeine for 4 h before the experiment. Upon arrival, participants read and signed the informed consent form and then practiced a version of the EST containing stimuli from the neutral and negative conditions. Their practice data were checked to assure comprehension of the task. Participants sat in a chair placed 142 cm from the testing monitor. The experimenter remained behind the participant and out of the participant's visual field throughout the session. EEG recording occurred during 1) eyes-open passive fixation, 60–90 seconds, and 2) the two randomly presented conditions of the EST (neutral or negative), approximately 230 s each (actual duration depended on participants' reaction times). 3. Results The current study investigated the EEG activity of 49 women with low-anxious, high-anxious, or repressor coping styles while they performed a modified version of the EST that contained neutral and negative words. Eysenck and Derakshan's (1997) attention bias theory provides a strong framework for exploring the relationship between patterns of performance measures, cortical activity, coping style, and levels of the EST. 3.1. Self-reported distracting thoughts When asked to rate the number of distracting thoughts they had during the conditions, participants reported having more distracting thoughts during the negative than the neutral conditions. The number of distracting thoughts was assessed at the end of each condition by asking participants to rate their distracting thoughts on a scale where zero equaled no distracting thoughts, five was a moderate number of distracting thoughts, and ten was so many distracting thoughts that it was difficult to pay attention to the task. A mixed ANOVA examined the impact of task valence and coping style [valence(2) × coping style (3)] on number of distracting thoughts (see Fig. 1).

Task valence significantly impacted the number of self-reported distracting thoughts [F(1, 42) = 4.45, p b .050]. More distracting thoughts were reported in the negative than neutral condition. A post-hoc examination of the neutral condition did reveal a trend towards significance for coping style [F(2, 46) = 3.13, p = .054] in that high-anxious individuals reported significantly more distracting thoughts than low-anxious individuals [t(31) = 2.28, p b .03]. Error rate was unrelated to the number of distracting thoughts. The overall trend for distracting thoughts was not in the direction postulated by De Ruiter and Brosschot (1994). The high-anxious group reported the greatest number of distracting thoughts overall and also exhibited the longest reaction times overall. 3.2. Performance measures 3.2.1. Emotional Stroop task: reaction time Two 3 × 4 mixed ANOVAs [coping style(3) × interference condition (4)], one for the negative and one for the neutral forms of the EST, revealed that stimuli containing interference, such as a blue-nonsense probe or a red-word probe, resulted in longer reaction times than the no-interference stimulus (blue-word probe), F(3, 42) = 49.42, p b .0001, and F(3, 42) = 31.25, p b .0001 respectively (see Table 3). No significant differences between coping styles were identified. A one-way ANOVA comparing negative and neutral forms of the EST showed that reaction times were significantly longer during the negative form of the task than the neutral form of the task, F(1, 44) = 21.36, p b .0001. 3.2.2. Emotional Stroop task: errors A similar ANOVA was performed for number of errors. A main effect for interference type emerged, F(3, 42) = 17.79, p b .0001. Interference stimuli produced more errors than the non-interference stimuli for the neutral and negative conditions of the task, F(3, 42) = 6.72, p b .001 and F(2, 42) = 25.55, p b .0001, respectively. Repressors committed more errors than high anxious participants in the word interference condition of the negative EST t(26) = 2.09, p b .05. There were no other significant differences between coping style groups, which could be due to participants making few errors. 3.3. EEG data analysis EEG data were screened for artifact, and fast Fourier spectral analyses were performed from each channel (2 Hz–64 Hz) and mean magnitude was calculated for the following frequencies: broad band theta (3.5–7.45 Hz), low theta (3.5–5.45 Hz), high theta (5.5– 7.45 Hz), broad band alpha (7.5–13.45 Hz), low alpha (7.5–9.45 Hz), mid alpha (9.5–11.45 Hz), high alpha (11.5–13.45 Hz), broad band

Mean Number of Self-Reported Distracting Thoughts

were randomly presented over 100 trials in each condition. Participants pressed the letter “L” on a keyboard for a “target” stimulus consisting of a red nonsense letter-string (presented on 25% of trials) and pressed the letter “A” for all other word/color combinations. Each trial last 1500 ms; if the participant responded before the end of the trial the word remained on the screen until the end of the trial.

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3.5 3 2.5 2 1.5 Low-Anxious

1

High-Anxious Repressor

0.5 0 Neutral

Negative

Stroop Interference Task

Fig. 1. Mean number of self-reported distracting thoughts for low-, high-anxious, and repressor coping styles on the emotional Stroop interference task.

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Table 3 Mean RT by stimulus type for low-, high-anxious, and repressor coping styles on both conditions of the emotional Stroop task. Stimulus type

Low-anxious Neutral M SE Negative M SE High-anxious Neutral M SE Negative M SE Repressor Neutral M SE Negative M SE

Non-target

Color

Word

Target

606.28 36.90

675.84 40.83

613.64 41.64

704.51 32.61

610.44 44.60

761.53 52.96

628.96 42.50

703.47 37.96

626.06 36.90

730.75 40.83

641.66 41.64

762.60 32.61

656.41 44.60

798.64 52.96

681.75 42.50

761.46 37.96

643.17 38.30

746.71 42.37

691.92 43.21

789.27 33.85

671.09 46.28

846.54 54.96

714.09 44.10

783.64 39.40

(ANOVA). One problem is that said ANOVAs would indeed be separate, not taking into account any overlap in variance across the electrode sites, and would result in a redundant description of the data. DFA, being a more concise tool, takes this overlap into account by incorporating the shared variances, thus providing one analysis for an overlapping data set such as the one in the present study (Tabachnick and Fidell, 2001). All of the reported Fs were derived by Wilks' Lambda, and where appropriate, follow-up examinations were carried out with post-hoc tests. In order to examine the hemispheric distribution of spectral power within each of the tested frequency distributions, mixed ANOVAs [coping style (3) × hemisphere (2) × task (3)] were conducted. Site was used as a factor in the ANOVAs instead of deriving laterality ratios, because laterality ratios have been criticized for their inability to distinguish between the absolute contributions of the hemispheres (Beaumont et al., 1984). Mauchly's W was calculated for every test, and when necessary the F-values were those obtained after Greenhouse–Geisser corrections. Any significant findings were further analyzed using post hoc t-tests. 3.4. EEG data

beta (13.5–19.45 Hz), beta 13 (13.5–16.45 Hz), and beta 16 (16.5– 19.45 Hz). These frequencies are considered to reflect emotional processing (Crawford et al., 1996). Data were log transformed due to the commonly observed positively skewed frequency distribution of EEG with high kurtosis (Sterman et al., 1994). Discriminant Function Analyses (DFA) [coping style (3) × task (3)] were performed on each of the seven EEG bands relevant to the tasks in order to determine if differences between groups and conditions existed and if the differences were consistent within the bands. Historically, the purpose of DFA has been to predict group membership. Presently, DFA is also used to investigate differences among groups (Huberty, 1994). The questions addressed by DFA are the same as those addressed by multiple analyses of variance (MANOVA), but reversed. In essence, if coping styles differ significantly on their electrical activity at the various electrode sites in MANOVA, the pattern of EEG activity from these electrode sites will reliably reflect the different coping styles in DFA. However, the advantage of DFA over MANOVA is that DFA objectively reports how many effects exist in the data. With MANOVA, one would have to conduct separate follow-up analyses of variance

Fig. 2. Mean reaction time for low-, high-anxious, and repressor coping styles on the emotional Stroop Interference task.

3.4.1. Low and high theta activity (3.5–7.45 Hz) No significant differences. 3.4.2. Low alpha activity (7.5–9.45 Hz) The overall DFA for the low alpha band identified main effects for coping style and task condition, F(38, 228) = 1.64 and 1.55, p b .05 for both. Eigenvalues indicated a single effect related to coping style present at the left prefrontal (Fp1) and lateral frontal (F7 and F8) sites. Repressors produced more low alpha than low- (t = 2.32, p = .029) and high-anxious individuals (t = 2.66, p = .014; Fig. 2). The hemispheric analyses revealed no unique interactions among coping style, task, and hemisphere. 3.4.3. Mid alpha activity (9.5–11.45 Hz) In the mid alpha band, DFA revealed main effects for coping style and for task condition, respectively, F(38, 228) = 2.16 and 2.18, p b .001 for both. Eigenvalues revealed one effect of coping style on mid alpha activity, and examination of the univariate tests showed that this effect was present at the right lateral frontal site (F8). Followup analyses showed that repressors produced significantly more mid alpha than either low- or high-anxious participants (Fig. 3; t = 2.99, p = .006 and t = 1.97, p = .06, respectively). Mixed ANOVAs examining hemispheric distribution of mid alpha power revealed significant effects of hemisphere at frontal, central, parietal, and occipital regions. Participants generated more mid alpha at the left prefrontal (Fp1) than right prefrontal site (Fp2; t = 2.30, p = .027). At the central region, hemisphere interacted with task condition, F(2, 132) = 9.93, p b .0001. During the eyes-open condition more mid alpha occurred at the right central region (C4) than the left region (C3) while the opposite was true for the neutral condition. In the parietal region, task condition and site interacted, F(2, 132) = 3.59, p b .05. There were no differences in lateralization during the eyes-open and neutral versions of the EST, but mid alpha power was greater in the left (P3) than right (P4) parietal region during the negative version of the EST (t = 2.16, p = .037). Site and coping style measures interacted in the occipital region, F(2, 132) = 3.07, p b .05. Follow-up t-tests revealed a trend in which repressors produced a similar amount of mid alpha power to low- and high- anxious individuals in the (O2) region. However, low- and high-anxious individuals produced more mid alpha than repressors in the left occipital region (O1; t = 2.24, p = .031). 3.4.4. High alpha activity (11.5–13.45 Hz) In the high alpha band, main effects were identified for coping style and task condition, F(38, 228) = 2.19 and 2.24, p b .001 for both.

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Fig. 3. Errors for low-, high-anxious, and repressor coping styles on the emotional Stroop interference task.

The eigenvalues for coping style showed two effects. Univariate tests showed that the first effect was isolated to frontal sites (Fp1, F4, and FZ). Further comparisons revealed that repressors produced more high alpha than high-anxious individuals at (FP1; t = 2.06, p = .05). Together, low- and high anxious individuals produced less high alpha than repressors (t = 1.98, p = .055). The other effect of coping style was limited to the right lateral frontal site (F8). Repressors produced more high alpha than high-anxious individuals, who produced more high alpha than low-anxious individuals (Fig. 4). Further exploration revealed that repressors produced more high alpha power during the neutral form of the EST than the other groups (t = 2.30, p = .027), the other groups produced more alpha power during the eyes open condition (t = 2.42, p = .020), and there were no differences in alpha power during the negative form of the task.

3.4.5. Beta 13 activity (13.5–16.45 Hz) DFA identified a main effect of coping style, F(38, 228) = 1.97, p b .05. Eigenvalues revealed a single effect of coping style: repressors

produced more beta 13 than low- or high-anxious individuals. Univariate tests revealed that this effect was found at all sites except lateral frontal (F7, F8) and right fronto-temporal (T4), as seen in Fig. 5. The analyses of hemispheric differences identified significant interactions in the temporal and occipital regions. In the temporal region there was a significant interaction between coping style and electrode site, F(6, 132) = 3.92, p b .0009. There was a trend towards repressors producing more beta 13 in the posterior temporal region than low- individuals (t = 2.31, p = .029). Repressors also produced substantially more beta 13 in the posterior temporal regions (T6) than the anterior temporal regions (T4; t = 3.99. p = .002). 3.4.6. Beta 16 activity (16.5–19.45 Hz) A main effect of coping style type was identified, F(38, 228) = 2.80, p b .0001, and examination of the eigenvalues revealed a single effect of coping style on electrode site. Follow-up analyses showed this effect to be that repressors produced more beta 16 than low- or high-anxious individuals. The effect occurred in parietal (P3; t = 2.44, p = .019: P4; t = 2.55, p = .015: PZ; t = 2.50, p = .017), and right occipital (O2; t = 2.67, p = .011) sites by the univariate tests (Fig. 6). The hemispheric analyses revealed no unique interactions among coping style, task, and electrode site. 3.5. Summary of EEG findings

Fig. 4. Electrode sites where low alpha activity was significantly different across coping styles.

Discriminant Function Analyses revealed a single consistent effect of task condition on EEG. The effect appeared in low, mid, and high alpha bands. The effect was the result of greatest alpha being produced during the eyes open condition and the least being produced during the negative version of the EST. Between the three bands, several differences between log mean magnitudes and cortical distribution suggest one underlying pattern of alpha production that is strongest in the mid alpha power spectrum with a cortical maximum in the parieto-temporal region (Fig. 3). The DFAs revealed a complex pattern of differences related to coping style. Differences were identified in the low, mid, high alpha, beta 13, and beta 16 bands. In the alpha bands two different effects

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Fig. 5. Topographic distribution of mid alpha activity in repressors, low-, and high-anxious individuals during eyes open passive fixation, neutral Stroop, and negative Stroop conditions.

were identified on the basis of eigenvalue scores. The first effect was distributed across different frontal cortical sites in different alpha bands. Repressors produced more low and high alpha power at frontal sites than high-anxious individuals, who in turn produced more than low-anxious individuals. The second effect was observed exclusively at the F8 site. It was present in mid and high alpha bands, but log mean magnitude scores indicated it was predominantly a mid-alpha phenomenon. This effect was the result of greater mid and high alpha power in high-anxious participants than in low-anxious participants. Repressors still had the greatest log mean magnitude score of the groups. A main effect was identified for coping style type in the beta 13 and beta 16 bands. However, log mean magnitude scores indicated a posterior maximum as opposed to the frontal maximum observed in

the alpha bands. This effect was consistent across all sites, and similar to the first effect identified in the alpha bands. Repressors produced the most beta, and low-anxious individuals produced the least beta. The effect was more widely dispersed and stronger in the beta 13 band than in the beta 16 band. 4. Discussion The present study explored EEG differences to an emotional Stroop test in three coping style groups – repressors, low-anxious, and highanxious – while simultaneously recording reaction time. These dependent measures are addressed separately, starting with the behavioral measures. 4.1. Behavioral measures As is commonly seen in the literature, all individuals were more affected by word interference than color interference. Participants were also more affected by the negative form of the task than the

Fig. 6. Electrode sites where high alpha activity was significantly different across coping styles. Note. Two patterns occurred in the high alpha band. The first effect was observed in electrodes F1, F4, andFz, where repressors produced more high alpha than lowanxious individuals, and low-anxious individualsproduced more high alpha than highanxious individuals. The second effect occurred in electrode F8.Repressors produced more high alpha than high anxious individuals, who in turn produced more high alphathan low-anxious individuals.

Fig. 7. Topographic distribution of beta 13 activity in repressors, low-, and high-anxious individuals during eyes open passive fixation, neutral Stroop, and negative Stroop conditions.

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4.2. EEG activity

Fig. 8. Electrode sites where beta 16 activity was significantly different across coping styles.

neutral form. However, group RT EST performance differences did not emerge (Fig. 7), although repressors did make more errors on the task than high anxious individuals (Fig. 8). This coincides with the Brosschot et al. (1999) study in which the authors did not find any group effects on a version of the Stroop with threat-related words. The non-significant RT results for the repressor group as compared to the other groups were in the predicted direction. When considering the behavioral findings together, it is possible that a trade-off between reaction time and errors may have occurred. In the future a design of this study that controls errors could be utilized to test this theory. On the other hand, Weinberger et al. (1979) reported faster mean reaction times for low-anxious than repressor individuals to the aggressive and sexual sentence completion versions of the task, but participants did not differ on the neutral condition. It may be that the type of stimuli and the complexity of the task contribute to whether or not reaction time differences are seen among repressors. These findings were consistent with the results of Brosschot et al. (1999) who have argued that interference during the Stroop might be triggered by very general characteristics of the stimuli such as “threatening” as opposed to “socially threatening”. In the 1999 study, all participants responded to physically threatening words and these words appeared to differentiate between groups more so than other words. The researchers argued that threat bias during interference might occur relatively early during stimulus processing. It may be that threat processing, to more general aspects of a stimulus, does not adequately differentiate between groups. However, in the present study, the stimuli may not have been adequately threatening to engage early threat related processing. Another paradigm, such as the visual probe task (VPT) may access a later phase of threat processing. In Brosschot et al. (1999) responses to a VPT did differentiate between groups with different coping styles. The difference between early and late processing paradigms can be tested comparing Repressors, Low-, and HighAnxious individuals on EST and VPT versions of the test in the current study. Participants in Kline et al. (1998a) were measured at rest in either eyes-open or eye-closed conditions. It is interesting that differences in EEG between these coping styles can be observed at rest, and suggests that coping styles are ongoing processes that may interact with experimental conditions. Because coping may be more strongly influenced by trait rather than state variables, it may be that tasks which target ongoing states, such as emotional states, may be more suited to isolating behavioral effects. Tomarken et al. (1990) successfully used resting brain states to predict emotional responses to films. A paradigm in which a reaction time task is embedded within emotional film could access the ongoing nature of coping. A further explanation of the findings is that the negative stimuli used in the current study were not as “arousing” as stimuli presented in other research. In particular, Kline et al. (1998b) presented a condition with sexually taboo words which significantly impacted task performance.

4.2.1. Cortical distribution In the present study, increases in broad band alpha magnitude were identified in the right frontal region, and analysis of narrower EEG bands revealed that two different effects occurred across bands. Repressor women had more right medial and lateral frontal activation than low- and high-anxious individuals. This contradicts Tomarken and Davidson's (1994) observation that repressor women had greater relative left frontal activation which led them to theorize that the repressor coping style is correlated with resistance to psychopathology. However, as Kline and Allen (2008) discuss, the repressor coping style is more vulnerable to physical and emotional symptoms. They noted a tendency towards greater relative right frontal hemisphere activation in repressors. Because models of coping reflect an interaction between the coping style and the environment, it is possible that both types of activation are present in repressors. The left greater than right activation may occur when repressors are successfully able to avoid a negative stimulus (such as during an at rest condition), and a right greater than left activation when repressors are not able to avoid threatening stimuli (such as during an autobiographical memory task). Kline and Allen (2008) have labeled this latter group of repressors “failed repressors”. The relationship between greater right relative activation and the repressor coping style is further complicated by the impact of selfreported depression. Depression tends to correlate with hemispheric asymmetries in cortical activation. In the current study, the three groups did not differ on significantly on depression which may have contributed to the overall lack or findings related to right anterior activation. Tomarken and Davidson (1994) argue that a combination of heightened task focus and fewer self-directed ruminations are optimal for task performance. Individuals with depression or anxiety may not be able to perform tasks easily following errors, because of an increase in self-directed ruminations. Repressors, who self-report fewer self-directed ruminations and higher goal directed strategies, should continue to perform well on tasks that do not involve activation of the active inhibitory networks. Repressors produced more beta 13 than either low- or highanxious individuals, and this difference had a relative posterior maximum. In addition, in the posterior-temporal region, beta 13 was significantly greater in the right than in the left hemisphere for repressors but not for the other groups. Heller (1993) posits that the right parieto-temporal region plays an essential role in the modulation of emotional arousal. Greater right than left posterior temporal beta 13 may reflect a higher level of transient mood changes, but more likely reflects greater task vigilance associated with threatening stimuli reported by Kline et al. (1998b). The frontal distributions of the alpha bands contrasting with the posterior maximum beta 13 band may reflect the interplay between an anterior attentional system and a posterior arousal system. Theorists in the field of repressor research rarely explain the cortical processes underlying the mechanisms of repressive coping. Attention and avoidance are posited as potential processes; no model exists which incorporates the way that these mechanisms may actually function within the repressor coping style. Putnam et al. (2010) have suggested that the beta band is more informative when analyzed with respect to theta. They argue that the ratio of theta to beta is predictive or response-inhibition and affective states; specifically greater theta to beta ratio is predictive of trait approach motivation while lower ratios are predictive of anxiety. In the current study, theta remained unaffected by coping styles while Beta bands increased in repressors in relation to low- and highanxious individuals which may suggest an increase response inhibitory processing.

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4.2.2. Theta Whereas earlier repressor/EEG research has often evaluated broad alpha and theta frequency bands, this study assessed low and high theta, low, mid, and high alpha, and also two beta bands. Lorig et al. (1994–95) found that theta power was suppressed more in the right than left hemisphere during the recall of positive and negative words in repressors compared to non-repressors. The current study did not find any significant coping style differences in the theta bands (associated with arousal) during the EST. Broad band theta (4–7 Hz) has been associated with emotional states, induced stress, recall of emotional memories, and sexual arousal (for reviews, see Crawford et al., 1996). The lack of findings related to theta within the current study suggest that the paradigm did not illicit an emotional state within the participants. The beta 13–16 Hz band has been associated with task specific vigilance (Mann et al., 1996). The findings of greater Beta13 in repressors than other participants suggest greater task vigilance than other participants. Although greater right than left hemisphere Beta activity has been associated with positive emotions (Schellberg et al., 1990), low frequency beta in the temporal region is more commonly associated with negative relative to positive emotions (Cole and Ray, 1985). In the current study the greater temporal region Beta13 seems to suggest more transient negative attentional changes during the Negative task for Repressors than other participants. 4.2.3. Low alpha Because of the nature of the task, repressors were allowed to shift their attention away from the negative valence of the threatening words and engage in a rather shallow level of cognitive processing when making the decision if the stimulus was a target or not. These participants successfully employed their default strategy (Coifman et al., 2007) in order to cope with the threatening words. In order to further explore whether or not repressors were actively engaged in the task we examined whether participants who made fewer errors had longer reaction times. Repressors committed more errors during interference in the Negative Stroop Task than High Anxious individuals. To explore the relationship of errors to reaction we divided the coping style groups into sub-groups based on median number of errors (5), each group was subdivided into those who made fewer than five errors and those who had made five or more errors. A Chi-square analysis indicated no significant differences in the distribution of low and high error scores across the three groups Ns, χ2(5, N = 48) = 4.00. A mixed ANOVA examined the possible moderating effect of error rates on the reaction time data for the word interference condition. There was a significant interaction between coping style and error rate, F(2,42) = 5.13, p b .01. Low-anxious participants who made fewer errors had longer reaction times than those who made many errors. This suggests that the lowanxious individuals who made fewer errors were performing the task more carefully. Within the high-anxious group, there were no significant differences between individuals who made few errors and those who made many errors. By contrast, repressors who made five or more errors had significantly longer reaction times than those who made less than five errors. Follow-up analyses of reaction time across error groups and coping styles revealed significant differences between valence and coping style in the low error group, F(2,24) = 5.67, p b .01, such that repressors had the fastest reaction times, followed by high-anxious individuals, and then low-anxious individuals. In the high error group, there were no significant differences. Another way to examine this data is to explore the number of distracting thoughts participants reported following performance of each version of the task. Higher self-reported anxiety is associated with higher self-reports of distracting thoughts. In the current study, high-anxious individuals appeared to have greater interference from distracting thoughts across tasks than low- anxious individuals and repressors suggesting a relatively intransient anxiety state. An

examination of the self-reported numbers of distracting thoughts within the other groups revealed that low-anxious participants and repressors reported relatively more distracting thoughts during the negative condition than the neutral condition. These data suggest that repressors did not experience anxiety related to the task. In combination the post-hoc error analysis and self-reported distracting thoughts data suggest that repressors were not highly engaged in the task and the task did not produce anxiety in repressors. Either the demands of the task were simply not great enough to draw enough attention to the negative words or the perceived intensity level of threat was too low allowing participants to employ their default strategy (Coifman et al., 2007) in order to cope with the threatening words (as described by Langens and Mörth, 2003). This strategy would account for the increased low alpha activity seen in the repressor group. 4.2.4. Mid alpha The increase seen in repressors over the other two groups could be explained by fewer fluctuations in the attentional resources (Crawford et al., 1996) of repressors. Repressors reported fewer distracting thoughts during the task than high anxious individuals, but not low anxious individuals. However, repressors who committed more errors did not demonstrate faster reaction times as observed in the lowanxious group. The low-anxious individuals who committed fewer errors may have been performing the ask more carefully as shown by their reaction times. However, the RT/error tradeoff does not explain the findings related to repressors. Considered along with the self-report and behavioral data, the greater mid alpha power in repressors may suggest less task dependent attentional fluctuations than was observed in the other groups. 4.2.5. High alpha If general mental workload leads to desynchronization of high alpha (Crawford et al., 1996), it follows that repressors engaged in less mental workload than the other two groups. This finding coincides with the explanations set forth for low and mid alpha regarding the coping strategy employed by the repressor women in order to avoid the threatening stimuli. In this study, EEG bands typically associated with emotional arousal did not differ between groups and conditions which suggest that the task may not have triggered emotional resources. However, bands associated with attentional allocation to valence did differ between groups and conditions which suggest that participants did evaluate stimuli in the two conditions of the EST differently. Behavioral data and self-report data support the assertion that the neutral and negative forms of the task did impact participants differently. Following the study most participants reported that they noticed a difference between the two conditions of the EST (92%); however, only 2 were able to explain the difference between the stimuli. This provides a small indication that the emotional valence of the stimuli did not reach awareness, and that intentional avoidant processing of the stimuli did not occur. This suggests that valence of the stimuli did not reach a recognition threshold and that coping processing of the stimuli remained unconscious (Kline et al., 1998a,b; Langens and Mörth, 2003). 4.2.6. Beta 13 and 16 Both bands are considered to be indicators of emotional processing and vigilance (Crawford et al., 1996). Although repressors seemingly employed their default coping strategy when performing the task and avoiding the threatening content as suggested by activity in the three alpha bands, they may have still been more susceptible to the emotional information contained within the negative word condition, resulting in more beta 13 and 16 than the low- and high-anxious women. However, the EEG data across coping styles was only differently affected by task within bands in which transient

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attentional states predict power such as high alpha. This suggests that most of the data can be explained by more stable trait variables. 4.2.7. Task condition The attention styles of repressors, low-anxious and high-anxious women were not contingent upon task condition (eyes-open, neutral, or negative). It is possible that the artificial nature of a laboratory environment forced all participants to engage in same-level processing throughout the study, even in the absence of negative stimuli. The current study did not involve pleasant words as a control condition. Kline et al. (1998a,b) identified right frontal alpha suppression in high defensive participants to sexual, but not pleasant words, when the words were presented near the recognition threshold. However, participants detected both classes of words with lower accuracy. This suggests that the relationship between defensiveness and pleasant stimuli is also theoretically relevant when exploring the repressor coping style. Future research should incorporate positive stimuli as an experimental condition. One particularly interesting approach may be imbedding event related stimuli within emotion provoking films. Event-related measures would be able to access the transient attention related phenomenon while EEG data could be collected to assess longer duration mood states. 4.3. Conclusion The repressor coping style was originally proposed as a way to account for discrepancies between self-reported anxiety and autonomic arousal. Only the self-regulation theory of health attempted to explain how the mechanism of repressive coping may result in increased autonomic arousal (Jamner et al., 1988). The current study applied the concepts proposed by Derakshan and Eysenck (1998) to a physiological model of attention and arousal. During periods of negative stimulation, it is likely that attentional modulation resulting from interpretive bias affects the anterior attentional system while emotional regulating processes affect the posterior system. Both outcomes may differentiate repressors from low-anxious and highanxious individuals. EEG evidence from this study suggests that repressor women are sensitive to emotional stimuli but do not process it as fully as other individuals. This is indicated by increased mean magnitude in bands negatively correlated with attention and increased mean magnitude in bands related to emotion. The EEG findings also indicate that sustained attentional processes fluctuate less in repressors than other individuals (because they remain consistently low). Many of the current findings coincide nicely with Eysenck's four factor theory (Derakshan and Eysenck, 1997) and provide an excellent point of departure for future research. For example, future studies could consider developing a task that requires an active inhibitory process to high levels of threat rather than the passive process presumably used by participants in this study. This study was limited inability to identify a defensive group in the original sample of 470 volunteers. Kline and Allen (2008) suggest that defensive individuals often self-report psychopathological symptoms associated with distress in social contexts. Defensive individuals may have been unwilling to attend testing sessions. However, our BDI scores were consistent with Kline and Allen's (2008) sample of women [M = 7.98 (5.26) vs. M = 7.22 (5.99)], while our sample selfreported a lower SDS scores than were reported by Kline and Allen [M = 13.86 (1.95) vs. M = 16.25 (4.78)]. Kline et al. (1998b) theorized that defensiveness may actually serve to increase stress when left frontally instantiated cognitive and motivational systems are not involved in the processing, and in this study we were not able to address that aspect of the repressor/ defensor construct. The conclusions from this study can only be applied to repressors and not defensive individuals.

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