Personality and Individual Dierences 28 (2000) 1063±1077
www.elsevier.com/locate/paid
Trait anxiety, defensiveness and selective processing of
threat: an investigation using two measures of attentional
bias
Karin Mogg*, Brendan P. Bradley 1, Claire Dixon, Susan Fisher,
Helen Twelftree, Andrew McWilliams
Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge, CB2 3EB, UK
Received 14 December 1998; received in revised form 21 June 1999; accepted 26 June 1999
Abstract
Attentional biases for threat were examined in a non-clinical sample (N = 60), with each participant
tested on both the modi®ed Stroop colour-naming and dot probe tasks. Three groups were selected on
the basis of trait anxiety and social desirability scale (SDS) scores: ``low anxiety'' (LA: low trait, low
SDS), ``repressor'' (REP: low trait, high SDS) and ``high anxiety'' (HA: high trait, low SDS). Results
from the colour-naming task suggested that high levels of defensiveness (in combination with low trait
anxiety) were associated with greater avoidance of threat. The REP group showed less interference in
colour-naming threat than neutral words; whereas the HA group showed increased interference due to
threat words. On the dot probe task, there was a general tendency for this non-clinical sample as a
whole to show avoidance of social threat relative to neutral words, but there was no bias for physical
threat words. Avoidance of social threat was signi®cant only within the REP group. No relationships
were found between the measures of cognitive bias from the two tasks, suggesting dierent underlying
mechanisms. Results are discussed in relation to previous ®ndings and theoretical views of the eects of
anxiety and defensiveness on the processing of threat. 7 2000 Elsevier Science Ltd. All rights reserved.
Keywords: Anxiety; Defensiveness; Attentional bias
* Corresponding author.
1
Correspondence may also be addressed to Brendan P. Bradley
0191-8869/00/$ - see front matter 7 2000 Elsevier Science Ltd. All rights reserved.
PII: S 0 1 9 1 - 8 8 6 9 ( 9 9 ) 0 0 1 5 7 - 9
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1. Introduction
There has been considerable interest in research into attentional biases for threat information
in anxiety because recent cognitive theories have proposed that such biases may play a key role
in the development and maintenance of clinical anxiety states (e.g., Mathews & MacLeod,
1994; Eysenck, 1992; Williams, Watts, MacLeod & Mathews, 1997). It is well-established that
clinically anxious individuals show an attentional bias towards threat cues (e.g., reviews by
Mathews & MacLeod, 1994; Mogg & Bradley, 1998). If such biases do indeed provoke or
intensify clinical anxiety states, then it may prove useful for anti-anxiety treatments to target
them; i.e., to encourage anxious patients to adopt a more ``normal'' attentional style. However,
a potential problem with such an approach is that there is considerable uncertainty about what
constitutes a normal pattern of bias, as the speci®c emotional and personality variables that
determine the presence or absence of attentional biases for negative information in the normal
population are not well understood.
One key issue is whether normal, low anxious individuals have a tendency to divert their
attention away from unpleasant information, or whether they have no attentional bias, either
towards or away from threat. A tendency to disregard trivial unpleasant stimuli in the
environment might serve at least two useful functions. First, it would seem helpful in
maintaining attention on current goals and in protecting against the distracting eects of minor
task-irrelevant negative cues. Second, it may assist in mood regulation; that is, in reducing
anxious mood and in maintaining positive mood states. Experimental evidence of avoidance of
mildly aversive information has been suggested by several studies (e.g., avoidance of threat
words or faces in normal or non-dysphoric samples; MacLeod, Mathews & Tata, 1986;
Bradley, Mogg, Millar, Bonham-Carter, Ferguson, Jenkins & Parr, 1997), although it does not
seem to be a very robust eect given that it has not been universally found in studies of
attentional bias.
One reason why avoidance of threat may be dicult to demonstrate reliably is that it may
not simply be a function of low anxiety, but it may also be determined by other personality
variables, such as defensiveness. One proposal is that there are two subtypes of low trait
anxious individuals, who can be discriminated on the basis of scores on the Social Desirability
Scale (SDS; Crowne & Marlowe, 1964). High SDS scores are assumed to re¯ect high levels of
defensiveness, a high need for social approval, and a reluctance to report negative emotional
states. Thus, one may distinguish between low trait anxious individuals with low levels of
defensiveness (i.e. ``true low anxious''), and those with high levels of defensiveness (i.e., socalled ``repressors''). Weinberger, Schwartz and Davidson (1979) found that repressors
exhibited greater somatic responses to stress than did low trait anxious individuals, suggesting
that repressors are physiologically anxious despite their self-reports of low subjective anxiety.
Thus, repressors may resemble high trait anxious individuals in terms of their physiological
and cognitive responses to threat, but may consistently under-report their anxiety levels
because of concern to make a positive impression on others. An alternative view is that
repressors have a defensive bias in selective attention; i.e., a cognitive ®lter, or schema, which
results in avoidance of negative or threatening cues (Bonanno & Singer, 1990). Indeed,
Eysenck (1997) speci®cally proposed in his new cognitive theory of anxiety that repressors have
a cognitive bias opposed to the processing of threat, whereas high trait anxious individuals
K. Mogg et al. / Personality and Individual Dierences 28 (2000) 1063±1077
1065
have a bias in favour of threat, and low trait anxious individuals have no bias (see also
Derakshan & Eysenck, 1997).
Experimental evidence of the relative eects of trait anxiety and defensiveness on attentional
biases is mixed. Such research has typically compared three groups: low anxiety (LA; low
anxiety, low SDS), repressor (REP; low anxiety, high SDS) and high anxiety (HA; high
anxiety, low SDS). The fourth combination, so-called ``defensive high anxiety'' (i.e., high
anxiety, high SDS) seems to be relatively uncommon (Weinberger et al., 1979). In one study,
using a modi®ed Stroop task to investigate processing biases for threat, Dawkins and Furnham
(1989) found that REP and HA were slower to name the colours of threat than neutral words,
whereas LA showed no eect. These results suggested not only dierent patterns of cognitive
bias for threat within those reporting low trait anxiety (i.e., LA and REP), but that repressors
resembled high trait anxious individuals in showing vigilance for threat.
However, Fox's (1993) study suggested the opposite conclusion. She used a dot probe task
to assess attentional bias, in which pairs of words were presented for 500 ms, one word above
the other, and participants read aloud the upper word. On occasional trials, a dot probe
appeared in the location of one of the words, and participants were required to respond to the
probe as quickly as possible by pressing a key. The rationale for the task is that participants
are faster to respond to probes in attended rather than unattended spatial locations (e.g.,
Posner, Snyder & Davidson, 1980); so the pattern of RTs to probes indicates the allocation of
attention to the preceding words. This task had been previously used by MacLeod et al. (1986)
to demonstrate an attentional bias for threat words in generalised anxiety disorder (GAD).
Fox found that the HA group were faster to respond to probes replacing social threat words
than neutral words, consistent with vigilance for threat. By contrast, the REP group was
relatively slower to detect probes replacing social threat words, which suggested attentional
avoidance of social threat. The LA group showed no bias. Further evidence that was consistent
with an avoidant bias in repressors was suggested by a dichotic listening study where repressors
showed less disruption by negative words on the unattended channel than high trait anxious
individuals (Bonanno, Davis, Singer & Schwartz, 1991).
One variable that might account for such discrepant ®ndings is the use of dierent tasks to
assess attentional biases. Evidence suggesting vigilance for threat in repressors was obtained
from the card version of the Stroop, but this task has some drawbacks. Although interference
eects are typically interpreted in terms of attention being preferentially allocated to the threat
content, this interpretation is not entirely certain, because the interference eect may not
necessarily occur at the input stage of information processing, but at a later response selection
stage (e.g., C.M. MacLeod, 1991). Further interpretative diculties with the Stroop task have
been noted by de Ruiter and Brosschot (1994). On the one hand, interference eects might
re¯ect attentional vigilance, i.e., impairment in colour-naming is due to preferential allocation
of attention to the threat word content, consistent with the threat interference eects found in
high anxious individuals. On the other hand, interference eects might re¯ect cognitive
avoidance, whereby the impairment in colour-naming is due to increased processing resources
and eort being required to direct attention away from negative information; which may
account for the interference eects found in repressors. Their criticisms highlight the
importance of not relying on just one task to assess attentional biases.
The main aim of the present study was to investigate the eects of anxiety and defensiveness
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on attentional biases for threat information in a normal sample. A novel feature of the study
was that each volunteer was tested on two measures of attentional bias, so that we could
examine, within the same sample of participants, whether the use of dierent tasks may explain
the discrepant ®ndings noted above. One task was a computerised version of the emotional
Stroop task, similar to that used by Mogg, Bradley, Williams and Mathews (1993) to
investigate selective processing of threat information in GAD. In this task, words were
presented individually on a background ¯ash of colour, and vocal RTs and errors were
recorded separately for each word (which has an advantage over the card version of the Stroop
where RT data and errors are confounded). The second measure of attentional bias was
obtained from the dot probe task. One advantage of this task is that it does not rely on
interference eects to measure attentional biases, and so vigilance for threat should be evident
from relatively faster responses to probes in the location of threat words. The task used here
was similar to that used by Mogg, Bradley and Williams (1995), in which on each trial, a word
pair was brie¯y presented, immediately followed by a dot probe in the location of one of
words, and participants indicated the position of the probe as quickly as possible by pressing
one of two response keys. This forced-choice version of the task was based on that used by
Posner, Snyder and Davidson (1980, Experiment 3).
One prediction was that high trait anxiety should be associated with greater vigilance for
threat words relative to neutral control words, following from cognitive formulations of
anxiety±congruent biases in selective attention. This eect should be evident from slower RTs
to threat than neutral words on the Stroop task, and faster RTs to probes replacing threat
than neutral words on the dot probe task. A second prediction was derived directly from Fox's
(1993) ®ndings and Eysenck's (1997) theory Ð that is, repressors should show attentional
avoidance of threat words. Moreover, such avoidance should be most apparent for words
related to social threat (Fox, 1993). This eect should be evident from faster RTs to threat
than neutral words on the Stroop task, and faster RTs to probes replacing neutral than threat
words on the dot probe task.
2. Method
2.1. Participants
One hundred and seventy four students volunteered for the study and returned by post a
screening questionnaire consisting of 20 items from the Taylor Manifest Anxiety Scale (TMAS)
and 10 from the SDS. The short-form TMAS was used for screening because it provides a
convenient estimate of trait anxiety, with True/False response format compatible with the SDS,
and it correlates 0.93 with the full TMAS (Bendig, 1956). The short-form SDS (Form X1,
Strahan & Gerbasi, 1972) has been found to correlate 0.96 with the full SDS (Fischer & Fick,
1993). To minimise the proportion of the sample with mid-range levels of anxiety and
defensiveness, those with extreme TMAS and SDS scores were favoured in recruitment (except
for those with high scores on both, i.e., ``defensive high anxious''). There were 60 in the ®nal
sample.
K. Mogg et al. / Personality and Individual Dierences 28 (2000) 1063±1077
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2.2. Materials
The stimulus words were taken from previous research into anxiety-related attentional biases
(e.g., Fox, 1993; Mogg et al., 1993, 1995). There were two types of threat words: 48 related to
physical threat (e.g., cancer, mutilated) and 48 related to social threat (e.g., despised, pathetic).
Another 48 categorised neutral words (household-related words, e.g., toaster, furnished) served
as control stimuli. The three word sets were matched for length and frequency using Carroll,
Davies and Richman's (1971) norms. For the dot probe task, each word was paired with a
length and frequency matched uncategorised neutral word (e.g., downwind, mayor) to form
144 word pairs. For the Stroop task, an additional 48 uncategorised neutral words (length and
frequency matched with the categorised neutral words) were used as ®llers and to address a
subsidiary issue regarding the eect of word-categorisation on colour-naming interference.
Each set of words was divided into two equivalent lists, matched for length and frequency,
so that each participant received one list (i.e., half the words) in the dot probe task, and the
other in the Stroop task. The allocation of the word lists to the two tasks was counterbalanced
across participants. Thus, for each person, 72 word pairs were presented in the dot probe task
(i.e., 24 social threat, 24 physical threat and 24 categorised neutral words, each paired with an
uncategorised neutral word), and 96 words were presented in the Stroop task (24 social threat,
24 physical threat, 24 categorised neutral, 24 uncategorised neutral). The tasks were run on a
IBM 286 PC with MEL version 1 software (Schneider, 1988) and MEL response box with
built-in voice key.
2.3. Procedure
Half the participants received the Stroop task before the dot probe task, and vice versa for
the other half. Each was seated about 60 cm from the screen. In the modi®ed Stroop task,
there were 15 practice and three buer trials and 96 test trials presented in a new random
order for each person. The participant started each trial by pressing the keyboard space bar. A
®xation box (15 35 mm) then appeared for 500 ms in the centre of the screen. This was
replaced by a word in white uppercase letters (approx. 5 mm high) on a background patch of
colour that was either red, green or blue. To restrict the display of the colour (which ®lled one
line across the screen), each side of the screen was masked with black card (11 3.5 cm). The
colour background and word appeared simultaneously, with the colour displayed only for one
screen refresh (with a 14 ms refresh interval), while the word remained on the screen on a
black background until the participant's vocal response. They were instructed to ignore the
word, and to say aloud the colour as quickly as possible into a microphone, without making
errors. The experimenter recorded the content of the response (red, green, blue or other) by
pressing one of four keys.
In the dot probe task, there were 12 practice and 4 buer trials, followed by 72 test trials in
a new random order for each person. Each trial started with a ®xation cross for 500 ms in the
centre of the screen. This was replaced by a word pair in white uppercase letters for 500 ms
(approx. 5 mm high), with one word above and one below the central point (words were
approximately 3.8 cm apart). Immediately after their oset, a small dot probe appeared in the
location of one of the words, and remained displayed until the participant's response. They
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K. Mogg et al. / Personality and Individual Dierences 28 (2000) 1063±1077
were instructed to press either an upper or lower response key as quickly as possible, while
avoiding errors, to indicate the position of the probe. Threat words and probes were presented
in the upper or lower position of the display with equal probability. The inter-trial interval
varied randomly between 750, 1000 and 1250 ms.
After the attentional tasks, questionnaires assessing mood and personality were given
including state and trait versions of the State Trait Anxiety Inventory (STAI; Spielberger,
Gorsuch, Lushene, Vagg & Jacobs, 1983), Social Desirability Scale (SDS; Crowne & Marlowe,
1964), Beck Depression Inventory (BDI; Beck, Ward, Mendelson, Mock, & Erbaugh, 1961)
and ratings of physical and social worries. For the latter, participants rated their negative
thoughts and worries on two 9-point scales (ranging from 0=``not at all'' to 8=``extremely'')
and were asked to indicate how much they had been recently troubled by (i) anxious thoughts
about physical health concerns (e.g., illness, death or accidents), (ii) anxious thoughts about
social concerns (e.g., getting on with other people, embarrassment). These worry ratings have
been previously used to assess worry±congruent attentional biases in clinical anxiety on both
the Stroop and dot probe tasks (e.g., Mogg, Mathews, & Weinman, 1989; Mogg, Mathews, &
Eysenck, 1992).
3. Results
Alpha level was set at 0.05 level, two-tail, throughout.
3.1. Group characteristics
Participants were allocated to three groups according to their scores on STAI trait anxiety
and the full version of the SDS (these had been administered under standardised conditions, in
contrast to the brief postal, screening measures). The groups were determined according to the
following criteria: (1) Low anxious (LA), with trait anxiety scores of less than 37, and SDS less
than 15; (2) Repressors (REP), with trait anxiety scores less than 37, and SDS of 15 or more;
and (3) High anxiety (HA), with trait anxiety scores of 44 or more, and SDS less than 15.
These cutos1 produced three approximately equal-sized groups (ns were 16, 14 and 16,
respectively), which were similar in age and gender ratio, and also SDS and trait anxiety where
appropriate. That is, the HA and LA groups diered signi®cantly in trait anxiety, but had
comparable SDS scores; while the LA and REP groups diered signi®cantly in SDS, but had
1
Division of the sample using normative means as cutos (i.e., 40 on trait anxiety, 16 on SDS) produced three
unequal-sized groups: 22 LA, 13 REP and 23 HA, with only 2 volunteers not falling into these groups due to above
average scores on both measures. Results using these cutos were similar to those obtained from the main analyses
using more equal-sized groups. That is, for the Stroop task, there was a signi®cant eect of group on the interference eect of threat (F(2,52)=9.97, p < 0.05); with REP showing less interference of threat than neutral words
(ÿ14.0 ms), HA showing greater interference of threat than neutral (7.5 ms), and LA showing no bias (0.5 ms). For
the dot probe task, there was a signi®cant eect of threat type, but not of group, on bias scores (F(1,54)=4.28, p <
0.05); with greater avoidance of social threat (ÿ6.1 ms) than physical threat (ÿ0.5 ms) words. Mean social threat
bias scores were ÿ6.5, ÿ12.8 and ÿ2.3 ms for LA, REP and HA, respectively. Thus, these analyses produced similar
®ndings, but with the disadvantage of unequal sample sizes.
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K. Mogg et al. / Personality and Individual Dierences 28 (2000) 1063±1077
similar trait anxiety scores. Group comparisons using analysis of variance (ANOVA) and
Student±Newman±Keuls contrasts (see Table 1a) showed that the HA group had signi®cantly
higher trait and state anxiety, Beck depression and social worry scores compared with each of
the LA and REP groups, who did not dier on these measures. The REP group diered
signi®cantly from the LA group only in SDS scores. The three groups did not dier in physical
worry scores. Fourteen participants did not ful®l the selection criteria for the three groups
largely due to having mid-range trait anxiety scores, although their data were included in
correlational analyses conducted for the whole sample.
3.2. Preparation of RT data
Data from trials with errors were discarded. Box and whisker plots then were used to inspect
the RT data from each task and to determine outliers. Consequently, RTs of 200 ms or less
were excluded from both tasks, and also those of 900 ms or more in the Stroop task, and 750
ms or more in the dot probe task. Box and whisker plots also indicated that participants' data
were outliers if more than 20% were outside the RT cutos, or more than 10% were errors,
and so these were excluded from the analyses (one HA and one LA were lost from the Stroop
task, one REP from the dot probe task). Following these exclusions, the mean percentage of
data lost was 3% as errors, and 3% as outliers for the Stroop task; and 2% as errors and 2%
as outliers for the dot probe task. The three groups did not dier signi®cantly in error or
outlier rates in either task. The groups also did not dier signi®cantly in overall mean RT on
either task (see Table 1 for mean RTs in each condition).
3.3. Modi®ed Stroop task
Bias scores were calculated for each type of threat word by subtracting the mean RT for
control words (i.e., categorised neutral) from the mean RT for threat words. This produced
two bias scores for each participant: one for social threat, and the other for physical threat
words. Positive values of the bias scores indicate a greater interference eect of threat words,
relative to neutral control words, on colour-naming performance. The mean bias scores of each
Table 1a
Group characteristics
Gender ratio
Age
Trait anxiety
Social desirability
State anxiety
Beck depression
Social worry
Physical worry
ab
LA
REP
HA
F(2,43)
p
8/8
20.0
31.6a
9.4a
31.1a
5.6a
2.5a
2.6
7/7
19.9
31.0a
19.8b
31.2a
3.3a
2.6a
2.2
8/8
19.4
52.4b
8.8a
44.8b
13.7b
5.1b
2.3
1.12
67.95
40.95
20.75
20.76
13.76
0.21
ns
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
ns
Values with dierent superscripts dier at 5% level 2-tail.
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K. Mogg et al. / Personality and Individual Dierences 28 (2000) 1063±1077
Table 1b
Mean RTs for each word type condition in Stroop task
Social threat
Physical threat
Categorised neutral
Uncategorised neutral
LA
REP
HA
457.1
460.4
457.6
457.6
494.3
492.1
504.9
502.7
483.7
476.1
473.6
474.9
group are shown in the top part of Fig. 1. These scores were entered into a 3 2 mixed design
ANOVA with one between-subjects variable of group (3: LA, REP, HA) and one withinsubjects variable of threat type (2: social, physical). This showed a signi®cant main eect of
group on threat bias scores (F(2,41)=6.05, p < 0.01). The main eect of threat type (social vs
physical), and the group threat type interaction, were not signi®cant (Fs < 1).
Regarding the main eect of group on bias scores, Student±Newman±Keuls contrasts
showed that the REP group showed signi®cantly less interference in colour-naming threat
words (relative to neutral words) compared with both the LA group (mean bias scores were
ÿ12 ms vs 1 ms, p < 0.05) and the HA group (ÿ12 vs 6 ms, p < 0.05). The HA and LA
groups did not signi®cantly dier from each other in threat bias scores. Contrasts of the bias
scores against zero (where 0=no bias) indicated signi®cantly less interference of threat than
neutral words in the REP group (t(13)=2.39, p < 0.05); and signi®cantly greater interference
of threat than neutral words in the HA group (t(14)=2.28, p < 0.05).
Speci®c hypothesis-driven analyses were also conducted to test the prediction from Fox
(1993) of greater avoidance of social threat words in repressors. The three groups signi®cantly
diered in social threat bias scores (F(2,41)=5.92, p < 0.01), with the REP group showing
signi®cantly less interference of social threat, relative to neutral words, than the HA group
(Student±Newman±Keuls, p < 0.05). Contrasts of the social threat bias scores against zero
indicated signi®cantly less interference due to social threat than neutral words in the REP
group (t(13)=2.37, p < 0.05), and signi®cantly more interference due to social threat than
neutral words in the HA group (t(14)=2.36, p < 0.05).
Pearson correlations were calculated using the data from the whole sample, including those
Table 1c
Mean RTs for each condition in dot probe task
Threat type
Threat position
Probe position
LA
REP
HA
Social
Upper
Upper
Lower
Lower
Upper
Upper
Lower
Lower
Upper
Lower
Upper
Lower
Upper
Lower
Upper
Lower
352.7
355.7
355.1
364.5
356.4
357.8
346.1
350.6
376.3
369.9
356.9
378.0
383.9
364.6
377.9
358.2
381.4
372.0
370.7
373.8
380.3
375.0
377.2
369.5
Physical
K. Mogg et al. / Personality and Individual Dierences 28 (2000) 1063±1077
1071
who did not ful®l the selection criteria for the three groups. The threat bias score correlated
signi®cantly and negatively with SDS (r=ÿ0.43, p < 0.01), and positively with trait anxiety (r
= 0.27, p < 0.05), state anxiety (r = 0.31, p < 0.05), Beck depression (r = 0.28, p < 0.05), and
social worry scores (r = 0.30, p < 0.05). There was no relationship between the threat bias
score and physical worry ratings (r=ÿ0.01, ns). The lack of a relationship between physical
worry and trait anxiety may be partly due to ¯oor eects, as we used a healthy young sample
of students who seemed to have a relatively low level of physical health concerns.
Fig. 1. Mean attentional bias scores (in ms) for social and physical threat words in low anxiety (LA), repressor
(REP) and high anxiety (HA) groups on the modi®ed Stroop and dot probe task.
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K. Mogg et al. / Personality and Individual Dierences 28 (2000) 1063±1077
When the eect of SDS scores was controlled using partial correlations, there was a nearsigni®cant trend for the threat bias score to be associated with social worry ratings (r = 0.25, p
< 0.07, two-tail). No other correlations approximated signi®cance after controlling SDS (e.g.,
threat bias and trait anxiety: r = 0.14, ns). However, when the eects of trait and state anxiety,
Beck depression and social worry scores were partialled out together, the threat bias score
remained signi®cantly and negatively correlated with SDS (r=ÿ0.38, p < 0.01).
With regard to inter-correlations between the questionnaire measures, SDS scores correlated
negatively with trait anxiety (r=ÿ0.34, p < 0.01) and Beck depression (r=ÿ0.46, p < 0.05),
but not signi®cantly with the other emotion measures. The emotion measures were all
positively and signi®cantly intercorrelated (rs > 0.51, ps < 0.01), with the exception of physical
worry scores (e.g., physical worry and trait anxiety: r = 0.02, ns).
A supplementary analysis was carried out to examine the eect of task order on bias scores
(i.e., whether the Stroop task preceded or followed the dot probe task). An ANOVA of bias
scores with group (3), threat type (2), and task order (2) as independent variables showed no
signi®cant order eects (e.g., group task order, F(2,38)=1.10, ns), so there was no evidence
that task order was a confounding factor.
To check a subsidiary issue regarding the eect of word categorisation on colour-naming
performance, an ANOVA was conducted of the RT data for the two neutral word types, with
group (3) and categorisation (2: categorised neutral versus uncategorised neutral) as
independent variables (see Table 1b for means). This showed no signi®cant results (e.g., main
eect of word categorisation: F < 1).
3.4. Dot probe task
Bias scores were calculated for each type of threat word by subtracting the mean RT when
the probe was in the same position as a threat word from the mean RT when the probe was in
the opposite location (MacLeod & Mathews, 1988; Mogg et al., 1995). The bias score
summarises the interaction eect of Threat position Probe position in the RT data. Positive
values of the bias score indicate relatively faster RTs for probes replacing threat rather than
neutral words, i.e., an attentional bias towards threat (vigilance); whereas negative values
re¯ect a bias away from threat. Two bias scores were calculated for each participant: one for
trials with social threat Ð neutral word pairs, and the other for physical threat Ð neutral
word pairs. Mean bias scores of each group are shown in the lower part of Fig. 1.
These scores were entered into a 3 2 mixed design ANOVA with one between-subjects
variable of group (3: LA, REP, HA) and one within-subjects variable of threat type (2: social,
physical). The main eect of group on bias scores (F < 1) and the interaction eect of group
threat type (F(2,42)=1.04, ns) were not signi®cant. However, there was a signi®cant main
eect of threat type (F(1,42)=5.00, p < 0.05), suggesting generally greater avoidance (i.e., more
negative bias scores) for social threat than physical threat words; see Fig. 1. Contrast of the
overall mean social threat bias score against zero indicated a signi®cant attentional bias against
social threat words (t(44)=3.40, p < 0.01), indicating that on trials with social threat words,
participants were signi®cantly faster to detect probes replacing neutral than threat words.
There was no evidence of an overall bias either for or against physical threat words (contrast
of bias score vs zero: t < 1, ns).
K. Mogg et al. / Personality and Individual Dierences 28 (2000) 1063±1077
1073
Speci®c hypothesis-driven analyses were conducted to examine whether Fox's (1993) ®nding
from the dot probe task of avoidance of social threat words in repressors had been replicated.
There was a non-signi®cant trend for the three groups to dier in bias scores for social threat
words (F(2,44)=2.08, p = 0.14). Mean social threat bias scores for the LA, REP and HA
groups were ÿ1.7 ms, ÿ13.7 ms and ÿ6.3 ms, respectively. Contrasts of the bias scores versus
zero indicated signi®cant avoidance of social threat words, relative to neutral words, in the
REP group (t(12)=4.80, p < 0.001), whereas the mean social threat bias scores of the LA and
HA did not dier signi®cantly from zero.
Correlations between the bias scores from the dot probe task and the questionnaire measures
showed a near-signi®cant trend for high SDS scores to be associated with greater avoidance of
social threat words (r=ÿ0.23, p = 0.08, two-tail). There were no signi®cant results.
A supplementary analysis was carried out to examine the eect of task order on bias scores
from the dot probe task. An ANOVA with group (3), threat type (2), and task order (2:
Stroop before dot probe task, and vice versa) as independent variables showed no signi®cant
order eects on bias scores (e.g., group task order, threat type task order: Fs < 1).
3.5. Relationship between bias scores from modi®ed Stroop and dot probe tasks
Pearson correlations showed no signi®cant relationships between the bias scores from the
two tasks across the whole sample. The mean threat bias scores from the Stroop task
correlated ÿ0.03 with those from the dot probe task. The social threat bias scores from the
two tasks correlated 0.01 with each other; and the physical threat bias scores correlated 0.13.
4. Discussion
One of the aims of this study was to investigate whether high levels of defensiveness are
associated with attentional avoidance of threat (cf. Fox, 1993; Bonanno & Singer, 1990), or
with greater vigilance for threat (cf. Dawkins & Furnham, 1989). The results from both
cognitive tasks were compatible in indicating that individuals with low levels of trait anxiety
and high levels of defensiveness (so-called ``repressors'') had a bias to allocate processing
resources away from social threat stimuli. Speci®cally, they were faster in colour-naming social
threat than neutral words, and they were faster in detecting probes that replaced neutral rather
than social threat words. These particular results were directly predicted from Fox's (1993)
®ndings, and are consistent with the view that high levels of defensiveness combined with low
trait anxiety are associated with an avoidant attentional style (although it should be noted that
the group dierence in bias scores on the dot probe task was not signi®cant; a point which we
shall return to later).
Nevertheless, the present results are contrary to those of Dawkins and Furnham (1989),
where repressors showed greater interference in colour-naming threat than neutral words. This
discrepancy may be due to methodological dierences between versions of the Stroop task. In
the computerised version used here, words were presented one at a time, and participants'
vocal responses terminated the threat display. Thus, an avoidant attentional style (as suggested
by faster RTs on trials with threat than neutral words) was eective in reducing exposure to
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K. Mogg et al. / Personality and Individual Dierences 28 (2000) 1063±1077
the threat stimuli in the present study. However, on the card version used by Dawkins and
Furnham (1989), participants were presented with blocks of 100 words, and an avoidant
attentional style would be ineective in removing the threat stimuli. Thus, one possibility is
that defensive individuals may show enhanced disruption or distraction eects of taskirrelevant threat when their attempts to avoid processing the threat are thwarted by the task
demands. Another possibility is that Dawkins and Furnham's results are not representative of
repressors, given a recent failure to replicate them with a card version of the Stroop task
(Myers & McKenna, 1996).
In the present study, the two cognitive tasks did not produce identical ®ndings. Signi®cant
group dierences in attentional bias were indicated by the Stroop task, but not by the dot
probe task. In the former task, the attentional bias was re¯ected by the dierence in colournaming times for threat versus neutral words and the results suggested vigilance for threat in
high trait anxiety, no bias in low trait anxiety, and avoidance in repressors (as predicted by
Eysenck's (1997) theory). Partial correlations indicated that the attentional bias for threat was
predicted by SDS scores, independently of anxiety or worry. There was also a near-signi®cant
trend for the bias to be predicted by social worry ratings, independently of the eect of SDS
scores. These results suggested that both worry and defensiveness contribute to the bias for
threat words.
On the other hand, the dot probe task appeared to be less sensitive to eects of anxiety and
SDS in this non-clinical sample, given the lack of signi®cant group dierences. Instead, it
indicated greater overall avoidance of social threat than physical threat words, with a nearsigni®cant trend in the correlational results for the former to be associated with increased
defensiveness. MacLeod et al. (1986) noted a similar general tendency for their non-clinical
sample to be avoidant of threat on the dot probe task, although the speci®city of this eect to
social versus physical threat words was not noted in their study. The ®ndings from non-clinical
studies using the dot probe task with word stimuli have been variable (e.g., review by Mogg &
Bradley, 1998), although evidence of trait anxiety-related biases has been obtained, for
example, under stressful conditions (e.g., MacLeod & Mathews, 1988), or with brief, masked
exposure conditions (e.g., Bradley, Mogg & Lee, 1997). In general, the dot probe task appears
to provide a relatively fragile index of anxiety-related attentional biases in non-clinical studies,
particularly when using word stimuli that have relatively mild threat value. However, it is
reassuring that more persuasive evidence of such biases has been found in non-clinical samples
with variants of the dot probe task using more salient stimuli, such as angry faces (e.g.,
Bradley, Mogg, Falla & Hamilton, 1998; Mogg & Bradley, 1999). One possibility is that, for
mild stimuli such as single threat words, high trait anxious individuals may ®nd it easier to use
strategies to counteract their vigilant tendencies, which may explain the diculty in reliably
demonstrating such vigilance in non-clinical studies on the dot probe task.
In the present study, there was no evidence whatsoever of positive relationships between the
cognitive bias measures from the dot probe and Stroop tasks. This suggests that performance
on each task may be tapping quite dierent underlying mechanisms. For example, the dot
probe task re¯ects biases in visual orienting that depend on the presence of threat cues in
dierent spatial locations in the visual ®eld. Thus, such biases may involve a variety of
operations in visual orienting, such as shifting, engagement and disengagement of attention
(e.g., Posner, 1995). By contrast, the Stroop task involves competition in processing dierent
K. Mogg et al. / Personality and Individual Dierences 28 (2000) 1063±1077
1075
attributes of a single stimulus presented within the focus of attention (i.e., colour versus
emotional content of word). Using the analogy of a ``spotlight of attention'', the dot probe
task may re¯ect the eect of threat cues on the scanning of the spotlight across dierent
regions of the visual ®eld, whereas the Stroop task involves a stationary spotlight where the
information at the focus of its beam must be disentangled. The present results highlight the
importance of clarifying the precise mechanisms underlying biases on various cognitive tasks.
Moreover, the speci®c mechanisms involved in the avoidant attentional style of defensive
individuals may not necessarily be the same as those underlying the vigilant attentional style of
generally anxious patients. For example, such avoidant and vigilant biases may vary in the
extent to which they involve shifting versus disengagement of attention, or the extent to which
they are automatic versus amenable to strategic control.
Despite the absence of signi®cant relationships between the dierent measures of attentional
bias, the results from the two tasks were compatible in suggesting not only that low trait
anxious individuals with high levels of defensiveness showed attentional avoidance of social
threat (as noted above), but also that low trait anxiety without high defensiveness was
generally associated with an unbiased attentional style (see Fig. 1). Both of these ®ndings were
predicted by Eysenck's (1997) cognitive theory of anxiety, which proposed that attentional
biases for threat-related information are in¯uenced by more than one personality variable,
namely, anxiety-proneness and defensiveness. The present results also highlight the importance
of including a measure of defensiveness in research into anxiety-related cognitive biases. If this
had not been included in the present study, analyses of the Stroop results by separating into
low and high trait anxiety groups would have suggested a marked eect of trait anxiety on the
processing of threat. This would seem to be a misleading interpretation of the data, which in
fact suggested instead that defensiveness (as re¯ected by SDS scores) was the more important
variable predicting the threat interference eect in this non-clinical sample. Indeed, no
signi®cant dierences in attentional bias were found between the high and low trait anxious
groups that had similar SDS scores. The main evidence for an anxiety-related bias was a
notable (near-signi®cant) trend for social worries to predict threat interference, independently
of defensiveness. Inclusion of a measure of defensiveness in future research may therefore
prove helpful in accounting for discrepant ®ndings across non-clinical studies.
On a more general note, it would seem preferable to use the term ``defensive, low anxious''
rather than ``repressor'' to refer to these individuals, given that this more objectively re¯ects
the criteria used in selection. Indeed, one reason why researchers may be reluctant to include
measures of defensiveness in their work is unease with the term ``repression'' and its Freudian
origins, and so more neutral (i.e., assumption-free) terminology would seem advantageous. The
study of the eects of personality variables, such as defensiveness and trait anxiety, on
information processing biases is not only of theoretical interest, but also has potentially
important clinical implications. For example, it is unclear whether attentional avoidance
strategies (as shown by defensive, low anxious individuals or ``repressors'') are protective
against clinical anxiety, and whether it is helpful to provide attentional retraining for anxious
patients to encourage them to adopt such an avoidant attentional style. Such clinical
interventions are indeed suggested by Williams et al.'s (1997) cognitive model of emotional
disorders, which proposes that attentional vigilance for threat is a key variable underlying
vulnerability to clinical anxiety (but see Mogg & Bradley, 1998, for further debate).
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K. Mogg et al. / Personality and Individual Dierences 28 (2000) 1063±1077
In summary, the present results suggest that high levels of defensiveness combined with low
trait anxiety were associated with an avoidant attentional style in this non-clinical sample. Our
®ndings also indicate that research into cognitive models of non-clinical and clinical anxiety
should not only routinely include a measure of defensiveness, but it should also seek
convergent evidence from more than one index of attentional bias, given that dierent tasks
are likely to re¯ect dierent underlying attentional mechanisms.
Acknowledgements
This work was supported in part by the Wellcome Trust. Karin Mogg holds a Wellcome
Trust Senior Research Fellowship in Basic Biomedical Science.
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