delusions demand attention

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Delusions Demand AttentionKate M. LeafheadPublished online: 18 Aug 2010.

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Delusions Demand Attention

Kate M. Leafhead

University of Durham, UK and MRC Applied Psychology Unit, Cambridge, UK

Andrew W. Young

MRC Applied Psychology Unit, Cambridge, UK

T. Krystyna Szulecka

Doncaster Royal Infirmary, UK

We used a variant of the Stroop paradigm to investigate attention bias in a youngwoman (JK) with delusional beliefs that she had died and that members of her

family had changed. JK was shown sets of words printed in different colours ofink, and was asked to name the colour of each word. Sets of words were chosen

which related to her delusions, and to possible contributory moods. The timestaken by JK to colour-name words in these lists were compared with her times to

colour-name sets of neutral words. There were three separate testing sessionswhich took place over a two-year period. In comparison to her times to name the

colours of words in the neutral lists, JK was significantly slower to colour-nametest lists containing words related to her delusional beliefs. When she was no

longer experiencing these delusions, however, she was no slower to colour-nameany of the test word lists. The results indicate that the Stroop paradigm can be

useful in investigating individual cases of delusions and in monitoring changes inattentional bias over time.

IN T R O D U C T IO N

There are still large gaps in our understanding of how delusional beliefs are

created and maintained. Generally, two main types of explanation have been

offered. The first views delusions as rational attempts at interpreting abnormal

experiences (Maher, 1974) , whereas the second argues that delusional beliefs are

Requests for reprints should be sent to Kate Leafhead, UMDS, Guys and St. Thomas’ s Medical

and Dental School, Division of Psychiatry and Psychology, St. Thomas’ Hospital, Lambeth Palace

Road, London SE1 7EH, UK.

We gratefully acknowledge the support provided by an MRC Research Studentship (KL) and a

grant from the EJLB Foundation (AY). We thank Dr Karel de Pauw for comments on an earlier draft

and Dr Ian Nimmo-Smith for statistical advice. We are indebted to JK for her patience and co-

operation during testing. Finally, we thank the referees for their helpful comments.

# 1996 Psychology Press, an imprint of Erlbaum (UK) Taylor & Francis Ltd

COGNITIVE NEUROPSYCHIATRY, 1996, 1 (1), 5±16

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the products of abnormal reasoning biases (Hemsley & Garety, 1986). However,

whilst these two approaches are conceptually distinct, both may offer valid clues

to the formation and maintenance of delusions, since it need not be the case that

all delusional beliefs reflect a single underlying cause.

A useful strategy may be, therefore, to look in detail at how particular

individuals develop specific delusional beliefs. One can then attempt to ascertain

whether similar mechanisms are involved in other delusionsÐ or, indeed, in

other forms of psychopathology. To this end, we have adopted the delusional

belief that one is dead (Cotard, 1882) as a model delusion; it is a highly

implausible belief that can be held with strong conviction despite clear

evidence to the contrary. For convenience, we refer to this delusion by the

eponym Cotard delusion, although we recognise that Cotard’ s (1882) case

reports involved more wide-ranging nihilistic beliefs (Young & Leafhead, in

press).

Our single case studies have suggested that the Cotard delusion is the result

of a misinterpretation of anomalous perceptual experiences (Wright, Young, &

Hellawell, 1993; Young, 1994; Young, Leafhead, & Szulecka, 1994; Young,

Robertson, Hellawell, de Pauw, & Pentland, 1992) . These perceptual anomalies

involve things seeming strange, unfamiliar or unreal, and a loss of emotional

responsiveness. Such strange experiences might potentially be interpreted in

many possible ways; we agree entirely with Kaney and Bentall’ s (1989) view

that the particular explanation an individual produces will depend on many

personal and social factors. In this respect, it is important that the Cotard

delusion commonly arises in the context of depression, since it has been shown

that depressed individuals tend to attribute negative events to internal rather than

to external causes (Candido & Romney, 1990; Kaney & Bentall, 1989) . Wright

et al. (1993) therefore suggested that the patients’ depressed mood contributes to

their seeking an internal cause for their perceptual problems, and erroneously

concluding that they must be dead.

This approach has a number of advantages; we draw attention to two here.

First, it generates readily testable predictions. For example, the delusion of being

dead should resolve in parallel with changes in the patient’ s mood, which

appears to be the case (Young et al., 1992; Young & Leafhead, in press).

Second, the approach can be extended to other delusions. In particular, it offers a

ready account of the Capgras delusion, in which patients claim that some of their

relatives have been replaced by duplicates or impostors (Capgras & Reboul-

Lachaux, 1923).

The Capgras delusion shows intriguing parallels to the Cotard delusion. Both

delusions can be produced by similar types of brain injury, and the patients can

show similar impairments on neuropsychological tests (Young, Reid, Wright, &

Hellawell, 1993; Young et al., 1992) . Most importantly, patients experiencing

the Capgras delusion also report similar perceptual anomalies to those involved

in the Cotard delusion. Against this background of similarities, the key

6 L E A F H E A D , Y O U N G , S Z U L E C K A

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difference seems to be that the Capgras delusion is associated with a suspicious

rather than a depressed mood, and is often accompanied by persecutory

delusions. Studies have shown that people with persecutory delusions tend to

attribute negative events to external rather than internal causes (Kaney &

Bentall, 1989; Candido & Romney, 1990). Hence, Young et al. (1993)

hypothesised that in the Capgras delusion a suspicious mood and persecutory

delusions cause patients to misattribute changes in their own perception to

changes in other people, which in turn leads them to infer that these must be

impostors.

In both the Capgras and Cotard delusions, therefore, there are at least two

interacting contributory factors; anomalous perceptual experience and disturbed

mood. The latter determines a particular interpretation of the former, which

results in the specific form of delusion. Again, we emphasise that this approach

leads directly to clear, testable predictions. In this case, it is clear that if patients

who had initially voiced the Cotard delusion change from being depressed to

being suspicious, they may shift to the Capgras delusion as an account of their

experiences; this has also been observed (Wright et al., 1993) .

Even though we have shown that the idea that the Capgras and Cotard

delusions result from an interaction of impairments has much to commend it, it

still seems to fall short of a complete account. Why, for example, do patients

remain convinced by explanations that seem so patently absurd to everyone

around them? In this respect, we have been struck by the potential parallel

between delusions and certain aspects of anxiety disorders. Specifically, we

have noticed that patients experiencing the Cotard delusion are preoccupied with

their thoughts of their own demise.

We were interested, therefore, in examining the possibility that delusion-

related preoccupation might be a contributory factory in the formation and

maintenance of delusions. To do this, we adopted a variant of the Stroop (1935)

task which has been widely used in the investigation of attentional biases in

anxiety disorders, and which has also been adopted in work on delusions by

Bentall and Kaney (1989) and Kinderman (1994).

Several studies have shown that patients suffering from anxiety disorders

show attentional biases toward stimuli related to their individual concerns (e.g.

Mathews & MacLeod, 1985; Williams, Watts, MacLeod, & Mathews, 1988) . A

well-established means of investigating this attentional bias in anxiety states is

the emotional Stroop paradigm, which is a variant of a colour-naming task

originally devised by Stroop (1935); in this task, the person is asked to name the

colours in which words are printed whilst trying to ignore the words themselves.

Attentional bias in the emotional Stroop task is reflected in a slowing of the

colour-naming of affectively salient words relative to the colour-naming of

affectively non-salient or neutral words.

We thus decided to investigate whether a patient, JK, would show a similar

attentional bias toward stimuli directly related to her delusional beliefs. To this

D E L U S IO N S D E M A N D A T T E N T IO N 7

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end, we used a variant of the Stroop task involving words related to the Cotard

delusion (which JK had experienced in subjectively convincing form), words

related to the Capgras delusion (which she had partially expressed), and words

related to possible contributory moods of depression, suspiciousness, and

anxiety. In addition, by repeated testing, we were able to monitor how changes

in JK’ s attentional biases related to changes in her delusional beliefs.

C A S E B A C K G R O U N D

JK, a 29-year-old woman of average intelligence, was admitted to hospital five

times over a four-year period for episodes of psychotic depression (Young &

Leafhead, in press; Young et al., 1994) . She responded well to ECT, but

developed spells of elated mood following treatment on three occasions. Her

EEG was normal, but a computed tomographic (CT) scan showed prominent

cortical sulci.

The latest of these episodes formed the focus of our investigation. When she

was most floridly ill, JK claimed that she was dead. She believed that her body

was going to explode, and on one occasion described herself as consisting of

mere fresh air. She tried to cut her wrists with a pair of bathroom scissors, but

her mother stopped her; JK said that if no one could help her, she wanted to be

put out of her misery. These clinical features are often noted in cases of the type

described by Cotard (1882); they have been reviewed by Young and Leafhead

(in press), who also give further details of these delusions and anomalous

experiences of JK’ s.

Formal testing showed that JK had face-processing difficulties (Young et al.,

1994); she was poor at recognising familiar faces, at identifying facial

expressions, and at matching and remembering unfamiliar faces. Her recognition

memory for unfamiliar buildings was similarly impaired. This profile of impaired

visual processing is consistent with other findings of visual impairments linked to

the Cotard delusion (Wright et al., 1993; Young et al., 1992) .

During the course of her illness, JK also said in discussion with one of the

authors that her mother did not exist, and later voiced beliefs that her mother and

brother had changed and were no longer the people they were before. Similar

features had been noted in some of Cotard’ s (1882) cases. They are interesting in

terms of the postulated relationship between the Cotard and Capgras delusions

referred to earlier.

IN V E S T IG A T IO N

M e th o d

Matched sets of five words were constructed. Words in the test sets related to

themes of death, depression, duplicates, suspiciousness, and anxiety. In addition,

two sets of neutral control words were prepared. Words were matched as far as

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possible across these sets for length (number of letters) and for frequency

(Hofland & Johansson, 1986) . The lists are given in the Appendix.

The rationale for use of each of these sets of words was as follows:

1. Death-related words: The five death-related words were used because JK

had experienced the delusion of being dead (Cotard delusion). However,

these words were chosen to represent the generic theme of death, rather

than being words used by JK herself. This was in order to match the death-

related words with the other word lists, which were also drawn up without

regard to whether JK had used such words to describe her delusions.

2. Depression-related words: A set of five words related to a general theme

of depression was included, because of the relationship of depression to

the Cotard delusion.

3. Words related to duplicates: A set of five words related to duplicates was

included, in view of the hypothesised relationship between the Cotard and

Capgras (relatives replaced by duplicates or impostors) delusions.

4. Suspiciousness-related words: A set of five words related to suspicious-

ness was used, because of the association of suspiciousness with the

Capgras delusion.

5. Anxiety-related words: A set of five words related to the general theme of

anxiety was included, to investigate whether attentional biases involving

generalised anxiety are contributory in delusions.

6. Neutral words A and B: Two sets of five neutral words were prepared, for

comparison to the test sets of words on colour-naming times.

Once provisional sets of words had been selected, they were presented to 10

independent raters who were asked to allocate each word to one of these 6

categories (i.e. to the 5 test groups or a neutral group). Words for which at least 8

of the 10 raters agreed with our own assignment were retained, and others were

discarded and replaced until this criterion was met. The words shown in the

Appendix are the final agreed sets.

The resulting sets of words were presented on white A4 cards. On each card,

50 words were printed in 12-point lower case Helvetica font, with each of these

words appearing in one of five different colours of ink. For any card, all of the

words came from one of the sets (i.e. each of the 5 words in a set was used 10

times on the appropriate card for that set). Each card showed 10 rows of 5 words

coloured in blue, green, brown, grey, or red. The words and colours were

arranged in a pseudo-random order, with each of the 5 words in the set used

appearing twice in each of the 5 colours.

JK’ s task was to name the colour in which each of the 50 words on each card

was printed, working from left to right and top to bottom. She was instructed to

ignore the meanings of the words and concentrate on naming the colours as

quickly and accurately as possible, and was given a practice list using a different

D E L U S IO N S D E M A N D A T T E N T IO N 9

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set of neutral words to ensure that she was able to name the colours accurately.

The test and neutral lists were then presented in a pseudo-random order,

ensuring that she finished on a neutral list. The time taken to colour-name all the

words on each card was measured with a stop-watch.

JK was tested on three separate occasions over a period of two years. Her

relevant delusional beliefs and mood scores on the HAD scale (Zigmond &

Snaith, 1983) for the three test sessions are shown in Table 1. During the first

testing session, JK was still convinced she was dead, and also had expressed

some strange feelings that her mother was not as she should be. In the second

testing session (4 months later), she thought that she might previously have been

dead, but was no longer fully convinced. However, she did feel that her mother

and brother were no longer the people they were before. In the third testing

session (18 months later), JK was no longer deluded, and stated that it was all

``just in my mind’ ’ .

The HAD scores show marked depression and anxiety at the time of JK’ s first

test session. Scores on this test have a maximum of 21, with published cut-offs

of 10 for depression and 10 for anxiety; scores of 8±10 are considered to fall in a

borderline range (Zigmond & Snaith, 1983) . The depression score improved

more quickly than her anxiety, but both were within the normal range by the

third test session. These scores thus mirrored the improvement in JK’ s mental

state.

For purposes of comparison, the same colour naming task was given to 10

control subjects with a mean age of 26.6 years (SD 3.06, range 20±30).

R e s u l ts

The measure of interest was the time needed to name the colours of each set of

words. However, before considering these colour-naming times in detail, we will

look at error rates.

T A B L E 1

J K ’s D e lu s io n a l B e l ie f s a n d H A D S c o r e s a c r o s s t h e 3 T e s tin g S e s s io n s

Session Delusional Belief HAD scores

Depression Anxiety

Test 1: She is dead.

Strange feelings about her mother.

17 15

Test 2: Thinks she may have been dead.

Mother and brother have changed.

7 14

Test 3: Delusions resolved.

JK says it was all ``just in my mind’ ’ .

0 6

1 0 L E A F H E A D , Y O U N G , S Z U L E C K A

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Errors can involve either reading a word instead of naming its colour (task

switching errors), or naming the colour incorrectly. Task switching errors were

very rare; they never involved more than a single word, and were immediately

self-corrected. JK did this twice, once on the anxiety word list, and once on her

first test with the death-related words. One control subject also switched to

reading a word on two occasions; one with the anxiety word list and one with

Neutral list A.

The other main type of error involves naming the colour incorrectly; these

were somewhat more common, and are presented in Table 2. This table shows

that JK’ s error rates were not different to the control mean for any of the critical

lists, and her colour-naming times were not affected by trading speed against

accuracy. However, JK did make an above normal number of errors to Neutral

list B in Test 2. This additional neutral list had been presented for the first time

in Test 2. Although this list consisted of concrete nouns, it is possible that JK

may have interpreted two of these (watch and telephone) as slightly sinister at

this time when she was voicing beliefs that her mother and brother had changed.

Having established that the data are not contaminated by speed-accuracy

trade-offs, colour-naming tim es were examined in two ways; first, by comparing

JK’ s performance to control subjects, and second, by comparing her own

naming times across test and neutral lists.

First, then, the comparison to controls. Means and standard deviations for the

naming times for each list by control subjects are shown in Table 3, together

with the times taken by JK on each of the three testing sessions. As can be seen

from Table 3, JK was slower than the controls for all lists. This slowing was

clearly evident even with neutral lists, and therefore seemed to reflect a general

rather than a specific effect of her illness.

In fact, generalised slowing of colour-naming times even for neutral lists is

commonly observed in psychopathological studies using the emotional Stroop

T A B L E 2

N u m b e r o f E r ro r s m a d e b y C o n t ro ls a n d b y J K in C o lo u r - n a m in g

W o r d L is t s

Word List Controls JK

Mean SD Test 1 Test 2 Test 3

Death 1.50 0.58 1 0 1

Depression 1.00 0.00 0 1 0

Duplicates 1.33 0.52 1 0 2

Suspicion 1.25 0.50 0 0 1

Anxiety 2.00 1.73 0 1 0

Neutral A 1.40 0.89 1 0 0

Neutral B 1.29 0.49 ± 3 0

D E L U S IO N S D E M A N D A T T E N T IO N 1 1

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paradigm (Bentall & Kaney, 1989; Kinderman, 1994) . However, more important

than JK’ s overall slowness is that Table 3 suggests her overall pattern of results

across conditions was different. Whereas the controls showed little variation in

their mean response times to each list (confirming that the lists were well-

matched), JK’ s performance was relatively unstable, with markedly long

response times to some lists in some testing sessions.

We therefore decided that a more useful strategy would be to undertake a

comparison of JK’ s colour-naming times for the test lists in relation to her own

times for the neutral lists. This allowed us to examine effects over and above any

general slowness or variability in JK’ s performance. To do this, we derived an

index of each of the test lists’ interference with colour-naming in each test

session by using the mean and standard deviation of JK’ s responses to the

neutral conditions as her own baseline. We then calculated z-score differences

between the length of time JK took to colour-name words in the test conditions

and that taken in the neutral conditions. These results are shown in Fig. 1. In

other words, Fig. 1 shows by how many standard deviations JK’ s naming times

for each of the test lists in each session were above or below her naming times

for the neutral lists.

Since the standard deviation of JK’ s naming times for neutral lists must be

considered an estimate of the true value, we used t-values to test whether the

colour-naming times for each of the test lists were significantly longer than

neutral times. We used 1-tailed probabilities because we were only interested in

whether JK would be slower to colour-name critical lists than neutral lists.

As shown in Fig. 1, in the first testing session JK took longer to colour-name

both the death-related word list {t = 4.75 (df = 4), P < 0.01} and the duplicates

word list {t = 3.75 (df = 4), P < 0.01}. In the second testing session, her response

times for the death-related words and neutral words did not differ significantly,

but she was still reliably slower for the words related to duplicates {t = 3.00

T A B L E 3

M e a n T im e s ( s e c o n d s ) ta k e n b y C o n t r o ls a n d J K t o C o lo u r - n a m e

W o r d L is t s

Word List Controls JK

Mean SD Test 1 Test 2 Test 3

Death 35.60 4.17 79 60 60

Depression 34.90 4.95 65 64 58

Duplicates 32.40 5.34 75 72 65

Suspicion 33.60 4.38 65 56 58

Anxiety 33.30 3.27 55 55 57

Neutral A 35.80 4.37 62 58 54

Neutral B 33.80 4.87 ± 62 64


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(df = 4), P < 0.05}. By the third testing session, JK was no longer significantly

slower for any of the critical word lists relative to her neutral baseline. At no

time during the course of her illness was JK significantly slower to colour-name

the lists of words related to more general themes of depression, suspiciousness,

or anxiety.

D IS C U S S IO N

Our results show a clear and striking relation between JK’ s delusional beliefs and

her colour-naming times for delusion-related words. When fully convinced she

was dead (in the first testing session), her time to colour-name death-related

words was longer than her time to name the colours of neutral words. When JK

was no longer convinced she had been dead (in the second and third test sessions),

her time to colour-name death-related words did not differ from her time to name

the colours of neutral words. Similarly, when JK had strange beliefs that members

of her family were not who they seemed (in the first and second test sessions), her

time to colour-name words relating to the theme of duplicates was longer than her

time to name the colours of neutral words, and when her beliefs returned to

normal (in the third test session) this difference also disappeared.

These attentional biases were to some extent specific to the content of JK’ s

delusions. In contrast to the striking interference from words that were directly

related to her delusions, her slight slowing in the first testing session for words

related to general themes of depression and suspiciousness did not reach

statistical significance. Similarly, at no point was there any interference from

words related to the general theme of anxiety.

F IG . 1 z-Score differences between JK’ s times to colour-name words in critical and neutral lists.


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The fact that JK showed attentional biases toward words related to death and

those related to duplicates lends support to the postulated relationship between

the Cotard and Capgras delusions (Young et al., 1994, 1992) , and the finding

that these additional biases receded in parallel with the delusions is consistent

with findings that attentional biases are significantly reduced when people with

anxiety disorders respond to treatment (Mattia, Heimberg, & Hope, 1993; Watts,

McKenna, Sharrock, & Trezise, 1986) .

We are not the first to use the Stroop paradigm to examine content-specific

attentional biases in delusions. Bentall and Kaney (1989) demonstrated that

patients suffering from persecutory delusions showed attentional bias on the

Stroop task toward words related to morbid suspiciousness (SPY, PERSECUTE,

etc.). They pointed out that such findings lend further support to previous studies

showing that cognitive abnormalities are implicated in delusions (Huq, Garety,

& Hemsley, 1988; Kaney & Bentall, 1989) . Bentall and Kaney (1989)

interpreted their findings as indicating that the attentional bias toward

delusion-salient material shown by patients suffering from persecutory

delusions leads to preferential encoding of such material, which in turn serves

to maintain an already-formulated delusion. Our findings are entirely consistent

with this explanation. Of course, it is possible that such biases may also be

involved in the formation (as well as maintenance) of delusions, but this has yet

to be demonstrated.

The fact that JK only showed interference effects for delusion-related words

raises the issue of specificity in attentional biases. Martin, W illiams, and Clark

(1991, p. 158) have claimed that the principal cognitive impairment in anxiety

disorders may be ``the presence of a set of beliefs which lead patients to

erroneously perceive certain predominantly non-threatening stimuli as threaten-

ing’ ’ . They argue that patients suffering from anxiety disorders should thus show

selective processing for stimuli that are salient to their specific beliefs, but not

for stimuli which are representative of general threat. We have shown this to be

the case in the Cotard delusion; JK showed interference effects only for words

related to the themes of her delusions, and only during the time in which she

held those delusional beliefs.

It is important to note that attentional bias is not in itself a pathological

construct. It is a mechanism we all haveÐ we attend to the sorts of things that are

salient or of interest to us. What appears to happen in the case of people who are

suffering from delusions is that their attentional biases toward material related to

their delusions lead them continually to find evidence which reinforces already

held delusions, resulting in further increased attention. This conclusion is

consistent with Martin et al.’ s (1991) hypothesis that selective attention to

disorder-specific stimuli may serve to maintain anxiety disorders.

Finally, we return to emphasise our view that delusions reflect an unfortunate

interaction between different contributory factors. Our findings of attentional

biases fit neatly alongside the idea that the Capgras and Cotard delusions reflect


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misinterpretations of abnormal experiences (Wright et al., 1993; Young, 1994;

Young et al., 1994, 1992) . The role of attentional biases is to reinforce and

maintain delusional beliefs by constantly focusing the patient’ s attention onto

any relevant information. This strengthens the patient’ s belief in the delusion,

making it almost a self-fulfilling prophecy. Moreover, the constant accumulation

of subjectively pertinent positive evidence following from biased attention will

make it much more difficult for the patient to break free from this cycle. By

exploring the parallels to mechanisms known to be involved in the creation and

maintenance of anxiety disorders, we have thus gained a clearer understanding

of an additional factor involved in delusions.Manuscript received 18 March 1995

Revised manuscript received 24 July 1995

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A P P E N D IX

W o rd lis ts

1. Death-related words: coffin, died, funeral, grave, undertaker.

Mean frequency = 32.60, SD = 43.33; Mean length = 6.40, SD = 2.30.

2. Depression-related words: defeat, depressed, failure, hopeless, sad.


3. Words related to duplicates: copy, double, duplicate, impostors, substitute.


4. Suspiciousness-related words: deceit, follow, spy, stare, suspicious.


5. Anxiety-related words: anxious, nervous, stress, tense, worried.


6. Neutral words A: anchor, basement, details, magazine, sell.


7. Neutral words B: jacket, jeans, telephone, walkman, watch.



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delusions demand attention

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