An evaluation of early and late stage attentional processing of positive and negative information in dysphoria

An evaluation of early and late stage attentionalprocessing of positive and negative information in dysphoria Matthew S.. In both studies, the dysphoric group showed significantly less a

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An evaluation of early and late stage attentional

processing of positive and negative

information in dysphoria

Matthew S Shane and Jordan B Peterson

University of Toronto, Toronto, Ontario, Canada

Depressive disorders may be characterised by hyperattention toward negative information, hypoattention toward positive information, or a combination of both processing biases In two studies, a dot-probe task was utilised to better ascertain the specific direction and time-course of these biases In both studies, the dysphoric group showed significantly less attentional allocation toward positive stimuli than the non-dysphoric group In study two, the dysphoric group also showed greater attentional allocation toward depression-specific stimuli Importantly, the bias toward depression-specific stimuli, and the bias away from positive stimuli, were uncorrelated with each other It may be that both biases can act as sufficient, but not necessary, characteristics of dysphoric processing An additional possibility is that the relative level of each bias type may best characterise dysphoric processing Each of these possibilities is discussed in turn.

A current controversy in research on information processing in depressionconcerns the existence and nature of attentional biases in depressedindividuals Cognitive models based on schemas (Beck, 1976) or associativenetworks (Bower, 1981) predict that individuals with depressive disordersshould show mood-congruent processing biases at all stages of attentionalprocessing (Ingram, Miranda, & Segal, 1998) Thus, according to thesemodels, depressed individuals should manifest hypervigilant orientingtowards negatively valenced information in their current environment (earlystage attentional processing) as well as increased sustained attention and

Correspondence should be addressed to: Matthew S Shane, Clinical Cognitive Neuroscience Laboratory, The MIND Institute, 1201 Yale Blvd NE, Albuquerque, NM 87131, USA E-mail: mshane@themindinstitute.org.

This research was supported by the Social Sciences and Humanities Research Council of Canada.

We gratefully acknowledge Chad Ebesutani and Laura Elinson for their help with data collection, and a number of anonymous reviewers for their excellent feedback.

COGNITION AND EMOTION

2007, 21 (4), 789 815

# 2007 Psychology Press, an imprint of the Taylor & Francis Group, an Informa business www.psypress.com/cogemotion DOI: 10.1080/02699930600843197

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rumination (later stage attentional processing) on such negative information(see Posner & Peterson, 1990, or LaBerge, 1995, for a discussion of early andlate stage attentional processing) Empirical support for these hypotheseshas been mixed, however While a number of studies have identified suchmood-congruent processing biases (Bradley, Mogg, & Lee, 1997; Gotlib &Cane, 1987; Ingram & Ritter, 2000; Mogg, Bradley, & Williams, 1995),others have failed to identify such biases (Hill & Dutton, 1989; MacLeod,Mathews, & Tata, 1986) Conversely, still other studies have reported thatdepression may be characterised by a lack of attentional bias towardspositive information, rather than an active bias towards negative informa-tion (Gotlib, McLachlan, & Katz, 1988; McCabe & Gotlib, 1995; McCabe,Gotlib, & Martin, 2000) This inconsistency has made it difficult forresearchers to form definitive conclusions regarding the nature of attentionalprocessing in depressive disorders.

A variety of methodologies have been adapted from cognitive psychology

to investigate selective attention in depressive and anxious disorders,including the emotional Stroop task (Mathews & MacLeod, 1986), thedeployment-of-attention task (DOAT; Gotlib et al., 1988), and the dot-probe task (MacLeod et al., 1986) The latter two have proven particularlyuseful because of their ability to distinguish between early and late stageattentional processing In the dot-probe task, which has been utilised in thepresent study, pairs of words or pictures (e.g., one negatively valenced wordand one neutrally valenced word) are presented on screen (e.g., for 500 ms or

1000 ms) followed by a dot probe in the location of one of the two precedingstimuli Participants are required to press one of two buttons to indicatewhich side of the screen the probe appeared on Prior research hasdetermined that participants’ reaction times are faster when the probeappears in the position of the attended-to stimulus Thus, attentional biasscores are calculated by subtracting probe detection speeds when the probeappears in the place of a negatively valenced stimulus from probe detectionspeeds when the probe appears in the place of a neutral stimulus Shortstimulus durations (e.g., up to 500 ms) have been used to measure early stageorienting processes, whereas longer stimulus durations (e.g., 1000/ms) havebeen employed when later stage sustained attentional processing is beingevaluated The DOAT works in a similar fashion, but uses a forced-choiceformat rather than relying on reaction times, asking participants to decidewhich of two coloured bars appeared first (in reality they both appearsimultaneously, but it has been found that the attended-to bar seems toappear first)

Researchers utilising relatively short stimulus durations (up to

500 ms post-stimulus onset) have generally failed to find consistent biases

in depressed individuals’ attentional processing Mogg et al (1995) found

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no evidence of attentional biases in depressed individuals when theprobe appeared 500 ms post-stimulus Bradley et al (1997) reported asimilar lack of attentional bias, both at 14 ms and 500 ms post-stimulus,

in naturally dysphoric individuals, and Mathews, Ridgeway, andWilliamson (1996) presented data suggestive of biases only after 1000 mspost-stimulus The consistency of these null findings suggest that depressivedisorders, unlike anxiety disorders (Broadbent & Broadbent, 1988; Mogg &Bradley, 1998), may not be characterised by hypervigilant orienting or

‘‘pre-attention’’ towards negative environmental stimuli (Bradley et al.,1997; Williams, Watts, MacLeod, & Mathews, 1997; see, however, Bradley,Mogg, & Williams, 1994, and Luecken, Tartaro, & Appelhans, 2004, forpotentially contrary evidence demonstrating biases during subliminalpresentations)

In contrast, when longer stimulus durations have been utilised (e.g.,1000/ms), some evidence for depression-related attentional biases hasbeen found Mogg et al (1995) found that clinical depression predictednegative attentional biases at 1500 ms post-stimulus, and Bradley et al.(1997) and Mathews et al (1996) both found similar biases at 1000 mspost-stimulus In each of these studies, depressed individuals were found tomanifest increased sustained attention towards the negative stimuli at theselonger stimulus durations, despite not showing orienting mechanisms morecharacteristic of anxiety disorders This pattern of attentional deploymenthas led Williams et al (1997) to hypothesise that the locus of depression-related biases may rest in later stage, elaborative processes This inter-pretation remains consistent with a rich literature base demonstrating ahigh degree of ruminative behaviour in depressed (Beck, 1976; Harrington

& Blankenship, 2002; Watkins & Brown, 2002) and dysphoric (Roberts,Gilboa, & Gotlib, 1998) individuals A number of additional studies havefailed to demonstrate even later stage attentional biases in depression,however (e.g., Hill & Dutton, 1989; MacLeod & Chong, 1998; Neshat-Doost, Moradi, Taghavi, Yule, & Dalgleish, 2000) and alternativehypotheses have been raised Murphy et al (1999) have, for instance,suggested that depressed individuals may have a more difficult timeshifting attention away from negative stimuli once attention has beenallocated, thus causing them to remain focused on the negative informationafter initial orientation in that direction (see also Ellenbogen, Schwartz-man, Stewart, & Walker, 2002; Rinck & Becker, 2004) It should be notedthat these two hypotheses are not necessarily mutually exclusive Difficultydisattending to negative stimuli could, for instance, play a role in thedepressed individual’s increased ruminative behaviour

To further cloud the issue, Gotlib et al (1988) have conversely suggestedthat it may be normal, rather than depressed, individuals who show biased

ATTENTIONAL PROCESSING IN DYSPHORIA 791

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attentional processing Utilising the DOAT, Gotlib et al (1988) found thatwhereas dysphoric individuals attended equally to negatively, positively andneutrally valenced words, non-dysphoric individuals attended more often

to positive than to negative or neutral words Thus, whereas the dysphoric participants were characterised by biased attention towardpositive stimuli, the dysphoric participants showed a lack of such bias intheir attentional processing This suggests that attentional processingbiased toward positively valenced information may act as a protectivefactor against the onset of depression and dysphoria (see Taylor & Brown,

non-1988, who have explicitly suggested that the use of ‘‘positive illusions’’,which are ‘‘cognitive filters that preferentially screen out negativeinformation’’, is commonplace, is a sign of mental health, and is negativelycorrelated with the onset of depressive symptomatology) Gotlib andcolleagues have replicated their findings a number of times, in bothclinically depressed patients (McCabe & Gotlib, 1995) and previouslydepressed patients (McCabe et al., 2000; see, however, Gotlib, Krasnoper-ova, Yue, & Joormann, 2004, for a recent non-replication using the dot-probe task) Only one study (McCabe & Toman, 2000) has, to date, variedthe stimulus durations in the DOAT, however (750 ms has been standard),making determination of early and late stages of attentional processingwithin this task difficult

Thus, the present set of studies was designed to further investigate theextent to which dysphoria is characterised by hypervigilance to negativeinformation, hypovigilance to positive information, or a combination ofboth processing biases To this end, dysphoric and non-dysphoric individuals(as determined by Beck Depression Inventory scores [BDI]; Beck & Steer,1993), were asked to perform a modified version of the dot-probe task,during which three different stimulus pairings were presented: positive neutral, negative neutral, and neutral neutral (filler) Reaction times onpositive neutral trials were used to index biases toward positive stimuliwhile reaction times on negative neutral trials were used to index biasestoward negative stimuli Separation of positive and negative stimuluspresentations was implemented quite purposely Although evaluating thenature of dysphorics’ attentional biases within situations characterised bythe simultaneous presentation of both positive and negative stimuli mayhold certain advantages (e.g., parsimony), such simultaneous presentationmakes it impossible to determine the individual influence of each stimulustype In such mixed-trials, for instance, a bias away from the negativestimulus, or a bias toward the positive stimulus, would be difficult todifferentiate through reaction-time measures A major purpose of thepresent study was to investigate the specific nature of positive and negative

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biases in dysphoria; thus, use of mixed positive negative trials would nothave served our purposes well.1

The present set of studies was also intended to investigate a number ofspecific issues regarding the nature of positive and negative biases First, wesought to determine whether these biases constitute global biases inattentional processing, as predicted by cognitive models based on schemas(Beck, 1976) or associative networks (Bower, 1981), or conversely are specific

to either early or late stages of processing The time of onset of probes wasthus varied across trials, and appeared either after a short duration (500 ms

in study one, and 200 ms in study two) or a long duration (1500 ms in bothstudies) Evidence of attentional biases on the short-duration trials is ofteninterpreted as indicative of biases in early stage attentional processing,whereas evidence of attentional biases on the long-duration trials is ofteninterpreted as indicative of later stage attentional biases

Second, we wanted to evaluate the possibility that the positive andnegative biases may exist as independent markers of dysphoria Davidson,Pizzagalli, Nitschke, & Putnam (2002) have suggested that symptoms ofdepression related to positive and negative emotions may manifest indepen-dently, and may be underlain by distinct proximal causes By using separatetrials to calculate positive and negative biases, it allows for the independence

of these biases to be evaluated in several ways First, and most directly, thecorrelation between the positive and negative biases could be calculated Alow correlation could suggest independence between attention allocatedtoward positive stimuli and attention allocated toward negative stimuli Inaddition, we were particularly interested in the possibility that dysphoricindividuals may manifest both positive and negative biases, but that eachbias may show a distinct temporal pattern

A further possibility is that dysphoria may be characterised by a relativebias toward negative information (in relation to positive information), ratherthan an absolute bias toward either bias type (see Siegle, Ingram, & Matt,

2002, for the suggestion that dysphorics’ negative biases may come at theexpense of attention allocated to more positive information) Thus, a finalaim of the present research was to evaluate the predictive value of bias1

It is important to recognise the benefits and drawbacks of our approach of using positive /

neutral and negative neutral trials, rather than integrated positive negative trials As was pointed out by an anonymous reviewer, our use of separate positive neutral and negative neutral trials could serve to minimise a true correlation between positive and negative attentional biases While acknowledging this, given that not all situations need be characterised

by the presence of both positive and negative stimuli, and because almost no situation (and perhaps no situation) could be characterised by the presence of only positive and negative stimuli, use of mixed positive-negative trials in the absence of any non-valent stimuli, could cause an equal enhancement of the true correlation Future research would benefit from a careful analysis of the benefits and drawbacks of each approach.

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differentials (BD), which were calculated by subtracting participants’ biases

to negative information from their biases to positive information Bysimultaneously taking into account the magnitude of both bias types, BDsmay prove capable of identifying smaller effect sizes than either absolutebias Theoretically, if BDs show superior prediction than positive andnegative biases it would imply that dysphoric individuals need notconsistently show strong attentional bias away from negative stimuli, norstrong bias toward positive stimuli Rather, any combination of attentionalprocessing resulting in a relative preference for negative stimuli may serve asthe crucial characteristic underlying dysphoric processing

STUDY ONE Method

Participants Ninety-seven undergraduate psychology students at theUniversity of Toronto volunteered for the study, in partial fulfilment ofcourse credit Of these participants, 66 were women and 29 were men Theirages ranged from 18 31 (M /20.43, SD /2.12)

Assessment of dysphoria Participants completed the Beck DepressionInventory (BDI; Beck & Steer, 1993), which has been shown in numerousstudies to be a reliable and valid measure of severity of depressive/dysphoricsymptomatology in college (Oliver & Burkham, 1979), community, andpatient samples (for a review see Beck, Steer, & Garbin, 1988) Those scoring

6 and below on the BDI were classified as non-dysphoric, whereas thosescoring 10 and above were classified as dysphoric By removing those scoringbetween 7 and 9, potential difficulty regarding categorising ‘‘slightlydysphoric’’ individuals was avoided These cut-off scores are consistentwith previous research utilising the BDI to establish research groups (e.g.,Tennen, Hall, & Affleck, 1995), and is in line with Kendall, Hollon, Beck,Hammen, and Ingram’s (1987) recommendations regarding use of the BDI

in non-clinical samples Only those participants who met these cutoffs(N /73) were included in the final analyses

In addition to the BDI, participants also completed the short-form of theTaylor Manifest Anxiety Scale (TMAS; Bendig, 1956), because priorresearch has demonstrated depressive and anxious disorders to be highlycomorbid The TMAS is a 20-item, true/false questionnaire that has beenshown to correlate highly with other measures of trait anxiety and negativeaffectivity (Watson & Clark, 1984)

Description of affective stimuli Stimuli were taken from the tional Affective Picture System (Lang, Bradley, & Cuthbert, 1995), which

Interna-794 SHANE AND PETERSON

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contains normative ratings of affective valence for each picture on a 9-pointscale from unpleasant (1) to pleasant (9) Forty positive, 40 negative and 120neutral pictures were chosen, based largely on these valence ratings Negativepictures were selected in accordance with their relevance to sadness andthreat, and included depictions of illness, disaster, drug injections andhomelessness Positive pictures included puppies, sunsets, sweet dessertsand flowers Neutral pictures were largely depictions of household items,such as lamps or chairs Each emotional picture (positive or negative) waspaired with a neutral picture, matching as closely as possible within each pairfor colour and shape of the focal object In total, there were 40 positive neutral, 40 negative neutral, and 20 neutral neutral trials The latter trialtype acted as filler, and was prepared so that emotionally valent stimuli werenot displayed on each trial, and to decrease the opportunity for participants

to determine the nature of the task Sexually explicit scenes from the IAPSwere not included in the stimulus sets, as their influence on general arousalprocesses remains somewhat unclear

Procedure After obtaining informed consent, participants completedthe BDI and the short-form of the TMAS Participants next completed thedot-probe task (designed using E-Prime software; PSInet Corporation) on aPentium II computer and a 15-inch monitor, in a quiet room in thelaboratory The dot-probe task consisted of 10 practice, and 100 experi-mental trials (comprising the 40 positive neutral, 40 negativeneutral and

20 neutral neutral picture pairs) The practice trials were formed by usingneutral neutral picture pairs not included in the experimental trials Eachtrial started with a central fixation cross for 500 ms, followed by a picturepair, with half the pairs being displayed for 500 ms and half for 1500 ms Thepositive or negative pictures appeared on the right or left side of the screenwith equal frequency, as did the probe In addition, the probe appeared inthe place of the emotionally valent pictures on half of the trials, and in theplace of the neutral picture on half the trials For the neutral neutral trials,the probe appeared on the right or left an equal number of times The trialswere presented in a different random order for each participant The dotprobe was displayed immediately following the presentation of the picturepair, and participants were required to press one of two keys to indicatewhich side of the screen the probe appeared on The left index finger wasused to hit the ‘‘Z’’ key for probes located on the left side, and the right indexfinger was used to press the ‘‘/’’ (slash) key for probes located on the rightside Participants were informed to respond as quickly as they could, whileremaining accurate The probe remained displayed until the participantresponded, or for a maximum of 10 seconds The intertrial interval was

1000 ms Upon completion of the dot-probe task, participants were awardedcourse credit, debriefed, and allowed to leave

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Group characteristics Women (M /8.30, SD /5.72) showed slightlyhigher BDI scores than men (M /7.92, SD /5.95), however, this differencedid not prove significant, t(71) /0.07, p /.79 Subsequent data was thus colla-psed across gender As expected, the dysphoric group (M /14.10, SD /3.84)was characterised by significantly higher levels of dysphoria than the non-dysphoric group (M /4.05, SD /2.01; t(71) //14.55, d /3.47, p B/.001) Inaddition, there was a trend toward the dysphoric group manifesting higher an-xiety than the non-dysphoric group (dysphoric group: M /29.73, SD /4.18;non-dysphoric group: M /27.98, SD /3.90; t(71) /1.84, d /0.43, p /.07)

Attentional biases Data from two participants (one dysphoric, one dysphoric) were not included in the data set due to complications during theadministration of the dot-probe task (the computer crashed in the middle ofthe task) Latency data from trials with errors (1.25% of all trials) were exclu-ded from the analyses, as were latencies below 200 ms (2 trials) and greater than

non-700 ms (2.21% of all trials) after inspection of box and whisker plots These off points, as well as the percentage of trials excluded based on those cut-offs,are comparable with that of previous research utilising the dot-probe paradigm(Bradley, Mogg, Falla, & Hamilton, 1998; Mogg, Millar, & Bradley, 2000).Mean RTs were collected for each group (see Table 1) and attentional biasscores were calculated for each trial type by subtracting the mean RTs whenprobes were in the same location as the emotional pictures from the mean RTswhen they were in the opposite location (Bradley et al., 1998; Mogg

cut-et al., 2000) Thus, bias to negative stimuli was calculated from participant’sRTs on negative neutral trials, and bias to positive stimuli was calculatedfrom participant’s RTs on positive neutral trials Positive values of each biasscore reflect attentional vigilance toward the valenced picture, whereasnegative values reflect attentional avoidance of the valenced picture Thesetwo bias scores were found to be uncorrelated with one another, r /.07, ns.These attentional bias scores were entered into a 2 /2 /2 mixed-designANOVA, with valence and duration as within-subject variables anddysphoria as a between-subject variable.2 A significant main effect of

2 Before calculating attentional bias scores, we entered the raw RT data into a 2 / 2 / 2 / 2 /

2 ANOVA with valence (positive, negative), duration (500 ms, 1500 ms), picture location (left, right), and probe location (left, right) as within-subject variables, and dysphoria (high, low) as a between-subject variable Significant main effects of picture location, F (1, 70) / 7.97, p B / 01, duration, F (1, 70) / 178.25, p B / 001 and valence, F (1, 70) / 88.30, p B / 001 were identified Of particular note, the predicted four-way interaction of dysphoria / valence / picture location

/ probe location reached significance, F (1, 70) / 4.83, p / 03, which provided the basis for the calculation of the attentional bias scores used in the remainder of the analyses The five-way interaction involving duration did not reach significance, F (1, 70) 1.46, p 2.

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duration was revealed, F(1, 70) /8.59, h2/.11, p B/.01, as was a significantinteraction between dysphoria and valence, F(1, 70) /4.11, h2/.06, p B/.05.The three-way dysphoria /valence /duration interaction did not reachsignificance, F(1, 70) /1.28, p /.20 We also performed a similar ANOVAincluding participants’ TMAS scores as a covariate to consider thepossibility that the observed effects may be due to higher levels of anxiety

in the dysphoric group In this analysis, the main effect of durationdisappeared (p /.50), however the predicted dysphoria /valence interactionremained significant, F(1, 69) /3.65, h2/.05, p /.05 Furthermore, theanxiety /valence interaction was nonsignificant, F(1, 69) /.19, p /.80.3Dissection of the significant dysphoria /valence interaction allowed for

an initial investigation into the influence of positivity and negativity biases indysphoria Figure 1a depicts this interaction in graphical form, with earlyand late biases collapsed As can be seen, non-dysphoric individuals showed

a slight vigilance toward positive stimuli, whereas dysphoric individualsshowed a more pronounced avoidance of positive stimuli Planned compar-isons confirmed that these attentional biases differed significantly from

TABLE 1 Mean response latencies to probes (in ms): Study one

Level of Exposure Picture Probe

Picture valence dysphoria duration location location Positive Negative Low 500 ms Left Left 433.31 (56.34) 440.16 (62.14)

Left Right 432.85 (61.07) 457.84 (59.62) Right Left 449.50 (66.66) 481.90 (63.58) Right Right 446.89 (59.14) 464.37 (58.18)

1500 ms Left Left 400.80 (49.77) 427.22 (56.67)

Left Right 393.23 (46.17) 425.14 (62.17) Right Left 399.62 (54.31) 418.88 (61.41) Right Right 407.61 (50.15) 412.88 (50.10) High 500 ms Left Left 429.65 (53.05) 441.70 (67.51)

1500 ms Left Left 393.43 (61.32) 433.18 (67.68)

3 Interpretation of these covariate analyses need be made with caution Miller and Chapman (2001) have pointed out that using a covariate that is highly correlated with the measure of interest may regress out substantial variance, and may leave a variable with little in common with the original construct With appropriate caution, we believe these covariate analyses remain useful, however, we also believe it important to note these issues of interpretation.

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–30 –20 –10 0 10

Dysphoric Nondysphoric

–30 –20 –10 0 10

–20 –10 0 10 20

short-PBL / bias to positive stimuli on late trials; NBL / bias to negative stimuli on late trials.

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each other, t(70) /2.13, d /.50, p /.04 However, neither bias differed fromzero [dysphoric: t(29) //1.55, d /.20, p /.13; non-dysphoric: t(41) /1.33,

d /.28, p /.19] In contrast, both dysphoric and non-dysphoric individualsshowed tendencies to avoid the negative stimuli, and this avoidance reachedsignificance for the non-dysphoric participants, t(41) //2.20, d /.33,

p /.03

Temporal characteristics Because this study represented one of the firstinvestigations of temporal differences between biases toward positive andnegative stimuli, we examined the pattern of biases on short- and long-duration trials separately, despite the nonsignificant three-way interactioninvolving duration (see Figures 1b and 1c) On short-duration trials, thedysphoric group showed pronounced avoidance of the positive pictures thatdiffered from zero, t(29) //2.35, d /.42, p /.03, and from the non-dysphoric group, t(70) /1.76, d /.41, p /.08, and unbiased processing ofthe negative pictures The non-dysphoric group, in contrast, showed theopposite pattern of processing: pronounced avoidance of the negativepictures that differed from zero, t(41) //3.59, d /.54, p B/.001, but notfrom the dysphoric group, t(70) //1.63, d /.39, p /.11, and equalprocessing of the positive pictures On long-duration trials, dysphoricindividuals showed no evidence of biases, while the non-dysphoric indivi-duals showed pronounced bias toward positive stimuli, t(41) /2.52, d /.39,

p /.02

Bias differentials Finally, we wanted to investigate the possibility thatthe relative magnitude of individuals’ biases toward positive and negativestimuli may provide a more robust indicator of dysphoric processing thaneither absolute bias To this end, we calculated bias differential (BD) scoresfor each participant by subtracting their bias toward negative stimuli fromtheir bias toward positive stimuli Positive BDs thus indicate an overall biastoward positive stimuli, whereas negative BDs indicate an overall biastoward negative stimuli BDs were found to correlate significantly withbiases toward both positive and negative stimuli, and also correlatedsignificantly with BDI scores, r //.23, p /02 Furthermore, the non-dysphoric group was characterised by highly positive BDs (M /13.13, SD /

31.27) that differed significantly from baseline, t(41) /2.72, d /.42, p /.01,and from the dysphoric group, t(70) /1.93, d /.46, p /.05 In contrast, thedysphoric group manifested slightly negative BDs (M //3.34, SD /41.04),which did not differ from zero, t(29) /0.45, p B/.60 Thus, non-dysphoricindividuals showed overall attentional patterns skewed toward positivestimuli, while the dysphoric individuals showed a mild, but nonsignificant,skewing toward negative stimuli To investigate the possibility that BDsadded to the prediction of dysphoria over and above either absolute bias

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score, a series of regression analyses were conducted in which the absolutebiases toward positive and negative stimuli were entered in block one, and

BD was entered in block two.4 Results demonstrate that BD successfullyentered into both regression models in block two, while knocking theabsolute bias scores out of the model (see Table 2)

Finally, early and late BDs were considered separately Non-dysphoricindividuals showed positive BDs at both early and late stages of attentionalprocessing (early: M /3.92, SD /47.09; late: M /12.87, SD /53.68), whiledysphoric individuals showed negative BDs at both stages of processing(early: M //24.31, SD /72.13; late: M //14.78, SD /90.82) A repeatedmeasures ANOVA with early and late BDs as within-subjects variables failed

to reach significance (p /.95)

Discussion

In the present study, only non-dysphoric individuals showed significantavoidance of negative stimuli, while dysphoric individuals showed signifi-cantly less attention to positive stimuli than non-dysphoric individuals Onthe whole, these findings are consistent with a myriad of previous researchidentifying one or the other of these biases in dysphoric and depressedpopulations (Bradley et al., 1997; Gotlib et al., 1988; Ingram & Ritter, 2000;Mogg et al., 1995) Our results do differ from previous findings in a number

of ways, however

First, most previous work has found that individuals in depressive statesshow pronounced vigilance toward negative stimuli In contrast, we reportunbiased processing in dysphoric individuals, and pronounced avoidance

4 For these continuous analyses, all participants including those with BDI scores between 6 and 10 were included in the analyses Results remained similar when excluding this group, however, the nature of continuous analyses required inclusion of the full sample of participants.

TABLE 2 Regression models using absolute biases and bias differentials to predict BDI: Study

one Predictor Standardised coefficient (b) p-value Model p-value Model 1 Bias to positive stimuli / 280 017 017 Model 2 Bias to positive stimuli / 156 215

Bias differential / 278 029 .005Model 1 Bias to negative stimuli 124 298 298 Model 2 Bias to negative stimuli / 060 641

Bias differential / 377 005 .010

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of negative information in non-dysphoric individuals One reason for thesedivergent results may pertain to the use of IAPS slides in the present study.Recent work suggests that the use of depression-specific stimuli may bepreferable to the use of broadly negatively-valenced stimuli, which caninclude a combination of threat-related, depression-related, and disgust-related stimuli, not all of which may be expected to elicit depression-related biases (Gotlib et al., 2004; Westra & Kuiper, 1997) The IAPSslides used in the present study may then have constituted too hetero-geneous a group of negative pictures to appropriately evaluate theprocessing biases present in dysphoria This could have had two effects.First, the extent to which the IAPS slides elicited biases within thedysphoric individuals may have been somewhat reduced Second, theinclusion of anxiety- and disgust-related stimuli may have unintentionallytapped alternate processing biases that could have been present within thenon-dysphoric population.

In study two, then, we ran a similar version of the dot-probe task utilised

in study one, but presented depression-specific words, instead of negativelyvalenced IAPS pictures Thus, three word-pair types were utilised in studytwo: positive neutral, depression neutral, and neutral neutral Positiveneutral trials were used to index participant’s bias toward positive stimuli,and depression neutral trials were used to index participant’s bias towarddepression-specific stimuli Our predictions were similar to study one, in that

we predicted the dysphoric group to manifest increased processing of thedepression-specific words In addition, based on the results of study one, weanticipated that the dysphoric group may also show increased avoidance ofpositive stimuli

A second difference between the results of the present study and those ofprevious research pertains to the temporal characteristics of the attentionalbiases Previous research has fairly consistently, although not unanimously,reported a late-stage bias toward negative stimuli in depressed or dysphoricindividuals, and, conversely, has failed to show the corresponding early stagebias (e.g., Suslow, Junghanns, & Arolt, 2004) The present study, in contrast,found no significant differences between early and late stage processing whenevaluating the relevant repeated-measures ANOVA, and subsequent ex-ploratory analyses, if anything, revealed stronger biases in the dysphoricgroup during early stage processing

To this we have two comments First, the present findings are not withoutprecedent, as a number of recent studies have reported increases in earlystage *and possibility even preconscious *susceptibility to stimuli indepression Lundh, Wikstrom, Westerlund, & Ost (1999), for instance,found that subliminal presentations of panic-related words correlatedsignificantly with level of trait depression Luecken et al (2004) have shownsimilar effects of subliminal stimuli in a dot-probe task not unlike the

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presently devised task These studies evaluated attentional patterns earlier,even, than the 500 ms timeframe utilised in the present study and togetherwith the present findings suggest the possibility of early stage biases indysphoric processing.

Second, it should be noted that the dysphoric group showed early stageprocessing biases not on negative neutral trials, but on positive neutraltrials Previous work demonstrating late stage biases in depression anddysphoria have reported such biases with regard to negative information Weare, however, unaware of any previous work evaluating the temporalpatterning of biases to positive stimuli in depression or dysphoria It may

be that biases to positive information have a different temporal pattern thanbiases to negative information In this regard, it is interesting to note that thedysphoric group only showed a bias toward positive information on short-duration trials

Another possibility, however, is that the early stage duration utilised in thepresent study (500 ms) may not have sufficiently tapped early stageattentional processing Recent evidence has suggested that individuals arecapable of shifting their attention within 200 300 ms of stimulus onset(Chun & Wolfe, 2001; Duncan, Ward, & Shapiro, 1995), and thus by 500 ms,

we may have already been evaluating later stages of attentional processing.This could explain why we did not obtain a significant interaction withduration in study one, and may further explain why we found suchpronounced biases during early stage processing To this end, study tworeduced the probe onset time in the early stage trials to 200 ms, in order toensure that we were accurately indexing the initial orienting tendency of allparticipants

STUDY TWO Method

Participants Eighty-one undergraduate psychology students at theUniversity of Toronto volunteered for the study, in partial fulfilment ofcourse credit Of these participants, 51 were women and 30 were men Theirages ranged from 18 29 (M /20.20, SD /1.74)

Assessment of dysphoria As in study one, participants completed theBDI, as well as the TMAS Again, as in study one, those scoring 6 and below

on the BDI were classified as non-dysphoric, whereas those scoring 10 andabove were classified as dysphoric (consistent with Tennen et al., 1995, and

in line with Kendall et al.’s, 1987, recommendations) Sixty-six participants(39 non-dysphoric, 27 dysphoric) met this final criterion and were included

in the subsequent analyses

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