individual differences in reward sensitivity and attentional focus

Individual differences in reward sensitivityand attentional focus

Cesar Avila*, Maria Antonia Parcet

Department de Psicologia Basica, Clınica i Psicobiologia, Apartat de Correos 224,

Campus de Ia Carretera de Borriol, Universitat Jaume I, 12080 Castello, Spain

Received 31 May 2001; received in revised form 1 November 2001; accepted 30 November 2001

Abstract

Two priming experiments were conducted to study the relation between attentional focusing and J.A.Gray’s personality dimension of impulsivity. Pre-target primes were centrally presented before expectedand unexpected targets that appeared after 100 or 500 ms in the same location. In Experiment 1 primes andexpected targets matched physically, whereas in Experiment 2 did not match physically. Participantscompleted the Sensitivity to Punishment and Sensitivity to Reward Questionnaire, a measure of Gray’sanxiety and impulsivity dimensions. Both experiments showed that, at the 500-ms stimulus onset asynchrony(SOA), participants with higher scores on the Sensitivity to Reward Scale (i.e. impulsives) obtained greaterdifferences between response times to expected and non-expected targets than low scorers. Discussion iscentered on the nature of over-focusing of attention in individuals with an overactive Behavioral ActivationSystem (BAS). # 2002 Published by Elsevier Science Ltd.

Keywords: Sensitivity to Reward; Behavioral Activation System; Priming; Expectations; Selective attention; Gray’smodel

Gray’s model of personality has described two main dimensions of personality, called anxietyand impulsivity (Gray, 1981). The best described is the anxiety dimension, which is conceptualizedas reflecting individual differences in sensitivity to punishment (see Gray, 1982). Some authorshave stressed that Gray’s description of trait anxiety is more successful in identifying the brainstructures and behavioral processes mediating anxiety [i.e. description of the Behavioral InhibitionSystem (BIS)] than it is in specifying cognitive processes which determine when the BIS is activated(Eysenck, 1992b). In the last 15 years, a great deal of research has addressed the cognitive processesunderlying trait anxiety (Eysenck, 1992a; Mathews & MacLeod, 1994; Mogg & Bradley, 1998;

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Wells & Matthews, 1994). However, less attention has been devoted to describing cognitive processesunderlying the Behavioral Activation System (BAS).

Gray has related his impulsivity dimension to individual differences in sensitivity to reward:impulsives (i.e. individuals with a strong sensitivity to reward) easily make approach responseswhen faced with a stimulus that signals the possibility of obtaining a reward or relieving apunishment. Despite the importance of Gray’s impulsivity dimension in several theories, a cleardescription of the cognitive functioning of the BAS in humans is far from complete. Although Grayhas never included them in his description of the outputs of the BAS. it is reasonable to assume thatactivation of the BAS implies an increase in conical arousal and a directing of attention towardrelevant signals (see Derryberry, 1991; Wallace, Bachorowski, & Newman, 1991; Wallace & New-man, 1997).

Research on Gray’s impulsivity dimension has shown that impulsive personalities (i.e. individualsscoring high on measures related to impulsivity) condition better with reward than non-impul-sives using diverse experimental paradigms (Avila & Parcet, 2000: Corr, Pickering, & Gray, 1995;Gupta & Shukla, 1989). Other studies have shown that impulsives are characterized by impairedaversive learning when they are responding for reward (Avila, Molto, Segarra, & Torrubia, 1995;Avila & Parcet, 2000; Grande, Avila, Molto, & Torrubia, 1993; Patterson, Kosson, & Newman,1987; Thornquist & Zuckerman, 1995). Patterson and Newman (1993) outlined specific condi-tions which contribute to impaired aversive learning in impulsive individuals. Impulsives easilyestablish strong approach response sets that are less susceptible to modification by punishment orchanging conditions. The key cognitive aspects of this response set (mediated by the BAS) wouldbe an effortful allocation of attention to goal-relevant stimuli and a stronger expectation ofreward. Once a strong approach response has been established, impulsives over-focus attentionon the goal which, in turn, limits response modulation, that is, processing of new information andresponse alternatives.

In the last years, the conceptualization of the BAS has evolved partially due to the advance inthe knowledge of the role of dopamine functions. A number of researchers has related per-sonality traits associated with the BAS to dopaminergic activity (see Depue & Collins, 1999;Matthews & Gilliland, 1999; Pickering & Gray, 1999). This association facilitates the developmentof a more global cognitive theory of BAS functioning because dopamine and the BAS, althoughrelated to incentive motivation, have been proposed to play a more general role in processing ofrelevant stimuli, and in preparing and programming goal-directed behavior. This framework goesbeyond simple motivational views of the BAS stating that this system is only involved in reward-directed behavior, and is consistent with its participation in cognitive processes that mediatedetection of reward and cues of reward, and response preparation (Robbins & Everitt, 1995). Thisnew framework may serve to explain why simple reward manipulations like those proposed byPickering, Corr, Powell, Kumari, Thornton, and Gray (1997) did not yield results a prioriconsistent with Gray’s model (see Corr, 2001). Consistent with this approach, our research group isdeveloping a research program designed to describe cognitive functioning of the BAS (Avila &Parcet, 1997; Avila, Barros, Ortet, Parcet, & Ibanez, 2001) using the framework developed byWallace and Newman (1997).

Wallace and Newman (1997, 1998) have outlined the role of the Non-specific Arousal SystemNAS) in Gray’s model, a hypothetical structure which receives outputs from the BIS and theBAS. The NAS is involved in facilitating dominant responses automatically elicited by aversive

980 C. Avila, M.A. Parcet / Personality and Individual Differences 33 (2002) 979–996

and appetitive stimuli that activate the BIS and the BAS, respectively. Thus, a strong NASreactivity made individuals prone to dysregulation, that is, to a failure to evaluate and correctdominant behavioral or cognitive responses that are inappropriate or maladaptive in the currentsituation. In individuals with an overactive BAS, Wallace and Newman proposed that the presenceof a goal would facilitate dominant responses that were successful in the past to achieve the goal,with the consequent curtailment of the controlled processing needed to evaluate the suitability ofthe response to the current situation. In the attentional domain, this process is due to theover-focusing of attention on goals.

There is some research showing that impulsive individuals over-focus on locations whererewarding stimuli are present. Derryberry and Reed (1994) employed a modified version of theorienting task developed by Posner. Using peripheral endogenous cues for orienting attention(Experiment 2), they studied target detection speed as a function of the interval between primeand target (100 or 450 ms), the value associated with each location (positive or negative), thefeedback on previous trials (reward or punishment) and personality. Interestingly, at the longinterval and after negative feedback, neurotic extraverts (i.e. impulsives) showed greater costs fordisengaging from a location associated with monetary rewards marked by a pre-determinedcolor. In another study, Howland, Kosson, Patterson, and Newman (1993) presented anexogenous cue that signalled the correct location (left or right) of a target stimulus 86% of the time.The interval between the prime and the target was always 1 s. Rapid responses were rewarded withmonetary incentives. Their results showed that undergraduates with low scores on the Gough’sSocialization Scale and incarcerated psychopaths made more errors on invalid trials (althoughdifferences were only found when the prime led participants to expect a right-handed response andthe imperative stimulus required a left-handed response).

Differences between groups in response times in valid and invalid trials did not reach significance.Consistent with Wallace and Newman’s (1997, 1998) model, these two results suggested thatdisinhibited individuals have greater difficulties using controlled processing to direct attentionaway from the locations and responses strongly associated with reward. In a third relevant study,Avila (1995) administered a Posner orienting task that served to study exogenous facilitation, andinhibition of return. Although there were no personality differences in exogenous facilitation, thetwo studies showed that neurotic, anxious and impulsive participants had a greater inhibition ofreturn at the long interval. Considering that there were only two possible spatial locations wherethe target could appear, these findings were interpreted as indicating that these personality groupsfocused more attentional resources on most probable target location once the other location hadbeen reviewed. From these studies, we may conclude that disinhibited individuals have a dominantresponse set that impairs the movement of their attention away from locations associated withreward or greater expectation of targets.

The present research aimed to isolate the specific attentional mechanism that underlies thisimpairment. The neuropsychological literature has shown that both spatial and identity/semanticinformation is processed separately within the brain in the dorsal and ventral pathways (seeUnderleider & Mishkin, 1982). A different functional specialization has been proposed for them(Milner & Goodale, 1995): the dorsal pathway basically processes spatial information for executingvisually guided behavior, whereas the ventral pathway is more focused on identity/semanticinformation to perceive and store visual experiences. All above-cited studies on impulsivityfollowed the same logic: detecting a target in an expected or reward-associated location is more

C. Avila, M.A. Parcet / Personality and Individual Differences 33 (2002) 979–996 981

rapid/accurate than in an unexpected or non-reward-associated location. These paradigms do notallow inferences to be made about the nature of this attentional deficit because two differentcomponents (one related to spatial location and the other to identity/semantic information)were associated with reward. One hypothesis is that this deficit is spatial in the sense of yieldingan impairment in attentional shifting when two locations are available. Thus, as in anxiety, thedeficit would only be found in location priming tasks with two or more competing spatiallocations. The other possibility is that this deficit is cognitive in the sense that impulsive indi-viduals focused on identity/semantic features of stimuli associated with reward/goal when otherunexpected targets are possible. Thus, an expectation of a determinate goal/reward would beneeded to find impaired cognitive processing of non-related or unexpected stimuli. The maindifference is that this cognitive focusing should be obtained without moving attention betweenseparate spatial locations. Previous data suggested that impulsives are not deficient in spatialprocessing in the absence of rewarding stimuli (Avila, 1995; Avila et al., 2001; Avila & Parcet,1997; Ball & Zuckerman, 1992). To the contrary, they seemed to shift their attention betweenstimuli more rapidly and display less interference than low impulsive individuals. Thus, wehypothesized that the attentional deficit of impulsives consisted of deficient attentional processingof unexpected stimuli when they have a strong expectation of a determinate goal. To test thissecond possibility, we designed a priming task that did not require shifting attention betweendifferent locations.

The experimental paradigm most often used in the investigation of expectation effects involvespriming. In each trial of the priming paradigm, a prime stimulus that may provide informationregarding attributes of the succeeding target stimulus is presented to a subject. Posner and Snyder(1975) developed several priming experiments to study attentional benefits and costs using a let-ter-match judgement or a categorization task. The idea underlying this procedure is that when aprime orients attention to a particular pathway, subsequent targets using the same pathway willbe facilitated because attention is already correctly aligned (i.e. valid trials). Then, responsesexpected after primes become dominant. However, if the target activates a different pathway thanthe one activated by the prime, then processing is delayed because extra time (i.e. controlledprocessing) is required for attention to shift from the primed to the targeted pathway (i.e. invalidtrials). The validity effect is illustrated when responses to valid trials are faster than responses toinvalid ones. Both types of trials could be compared with neutral trials in which the prime conveysno information about the target. Typical results have shown that valid trials produce attentionalbenefits and invalid trials cause attentional costs relative to neutral trials (Posner, 1978).

1. Experiment 1

In the present experiment, we aimed to investigate the attentional functioning of impulsivesusing an identity priming paradigm instead of a location priming paradigm (see Posner, 1978).This paradigm serves to study focusing of attention without moving attention within the visualfield. In this experiment, we have modified the procedure employed by Posner and Snyder (1975)in order to develop an identity priming task similar to that employed previously in locationpriming paradigms (see Derryberry & Reed, 1994; Howland et al., 1993). The task employed inthis study included two different targets and three different primes. We instructed participants to


press the ‘Z’ key of the keyboard of a computer if a ‘ZZZ’ target appeared and the ‘M’ key if a‘MMM’ target appeared. These targets might be preceded by a ‘Z’, ‘M’, or ‘+’ character at thesame location. Three different types of trials were considered: valid, invalid, and neutral. Validtrials were produced when prime was followed by expected target stimuli (e.g. a ‘Z’ followed by‘ZZZ’). Invalid trials were produced when prime was followed by unexpected target stimuli (e.g. a‘M’ followed by ‘ZZZ’). Finally, neutral trials are obtained when the prime did not say anythingabout the possible target (e.g. a ‘+’ followed by ‘ZZZ’). Positive expectations after a letter primewere formed by including more valid than invalid trials and informing participants of thiscontingency (letter primes matched targets on 80% of trials). To calculate precise measures ofattentional benefits and costs, valid and invalid priming stimuli should be compared with a neutralprime (i.e. those that activate a pathway not related to possible targets). Thus, benefits arecalculated by subtracting reaction times in valid trials from neutral ones, whereas costs arecalculated by subtracting reaction times in invalid trials from neutral ones.

Two different prime to target intervals of 100 and 500 ms were used. Results have shown apattern of costs and benefits that varies with the interval between the prime and the targetstimulus (Neely, 1977; Posner, 1978). These authors have proposed a two-component model oforienting. One component is automatically activated by the prime and is closely time-locked to itspresence. This bottom-up orienting causes primes to facilitate the processing of previously asso-ciated targets during a few milliseconds and with little diversion of processing resources fromother cognitive operations. The other component, called conscious, requires more effort and ismainly guided endogenously by expectations associated with the prime. This top-down orientingis a long-lasting process that serves to focus attention on the most probable targets. The 100 and500 ms stimulus onset asynchronies (SOAs) are related to the predominance of automatic andconscious preparatory mechanisms, respectively. Previous studies with impulsive undergraduates,psychopaths and hyperactive children have not found differences in automatic orienting (Avila,1995: Derryberry & Reed, 1994; Harpur & Hare, 1991; Swanson et al., 1991). However, these andother studies have found differences in strategic and endogenous orienting of attention towardrelevant or rewarding targets (Avila, 1995; Derryberry & Reed, 1994, Experiment 2; Dickman &Meyer, 1988; Harpur & Hare, 1991; Howland et al., 1993; Logan, Schachar, & Tannock, 1996).

In Experiment 1, we administered a Posner-type letter-discrimination task and the Sensitivity toPunishment and Sensitivity to Reward Questionnaire (Torrubia, Avila, Molte, & Grande, 1995:Torrubia, Avila, Molto, & Caseras, 2001) to a group of female undergraduates.1 Our mainhypothesis was that impulsive participants (those with high scores on the Sensitivity to RewardScale) would more effortfully over-focus their attention (i.e. benefits, costs, or both) toward targets

1 The SPSRQ was a valid and reliable measure of Gray’s personality dimensions. The Sensitivity to Punishment (SP)Scale was designed to measure individual differences in the responsivity of the BIS, whereas the Sensitivity to Reward(SR) Scale includes items that measure differences in the functioning of the BAS. As would be expected from Gray’s

model of E and N, psychometric studies show that high SR individuals are neurotic extraverts, low SR individuals arestable introverts, high SP individuals are neurotic introverts and low SP individuals are stable extraverts (Torrubia etal., 2001). Examples of items of the SP Scale are ‘‘Do you often refrain from doing something because of your fear of

being embarrassed?’’ or ‘‘Are you easily discouraged in difficult situations?’’, whereas examples of items of the SR scaleare ‘‘Does the good prospect of obtaining money motivate you strongly to do some things?’’ or ‘‘Do you generally givepreference to those activities that imply an immediate gain?’’. Furthermore, we have conducted some experimental tests

of Gray’s model using these Scales (Avila, 2001; Avila & Parcet, 2000; Torrubia et al., 1995).


signalled by the primes than non-impulsive participants. Thus, high SR participants would have moreproblems in altering this dominant response set than low SR participants. This greater biasing ofattention toward primes in high SR individuals was assumed to be related to their greater capacity todevelop conscious target expectations. Thus, differences in performance between SR groups wereexpected to be found at the 500 ins SOA (i.e. which allows for greater conscious attention and strongerexpectations), but not at the 100 ms. A secondary hypothesis was that high SR participants also wouldmake more errors in invalid trials at the long SOA due to their greater difficulties in altering anapproach response set (Howland et al., 1993; Logan et al., 1996; Patterson & Newman, 1993). Incontrast to Gray’s impulsivity, we predicted no differences in performance as a function of Sensitivityto Punishment in light of the fact that this priming task does not involve spatial attention. In a recentstudy, we argued that anxiety differences in attentional functioning in the absence of threat cues aremore dependent on spatial than identity features of stimuli (Avila & Parcet, 1997, 2002). Similarly,others have concluded that attentional bias toward threatening stimuli are only observed when there isa spatial competition between threatening and neutral stimuli (Mathews & Mackintosh, 1998).

1.1. Method

1.1.1. ParticipantsOne hundred and seventy-six female undergraduates enrolled in Psychology classes at the

Universitat Jaume I, completed the procedure of this study in partial fulfilment of a courserequirement. They were all right-handed. Mean age was 19.02 (S.D.=1.20) with a range between18 and 24 years. All participants completed the Sensitivity to Punishment and Sensitivity toReward Questionnaire (Torrubia et al., 1995, in press). Four groups were formed on the basis oftheir scores on the Sensitivity to Punishment and Sensitivity to Reward Scales, by dividingthe participants at the median on these two dimensions calculated in a large undergraduatesample (Torrubia et al., 2001). Participants scoring 12 or higher on the Sensitivity to PunishmentScale were designated as anxious (SP+), and participants scoring below 12 were classified asnon-anxious (SP�). Similarly, participants scoring nine or above on the Sensitivity to RewardScale were designated impulsives (SR+), whereas participants scoring below this cut-off scorewere classified as non-impulsives (SR�). This breakdown resulted in four groups of 32 SP�SR�,40 SP�SR+, 41 SP+SR�, and 63 SP+SR+, respectively.

1.1.2. Apparatus and taskThe experiment was run on a PC computer with a SuperVGA monitor. Responses were made

on the computer keyboard. Reaction times were recorded to the nearest millisecond. All primeand target distractor stimuli were regular capital letters (‘Z’, ‘M’, ‘ZZZ’ and ‘MMM’) orcharacters (‘+’) of the PC 80-column text mode. Participants completed a total of 400 trials.Fig. 1 illustrates the experimental conditions in this paradigm.

A prime stimulus (‘Z’, ‘M’, or ‘+’) followed by a target stimulus (‘ZZZ’ or ‘MMM’) waspresented in each trial. Participants were required to make speeded responses to the targetstimulus by pressing the appropriate key. They had to respond with their left index finger to the‘Z’ key if a ‘ZZZ’ target appeared, and to the ‘M’ key with their right index finger if a ‘MMM’target appeared. Targets remained on the screen until the subject responded. There was the samenumber of appearances for both target stimuli.


Experimental conditions were defined by the factorial combination of levels of prime stimulusvalidity (valid, neutral vs. invalid) and SOA (100 vs. 500 ms) and Response Hand (left to respondto ZZZ vs. right to respond to MMM). Trials were valid when the prime and the target stimulihad the same letter. Trials were invalid when the prime and the target stimuli had different letters.Finally, trials were neutral when the prime stimulus was ‘+’ because it provides no informationabout the target. There were 256 valid trials, 64 invalid trials and 80 neutral trials. Thus, validityof a ‘Z’ or an ‘M’ prime was 80%. Finally, half of the trials employed a prime to target interval of100 ms and half of 500 ms.

The task was administered in a silent room in groups of 6–10. The instructions emphasized thatresponses had to be as rapid as possible, and specify prime to target relationship. Participantswere informed that targets would be more probable after Z primes, that MMM targets would bemore probable after M primes, and that both possible targets were equally probable after+primes. Prior to performing the task, participants completed 30 practice trials. Valid, invalid, and

Fig. 1. Stimuli and conditions employed in the experiments.


neutral trials were presented in random order in two blocks of 200 trials. The inter-trial intervalrandomly varied between 1700 and 2200 ms.

1.2. Results

Trials with reaction times lower than 100 ms or greater than 1000 ms were excluded from theanalysis. This accounted for less than 1.5% of the data, and did not change the overall pattern ofresults. Cost and benefits were calculated for each condition, and were used to interpret theresults. Benefits were computed by subtracting reaction times on valid trials from reaction timeson neutral trials. Costs were computed by subtracting reaction times on invalid trials from reactiontimes on neutral trials. Mean of median reaction times and mean errors for valid, neutral andinvalid trials, and costs and benefits for both SOAs were calculated for later analysis.

1.2.1. Reaction timesMeans and standard deviations of median reaction times for each personality group appear on

Table 1. A 3�2�2�2�2 mixed-model analysis of variance was used to analyze reaction times.Validity (valid, neutral vs. invalid), hand (left vs. right) and SOA (100 vs. 500 ms) were includedas within-subjects factors, whereas SR (low vs. high) and SP (low vs. high) were used as between-subjects factors. The analysis yielded a significant main effect for SOA, F (1, 172)=1470.23,P<0.001, indicating that the long SOA produced faster response times than thc short one. TheValidity main effect was also highly significant, F(2, 344)=1125.27, P<0.001, with faster responsesfor valid than neutral trials, and also faster responses for neutral than invalid trials. Finally, the Handmain effect was also significant, F (1, 172)=14.92, P<0.001), indicating that right responses were

Table 1Reaction times as a function of personality group, side of the target stimuli, SOA and Validity: Experiment 1

Left side/Z response Right side/M response

SP�SR� SP�SR+ SP+SR� SP+SR+ SP�SR� SP�SR+ SP+SR� SP+SR+

100 msValid M 467 468 466 449 462 461 454 439

S.D. 88 56 67 57 88 58 61 53Neutral M 530 541 532 521 526 523 516 502

S.D. 88 64 65 65 104 64 71 62Invalid M 566 574 557 546 579 579 572 554

S.D. 92 95 65 65 89 75 73 63

500 msValid M 409 396 405 389 408 392 398 379

S.D. 80 44 49 49 97 54 58 43Neutral M 493 493 484 480 482 468 463 458

S.D. 82 65 64 63 82 65 72 66Invalid M 503 509 501 492 499 510 499 488

S.D. 89 71 75 71 87 87 70 71

SOA, stimulus onset asynchrony.


faster than left responses. These main effects were modulated by several significant interactions.First, the SOA�Validity interaction reached significance, F (2, 344)=18.27, P<0.001, indicatinggreater benefits at the long SOA (81 vs. 72) and greater costs as the short SOA (�41 vs.�23).Second, the Hand�Validity interaction was significant, F (2.344)=25.91, P<0.001, reflecting agreater validity effect for right than left responses (112 vs. 100 ms). Analysis of benefits and costsrevealed that this difference was due to greater costs for right than left responses (�42 vs.�21).Third, the SOA�Hand interaction was significant, F (1, 172)=4.95, P<0.03, indicating a greaterdifference between right and left responses at the long SOA (10 vs. 5). Finally, theSOA�Hand�Validity third order interaction also reached significance, F (2, 344)=3.42, P<0.04,reflecting greater benefits for left hand responses at the long SOA, and greater costs for the righthand responses at the short SOA.

Regarding personality factors, the relevant Validity�SR interaction [F (2, 344)=2.23, P=0.10]and Validity�SOA�SR interaction [F (2, 344)=1.66, P=0.19] did not reach significance. Plannedcomparisons were used to test our hypothesis regarding SR. We examined the SR�Validityinteraction at the long SOA (Fig. 2). As expected, this interaction reached significance, F (2,344)=7.14, P<0.001, indicating that the SR+group had a greater validity effect than the SR�

one (110 vs. 95). Cost-benefit analyses revealed that differences were due to a greater magnitudeof benefits (86 vs. 75), whereas no significant differences in costs were found (�24 vs. �20). Alsoas expected, no differences between impulsives and non-impulsives were found at the short SOA.Finally, groups scoring high and low on the SP Scale did not differ in performance.

1.2.2. Error analysesPreliminary examination of error data revealed floor effects. At the short SOA, 19% of

participants after the ‘ZZZ’ target stimuli and 14% after ‘‘MMM’ target stimuli made no errors.At the long SOA, 21% of participants after ‘ZZZ’ targets and 14% after ‘MMM’ targets made noerrors. As the distribution of error data violated the assumption of normality required forparametric analysis, a Puri–Sen–Harwell–Serin (PSHS) analysis was used, as in the Howland et

Fig. 2. Validity effects for SR+ and SR� groups at 100 and 500 ms stimulus onset asynchronies (SOAs): Experiment 1.


al. (1993) study. This allows analysis of covariance with ranked data and was found to beappropriate for analyzing group differences with exponential distribution such as data with flooreffects (Harwell & Serlin, 1988). To control for possible speed–accuracy trade-offs, we usedresponse latencies following valid instances of the same prime stimuli and SOA as covariates.

Our main hypothesis related to errors was that SR+ participants would make more errors thanSR� ones on invalid trials at the long SOA. A different analysis of covariance including SP andSR as between-subjects factors was conducted for errors at each different SOA and hand. Ourhypothesis was only confirmed for errors after targets demanding right responses (TS=4.00,P>0.05), indicating that, independently of their speed of responding, SR+ participants(M=11.22%) made more errors on invalid trials with a ‘Z’ prime followed by ‘MMM’ targetthan SR� participants (M=7.88%). This difference was not found for targets demanding leftresponses (TS=0.12, ns). No personality differences were for errors in valid and neutral trials.

1.3. Discussion

The priming task used in this study yielded the expected results. The analysis of response timesrevealed a significant main effect for validity. At both SOAs, response times were more rapid invalid than neutral trials, whereas neutral trials produced faster responses than invalid trials. Thus,primes have effectively served to align attention to related targets, improving detection whentargets corresponded with primes, and delaying responses when targets did not correspond withprimes. It is important to highlight for further interpretation of results that this paradigm yieldedmore benefits than costs because neutral primes were not associated to a response. The well-described SOA main effect showing faster response times at the long SOA has also been found inthis study, and should be interpreted as an ‘‘alerting effect’’ that reflects the build-up in phasicarousal or readiness. Finally, right-handed responses were faster than left-handed responses,especially in neutral trials.

The results obtained for response times provide good support for our hypothesis. When consciousprocessing is operating, data are consistent with the hypothesis that high SR individuals focustheir attention more on stimuli signalled by primes than low SR individuals. No differencesbetween the SR groups were obtained at the short SOA, indicating that they were more evidentwhen conscious processing of primes was more relevant than automatic processing. This patternof results could be indicating that individuals with an overactive BAS focused their attentionalresources more effortfully on informative prime stimuli strongly associated with targets, impairingthe processing of non-expected target stimuli. As the reaction time differences were more relatedto benefits than to costs, it could be argued that high SR individuals developed stronger andlonger-lasting expectations of targets after primes.

Analysis of errors gives partial support to our hypothesis because the predicted difference wasonly significant for right responses. Participants with an overactive BAS were less able to inhibitleft-handed responses at the long SOA when primes permitted conscious focusing of attention.However, the equivalent analysis for right responses yielded differences in the same direction, butthese did not reach significance. The finding that SR differences disappeared for neutral and validtrials suggests that high SR individuals’ difficulties were not general but specifically related todominant responses. Thus, error differences between high and low SR groups were onlysignificant in those invalid trials in which a prime oriented toward a left-hand response and the


target demanded a right-hand response. These could not be attributed to a different lateralizationof perceptual processes since all the stimuli were presented centrally. Conversely, these resultsappear to reflect differences in control of left and right responses. In sum, the error data ofExperiment 1 demonstrate that, in some cases, the stronger expectations of targets in individualswith an overactive BAS were associated with a response cost, that is, with a significant impairmentin the attentional processing of unexpected targets.

2. Experiment 2

Results of Experiment 1 confirmed that individuals with an overactive BAS focused on thetargets expected after primes at the long SOA. Such results have been attributed to differences inthe capacity for focusing on relevant information, and the different ability for inhibiting dominantresponses. However, as the prime and expected targets matched physically in the procedure ofExperiment 1, the obtained results could also be influenced by the automatic alignment of atten-tional resources toward physically similar targets. To discard this possibility, we designed asimilar procedure in which expected targets were physically different to primes, whereasunexpected targets were physically identical to primes. Concretely, participants were informedthat ‘Z’ primes would he more probably followed by MMM targets, and vice versa. Similarly toExperiment 1, instructions generated three different types of trials: valid, invalid, and neutral.Valid trials were produced when a prime letter was followed by an expected and physicallymismatching target (i.e. a Z prime followed by a MMM target). Invalid trials were producedwhen a prime letter was followed by an unexpected but physically matching target (i.e. a Z primefollowed by a ZZZ target). Finally, neutral trials were those with a ‘+’ prime. Positive expectationsafter a letter prime were formed by including more valid than invalid trials and informingparticipants of this contingency. Predictions in this experiment were specific to the SOA condition.At the short SOA, we expected to obtain faster response times when in invalid trials (thosematching primes and targets) than in valid ones (those mismatching primes and targets) due tothe automatic pathway described by Posner and Snyder (1975). However, valid trials were pre-dicted to be faster than invalid trials at the long SOA due to the conscious expectations generatedby instructions. Consistent with results of Experiment 1, we hypothesized that high SR partici-pants would show a greater conscious focusing on expected targets at the long SOA, and thiswould he manifested in both reaction and error data.

2.1. Method

2.1.1. ParticipantsFifty-two female undergraduates enrolled in Psychology classes at the Universitat Jaume I,

completed the procedure of this study in partial fulfilment of a course requirement. They wereall right-handed. Mean age was 19.25 (S.D.=1.74) with a range between 18 and 27 years. Allparticipants completed the Sensitivity to Punishment and Sensitivity to Reward Questionnaire.Group assignment was based on the same medians as those used in Experiment 1 . This break-down resulted in four groups of 8 SP�SR�, 13 SP�SR+, 13 SP+SR�, and 18 SP+SR+,respectively.


2.1.2. Task and procedureThe same equipment, stimuli and procedures as in Experiment 1 were used, with an unique

modification. As shown in Fig. 1, a ‘Z’ prime was associated with ‘MMM’ target, and an ‘M’prime with ‘a ZZZ’ target on 80% of trials. Contrarily, primeses were associated with physicallymatching letters on 20% of trials. The instructions emphasized this prime to target relationship.Number of trials and SOAs were as in Experiment 1.

2.2. Results

2.2.1. Reaction timesAs in Experiment 1, anticipations and slow responses were suppressed from analyses. This

accounted for less than 1% of the data. Means of median reaction times for each personalitygroup appear on Table 2. A similar 3�2�2�2�2 mixed-model analysis of variance was used toanalyze reaction times including Validity, Hand and SOA as within-subjects factors, and SR andSP as between-subjects factors. The analysis yielded a significant main effect for SOA, F (1,48)=240.83, P<0.001, indicating that the long SOA produced faster response times than theshort one. Although the Validity main effect was significant, F (2, 96)=18.42, P<0.001, this wasstrongly modulated by the SOA�Validity interaction, F (2, 96)=51,94, P<0.001. This interac-tion reflected that invalid trials yielded faster response times than valid and neutral trials at the100 ms SOA, but valid trials yielded faster response times than invalid and neutral trials at the500 ms. As expected, primes facilitated the processing of physically identified targets at the shortSOA, and the processing of expected targets at the long SOA.

Table 2Reaction times as a function of personality group. side of the target stimuli, SOA and Validity: Experiment 2

Left side/Z response Right side/M response

SP�SR� SP�SR+ SP+SR� SP+SR+ SP�SR� SP�SR+ SP+SR� SP+SR+

100 ms

Valid M 543 507 542 549 541 510 536 539S.D. 80 37 90 38 50 35 74 45

Neutral M 521 515 539 548 533 513 533 523

S.D. 60 38 86 48 72 44 75 48Invalid M 515 485 510 525 489 456 469 476

S.D. 74 29 82 53 67 39 66 47

500 msValid M 442 417 469 443 432 414 448 422

S.D. 69 63 78 58 58 61 74 52

Neutral M 466 455 473 470 462 444 474 440S.D. 52 31 65 52 41 43 72 54

Invalid M 455 454 474 497 451 445 453 448

S.D. 54 44 64 56 44 40 76 55

SOA, stimulus onset asynchrony.


The Hand main effect was also significant, F (1, 48)=27, 16, P<0.001, indicating faster rightthan left responses. Although the Validity�Hand interaction was significant, F (2, 96)=10.34,P<0.01, this was modulated by a three-way interaction involving Validity�Hand�SOA,F (2.96)=3.61, P<0.05. This interaction showed that the above-cited Validity � SOA interactionwas modulated by Hand. At the 100-ms SOA, the difference between valid and invalid trials wasstronger for right than left responses (�57 vs.�25), whereas at the 500-ms SOA the difference wasstronger for left than right responses (21 vs. 31).

As in Experiment 1, the SR�Validity interaction [F (2, 96)=2.41, P=0.09] andSR�SOA�Validity interaction [F (2, 96)=2.24, P=0.11] were not significant. Planned compar-isons were used again to test our hypothesis regarding SR. We examined the SR�Validity inter-action at the long SOA (Fig. 3). As expected, this interaction reached significance, F (2, 96)=3.38,P<0.05, indicating that the SR+ group had a greater validity effect than the SR�group (38 vs.10). Two more results are similar to those obtained in Experiment 1: (a) no differences betweenSR groups were found at the short SOA and (b) groups scoring high and low on the SP scale didnot differ in performance.

2.2.2. Error analysesAs in Experiment 1, floor effects were found in error rate distribution: at the short SOA, 9.6%

of participants made no errors alter both the ‘ZZZ’ and ‘MMM’ target stimuli. Equivalent datafor the long SOA were 7.1 and 9.6%, respectively. None of the error distributions followed anormal distribution (P<0.05).

Percentage of errors was analyzed as in Experiment 1. Covariates were response times in invalidtrials at the short SOA and response times in valid trials at the long SOA. Although differenceswere in the expected direction, these analyses did not reveal any significant personality effect. Themean percentage of errors at the long SOA for low and high SR groups were 4.46 and 7.46% forMMM responses, and 5.35 and 6.65% for ZZZ responses, respectively.

Fig. 3. Validity effects for SR+ and SR� groups at 100 and 500 ms stimulus onset asynchronies (SOAs): Experiment 2.


2.3. Discussion

The priming task used in this study also yielded the expected results. At the short SOA,response times were more rapid in invalid than valid trials. Thus, primes effectively alignedattention to physically identical targets, independently of expectations. This effect was consistentwith the bottom-up orienting pathway proposed by Posner and Snyder (1975). At the long SOA,response times were faster in valid than invalid trials. In this case, differences could be attributedto the top-down pathway guided by expectations. The lower magnitude of the validity effectssuggested that expectations in Experiment 2 were weaker than in Experiment 1, partially due tothe response incompatibility between primes and targets. Thus, orienting attention towardexpected targets in this procedure seems to require more effort than in Experiment 1, since itinvolves a carry-over from the automatically generated identical target.

Despite these differences in the overall task, personality results replicated those of Experiment 1showing that high SR participants focused consciously (at the long SOA) on expected targetsmore than low SR participants, requiring an extra time to shift from the primed to the targetedstimulus. In this case, as the targets signalled by the primes did not match physically, differencesin response times could not be attributed to similarity between both stimuli. Thus, we mayinterpret both results from Experiment 1 and 2 as showing differences in maintaining a dominantresponse set independently of the physical relationship between the prime and the target.

However, this procedure did not replicate SR differences in errors. When compared with thoseof Experiment 1, the present results showed that the percentage of errors on trials with unexpectedtargets were low. This may be a consequence of the differences between Experiments 1 and 2suggested above.

3. General discussion

We have conducted two priming experiments to investigate the nature of attentional functioningof individuals with an overactive BAS. When compared with low SR participants, the twoexperiments have shown that high SR participants were most focused on targets predicted byprimes, being slower to detect unexpected targets. Results showed that this attentional focusingof high SR participants yielded a greater number of errors in responses when primes werephysically and cognitively associated with targets (Experiment 1), but not when the relationshipbetween them was only cognitive (Experiment 2). These differences in errors were attributed tothe weaker expectations generated after primes in Experiment 2. Because of the relative specificityof these differences in errors, we will focus our discussion on the observed differences in reactiontimes.

The present results serve to specify the effects of reward cues on the attentional focusing inindividuals with an overactive BAS reported in previous studies (Derryberry & Reed, 1994;Howland et al., 1993). There are two important features. First, the cognitive task used in thisstudy did not involve rewards. Thus, the BAS is not only related to increased attention to rewardcues but also to greater focusing on cues that signal most probable expected targets. Hence, theBAS could be understood as a more general system activated to maintain expectations whenindividuals are involved in goal-directed behavior. Second, the priming task used in our study


never presented two stimuli at the same time. Thus, the attentional focusing differences associatedwith Gray’s impulsivity do not necessarily involve the use of competing spatial locations. Rather,these differences seem to be more related to the competition between the cognitive representationsof the identity/semantic features of the two possible target stimuli. In this sense, previous resultswith mixed spatial and identity reward cues could be understood in a similar way (Derryberry &Reed, 1994: Howland et al., 1993: see also Ball & Zuckerman, 1992, for a similar result with theSensation Seeking Scale). These studies showed that disinhibited individuals focused on rewardcues marked with a specific cognitive identity or semantics (i.e. a color) and a physical spatiallocation. Following our results and the lack of impulsivity differences in spatial processing (Avila,1995; Avila & Parcet, 1997; Avila et al., 2001), we may conclude that the identity or semanticinformation of the goal is more important for disinhihited individuals than its spatial location.This second aspect is very important because it implies that over-focusing in individuals with anoveractive BAS would be more related to identity/semantic as opposed to the spatial features ofexpected stimuli. More research is needed to confirm this possibility.

A third important point is the fact that differences between SR groups were only found at thelong SOA. This suggests that differences in attentional functioning between high and low SRgroups were more probable when conscious processing is more relevant, which is consistent withprevious results showing that greater focusing of attention in individuals with an overactive BASis produced at long SOAs (Avila, 1995; Derryberry & Reed, 1994). This fact should be interpretedas indicating that focusing is not exogenously and directly produced by the stimulus, but requiresan effortful, voluntary, and expectation-guided orienting of attention toward relevant primes.Thus, attentional orienting to primes in impulsives seems to involve the development and overtimemaintenance of strong expectation about targets.

Gray’s description of BAS outputs only includes an approach response that facilitates responseprograms associated with the cue (Gray, 1987). However, it has been suggested that the BASshould also mediate over-focusing of attention toward cues for reward and non-punishment(Derryberry, 1991; Wallace & Newman, 1997). This study may help to clarify this process. Datafrom this study and those obtained by Derryberry and Reed (1994), provide no evidence of BASdifferences in the automatic processing of stimuli signalling reward and non-punishment. Rather,they are more prone to conscious focusing of attention on information carried by such stimuli.

The greater difficulties of high SR individuals for responding to unexpected targets are inagreement with the Wallace and Newman’s model, which predicts that the BAS output to theNAS entails (a) the over-focusing of attention towards a motivationally significant stimulus, (b)the consequent curtailment of controlled self regulation, and (c) an increased probability that aperson’s dominant responses will be manifested without adequate evaluation of the suitability ofthe response to the current situation. As the nature of focusing in these individuals is cognitiveand conscious, present results may serve to describe this process more specifically: their strongability for maintaining the identity/semantic features of the expected stimuli on-line would impairtheir processing of identity/semantic features of other unexpected or secondary stimuli. Theseresults may also explain response modulation deficits typically obtained in individuals with anoveractive BAS (Avila et al., 1995; Patterson et al., 1987; Wallace et al., 1991; see also the modeloutlined by Patterson & Newman, 1993). In fact, the stronger ability for maintaining expectationson-line could be the first step to the passive avoidance deficits observed in impulsives. Avila (2001)has shown that these deficits only appear in appetitive contexts when aversive contingencies


compete with dominant goal-directed behavior. Over-focusing on reward would contribute topreservation in goal-directed behavior.

The results of our priming tasks did not yield any significant differences associated with theGray’s anxiety dimension. When comparing with the cognitive nature of the biases toward positivestimuli of impulsive individuals, anxious individuals’ biases toward threatening information havea spatial nature because they have only been found when the task involved a competition betweenthreatening and neutral material (Mathews & Mackintosh, 1998). Thus, anxious individualswould give a stronger priority to threatening information when a competing neutral stimulus ispresented in a different spatial location. Another difference between anxiety and impulsivity is relatedto the automatic nature of the bias. Whereas we have proposed that biases associated with theBAS are conscious (require long SOAs), attentional biases of anxious individuals could be auto-matic or conscious (Derryberry & Reed, 1994; Mogg & Bradley, 1998) due to the existence of twodifferent systems to evaluate threatening information (Ledoux, 1996; Mathews & Mackintosh, 1998).

Results obtained in the present and previous studies suggest that differences in cognitive functioningin impulsive and disinhibited individuals are complex. The starting point is the assumption thatthe major function of impulsivity (as described by Gray) is the early detection of signals ofreward. Thus, attentional functioning should serve to favor processing of rewarding stimuli whenthey are present, and favor scanning the environment (i.e. exploratory behavior) for possiblerewards when they are not present. This attentional functioning could he manifested in, at least, threedifferent ways. First, the present study shows that high SR participants are more able to focustheir attention on the identity features of the most probable target stimulus. Second, some studiesusing versions of the coven attention paradigm developed by Posner have shown that impulsivesfocused their attention on locations associated with reward, having problems in disengaging andmoving attention toward other locations (Derryberry & Reed, 1994; Howland et al., 1993).Finally, some studies have shown that impulsives process distractors deeply in the absence ofrewarding stimuli (Avila & Parcet, 1997) and that impulsives are better at shifting attentionbetween different stimuli (Ball & Zuckerman, 1992; see also Newman & Wallace, 1993 for similarresults in psychopaths). Although more research is needed to describe their cognitive functioningprecisely, these data depicted an attentional functioning highly consistent with functions of the BAS.

Acknowledgements

This research was supported by a grant P1A98–09 from the Fundacio Caixa-Castello. Wewould like to acknowledge the contribution of Sybil Eysenck and two anonymous reviewers to anearlier version of this manuscript.

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