Divided visual attention in psychopathic and nonpsychopathic offenders

Person. indiuid. D$J Vol. 24, No. 3, pp. 373-391, 1998 Q 1998 ElsevierScienceLtd. All rights reserved

Pergamon

Printed in Great Britain 0191-8869/98

PII: s0191-8869(97)00176-1

DIVIDED VISUAL ATTENTION IN PSYCHOPATHIC NONPSYCHOPATHIC OFFENDERS

%19.00+0.00

AND

David S. Kosson Finch University of Health Sciences, The Chicago Medical School, North Chicago, IL 60064, U.S.A (Received 2 January 1997)

Summary-Although learning and physiological studies have suggested that criminal psychopaths are characterized by excessive selective attention, divided attention studies have demonstrated deficits suggesting inadequate breadth of attention but not reduced attention to explicit secondary contingencies. Divided attention studies also suggest poorer information-processing in psychopaths given left hemisphere activation regardless of selective attention. To provide more powerful tests of these hypotheses, 129 righthanded male inmates, assessed by Hare’s Psychopathy Checklist-Revised (PCL-R) (Hare, 1985), completed a divided visual field task with two lateralized stimuli per trial under conditions promoting attention relatively focused on one of the tasks or equally divided between the two tasks. Under focusing conditions promoting left hemisphere activation, psychopaths misclassified more secondary task and marginally more primary task targets than nonpsychopaths. Psychopaths also overresponded to distracters on both tasks under focusing conditions, replicating reduced breadth of attention but not inattention to secondary targets. However, no performance= deficits were evident under equally divided attention conditions. Regressions indicated that both empirically validated dimensions of psychopathy contributed to observed deficits. Reduced breadth of attention under focusing conditions and cognitive deficits given left hemisphere activation appear viable explanations of psychopaths’ performance deficits. @Y1998 Elsevier Science Ltd. All rights reserved Keywords: psychopathy, divided attention, cognition, visual field, activation

hemispheric

asymmetry,

selective attention,

sociopathy.

For over four decades, the study of psychopathy has been dominated by clinical descriptions which emphasize emotional deficits. Psychopaths are said to engage in impulsive antisocial behavior and display unstable relationships with others, because they have a blunted capacity for emotion, which interferes with understanding the emotional significance of events and the meaning of their actions (Cleckley, 1941; Lykken, 1957). According to these accounts, psychopaths are basically rational or cognitively intact, but because they lack emotional depth, their appraisals of situations also lack depth, and they are unable to anticipate the emotional consequences of their actions for themselves or others. In other words, psychopaths may sometimes display cognitive deficits, but these are secondary to emotional pathology. Recently, studies of psychopaths’ physiology and behavior have challenged this notion and suggested that psychopathic behavior is directly related to anomalies in attentional functioning. Psychopathic inmates display not only less electrodermal reactivity to noxious stimuli than nonpsychopathic inmates (Hare, 1978) but also smaller event-related potentials (ERPs) following irrelevant stimuli (Jutai and Hare, 1983) and larger ERPs following presentation of target (i.e., relevant) stimuli (Raine and Venables, 1988). Thus, Hare (1982; Jutai and Hare, 1983) have proposed that psychopaths allocate more attention than nonpsychopaths to immediate goals and less attention to a variety of other events (Harpur and Hare, 1990; Raine, 1989). Further, psychopaths’ learning deficits are often moderated by changes in the salience of important contingencies (Newman and Kosson, 1986; Newman et al., 1987). Newman and Kosson (1986) suggested that overresponsiveness to an immediate contingency may result in reduced attention to peripheral contingencies, which in turn may underlie psychopaths’ passive avoidance learning deficits. In suggesting that psychopaths’ attentiveness to one contingency is at the expense of

Correspondence should be addressed to: David S. Kosson at the Department of Psychology, Finch University of Health Sciences/The Chicago Medical School, 3333 Green Bay Road, North Chicago, IL 60064, U.S.A. 373

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David S. Kosson

reduced attention to competing contingencies, these studies predict deficits in situations requiring the distribution of attention among multiple contingencies. Thus, recent hypotheses for cognitive function in psychopaths have converged in a proposal of excessive selective attention or over-focusing, which explains psychopaths’ poor judgement and insensitivity to consequences as stemming from an over-allocation of processing resources to immediate, primary tasks. Although the learning and physiological studies reviewed above provide important evidence about psychopaths’ cognitive functioning, these studies generally required attention to a single set of targets or required the learning of implicit contingencies; therefore, their implications for psychopaths’ performance in situations with more than one meaningful stimulus and unconfounded by learning requirements are unclear. Moreover, the proposal of an excessive focus on some stimuli at the expense of other important stimuli is more straightforwardly examined with divided attention paradigms than with selective attention or learning paradigms, because divided attention studies provide direct measures of responsiveness to two distinct contingencies. Several divided attention studies of psychopaths have now been reported. These studies have consistently suggested that psychopaths perform poorly in dual-task situations (Kosson and Harpur, 1997). At the same time, most dual-task studies have not obtained the specific pattern of group differences predicted by over-focusing (Kosson, 1996; Kosson and Newman, 1986; Kosson and Newman, 1989). Kosson (1996) attempted to resolve this issue by measuring excessive selective attention at two distinct levels. In this study, participants were asked to complete both a visual primary task and an auditory secondary task, each containing both targets and distracters. Participants were instructed to press keys to classify both the frequent primary task targets presented visually (i.e., 67% of visual stimuli constituted targets) and the less frequent secondary task targets presented auditorially (33% of auditory stimuli constituted targets), but they were told to avoid responding to distracters, whether these appeared on the screen or through the speaker. Thus, the paradigm required both determining in which of three categories each target stimulus belonged (e.g., letters, numbers, or both) as well as distinguishing targets from distracters on the basis of gross physical stimulus characteristics (e.g., horizontal or vertical orientation of a frame surrounding stimuli). The strong form of the over-focusing hypothesis predicts that psychopaths will perform especially well at classifying primary task targets but not so well at classifying secondary task targets. Contrary to this prediction, psychopathic inmates were no better than nonpsychopathic inmates at classifying the frequent primary task targets and were no worse than nonpsychopathic inmates at classifying the less frequent secondary task targets. However, this study also permitted assessment of selective attention at a second level. Because two thirds of trials contained stimuli requiring responses, a modified over-focusing hypothesis predicts that, even if psychopaths do not pay less attention to secondary task targets than do nonpsychopaths, they will allocate more of their attention than nonpsychopaths to the stimulus dimension relevant to classifying targets (letters vs numbers) at the expense of insufficient attention to the dimension distinguishing targets from distracters (frame orientation). In fact, compared with nonpsychopaths, psychopaths overresponded to both the primary task distracters and the secondary task distracters: they more often pushed keys for these irrelevant stimuli as if they were relevant. Thus, it appeared that their concentration on classifying targets may have led psychopaths to neglect to consider whether the stimuli presented were targets or distracters. In short, reduced attention to a peripheral contingency is broadly consistent with the notion of excessive selective attention in psychopaths. It may be argued that such reduced breadth of attention represents a degree of over-focusing. Whereas psychopaths may not invest less attention than nonpsychopaths in processing moderately infrequent targets, they may invest less attention in especially peripheral processing requirements, especially in complex, multi-faceted situations. From this perspective, psychopaths would display secondary task deficits if secondary task targets were sufficiently rare. Alternatively, it may be argued that psychopaths and nonpsychopaths allocate comparable attention to all explicitly designated targets but that psychopaths pay less attention to non-target information or to subtle and to implicit information than nonpsychopaths. In either case, this finding represents preliminary evidence of excessive selective attention or reduced breadth of attention in a divided attention situation.

Divided visual attention in psychopaths

315

Divided attention studies have identified another apparent cognitive deficit in psychopaths: psychopaths may be characterized by generally less efficient processing of important signals given momentary heavy demands on left hemisphere-specific resources. According to Rizzolatti and Gallese (1988), attentional, perceptual, and motor processes are mediated by common systems loosely associated with each cerebral hemisphere and corresponding subcortical areas. Consistent with this perspective is evidence that left hemisphere attentional resources may be activated in a variety of different ways, ranging from speech preparation and subvocalization (Kinsbourne, 1970, 1973) to irrelevant activity of the right hand (cf. Robertson and North, 1993). Although simple brain damage models of psychopathy do not appear tenable (Hare, 1979; Hart et al., 1990), there is increasing evidence of subtle cognitive deficits in psychopaths linked to left hemisphere function. For example, in one dual-task study (Hare and McPherson, 1984), inmates were asked to remember words presented to the right and left ears simultaneously. Psychopaths remembered fewer words presented to the right ear (left hemisphere) than did nonpsychopaths. In another study, psychopaths displayed poorer abstract classification of words presented to the right visual field compared with words presented to the left visual field (Hare and Jutai, 1988; see also Howland et al., 1993; Raine et al., 1990). The left hemisphere activation proposal was also addressed in the dual-task study described above. As noted earlier, participants in this study completed a primary visual task and a secondary auditory task; they were randomly assigned to use one hand to respond to the targets of each task. Based on evidence that voluntary hand movements prime resources in the contralateral hemisphere (Robertson and North, 1993) Kosson (1996) assumed that left hemisphere resources would be most activated when most targets required right-handed responses (i.e., when the primary task was completed using the right hand). Consistent with the left hemisphere activation hypothesis, psychopaths displayed a trend toward less accurate responses than nonpsychopaths to primary task targets when task demands were greatest but only for participants who used their right hand much more than their left hand. The left hemisphere activation idea is consistent with recent models of hemispheric arousal and performance efficiency. Whereas moderate arousal of a hemisphere is believed to enhance the efficiency of hemisphere-specific resources, excessive arousal is said to produce performance decrements (Kinsbourne and Byrd, 1985). In this context, psychopaths’ pattern of deficits in several different conditions paired with adequate single-task performance suggests the possibility of a dynamic mechanism: psychopaths may be prone to momentary over-arousal of left hemisphere resources and may be expected to show poor judgement, impulsivity, and callousness only given appetitive motivational states (Davidson, 1984) and/or cognitive processing demands (Kinsbourne, 1973) that prime or activate left hemisphere resources.* Although both over-focusing and left hemisphere overactivation provide parsimonious accounts of many features of psychopathy, previous dual-task studies provide relatively limited tests of both proposals. Regarding over-focusing, the author’s previous studies involved visual primary tasks and auditory secondary tasks. Because processing resources may be modality-specific (Wickens et al., 1981) resources not allocated to a primary visual task may not be otherwise available to a secondary auditory task (Navon and Gopher, 1979). In short, the proportion of visual processing resources psychopaths allocated to a primary visual task in these studies may not have affected the availability of auditory processing resources for a secondary auditory task. Thus, the lack of evidence of secondary task deficits in these studies may reflect the insensitivity of intermodal attention tasks for showing over-focusing. A more powerful way to test over-focusing is to use two tasks of differing relevance in the same sensory modality. In addition, because stimuli in earlier studies were presented centrally (Kosson, 1996) or bilaterally (Kosson and Newman, 1986), inferences about involvement of left hemisphere resources are somewhat speculative. Even though lateralized responses may prime hemisphere-specific resources (Robertson and North, 1993), most studies designed to prime hemisphere-specific resources depend upon * Note that the hypothesis of situation-specific overarousal of left hemisphere processing systems does not contradict the hypothesis of chronic underarousal in psychopaths (Quay, 1965; Raine, 1993). Indeed, suggestions linking activity in left lateral&d dopaminergic pathways to stimulant effects (Wise and Bozarth, 1985) and to motor readiness (Tucker and Williamson, 1984) provide a possible mechanism for states of stimulation that underaroused individuals are said to pursue.

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lateralized stimulus presentation with or without lateralized responses (Reuter-Lorenz et al., 1990). Thus, implications of extant data for hemisphere-specific mechanisms are tentative. The present study was designed primarily to provide direct tests of the two hypotheses that psychopaths’ divided attention deficits stem from poorer information-processing given left hemisphere activation versus reduced attention to peripheral tasks or stimuli (over-focusing). As in prior divided attention studies, participants were asked to classify up to two stimuli per trial, and for those assigned to one of two relatively focused attention (RFA) conditions, target frequency was nearly twice as high in one stimulus set (67% of stimuli) as in the other (36%). To provide a sensitive test of the over-focusing hypothesis, this study employed a divided visual field procedure in which each stimulus set was lateralized to a different visual field. Thus, this paradigm permitted a direct test of over-focusing given two explicit stimulus sets in the same modality.* Because the two tasks required virtually identical processing, any visual processing resources that could be allocated to one task were in principle also useful for the other task. If psychopaths allocate too many visual processing resources to a primary visual task, as suggested by the strong form of the over-focusing hypothesis, they should have fewer visual processing resources available for a secondary visual task; consequently, psychopaths should outperform nonpsychopaths in classifying primary visual task targets at the expense of poorer performance in classifying secondary visual task targets. This study also provided an opportunity to examine the robustness of reduced breadth of attention in psychopaths. As in the prior study, each task was two-dimensional: participants decided whether stimuli were targets or distracters and in which category targets belonged. If a focus on a demanding primary task induces reduced breadth of attention in psychopaths, they should incorrectly respond to distracters (as if they are targets) under RFA conditions more often than nonpsychopaths. The divided visual field technique also provided a more powerful way to test the left hemisphere activation hypothesis. Because the RFA conditions presented roughly twice as many targets in one visual field as in the other, some participants were presented with a majority of target stimuli in either the right visual field (RVF); others, with the majority of targets in the left visual field (LVF). Given that unilateral visual stimulation produces asymmetric hemispheric activation (Davidson et al., 1985), the lateralization of most meaningful stimuli (i.e., targets) to the RVF should also induce greater left hemisphere than right hemisphere activation. Indeed, evidence from tachistoscopic paradigms suggests that divided visual field presentation yields greater hemispheric asymmetries than unilateral stimulus presentation (McKeever, 1986). Moreover, under such conditions, participants may be expected to attend preferentially to the RVF (Reuter-Lorenz et al., 1990) and to make more eye movements to the RVF, both of which are associated with greater left hemisphere activation (Harter and Anllo-Vento, 1991; Kinsbourne, 1983; Rizzolatti and Gallese, 1988). In short, the use of lateralized target stimuli as well as lateralized responses (Kosson, 1996) provides a more powerful method of priming hemisphere-specific resources and a method more consistent with prior studies of hemisphere asymmetry. Thus, the left hemisphere activation hypothesis predicts a pattern of performance deficits for psychopaths given primarily RVF targets and right hand responses (but not given primarily LVF targets and left hand responses). Predictions are summarized in Table 1. In summary, the strong form of the over-focusing hypothesis predicts superior primary and inferior secondary task performance for psychopaths in a RFA condition regardless of the visual field to which primary task targets are presented. The weaker form of over-focusing predicts over-responding to distracters by psychopaths under demanding conditions. By contrast, the left hemisphere activation hypothesis predicts deficits for psychopaths given primarily RVF targets requiring right hand responses but not given primarily LVF targets. Although the hypotheses are not contradictory, they make relatively independent predictions. Thus, it is possible that results could be consistent with both hypotheses, with only one hypothesis, or with neither hypothesis. The present study was also designed to address specific questions suggested by previous research. l

The term “dual-task paradigm” usually refers to situations in which participants work at two different tasks simultaneously, whereas divided VF paradigm implies only that stimuli may appear in the RVF or in the LVF. Although neither term is fully descriptive of the current paradigm, the term dual-task is retained in this paper, because some divided VF paradigms present only one stimulus per trial. However, it should be kept in mind that not all dual-stimulus trials contained two targets; some contained one or two distracters instead of targets. Only trials containing two targets required independent overt responses to both stimuli presented.

317

Divided visual attention in psychopaths Table 1. Experimental hypotheses and predicted performance differences for various types of stimuli Predicted group differences in performance Equally divided attention conditions Relatively focused attention conditions Accuracy of target classification Hypothesis Over-focusing (Strong Form) Over-focusing (Weak Form) Left Hemisphere Activation

PT

ST

PSY > NON

PSY < NON _

PSY < NON with RVF PT

Error rate for responses to distracters PT

ST

PSY > NON

PSY > NON

Accuracy of target classification PT

ST

-

Error rate for responses to distracters PT

ST

?

?

-

PSY < NON with RVF PT

Nore: No predictions are made for cells with dashes. RFA = Relatively Focused Attention Condition; PT = Primary Task; ST = Secondary Task; PSY = Psychopaths; NON = Nonpsychopaths.

Because Kosson (1996) examined dual-task performance only when one task contained twice as many targets as the other, an Equally Divided Attention (EDA) condition was added. In this condition, both stimulus sets contained an equal frequency of targets (Table 1). Although an earlier study had reported trends toward deficits for psychopaths on both tasks under EDA conditions (Kosson and Newman, 1986), a lack of control over situational parameters suggests that the visual task nevertheless functioned as a primary task. Thus, comparisons identical to those in Condition RFA were conducted for Condition EDA. Because both tasks should be equally salient in this condition, the over-focusing hypothesis predicts no differences in psychopaths’ distributions of attention to the two tasks. However, this condition permits within-group tests of the over-focusing hypothesis by examining the differences in performance from Condition EDA to Condition RFA: the over-focusing hypothesis predicts a greater improvement in primary task accuracy and a greater decline in secondary task accuracy for psychopaths than for nonpsychopaths. The left hemisphere activation hypothesis also predicts no group differences in the EDA condition: because targets are equally likely in the RVF and the LVF, targets demand an equal frequency of right-handed and left-handed responses. Thus, the EDA condition should induce relatively equal left hemisphere and right hemisphere activation. On the other hand, if psychopaths display performance deficits whenever a situation requires regular attention to the RVF and frequent right-handed responses, psychopaths may display performance deficits even under EDA conditions with lateralized stimuli and responses. Predictions are less clear for the reduced breadth of attention hypothesis. If psychopaths’ reduced breadth of attention is a function of their focus on an immediate primary task, then psychopaths should have no difficulty identifying and inhibiting responses to distracters under EDA conditions. By contrast, if psychopaths are generally prone to reduced breadth of attention in multidimensional processing situations, then they should be less sensitive than nonpsychopaths to stimulus dimensions distinguishing targets from distracters even when responding to two equally important target sets. The lack of a clear prediction regarding group differences in responses to distracters in this condition is indicated by a question mark in Table 1. Finally, the study addressed through supplementary analyses three important questions about the psychopathy construct. First, this study provided a preliminary examination of the relations between cognitive processing deficits and the two empirically validated dimensions of psychopathy. Although most contemporary studies of the disorder are based on comparisons of discrete groups high versus low in Psychopathy Checklist-Revised (PCL-R) scores (Hare, 1991), factor analyses of PCL-R scores identify two distinct dimensions which correlate differently with several experimental and real world criteria (Harpur et al., 1989). The dimension associated with an impulsive, antisocial lifestyle (viz., Factor 2) uniquely predicts school failure, criminal activity, and substance abuse. The dimension considered the affective and interpersonal core of psychopathy (viz., Factor 1) contributes uniquely to some emotional processing deficits (Harpur et al., 1989; Patrick, 1994), and interactions between the two factors appear to predict violence (Harpur and Hare, 1991; Kosson et al., 1997). No studies to date have reported the factor(s) predicting information-processing deficits in psycho-

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David S. Kosson

paths. To examine whether both dimensions of psychopathy contribute to cognitive deficits, multiple regression analyses examined the contributions of these dimensions of psychopathy to observed performance differences. Second, because anxiety appears to moderate many of the performance deficits of psychopaths (Smith et al., 1992), anxiety was also included in these regressions. Indeed, whereas Kosson (1989) reported a significant Psychopathy x Anxiety interaction suggesting primary task superiority for low-anxious psychopaths, other studies have not identified such interactions (Howland et al., 1993). Thus, regression analyses provided tests of this interaction in the context of divided visual attention. Third, to further assess the similarity of psychopathy across cultural groups, both African-American and White male inmates participated in this study, and race was included as a factor in preliminary analyses. Where Psychopathy x Race interactions were evident in omnibus analyses, these were examined. A previous study had noted similarities between African-American and White male inmates with high PCL-R scores in passive avoidance learning and criminal versatility and apparent differences in the factor structures underlying PCL-R scores (Kosson et al., 1990). The present study permitted an examination of whether race interacted with psychopathy in the prediction of cognitive deficits.

METHOD Participants

Participants were 129 right-handed male inmates at a medium-security federal correction-d institution in central North Carolina. Men were selected using Hare’s Psychopathy Checklist-Revised (PCL-R; Hare, 1985), a behavioral checklist with demonstrated reliability and validity for selecting psychopaths among incarcerated White males (Hare, 1991) and preliminary validity among incarcerated African-American males (Kosson et al., 1990). Eligible participants were inmates under 45 years of age whose files indicated at least below average intelligence, fourth grade reading ability, and no psychotropic medication or active psychosis. PCLR ratings were based on a semi-structured interview designed for this purpose, usually lasting 6075 minutes, and a review of each man’s institution file. Each participant was assigned a rating of 0 (denoting absence), 1 (denoting ambiguity), or 2 (denoting presence) points for each PCL-R item for which information was available. Although scoring was based on the 1985 manual, scoring changes in the 1991 PCL-R manual suggested that the latter would yield slightly higher PCL-R scores. In particular, where inmates’ self-reports suggest greater antisocial behavior than their files, interview information is now accepted as valid on PCL-R items 18 (Juvenile Delinquency), 19 (Revocation of Conditional Release), and 20 (Criminal Versatility; Hare, 1991). Consequently, men with PCL-R total scores of 28.5 or higher and with PCL-R scores of 18.5 or lower, were considered psychopaths and nonpsychopaths, respectively. Handedness was determined via self-report of the hand(s) with which participants perform each of 13 common activities (Chapman and Chapman, 1987). Men endorsing the right hand for 9 or more items and using their right hand to do so were considered right-handed. Of 143 right-handed males completing the study, 14 were eliminated for the following reasons: 3, due to loss of data; 5, for performance at or near chance on single-task baselines; 5, for responses to distracters on most single-task trials; 1 for a missing finger. One additional participant was eliminated from Analyses of Covariance (ANCOVAs) but not Analyses of Variance (ANOVAs) due to loss of single-task data. The remaining 128 participants included 31 psychopathic inmates, 38 nonpsychopathic inmates, and 59 men with PCL-R scores between 18.5 and 28.5. Four participants who were neither White nor African-American were also excluded from analyses which included race as a factor. Sample characteristics are summarized in Table 2. Task and apparatus

The visual task was based on that of Kosson (1996). It was introduced as a single-task baseline of 96 trials with one stimulus per trial. The dual-task or divided visual field task of 288 trials followed, containing two stimuli per trial. Each stimulus consisted of a string of eight symbols in a horizontal line on either the left or right half of a Zenith ZCM 1390-2 monitor. Half of the strings

319

Divided visual attention in psychopaths Table 2. Characteristics of participants in PCL-R-defined groups Psychopathic (N = 3&31) Measure

Mean

PCL-R Age (years) SILS, v SILS, NV Welsh Anxiety NPD, SCID BPD. SCID NPI

31.75* 31.16 45.10 50.90 9.35 4.31 3.84* 18.44

SD 2.21 6.55 9.87 11.31 7.82 1.96 I .87 8.40

Middle (N = 54-58) Mean 23.78’ 29.22 45.17 51.06 8.24 3.72 2.88* 16.70

SD 2.91 6.00 10.12 9.61 7.61 I .45 1.94 6.62

Nonpsychopathic (N = 33-37) Mean

SD

13.76* 29.68 45.39 52.67 9.38 4.00 3.08 16.86

3.80 6.29 9.57 8.25 7.08 1.45 I .98 6.43

Nofe: PCL-R = Psychopathy Checklist-Revised. SILS, V (NV) = Shipley Institute of Living Scale, Verbal (Nonverbal) subtest; NPD (BPD), SCID = Narcissistic Personality Disorder (Borderline Personality Disorder) subscale, Structured Clinical Interview for the DSM-III-R, Self-Report Version; NPI = Narcissistic Personality Inventory. *Groups differ significantly, P i 0.05.

contained all letters or all numbers; the other half contained six or seven symbols from one of these categories and two or one of the other. Strings appeared in green or yellow: those stimuli in green were designated targets, and those in yellow, distracters. Participants were asked to classify all targets presented into one of three categories: all letters, all numbers, or mixtures of the two, and to ignore distracters. Sample dual-task trials are shown in Fig. 1. The focusing manipulation and experimental conditions are discussed below. Thus, the task required participants to identify each individual component of each target string (e.g., a letter) and compare the results of these identifications across the eight elements of a string, with the latter process thought to require limited capacity resources. Detecting a mismatch (i.e., letter and number) would indicate a mixed stimulus and terminate the process. Categorizing a pure stimulus required exhaustive analysis of each individual symbol. Because distinguishing different colors requires little effort or capacity for most adults (Treisman and Gelade, 1980), discriminating targets from distracters was considered a relatively peripheral cognitive demand. Stimulus presentation and data acquisition were controlled by a computer program written for this purpose and executed on a Zenith ZCV-2526-EY (286) computer and Scientific Solutions Labmaster DMA board. A copy of the program is available upon request. Each stimulus was displayed for 350 ms, a duration used in previous studies (Kosson, 1996). The stimulus onset asynchrony (SOA) between the two strings of dual-task trials varied equiprobably (within subjects) between 250 and 500 ms. Participants responded to each LVF target by pressing the S, D, or F key of a Zenith ZKB-2 keyboard with the ring, middle, or index finger of their left hand to indicate a letter, number, or mixed stimulus, respectively. Similarly, RVF targets required a J, K, or L keypress with the middle three fingers of the right hand to indicate letter, number, or mixed stimuli. Responses with latencies under 40 ms or over 3040 ms were ignored.* Because distances from participants’ eyes to the screen were measured but not fixed, stimulus size estimates are approximate. Each symbol subtended approximately 0.2 degrees of visual angle. The more central edge of each string was approximately 0.6 degrees from a central fixation point; the peripheral edge, 2.3 degrees away. Each string was centered within a square frame of the same color which subtended approximately 2.1 x 2.1 degrees of visual angle. Instructions emphasized both speed and accuracy: participants earned one to three points per correct target classification, depending on speed of response; they lost one point for errors and responses to distracters. Because Federal Bureau of Prison rules prohibit payments to inmates for research participation, participants were offered snacks at the end of the task, with the number of snacks offered based on number of points earned. As a further reward, a downhill skier video game *An error in the computer program was discovered, which indicates that, on a small percentage of trials, participants received positive reinforcement for responses that were actually late (i.e., with latencies between 3.0 and 3.3. s) and punishment for some correct responses (i.e., those with latencies of 2.7-3.0 s). However, such errors occurred on only 0.4% and 0.2% of dual-task trials, respectively, and had no discernible effect on results reported here.

380

David S. Kosson

Target-Target

Trial Type

‘i’nsk and Sliumlus

Secomlnr~

I..OCillioli

‘I’nsk=LVI: ‘I‘c~sk=ltVF

I’riuinry

Target-Distractor

SecolKtnry

Priatnry

‘I’nsk=I,VF

‘I’nsk=RVI:

-.Stitllrllus OllSCl

0 Ills

cl 3927txsa

FWQ7XNRK r-

250 or 500 IIIS

.Response Hand

Left Eiand

Right Hand

Left Hand

Right Hand

Correct Response

Letters

Mixed

Mixed

Fig. 1. Sample sequences of events for two types of dual-task trials for a participant receiving primary task stimufi in the right visual field (RVF) and secondary task stimuli in the left visual field (LVF). Participants responded to stimuli with the hand on the same side as the visual geld in which task stimuli were presented, and RVF versus LVF presentation of primary task stimuli was counterbalanced across participants. Italicized letters and numbers within rectangles denote presentation of target strings (appearing to participants in green), non-italicized letters and numbers denote presentation of distractor strings (appearing to participants in yellow).

appeared on the monitor, interrupting the visual task, whenever a participant earned a predetermined number of points. In this game, depressing a keyboard key altered the direction in which a “skier” progressed down a “ski slope” to avoid “trees” on the slope and “barriers” at each side of the slope. Participants earned extra points by skiing through and into various reward objects appearing on the slope resembling snowmen, soda cans, etc. Crashes resulted in loss of one point, and successful compietion of a slope earned three points, Participant ratings suggested that both the skier game and the divided VF task were moderately to very interesting. Focusing manipulation. As in previous studies (Kosson, 1996; Kosson and Newman, 1989), dualtask target frequency was manipulated to induce a relative focus on one of the two tasks or an equal division of attention between the two tasks. In the Relatively Focused Attention (RFA) condition, approximately 67% of the strings on one side of the screen were targets, compared with 36% of the strings on the other side. The stimulus set consisting of 67% targets is here considered participants’ primary task; the stimulus set containing 36% targets, their secondary task. Thus, each trial block contained 96 primary task targets, 48 primary task distracters, 52 secondary task targets, and 92 secondary task distracters. As noted above, targets appeared in green; distracters, in yellow. By

Divided visual attention in psychopaths contrast,

381

in the Equally Divided Attention (EDA) condition, 72 targets and 72 distracters appeared

in each VF. Thus, the overall proportion of stimuli constituting targets varied slightly from Condition EDA (50%) to Condition RFA (51.4%). Half of participants in Condition RFA completed the primary task with their dominant (right) hand and the secondary task with their left hand; the other half completed the tasks with their opposite hands. In each case, they completed the singletask with the hand that later classified primary task stimuli. Thus, any residual effect of single-task practice could be expected to strengthen the focusing manipulation. Because the two stimulus sets were equivalent in Condition EDA, they are here referred to as task one and task two. The task one stimulus set was arbitrarily assigned to the RVF for half of participants and to the LVF for the other half (with the task two stimulus set presented in the opposite VF). Concurrent load. In dual-task situations, concurrent load refers to the demand placed on a participant’s processing resources by presentation of an additional stimulus or target during the time he is processing a target. The impact of concurrent load on performance was assessed in several ways to verify the dual-task assumption that each set of task demands interferes with completing the other, and to provide information about how participants distributed attention between task demands. First, dual-task trials presented either one or two targets requiring responses: targettarget trials were trials presenting two targets; such trials demanded greater processing than targetdistractor trials, which presented one target and one distractor. Second, targets occurring as the first stimulus of a trial were distinguished from those occurring as the second stimulus of a trial. Kosson (1996) found that order of stimulus presentation affects performance, with poorer performance obtained for second-occurring targets on target-target trials. Third, within the range of SOAs used, the shorter the time between successive stimuli, the more likely it is that an informationprocessor’s resources will be occupied by one stimulus at the time a second stimulus is presented. Thus, poorer performance was expected for the shorter SOA (250 ms) than the longer SOA (500 ms). In sum, dual-task performance was expected to be superior on target-distractor than on targettarget trials, for initial-occurring targets of target-target trials than for second-occurring targets, and for long SOA trials than for short SOA trials. Procedure

Participants completed the semi-structured interview and a variety of self-report scales during their first day of participation, including the Narcissistic Personality Inventory (Raskin and Hall, 1979), the Narcissistic and Borderline Personality Disorder subscales of the self-report Structured Clinical Interview for DSM-III-R Personality Disorders (Spitzer et al., 1990), the Welsh Anxiety scale (Welsh, 1956), a handedness inventory (Chapman and Chapman, 1987) and the Shipley Institute of Living scale (Zachary, 1986), a brief IQ test. The dual visual task was administered on a separate day by one of two male graduate students or the author. Experimenters were blind to PCL-R and self-report scores. Following a description of the study, those consenting to participate were given instructions and practice on the skier game, then a single-task baseline of 96 trials, and two dual-task blocks of 144 trials each. The overall proportion of stimuli that were targets was approximately equal in single- and dual-task conditions. Rest periods occurred every 72 trials, and participants initiated subsequent trial blocks themselves. The task was interrupted periodically by the skier game, as noted above.

RESULTS

Accuracy, correct response latency, and responses to distracters were analyzed separately. Response latency analyses include all correct responses within 0.04 and 3.04 s of target onset. Preliminary analyses assessing single-task performance and assumptions are presented first, followed by results of planned contrasts. Finally, supplementary regression analyses are summarized. Significant interactions were examined via analyses of simple effects and interaction contrasts. In each dual-task ANCOVA, the corresponding single-task dependent variable was employed as a covariate to remove any effects of individual differences in processing capacity invested in the situation before assessing divided attention performance. Thus, single task accuracy was the covariate in dual-task accuracy analyses; single-task response latency, in dual-task response latency

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analyses, and responses to single-task distracters, in analyses of responses to dual-task distracters. Including a measure of overall capacity or effort is especially useful in studying groups like psychopaths whose poor performance has sometimes been attributed to lack of motivation (Schmauk, 1970). Covariates proved to be related to dual-task dependent measures for accuracy (F(1, 49) = 54.78, P < 0.001) and response latency (F(1,49) = 58.05, P < 0.001) but not for responses to distracters (F( 1, 49) = 1.60, P > 0.20). Although ANOVAs and ANCOVAs yielded highly similar results, comparisons based on ANCOVAs were more powerful, because covariates reduced betweensubjects error terms substantially. Preliminary analyses Tests of assumptions. To test the assumption of parallel regression surfaces across levels of between-subjects factors, each covariate was regressed onto the corresponding dual-task measure along with between-subjects factors, and interactions of between-subjects factors with covariates were examined. Analyses indicated no violations of the assumption for accuracy. However, effects were obtained for response latency and distractor responses for one of ten interactions assessed. Therefore, wherever ANOVAs and ANCOVAs yielded different results, both are reported. To examine assumptions of the dual-task method, preliminary analyses of accuracy and response latency included all design factors. Accuracy of responses to dual-task targets was examined via a 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 (Group x Condition x Hand Assignment x Race x Task x Order x Number of Targets x SOA x Block) ANCOVA, in which the first four factors varied between subjects, and the other five, within subjects. The two levels of task address responses to primary task vs secondary task targets in Condition RFA and to the two equivalent stimulus sets (task one and task two) used in Condition EDA. Thus, Condition x Task interactions are more meaningful than main effects for either independent variable. The levels of hand assignment denote whether the primary task (Condition RFA) or task one (Condition EDA) was assigned to the right hand and RVF or the left hand and LVF. A similar analysis was conducted for dual-task response latency, but to ensure four correct responses per cell, per participant, this analysis collapsed across SOA and Block. The effectiveness of the focusing manipulation at inducing participants in Condition RFA to attend to the primary task over the secondary task was demonstrated by a Condition x Task interaction for accuracy (F(1, 50) = 10.63, P < 0.01) indicating greater accuracy for the primary than secondary task in Condition RFA (F(1, 50) = 10.00, P < 0.01) whereas in Condition EDA, the task designated task two yielded marginally superior accuracy, (F(1, 50) = 3.71, P = 0.06). Response latency analyses revealed a similar Condition x Task effect (F( 1, 50) = 3.15, P = 0.08). The dependence of the two tasks on shared processing resources is critical for testing the overfocusing hypothesis. However, if performance on tasks involving bilateral stimulus presentation is mediated by partially independent hemisphere-specific resources, this assumption might not be warranted. Nevertheless, that each task interfered with the other was demonstrated by highly reliable effects of number of targets per trial (for accuracy, F(1, 50) = 238.19, P < 0.001; for response latency, F(1, 50) = 169.46, P < 0.001). However, contrary to assumptions, an order effect indicated that responses were faster to secondoccurring targets than to initial-occurring targets, F( 1,50) = 1,065.4, P < 0.001. Although accuracy was also higher for second-occurring targets (F( 1,50) = 13.77, P = O.OOl),higher-order interactions indicated that the greater accuracy for second-occurring targets was reliable only in Condition EDA when the initial stimulus was a distractor (F(1, 50) = 26.06, P -c 0.001). Nonetheless, the absence of superior accuracy for initial versus second-occurring targets indicates that, in contrast to Kosson (1996), some of participants’ processing resources were as available to process second-occurring targets as to process initial-occurring targets. This finding suggests greater independence of processing resources mediating cognitive processing in the current divided visual field paradigm than in the intermodal paradigm with centrally presented stimuli and is consistent with models of partially separable processing resources in the left and right hemispheres (Polson and Friedman, 1988). Considered together, the findings for order and number of targets suggest that, although each task interfered with the other, such interference may have been limited to particular stages of processing such as response selection (cf., Pashler and O’Brien, 1993). Participants’ faster but equally accurate responses to second targets also suggest that initial stimuli may have contributed to preparation for

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second-occurring targets. Such alerting effects are well documented (Posner, 1978) and are not discussed further. SOA effects were also complex, depending on combinations of several withinsubjects factors. In sum, preliminary analyses demonstrated the effectiveness of the focusing manipulation and that classification of a target in one VF was impaired by the occurrence of a target in the other VF, although the interdependence of the tasks was less consistent across situational parameters than for intermodal divided attention (Kosson, 1996). Baseline measures. Single-task performance data were analyzed by separate 2 x 2 x 2 x 2 (Groupx Condition x Hand Assignment x Race) ANOVAs for accuracy and response latency. Neither analysis revealed any main effects or interactions involving psychopathy. Planned comparisons

Design factors that did not affect group differences were omitted from principal analyses. Thus, planned comparisons addressing interference and left hemisphere inefficiency were based on 2 x 2 x 2 x 2 x 2 (Group x Condition x Hand Assignment x Task x Number of Targets) ANCOVAs for accuracy and response latency. These analyses included 31 psychopaths and 38 nonpsychopaths. Planned comparisons for breadth of attention were based on a similar analysis of the percentage of distracters to which participants responded. However, this analysis was limited to single-target trials (containing one target and one distractor), because the processing of a target reduces the attention available to process a distractor. Thus, number of targets was omitted as a factor. In addition, because preliminary analyses had revealed interactions between psychopathy and race and trial block, these factors were retained. Consequently, responses to distracters were assessed via a 2 x 2 x 2 x 2 x 2 x 2 (Group x Condition x Hand Assignment x Race x Task x Block) ANCOVA, using percentage of responses to single-task distracters as a covariate, and including 30 psychopaths and 36 nonpsychopaths identified as White or African-American. Where higher-order interactions affect interpretation of comparisons, their implications are addressed. 0ver:focusing: Differences in target processing. Two kinds of comparisons addressed predictions of the strong form of the over-focusing hypothesis. To address the predictions of primary task superiority and secondary task inferiority, psychopaths’ and nonpsychopaths’ performance on each task in Condition RFA were first compared. Collapsing across visual field/hand assignments, there were no reliable group differences in primary task accuracy (71.5 vs 76.2% correct for psychopaths and nonpsychopaths), F(l, 121) = 2.66, P = 0.11, but psychopaths performed significantly worse than nonpsychopaths on the secondary task (67.0 vs 73.3% correct), F(l, 121) = 4.75, P < 0.05. Next, the difference in performance within each group for participants in Condition RFA vs EDA was examined. Contrary to the predictions of over-focusing, these contrasts indicated greater superiority of primary task performance in RFA (relative to task one in EDA) for nonpsychopaths than for psychopaths (12.0 versus 6.0% improvement), F(l,61) = 5.44, P < 0.05, and a greater change in secondary task performance (relative to task two in EDA) for nonpsychopaths than for psychopaths (5.6% improvement in RFA vs 0.3% decline), F(1,61) = 4.17, P < 0.05. Thus, accuracy data provide little evidence consistent with the over-focusing hypothesis. Psychopaths’ and nonpsychopaths’ correct response latencies were compared via a set of comparisons parallel to those for accuracy. These revealed no differences between psychopaths and nonpsychopaths in primary task (1610 vs 1571 ms) or secondary task (1689 vs 1673 ms) response latency, both Fs(1, 121) < 1. Similarly, there was no evidence for greater differences between secondary task and task two latencies or between primary task and task one latencies as a function of condition (RFA vs EDA) for psychopaths than for nonpsychopaths (both Fs < 1). Over-focusing: Breadth of attention. To assess attention allocated to peripheral contingencies, planned comparisons examined the percentage of responses to distracters of each task made by each group in Condition RFA. As seen in Fig. 2, psychopaths responded to both more primary task distracters, F( 1, 99) = 17.14, P < 0.001, and more secondary task distracters, F( 1, 99) = 6.99, P = 0.01, than nonpsychopaths. However, their overresponding did not interact with laterality. Comparisons specific to each hand assignment/VF also suggested deficits for psychopaths on both primary and secondary tasks given both a RVF primary task (F(l, 99) = 5.49, 3.59; P < 0.05, P = 0.06), and given a LVF primary task (F(l, 99) = 14.64, 3.38; P < 0.001, P = 0.07). Thus, as in the intermodal attention study (Kosson, 1996), psychopaths were less responsive than nonpsychopaths to distinguishing targets from distracters, and this unresponsiveness was unaffected by

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0.0

,

I Right band

Left Hand

Hand Assigned to Primary Task

Fig. 2. Percentage of primary task and secondary task distracters to which psychopaths psychopaths responded in the Relatively Focused Attention (RFA) condition.

and non-

the relative priority of the two tasks. Comparisons based on unadjusted means yielded similar findings, although comparisons conducted separately for each VF condition were weaker than those based on ANCOVAs. * Unadjusted means (and SDS) for psychopaths and nonpsychopaths were 5.3% (6.0) vs 1.O% (2.1) for percentage responses to primary task distracters and 3.0% (4.2) vs 0.6% (0.8) for secondary task distractor responses. However, these findings are qualified by interactions involving race and block in the omnibus ANCOVA. In particular, a Group x Race interaction (61, 49) = 6.54, P = 0.01) indicated that group differences were reliable for White (F(1,49) = 15.06, P c 0.001) but not for African-American participants (F(1, 49) < 1). A Group x Race x Block (F(1, 50) = 5.03, P < 0.05) interaction also demonstrated that White psychopaths overresponded to distracters only during the initial dualtask trial block (F( 1,99) = 25.62, P < 0.001); no group differences were evident in the second block of dual-task trials or for African-American participants (all Fs( 1, 99) < 1). Left hemisphere activation. To evaluate the prediction of performance deficits for psychopaths given a RVF primary task, the performance of each group in Condition RFA was compared within each VF/hand assignment. As shown in Fig. 3, among participants using their right hands to complete a RVF primary task, psychopaths in Condition RFA classified secondary task targets less accurately than did nonpsychopaths (64.6 vs 75.2% correct), F(1, 121) = 7.37, P < 0.01. However, psychopaths also classified primary task targets less accurately than nonpsychopaths (71.7 vs 79.1% correct), a difference that approached significance, F( 1, 121) = 3.58, P = 0.06. An additional comparison demonstrated that the group difference in secondary task accuracy was not significantly greater than the difference in primary task accuracy, F( 1, 121) < 1. By contrast, for those using the left hand to complete a LVF primary task, there were no group differences in secondary task (69.3 vs 71.3% correct) or primary task (71.3 vs 73.4% correct) accuracy, both Fs < 1. Although comparisons based on the ANOVA yielded no group differences given a RVF primary task, a comparison of unadjusted means with those in Fig. 3 reveals similar mean differences; the chief difference is in the error term (MSE = 275.7 in ANOVA vs 146.3 in ANCOVA). Unadjusted *Whereas comparisons collapsing across VF conditions indicated overresponding for psychopaths on both tasks, most comparisons within VF conditions fell short of conventional levels of significance (F(1, 102) = 3.00, I .5 1, P = 0.09, ns for primary and secondary task distracters with a RVF primary task; F(1, 102) = 10.44, 2.66, P = 0.002, 0.11, for primary and secondary task distracters with a LVF primary task).

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in psychopaths

0.80 ,

I I

I

Right Hand

Lefl Hand

Hand Assigned to Primary Task

Fig. 3. Primary and secondary task accuracy for psychopaths and nonpsychopaths Focused Attention (RFA) condition.

in the Relatively

Table 3. Intercorrelations among primary task (PT) and secondary task (ST) performance measures, unadjusted by covariates Measure 1. 2. 3. 4. 5 6.

PTAC STAC PTRL ST RL PTDRs STDRs

I

2 0.69’;’

3 -0.41”’ -0.32”’

4 -0.26” -0.32”’ 0.32”’

5

6

-0.08 -0.23** 0.04 0.12

-0.14 - 0.26’* 0.13 0.03 0.69*‘*

AC = accuracy; RL = response latency; DRs = distractor responses; N = 129. ***p < 0.001. **p < 0.01.

(and standard deviations (SDS)) for psychopaths and nonpsychopaths with the primary task assigned to the RVF were 63.4 (20.6) vs 72.5 (5.7)O/, correct for the secondary task, F(1, 124) = 2.87 P = 0.09, and 70.5 (13.3) vs 76.3 (5.7)% correct for the primary task, F(1, 124) = 1.20, P > 0.25. Corresponding comparisons for correct response latencies also revealed no group differences given a RVF primary task (for secondary task: 1931 vs 1909 ms; for primary task: 1600 vs 1500 ms), or a LVF primary task (for secondary task: 1447 vs 1437 ms; for primary task: 1620 vs 1641 ms), all Fs( 1, 12 1) < 1, and no differences in magnitude of hand assignment/VF effects on response latency for psychopaths versus nonpsychopaths (F( 1, 121) < 1). Equally divided artention condition. Performance in this condition was examined to further assess the robustness of psychopaths’ performance deficits across changes in the relative priority of the two tasks. Group comparisons on accuracy suggested neither deficits nor advantages for psychopaths under equally divided attention. Differences between groups were small and nonsignificant for both tasks in both visual fields, all Fs < 1.6. Similarly, no group differences in response latency were observed for either task in either VF, all Fs < 1. Finally, analyses of responses to distracters revealed that psychopaths displayed no overresponding to distracters of either task given either hand assignment, all Fs < 1.

means

Supplementary analyses Intercorrelations between performance indices (Table 3) reveal that better performance on each measure was associated with better performance on other measures. No tradeoffs between speed

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Table 4. Increment in multiple R’ (A R*) and Beta (8) for predictors contributing to the prediction of dual-task performance criteria in the relatively focused attention (RFA) condition

Step Covariate/HA’ FI F2 Anxiety FlxF2 FI xF2xHA FlxAxHA

PT Target Accuracy AR* B 0.46**’ _ 0.04t _ 0.05’ _

0.67 _ 0.21 _ -0.51

ST Target Accuracy AR’ 0.26*** _

0.06’ 0.06*

B 0.51

PT Distractor Responses AR2 B 0.09t

0.30

0.14”

0.44

1.45 -0.55 0.04t

0.33

ST Distractor Responses AR’ 4 0.09t 0.10’

0.27 0.31 _ _ _

Note: The order of rows corresponds to the order of entry of predictors in the hierarchical multiple regression. The other model reversed the order of entry of PCL-R Factor 2 (F2) and PCL-R Factor I (Fl). When F2 was entered before Fl in predicting responses to Secondary Task (ST) Distracters, the AR2 for F2 was 0.07, P < 0.05, B = 0.27, and Fl was nonsignificant. PT = Primary Task; HA = Hand Assignment. “B values correspond to the single-task baseline, which always yielded a larger b than did HA. tP 4 0.10. ‘P < 0.05. **p < 0.01. ***p < 0.001.

and accuracy or between responsiveness to targets versus distracters were evident. To examine the relative contributions of the two validated dimensions of psychopathy to observed performance deficits, hierarchical multiple regressions were conducted. Although this technique does not distinguish separate groups of individuals, multiple regressions are often more powerful than ANOVA approaches, because they examine predictor-criterion relations across the full range of predictor scores (Cohen and Cohen, 1983). Moreover, hierarchical regression techniques are more informative than simultaneous techniques when predictors are correlated (Cohen and Cohen, 1983), as are PCLR factor scores (Harpur et al., 1989). Following recommendations of Harpur et al. (1989), factor scores were computed via unit-weighted sums of scores of PCL-R items defining each factor. These analyses included 15 psychopathic and 21 nonpsychopathic inmates in Condition RFA whose data were included in principal analyses, plus 20 inmates with intermediate PCL-R scores. Data for three participants were not included, because anxiety scores were unavailable. Two regressions were conducted for each of the four performance criteria for which comparisons suggested deficits for psychopaths: primary and secondary task accuracy in Condition RFA given a RVF primary task, and percentage responses to distracters for each task in Condition RFA. The two regression models differed only in order of PCL-R factors. Because regressions included only the 56 participants in Condition RFA, the number of predictors in each model was limited to six or fewer (i.e., approximately one predictor per ten participants). Thus, the sequence of steps in the model depicted in Table 4 was: a covariate set comprised of single-task performance and hand assignment, Factor 1 score, Factor 2 score, Welsh anxiety score, and up to two interactions between these predictors incrementing prediction at P < 0.10. The other model was identical except that the order of the PCL-R factor scores was reversed. Thus, comparisons across regressions indicate whether a predictor or interaction accounts for significant criterion variance after controlling for single-task performance and hand assignment, as well as other predictors already entered.* Results of regressions are shown in Table 4. Anxiety did not contribute significantly to predicting performance deficits either singly or in interaction with PCL-R factors and is not discussed further. PCL-R Factor 2 contributed uniquely to predicting responses to primary task distracters, and either factor predicted responses to secondary task distactors if entered prior to the other, indicating that variance shared between the PCL-R factors accounted for the significant variance in this criterion. Thus, PCL-R Factor 2 appears sufficient to predict psychopaths’ reduced breadth of attention. However, interactions involving both factors uniquely predicted inaccuracy for targets on both tasks. Thus, traits assessed by both factors appear necessary to predict divided attention deficits associated with left hemisphere activation. These findings further corroborate the suggestion that * Regressions that included SILS full-scale intelligence scores on a separate step foilowing entry of the covariate and hand assignment yielded findings quite similarto those reported here. In none of these analyses did intelligence contribute

significantly to predicting dual-task performance, suggesting that correlations between intelligence and dual-task performance reflected variance largely accounted for by single-task performance.

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target inaccuracy and responses to distracters reflect different underlying processes: not only are these performance criteria differentially associated with hand assignment and VF; they are related to the PCL-R factors in different ways. DISCUSSION The replication of deficits predicted by both the left hemisphere overactivation and the excessive selective attention hypotheses provides additional evidence that psychopaths are characterized by specific divided attention deficits. Moreover, observing similar deficits in a divided visual field paradigm as were reported in a visual-auditory task combination (Kosson, 1996) indicates that these deficits generalize across some changes in lateralization and modality of task stimuli. First, under conditions designed to maximize demands on left hemisphere processing resources, psychopaths misclassified more secondary task targets and marginally more primary task targets than nonpsychopaths. Psychopaths displayed no comparable deficits under conditions maximizing demands on right hemisphere resources or under conditions making equal demands on left and right hemisphere resources. Whereas Kosson (1996) reported deficits for psychopaths completing a primary task with the right hand, stimuli in that study were centrally presented. Thus, inferences regarding involvement of hemisphere-specific resources were tentative. Demonstrating similar deficits given lateralized stimuli and lateralized responses further implicates left hemisphere-specific processing resources in performance differences. Second, replication of psychopaths’ overresponding to distracters across both visual field conditions and tasks provides additional evidence of consistency with respect to excessive selective attention. As in Kosson’s (1996) study, psychopaths’ performance suggests reduced breadth of attention but not inattention to explicitly designated secondary task targets. Thus, data from both studies are consistent with the weaker but not the stronger form of the over-focusing hypothesis. Moreover, as in the prior study, psychopaths overresponded to distracters under conditions designed to activate right hemisphere resources as well as under conditions designed to activate left hemisphere resources. Thus, psychopaths’ unresponsiveness to a peripheral stimulus dimension appears more general than their inaccuracy in classifying targets. Nevertheless, psychopaths and nonpsychopaths displayed comparable ability to inhibit responses to distracters and classify targets under equally divided attention conditions. This finding demonstrates that psychopathic criminals are as capable as nonpsychopathic criminals of divided attention per se. In summary, whereas psychopaths’ excessive selective attention was apparent only given relatively focused attention (i.e., two tasks differing in target frequency), deficits associated with left hemisphere activation were evident only given relatively focused attention to a RVF task. Both deficits point to cognitive mechanisms that may underlie central traits of psychopathic individuals, and their situational specificity may help to explain apparent inconsistencies in accounts of psychopaths’ social and cognitive adeptness: psychopaths are capable of logical reasoning and sound judgement which does not always translate into planful, responsible behavior in their daily lives (Cleckley, 1941). Present results suggest that psychopaths may be most prone to maladaptive behavior in situations that involve all of the following: (1) an immediate primary goal, (2) which triggers left hemisphere processing, and (3) occurs in the context of concurrent secondary goals. Under such conditions, psychopaths are likely to display both inefficient processing and an excessive focus on the most salient dimensions of the situation. In the absence of immediate goals, when completing single-tasks, and when evenly dividing attention, psychopathic offenders may be cognitively indistinguishable from nonpsychopathic criminals. Considered separately, each cognitive deficit has important implications for our understanding of psychopaths. Reduced breadth of attention may characterize psychopaths whenever their cognition and behavior are dominated by short-term goals and desires, which may be quite often (Arieti, 1978; Shapiro, 1965). In particular, such deficits may be predicted in many multidimensional situations. One important subset of these consists of interpersonal interactions, which are often distinguished by a multiplicity of both goals and cues (Dodge, 1991; Dodge et al., 1989). This mechanism may help to explain why psychopaths may seem unresponsive to subtle social signals despite an apparent adequate ability to learn, as well as their well replicated passive avoidance learning deficits (Lykken, 1957; Newman and Kosson, 1986).

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Similarly, activation of left hemisphere-specific resources may be relatively common. Not only are left hemisphere resources implicated in language processing (Nelson et al., 1990); left hemisphere resources may also mediate the programming of other action and information-processing sequences (Goodale, 1988). Thus, relatively deficient processing may be expected when cognitive processing sequences and action sequences figure prominently in psychopaths’ immediate goals, as for example during many interpersonal exchanges (cf., Gillstrom and Hare, 1988) and during the execution of complex plans. Moreover, to the extent that appetitive motivational states are mediated by activation of left frontal brain systems (Davidson, 1984; Tucker and Williamson, 1984), it is likely that psychopaths’ reported proclivity for attending to immediate, tangible goals may frequently involve left hemisphere activation. Whether psychopaths’ less accurate responses to targets would generalize to equally divided attention given even greater demands on left hemisphere resources cannot be addressed by the current study, because differential left hemisphere activation and relatively focused attention were confounded. As noted earlier, the equally divided attention condition was expected to place substantial demands on participants’ left and right hemispheres. However, studies by Hare and his colleagues suggest that left hemisphere activation deficits do not require a primary and secondary task. Hare and McPherson (1984) and Hare and Jutai (1988) reported relatively poorer responsiveness to right perceptual field stimuli for psychopaths than for nonpsychopaths despite an equal frequency of targets in the left and right perceptual fields. In contrast to the current dual-task requiring categorizations of letters and numbers, those studies employed linguistic tasks for which left hemisphere advantages have been reported given equal stimulation of left and right hemispheres, and both studies replicated right perceptual field advantages for nonpsychopathic participants. No comparable difference was shown by nonpsychopathic participants in the current study in Condition EDA. Current results do not firmly rule out the strong form of the over-focusing hypothesis, although maintenance of the hypothesis appears to require some revisions. Psychopaths’ poorer overall performance on the secondary task under RFA conditions is partially consistent with an excessive focus on the primary task. From this perspective, it might be argued that the absence of the predicted primary task advantage for psychopaths reflects the partial independence of processing resources mediating primary and secondary task performance in divided VF paradigms. However, it remains problematic that psychopaths in Condition RFA performed the secondary task as accurately as psychopaths in Condition EDA. Still more convincing is the consistency of findings across studies: psychopaths have displayed performance deficits in three of three dual-task studies designed to test over-focusing, and in none of these was psychopaths’ performance suggestive of a greater tradeoff between tasks as predicted by the strong form of over-focusing. Nevertheless, it remains possible that psychopaths would display reduced responsiveness to explicit secondary task targets if the ratio of primary task to secondary task targets presented was substantially higher than the approximate 2 : 1 ratio tested by studies to date. At least two alternative explanations for psychopaths’ reduced accuracy given primarily RVF targets must be noted. First, although psychopaths displayed performance deficits on both tasks under conditions with maximum demands upon left hemisphere resources, inspection of Fig. 3 suggests that psychopaths’ primary task performance was similar across the RVF and LVF conditions. By contrast, nonpsychopaths performed the primary task nonsignificantly more accurately in the RVF than in the LVF condition (F(1, 121) = 2.27, P > 0.10). Although there is no precedent for specifying normative performance comparing dual-tasks with LVF vs RVF primary tasks, there is evidence that nonclinical populations display greater reliance on left hemisphere resources under two-stimulus than under single-stimulus conditions (Reuter-Lorenz et al., 1990; Umilta and Nicoletti, 1985). In this context, these results may be viewed as consistent with Hare et d’s (1988) proposal that psychopaths display reduced lateralization on tasks for which nonpsychopaths display left hemisphere advantages. On the other hand, this explanation is not easily applied to findings by Kosson (1996) and Hare and Jutai (1988) indicating bigger changes in psychopaths’ than in nonpsychopaths’ performance associated with left hemisphere vs right hemisphere activation. Further research is needed to distinguish between reduced lateralization and left hemisphere-specific deficit explanations of psychopaths’ performance deficits. Second, because eye movements were not prevented, it is possible that eye movement strategies or

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scanning dysfunctions contributed to psychopaths’ observed deficits. Saccades are usually organized around objects or targets to be processed, directed to locations where targets are expected, and follow shifts of attention (Henderson, 1992; Kahneman and Treisman, 1984; Shepard et al., 1986); thus, individual differences in the ability to foveate targets or in efficiency of left-to-right scanning strategies linked to reading could also account for observed deficits (White, 1972). However, these possibilities do not provide parsimonious explanations of psychopaths’ deficits for several reasons. First, there were no significant interactions suggesting that eye movements/attention shifts interfered with processing targets for either task in either visual field/order combination or impacted psychopaths differently from nonpsychopaths. Second, no evidence to date suggests that psychopaths display unusual scanning strategies or deficient eye movements (Raine and Venables, 1990). Finally, scanning explanations are not easily applied to previous studies using centrally presented stimuli (Kosson, 1996), dichotic listening paradigms (Hare and McPherson, 1984; Raine, er al., 1990), or techniques to prevent eye movements (Hare and Jutai, 1988) yet all these studies obtained results consistent with the left hemisphere activation hypothesis. Nevertheless, the novelty of the current paradigm remains a reason for caution in the interpretation of these findings. Although the RFA/RVF condition was designed to demand attentional, perceptual, and response processing from left hemisphere resources, the current paradigm does not provide an independent index of the extent to which the manipulation increased reliance on left hemisphere-specific processing versus promoted integrated processing across the hemispheres. It has been argued that paradigms presenting stimuli bilaterally reduce interhemispheric transfer compared with paradigms presenting stimuli unilaterally (Boles, 1990). However, such arguments have usually been based on shorter stimulus durations than those used here. Indeed, the study of divided attention in psychopaths is in its infancy. In spite of the overall similarity of findings to those reported by Kosson (1996) and Kosson and Newman (1986) the variability in participants’ performance in different paradigms also suggests that dual-task performance patterns depend in part on combinations of situational parameters not fully understood. Two additional findings of the current study are noteworthy. First, multiple regression analyses provide the first evidence that some of psychopaths’ cognitive deficits, like their violent behavior (Harpur and Hare, 1990) are predicted by an interaction between PCL-R factors. Such evidence strengthens the argument that assessing both psychopathy dimensions yields information beyond that associated with PCL-R Factor 2 alone and contributes to arguments that psychopathy is not equivalent to Antisocial Personality Disorder as measured by the Diagnostic and Statistical Manual of Mental Disorders, Third edition-revised (American Psychiatric Association, 1987) which correlates significantly more highly with Factor 2 than with Factor 1 (Harpur et al., 1989). Finally, the present study also provides an extension of the left hemisphere activation hypothesis but not the reduced breadth of attention hypothesis to incarcerated African-American male psychopaths. A previous study noted both similarities and differences between incarcerated AfricanAmerican and White males with high PCL-R scores (Kosson et al., 1990). With respect to reduced accuracy under conditions promoting reliance on left hemisphere resources, African-American and White male psychopaths displayed similar divided attention deficits. At the same time, the absence of overresponding to distracters in African-American psychopaths suggests an apparent difference between these populations that appears worthy of replication. AcknoIl,lengements-This research was funded by National Institute of Mental Health Grant R29-MH49111 and by UNCG Research Council Grant 55561 I. I wish to thank the staff of the Research Department at the Federal Correctional Institution at Butner for their consistent cooperation with the project. Special thanks are due to Bernadette Pelissier, Tom Marsh, Douglas Yearwood, Marty Hill, Karen Childress, Dana Tipton, and Connie Hobbs; to Tim Mullin for suggesting the use of video games as rewards; to Brian Steuerwald and John Askew for their help in testing participants; to Deborah Carraway for help with statistical analyses; and to Jackie Henry, Steven Jones, and John Libby for conducting interviews.

REFERENCES American Psychiatric Association (1987). Diagnostic and statistical manual of mental disorders, 3rd ed., revised. Washington, DC: Author. Arieti, S. (1978). Psychopathic personality: Some views on its psychopathology and psychodynamics. On schizophrenia, phobias, depression, psychotherapy and the farther shores of psychiatry (pp. 202-215). New York: Brunner/Mazel. Boles, D. B. (1990). What bilateral displays do. Brain and Cognition, 12,205-228. Chapman, L. J., & Chapman, J. P. (1987). The measurement of handedness. Brain and Cognifion, 6, 175-183.

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