A critical question in psychopathy research concerns the reasons why psychopathic individuals focus on personal goals and ignore considerations that might otherwise inhibit their inappropriate behavior. Broadly speaking, there appear to be two different categories of explanations for this phenomenon. Psychopathic individuals may a) be less motivated to respond to inhibitory cues or b) have an attentionally mediated deficit that reduces processing of inhibitory cues that are peripheral to their primary focus of attention. Theories of psychopathy positing an emotion deficit such as low fear (Lykken, 1957, 1995) or empathy (Blair et al., 2002; Blair, 2004) as the fundamental psychopathic deficit are consistent with a motivational deficit; that is, emotional information related to behavioral inhibition is understood to be less meaningful for psychopathic individuals.

Newman and colleagues, on the other hand, have theorized that psychopathic individuals’ insensitivity to inhibitory cues, including emotional information, is attentionally mediated (e.g., Newman & Lorenz, 2003). They describe the specific attentional problem of psychopathic individuals as a response modulation deficit. Response modulation is defined as a relatively brief and automatic interruption of goal-directed behavior that occurs in response to salient stimuli or feedback that are outside the current focus of attention. Thus, the proposed response modulation deficit holds that psychopathic participants are less likely to be affected by or use secondary, contextual information when it is extraneous to their dominant response set (Patterson & Newman, 1993; Newman & Wallace, 1993). Consequently, insensitivity to inhibitory or emotional cues may not reflect the fact that they are fundamentally less meaningful to psychopathic individuals; rather, psychopathic individuals’ sensitivity to such cues may be insufficient when their attention is directed elsewhere (e.g., engaged in goal-direct behavior).

A number of empirical results provide support for the response modulation hypothesis. For example, Newman and Kosson (1986) administered a go/no-go discrimination learning task in which participants were required to press a button when particular stimuli were presented on a computer monitor to earn money and to inhibit pressing when other stimuli were presented to avoid losing money. As predicted, psychopathic participants more frequently failed to inhibit punished responses than non-psychopathic controls. To examine whether this deficiency was due to a deficit in response modulation or a generally impoverished response to punishment (i.e., a motivational or emotional deficit), Newman and Kosson (1986) administered a slightly modified version of the task that omitted the reward contingency. Instead, participants began with a cash stake and lost money each time that they responded to “no-go” stimuli or failed to respond to “go” stimuli. Under these circumstances, psychopathic and non-psychopathic participants displayed comparable passive avoidance.

Sensitivity to threat cues is often assessed using psychophysiological measures like skin conductance (SC) because behavioral measures such as passive avoidance may reflect deliberate inhibition rather than emotion-mediated learning. Thus, Arnett, Smith, and Newman (1997) examined SC responses under the same conditions employed by Newman and Kosson (1986). Paralleling results from the Newman and Kosson study, psychopathic individuals displayed significantly weaker SC responses to threat cues than controls while responding for rewards, but showed comparable SC responses to the same stimuli in a punishment-only condition. Thus, psychopathic individuals’ physiological sensitivity as well as their behavioral sensitivity to inhibitory information appears to be a function of their attentional set. That is, when threat cues are part of the dominant response set (primary focus of attention), psychopathic individuals show no difference in their behavioral or psychophysiological response to them.²

The above results are externally valid and consistent with predictions generated by the response modulation hypothesis, but do not represent direct tests of the response modulation hypothesis. Because the passive avoidance deficits demonstrated by psychopathic offenders occur in conditions involving an approach-avoidance conflict, it is unclear whether the poor performance of psychopathic individuals in these tasks is truly attentionally mediated, or reflects fundamental motivational or emotional processes that bias the perceived relevance of approach and avoidance contingencies. More powerful evidence for the role of attention in mediating sensitivity to inhibitory cues comes from Hiatt, Schmitt, and Newman (2004), who employed variations of the standard Stroop task to investigate the role of attentional focus without this motivational component. Paralleling results from the passive avoidance studies, psychopathic individuals displayed less interference from incongruent stimuli than controls when the incongruent cues were peripheral to their primary focus of attention, but showed comparable interference when they were not. More specifically, the groups did not differ on the standard Stroop task in which the color and word cues are presented in the same location, whereas psychopathic participants displayed less interference than controls when the color and word were spatially separated (see also Newman, Schmitt, & Voss, 1997; Smith, Arnett, & Newman, 1992; cf. Mitchell, Richell, Leonard, & Blair, 2006). Similar results have also been found using female psychopathic and non-psychopathic offenders (Vitale, Brinkley, Hiatt, & Newman, 2007).

These response conflict tasks support the response modulation hypothesis, but may not preclude a motivational explanation. Psychopathic individuals may approach these tasks differently than non-psychopathic individuals, giving less weight to potential errors generated by the incongruent information, which may account for the observed differences in performance. In other words, the emotional or motivational weight of the distractors, and the influence that this has on the performance of non-psychopathic individuals, may reflect a fundamental responsivity to information that calls for pausing or re-evaluating behavior that psychopathic individuals lack. Moreover, the relative “lack of concern” for inhibitory information displayed by psychopathic individuals on such measures may be functionally similar to the lack of concern for the rights and feelings of others or the fearlessness described in other theories of the psychopathic deficit.

In the context of a response conflict task, a more elegant and compelling test of response modulation would manipulate the focus of attention, while keeping all other variables constant. This approach allows for a direct test of the role of attention in the moderation of response to inhibitory information, while holding the emotional and motivational aspects of the task relatively constant. The experiment presented here provides such a test, using a modified version of the classic flanker task (Eriksen & Eriksen, 1974). In this version of the task, some trials include pre-target attentional cues that indicate where the target stimulus will appear, while other trials draw attention to both target and distractor locations. When afforded a pre-potent attentional focus that creates a dominant response set for critical information, the response modulation hypothesis predicts that psychopathic individuals will be relatively unaffected by information in an unattended location. Conversely, when attention is cued to both the target and distractor location, there is no primary focus of attention; thus, psychopathic and nonpsychopathic participants should not differ. This is consistent with the results for basic Stroop tasks, where psychopathic individuals do not differ, as the spatially integrated presentation of primary and secondary information precludes a pre-target focus of attention on relevant information (see Hiatt et al., 2004).

In this study, we employ two different cuing manipulations, exogenous and endogenous cues, to evaluate the generality of the predicted effect. Exogenous cues draw attention to a location automatically. For example, flashing a box somewhere on a computer screen automatically draws a participant’s attention to that location. Endogenous cues, on the other hand, direct individuals to shift their attentional focus (McCormick, 1997; Theeuwes, 1991, 1994; Yantis, 1993). For example, an arrow that appears at fixation and indicates where a target will appear will not automatically draw attention to the proper location, but will direct the participant to shift attention effortfully to that location. The differential effects of these cue types will be investigated, although the response modulation hypothesis does not predict differential effects for these cue types. For response modulation, the critical dimension is engagement of attention rather than the means by which attention is engaged.

The response modulation hypothesis predicts that psychopathic participants will show at least as much interference as non-psychopathic participants in trials where no pre-target focus of attention exists. When cued to the target location, however, it predicts that psychopathic participants will show less interference from distracting information than non-psychopathic individuals. It is important to note that cuing is expected to reduce interference in all participants; the response modulation hypothesis predicts that the effect of cuing on selective attention will be significantly stronger in psychopathic participants. Such results would provide further support for the response modulation hypothesis and, critically, would confirm that this is causally related to attentional focus. Moreover, by including conditions that differ only in attentional focus, tonic differences in motivation or processing of emotional information would appear insufficient to explain why primary psychopathic individuals exhibit this difference.

According to the response modulation hypothesis, (a) individuals with primary psychopathy are relatively insensitive to contextual information, (b) this neglect of contextual information undermines their responsivity to a variety of environmental stimuli that normally facilitate self-regulation, and (c) their diminished response to contextual information (i.e. information that is peripheral to a pre-potent focus of attention) is moderated by attentional factors. In light of existing support for the first two propositions (Hiatt et al., 2004; Newman et al., 1997; Newman & Kosson, 1986), the current study was designed to evaluate the role of attention in moderating the insensitivity to contextual information that characterizes primary psychopathy.

Toward this end, we manipulated participants’ pre-potent focus of attention while examining the effects of peripheral, response-incongruent information on behavior. Based on previous research (Hiatt et al., 2004; Smith et al., 1992; Munro, Dywan, Harris, McKee, Unsal, & Segalowitz, 2007), we assumed that there would be no group differences in interference unless the incongruent information was peripheral to a pre-potent focus of attention. That is, we predicted that individuals with primary psychopathy would display reduced interference to incongruent information once their attention was directed to a target location. As noted above, the results provided strong and specific support for this hypothesis and, thus, demonstrate that attention plays a pivotal role in moderating sensitivity to contextual information in primary psychopathy.

The present results also clarify the implications of the response modulation hypothesis for primary psychopathic individuals’ performance on Stroop-like tasks. Previous research with modified Stroop tasks demonstrates that they display reduced interference when the to-be-attended and to-be-ignored aspects of the stimuli are spatially distinct, though they show normal interference when the information is spatially integrated, as it is in the standard Stroop task (Hiatt et al., 2004). Based on these findings, Hiatt and colleagues proposed that psychopathic individuals display superior selective attention under conditions that allow them to focus on one aspect of a visual display. However, this interpretation was speculative because attention was not manipulated in their experimental tasks. The present findings do not negate the possibility that spatial separation is important for observing a lack of responsivity to inhibitory stimuli, but they do suggest that it is not sufficient. The incongruent stimuli in the present study were spatially separated in both the “cued” and “uncued” trials, yet primary psychopathic participants differed only in the “cued” condition.

Further clarification is provided by the Mitchell et al. (2006) study that examined the effects of presenting emotional distractors before and after a neutral target stimulus in a perceptual discrimination task. As expected, psychopathic individuals were less distracted by these temporally distinct emotional distractors. According to the authors, the results could be interpreted as “in line with the response set modulation account by suggesting that individuals with psychopathy present with reduced processing of the information peripheral to the dominant response set if it is spatially and temporally peripheral to the information necessary for the dominant response set” (p. 564). We agree that these results are in line with the response modulation hypothesis and, moreover, agree that temporal as well as spatial separation will often be sufficient to reveal group differences in response modulation. However, we believe that this characterization of the response modulation deficit is incomplete. The critical dimension relates to whether or not a pre-potent focus of attention exists (regardless of whether there is spatial or temporal separation). When a pre-potent focus of attention exists, it biases attention towards specific stimuli or dimensions and causes other information to be outside of that focus, so that response modulation is needed to process the secondary information. In past research, this focus has been established by a response bias, as in the passive avoidance task employed by Newman and Kosson (1986), spatial separation, as in the modified Stroop tasks used by Hiatt et al. (2004), and temporal separation, as in the task presented by Mitchell and colleagues (2006).

Prior to investigations of response conflict tasks (e.g. modified Stroop tasks), much of the research on response modulation deficits in psychopathy used monetary rewards and punishments. The use of these incentives was important to ensure adequate motivation for task performance and to demonstrate the importance of response modulation deficits for maladaptive behavior (i.e., failure to inhibit responses that result in loss of money). In addition, it was initially proposed that establishing a dominant response set for reward was crucial for observing psychopathy-related deficits in response modulation (Gorenstein & Newman, 1980). However, following a series of experiments in which primary psychopathic participants displayed passive avoidance deficits only when afforded a prepotent focus of attention, Newman, Patterson, Howland, and Nichols (1990) proposed that the presence of a dominant response set, rather than hypersensitivity to reward or behavioral activation, was responsible for their response modulation deficits. The current results bolster this interpretation of the primary psychopathic deficit in response modulation as a situation specific “inattention” to information that is not part of a pre-potent focus of attention or dominant response set.

On the surface, the association between past research on passive avoidance learning and research involving response competition tasks may appear to be remote because of the extent to which the experimental manipulations and dependent measures differ. Indeed, individuals with primary psychopathy typically display a performance deficit on passive avoidance tasks, whereas they display less interference (i.e., better performance) when presented with response incongruent distractors. Nevertheless, performance on both paradigms is a function of participants’ sensitivity to contextual information and affected by response modulation (albeit in opposite directions). While the differences between the paradigms can be distracting, philosophy of science underscores the importance of conducting such conceptual replications as a means of evaluating the generality of a theoretical model and ruling out experiment-specific factors as alternative explanations for one’s findings. From this perspective, a greater difference between experimental contexts results in a more powerful conceptual replication.

Of course, when evaluating theoretical predictions in disparate experimental contexts, there is no guarantee that the same processes are responsible for the ostensibly related behaviors. Indeed, it is likely that different psychological processes and neural mechanisms are at play in a passive avoidance task as opposed to a Stroop or flanker task. Nevertheless, the utility of a theoretical model relates to its ability to generate valid predictions across a range of circumstances. To the extent that predictions are consistently supported in different experimental contexts, such results imply that the theoretical principles as opposed to task-specific factors are responsible for the observed results. In our view, the situation-specific insensitivity to peripheral information in the present study reflects the same response modulation deficit that underlies observed passive avoidance deficits in psychopathic offenders. While, in this case, the response modulation deficit led to superior performance under specific conditions, we propose that the observed group difference actually reflects a response modulation deficit that hampers self-regulation in situations that require individuals to alter or suspend goal-directed behavior in order to accommodate relevant peripheral information.

With regard to the clinical significance of the current findings for psychopathic behavior, MacCoon, Wallace and Newman (2004) have elaborated a model that clarifies the implications of response modulation deficits for the disinhibited behavior of psychopathic individuals. According to these authors, self-regulation depends upon a person’s ability to maintain a context appropriate balance of attention to primary (i.e., top-down) and peripheral (i.e., bottom-up) cues. The “context-appropriate” aspect of this proposal highlights the fact that the value of maintaining or shifting the focus of attention will vary according to the demands of a situation. Although successful goal-directed behavior depends upon a person’s ability to maintain a top-down focus on the goal in spite of myriad distractors, it is also dependent upon one’s ability to revise a strategy in response to bottom-up cues indicating that this strategy is no longer appropriate. Newman and colleagues have proposed that a deficit in response modulation, as manifested in primary psychopathy, will attenuate a person’s sensitivity to interpersonal cues that conflict with their immediate goals, render them oblivious to affective information unless it is an integral aspect of their goal-directed behavior, and undermine their consideration of information that might otherwise serve to inhibit inappropriate impulsive and antisocial behavior (Newman & Lorenz, 2003; Patterson & Newman, 1993; see also Hare, 1998).

This theoretical model of psychopathy also provides insight into the real-world behavior of psychopathic individuals. For example, in Psychopathy: Theory and Research, Hare (1970) describes a man who escaped from a prison hospital and returned to his lifestyle of making money through fraud and other illegal activities. He presented himself as the head of a philanthropic organization and enlisted the help of religious groups to help him raise funds. To expedite his fundraising, he made an impressive appearance on a local television station. His plea proved highly effective in meeting his immediate goal, as he successfully solicited significant donations. Outside of the scope of his goal, however, there were obvious negative consequences to appearing on television as a fugitive; indeed, the event led to his re-arrest. For a less psychopathic individual, the consequences of television exposure would almost certainly have engendered response conflict and led to a different decision. While this example may seem distinct from the methodology and findings of the laboratory task presented here, the same principle is at work. That is, this individual failed to make use of salient, inhibitory information that was outside of his prepotent focus of attention. We propose that such deficits are a function of attentional focus, and have relevance in situations ranging from simple cognitive tasks to real-world antisocial behavior.

Regarding potential limitations of this study, it is worth noting that the predictions and results are specific to a comparison of low-anxious psychopathic and non-psychopathic individuals. The importance of distinguishing between primary (i.e., low-anxious) and secondary (i.e., high-anxious) psychopathic subtypes has been emphasized for decades (Cleckley, 1976; Hare, 1970; Karpman, 1946), because high levels of neurotic anxiety can give rise to antisocial syndromes that mimic primary psychopathy but are etiologically distinct. Moreover, such proposals are supported by a wealth of laboratory evidence (see Brinkley et al., 2004; Newman et al., 2005). While this strategy limits the generalizability of our findings to a subset of psychopathic individuals, it is our contention that the “classic” (i.e., Cleckley, 1976) description of psychopathy defines a relatively homogeneous group in terms of the manifestation of psychopathic traits, behaviors, and underlying etiological processes (Brinkley et al., 2004).⁸

Finally, although motivational and emotional factors were well matched across the cuing conditions, these variables were not experimentally manipulated. Thus, the results of this specific study cannot be presented as underlying or explaining the obvious emotional impairments associated with psychopathy. Nevertheless, we believe that the response modulation hypothesis posits a mechanism within which performance differences on both cognitive and affective deficits can be understood (see Newman & Lorenz, 2003). Conversely, theories that posit emotion deficits as the proximal mechanism for psychopathy appear unable to explain the results presented here. We acknowledge the possibility that psychopathy may reflect multiple independent deficiencies (e.g., Patrick, Hicks, Nichol, & Krueger, 2007; Fowles & Dindo, 2006) rather than a single information processing deficit (Brinkley et al., 2004). However, given the viability of the unitary model, we propose that studies of emotion processing and other putative deficits should manipulate attention to evaluate the importance of response modulation for any observed deficits. If, as we have proposed, this attentional deficit is a core aspect of primary psychopathy, then attention may also moderate the expression of these deficits. Although there is already some evidence to support this speculation, (e.g., Arnett et al., 1997; Dvorak-Bertsch, Curtin, Rubinstein, & Newman, in press; Newman & Kosson, 1986), additional studies are needed.