5. Discussion
This study contrasted the associations between ANS reactivity to a SSST and the countdown task (signaled and unsignaled noise blasts). Results provide additional evidence that an accurate characterization of associations between ANS reactivity and psychopathy requires attention to: 1) the stressor used to induce change, 2) the measure of ANS activity, 3) the characterization of psychopathy, and 4) sex differences in associations.
Analyses indicated HRR to signaled noise blasts in the countdown task was negatively associated with SRP total scores and scores on three of the factors in the full sample, but only the association between HRR and SRP-IPM remained statistically significant after the sample was restricted to females. In addition, HRR to signaled noise blasts had a negative association with SSS-V total scores and the SSS-V disinhibition scales in the full sample but not among females. In contrast, HRR to the social stressor was not associated with psychopathic traits in either the full sample or the female only subsample.
Negative associations between HRR to signaled noise blast and psychopathic traits are inconsistent with Wang et al. (2012) and with earlier work showing small samples of male criminal psychopaths show increased HRR to signaled noise blasts relative to non-criminal psychopaths (Hare, 1982; Hare et al. 1978; Ogloff et al., 1990), but fit well within accounts of psychopathy emphasizing reduced ANS reactivity in anticipation of aversive stimuli (e.g. Arnett, 1997; Lyken, 1995). Wang et al. (2012) reported larger HR acceleration during signaled noise blasts was associated with callousness-disinhibition in both boys and girls. More recently, MacDougall et al. (2019) found no association between HRR to noise blasts and psychopathic traits in juvenile male offenders. Inconsistent results highlight the need for replication with attention to the potential influence differences across the measurement of psychopathic traits and differences across sex in associations between ANS reactivity and psychopathy.
In the current study, SCR to both signaled and unsignaled noise blasts during the countdown task was positively associated with SSS-V Boredom in the full sample but not with the sample restricted to females. Positive associations between SCR to signaled and unsignaled noise blasts results stand in apparent contrast to negative associations and psychopathic traits reported in earlier work, but differences may be reconciled to a certain extent with a consideration of measurement and variation in associations across sex. Negative associations in prior work were reported for measures capturing Factor 1 psychopathy including manipulative/deceitfulness (Wang et al., 2012), callous-unemotional traits (McDougal et al., 2019), and fearless dominance (Dindo & Fowles, 2011). The current analyses found an association between SCR during the countdown task and sensation seeking, a trait that can be conceptualized as a facet within Factor 2 psychopathy but has little to no overlap with the callous egocentricity that underpins much of Factor 1 psychopathy. In addition, negative associations between SCR to noise blasts and Factor 1 psychopathy traits may be specific to males and therefore attenuated in our sample which was predominantly (77%) female. This suggestion receives some support from Wang et al. (2012) who found fewer SC responses during signaled noise blast anticipation were associated with an increased manipulative/deceitful factor derived from Lynam’s (1997) Childhood Psychopathy Scale among males but not females. Thus, SCR during the countdown task may be positively associated with facets within Factor 2 psychopathy as evidenced here, but negatively associated with Factor 1 psychopathy among males as indicated by prior work. Unfortunately, due to very small within stress task group sizes with the sample restricted to males we were unable to replicate our analyses in a male only sample.
In the results reported here, SCR during the SSST was negatively associated with the Interpersonal Manipulation factor of the SRP-III both in the full sample and with the sample restricted to females. This association was somewhat surprising as Dindo and Fowles (2011) report that SCR to the SSST was positively associated with Impulsive Antisociality (PPI-2) but not associated with Fearless Dominance (PPI-1). The lack of an association between Fearless Dominance and SCR to the SSST in Dindo and Fowles (2011) would lead to the anticipation that Interpersonal Manipulation would not be associated with SCR to the SSST as the correlation between Interpersonal Manipulation and some of the subscales that comprise Fearless Dominance is very strong (e.g., Machiavellian Egocentricity (PPI) r = .75, Seibert et al., 2011). Nonetheless, differences across studies may be due to the measures used or sex differences as with the association between SCR to noise blasts and psychopathic traits discussed above.
While the focus of the current work was on differences in associations between ANS reactivity and psychopathic traits across the countdown task and the SSST, results also inform the associations between ANS measures taken at rest and psychopathic traits. The current analyses found a negative and statistically significant association between RSC and SSS-V total scores that was present in the full sample and with the sample restricted to females. This association is consistent with prior reports of a negative association between RSC and sensation seeking (Gatzke-Kopp et al., 2002; Plouffe & Stelmack, 1986). In contrast, RHR was not associated with psychopathic traits in the results presented here.
The implications of the current work for our understanding of associations between ANS activity and psychopathic traits should be conditioned by consideration of certain aspects of the study’s methodology. While the current work has virtue in that it is the first to use a randomized design to explore differences in associations between ANS activity and psychopathic traits across stressors, this methodology resulted in a relatively small overall sample size and even smaller within condition sample sizes. The study’s small sample size increases the susceptibility to Type I error and thus limits the weight that should be give conclusions regarding variation in association across tasks. Risk for Type I error was also increased through multiple comparisons. Thus, strong conclusions await replication of the associations reported herein. However, potential differences in associations between ANS and psychopathic traits suggests that research in this area should consider different measures and focus on psychopathy factors rather than total scores. This approach necessitates multiple comparison in studies considering different aspects of ANS activity (SC and HR), different stressors, and different measures of psychopathy. In addition, the sample used here was predominantly female. While this can help to shed light on the extent to which findings based on samples of males generalize, we were unable to directly consider differences in associations across males and females. Lastly, the sample was drawn from university students and as such average values on psychopathy scores are lower than at-risk or forensic samples (e.g., Sandvik et al., 2012).
Nonetheless, the current results contribute to growing evidence that associations between ANS responsivity and psychopathic traits vary across stress task. Within this line of research there is accumulating evidence that ANS responsivity to noise blasts is negatively associated with Factor 1 psychopathy (Fung et al., 2005; McDougal et al., 2019; Wang et al., 2012). Evidence regarding associations between ANS responsivity to SSSTs and psychopathic traits is less consistent. Here we find a negative association between SCR during the SSST and SRP-IPM while prior work has found evidence of a positive association between SCR during the SSST and PPI Factor 2 Impulsive Antisociality. While differences across studies may be attributable to the measurement of psychopathy and sex differences in sample composition, they suggest that our understanding of the role of ANS in the development of psychopathic traits may be furthered by additional work paying specific attention to variation in associations across stressor type while also considering variation across the conceptualization and measurement of psychopathy.