1. Introduction
Psychopathy is characterized by a cluster of personality traits
including a lack of affect, egocentricity, manipulativeness, and a
tendency toward risky and antisocial behavior (Cleckley, 1941; De Brito
et al., 2021; Hare & Neumann, 2008). The deleterious consequences of
these traits including risk for antisocial and criminal behavior has
motivated considerable research into the potential physiological
underpinnings of psychopathy. Among these studies a growing body of
research has shown that autonomic nervous system (ANS) activity at rest
and in response to stress is associated with psychopathic traits (de
Looff et al., 2021; Lorber, 2004; Portnoy & Farrington, 2015).
Associations between ANS activity and psychopathic traits may be
understood in the context of ANS function. The ANS includes the
sympathetic and parasympathetic nervous systems (SNS, PNS; Gabella,
2001). The SNS is responsible for a variety of physiological and
psychological changes in support of the body’s response to stress and
can be roughly characterized as potentiating the ‘fight or flight
response’. In contrast, the PNS enacts physiological and psychological
changes to return the body to homeostasis after stress (Akselrod et al.,
1981; Warner & Cox, 1962). Studies exploring the association between
ANS activity and psychopathic traits often index ANS activity with heart
rate (HR) and skin conductance (SC).
Heart rate is influenced by both the SNS and PNS with the SNS exerting
an excitatory influence and the ANS an inhibitory influence. SC is
influenced solely by the SNS. ANS hypo-activity in response to stress
may be associated with the development of personality traits
characterized by blunted affect through impaired fear conditioning
(Lykken, 1957). The suggestion that ANS activity is associated with
psychopathic traits through fear conditioning is supported by work
showing reduced SC reactivity (SCR) in anticipation of aversive stimuli
(e.g. Arnett, 1997, Lyken, 1995). Raine (2002) suggested that low
resting heart rate may be associated with increased risk for antisocial
behavior through either fearlessness or sensation seeking. Subsequent
work has found support for the mediating role of sensation seeking in
the HR-antisocial behavior relationship (Portnoy et al., 2014; Sijtsema
et al, 2010),
Three meta-analyses have explored the association between ANS activity
and psychopathic traits. Lorber (2004) reported resting HR (RHR) was not
associated with psychopathy (d = .06, p >
.05), while Portnoy and Farrington (2015) later reported a negative
association (d = -.19, p < .05). In a recent
meta-analysis by de Looff et al. (2021), RHR had a negative and
statistically significant association with Factor 2 psychopathy
(ES = - 0.16, p = .017), while the association between RHR
and Factor 1 psychopathy was negative but lacked statistical
significance (ES = - 0.21, p = .059). Factor 1 psychopathy is
characterized by a manipulative and callous egocentricity while Factor 2
centers on tendency to engage in impulsive and antisocial behaviors
(Karpman, 1948). Variability in the results for associations between SC
and psychopathic traits are even more pronounced. For example, Lorber
(2004) found SC and SCR were negatively associated with psychopathy (SCd = -.30, p < .05, SCR d = -.31, p< .05). Later, de Looff et al. (2021) disaggregated studies of
SC level and SC response and found neither was associated with
psychopathy (SC level ES = 0.01, p = .887; SC responseES = -0.12, p = .148).11Skin conductance response
is commonly measured as an increase in conductivity exceeding .05
microsiemens in amplitude (e.g., Fung et al., 2005; Wang et al.,
2012). Skin conductance level is the average value of skin conductance
for a given time period. de Looff et al. (2021) also SCR for measures
of SC level and SC response were not related to psychopathy (SCR level,ES = -0,14, p = .137; SCR response ES = 0.12, p =
.162).
While meta-analyses offer some evidence for associations between ANS
activity and psychopathic traits, it is possible that results obscure
important variation across studies that can help to specify the role of
ANS activity in the development of psychopathy. Specifically, aggregate
associations between ANS reactivity and psychopathy factors may mask
important variation across the type of stimulus used to illicit change
in ANS activity. In what is to our knowledge the only direct
investigation of the role of stimulus type in associations between SCR
and psychopathy factors, Dindo and Fowles (2011) found SCR during social
stressor speech task (SSST; preparation and delivery of a speech about
one’s faults) was positively associated with Psychopathic Personality
Inventory Factor 2 - Impulsive Antisociality (PPI-2; Lilienfeld &
Andrews, 1996), while SCR in
response to signaled noise blasts during the countdown task was
negatively associated with PPI-1 - Fearless Dominance.
Negative associations between SCR to signaled noise blasts and aspects
of psychopathy consistent with Factor 1 have been found by other work
(Fung et al., 2005; McDougal et al., 2019; Wang et al., 2012).
For example, studies in children
and adolescents have found SCR resulting from noise blasts during the
countdown task is negatively associated with total psychopathy scores,
(Fung et al., 2005), manipulative/deceitfulness (Wang et al., 2012), and
callous-unemotional traits (McDougal et al., 2019). In contrast,
research testing associations between psychopathy factors and SCR to the
SSST finds SCR is not related to callous unemotional traits but provides
some equivocal evidence for an association between the SSST and the
sensation seeking facet of Factor 2 psychopathy (Kavish et al., 2019;
Portnoy et al. 2020). Both Kavish et al. (2019) in a large university
sample and Portnoy et al. (2020) in a sample of physically maltreated
youth reported that the SSST was not associated with aspects of
callousness captured by the Inventory of Callous Unemotional Traits
(ICU; Frick, 2004). Kavish et al. (2019) also found SCR in response to
the SSST was not associated with total psychopathy scores or scores on
psychopathy factors present in the Levenson Self-Report Psychopathy
Scale. However, SCR in response to the SSST was positively associated
with thrill seeking as measured by the Sensation Seeking Scale - Form V
(SSS-V; Zuckerman, Eysenck, & Eysenck, 1978). Studies have also shown
that associations between HRR and psychopathy factors vary considerably
across experimental stimuli. HRR from the SSST was not associated with
callous unemotional traits in the work of Portnoy et al. (2020) or
Kavish et al. (2019). In
contrast, Wang et al. (2012) reported increased HRR during the countdown
was positively associated with callous/disinhibited scores in a sample
of children.
Collectively the studies reviewed above suggest that associations
between ANS reactivity and psychopathy factors are influenced by the
stimuli used to elicit reactivity and by the ANS measure (HR/SC).
Research in this area also suggests that relatively minor differences in
the conceptualization of psychopathic traits may influence results. For
example, SCR for signaled noise blasts were negatively associated with
callous-unemotional traits in the work of MacDougall et al. (2019) but
not related to callousness-disinhibition in the work of Wang et al.
(2012).
While the potential influence of heterogenous experimental stimuli on
patterns of association between ANS activity and psychopathic traits has
long been recognized (Lorber, 2004), relatively little direct attention
has been given to the influence of different stimuli on the strength of
association between ANS activity and psychopathic traits. To our
knowledge Dindo and Fowles (2011) present the only study to directly
contrast results from a social stressor with those from an anticipation
of noise task. In their study all subjects were exposed to four
experimental paradigms. The countdown task and the social stressor were
the third and fourth.22Results for the first two experimental
paradigms (concealed information and picture viewing) were not
presented and were described by the authors as “somewhat complex and,
for that reason, were not as clearly of theoretical relevance” (Dindo
& Fowles, 2011, p. 560). It is possible that the strength of
association between SCR and psychopathy factors during these later
experimental paradigms was attenuated. Therefore, to further inform our
understanding of the association between ANS activity and psychopathic
traits we extend the work of Dindo and Fowles (2011) by randomly
assigning subjects to either the countdown task or the SSST. We also
explore the influence of the quantification of psychopathy on results
through the use of multiple measures of psychopathic traits.