RESPONSE MODULATION, PSYCHOPATHY, AND ERPS
S1
Supplementary Materials
Distribution of Fearless Dominance and Impulsive Antisociality Scores
Because participants were only selected based on either their Fearless Dominance (FD) or
Impulsive Antisociality (IA) score and not both, the score on the factor for which they were not
selected was free to vary. This resulted in an approximately normal distribution of FD and IA
scores (See Figures S1 and S2, respectively; |skewness| < 0.25, |kurtosis| < 0.72). Additionally,
the Triarchic Psychopathy Measure (Patrick, Fowles, & Krueger, 2009; Patrick, 2010) was
administered during the laboratory session as a measure of psychopathy separate from the MPQ
estimated scores. FD and IA correlated in the expected ways with Triarchic scores indicating that
they were accurately estimated by the MPQ and adequately represented in our sample (see Table
S1). Table S1 also provides test-retest correlations between the screening and laboratory sessions
for FD and IA.
Participant Exclusion
Participants who were excluded because of bad performance did not differ in their levels
of fearless dominance (FD), t(76) = -0.45, p = .657, or impulsive antisociality (IA), t(76) = 0.18,
p = .860, from participants who were included in this study. The mean fearless dominance score
was -0.14 (SD = 0.79) for included participants and -0.02 (SD = 0.90) for excluded participants.
The mean impulsive antisociality score was -.18 (SD = 0.71) for included participants and -0.22
(SD = 0.70) for excluded participants.
ERN and N1 Peaks
As shown in Figures S3 and S4, ERNs in all conditions were maximal at FZ, as was the
N1 to the stop signal. The N1 distribution in this study was consistent with previous literature
(Näätänen & Picton, 1987). Although the ERN is traditionally reported at FCz, EEG was not
RESPONSE MODULATION, PSYCHOPATHY, AND ERPS
S2
recorded from this site because of equipment limitations. However, the ERN has been reported
previously at FZ (Hajcak, Moser, Yeung, & Simons, 2005; Hajcak & Simons, 2008) with similar
properties as those observed in this study. Table S2 gives the means and standard deviations for
these components.
Relationships between IA, Behavioral Performance, ERPs, and Gender
Because our sample was 56% women, correlations were computed between IA,
behavioral performance measures, ERPs and gender. Only the ERN following correct lexical
decisions was correlated with gender at a trend level, r(65) = .24, p = .052. No significant
correlations were observed between gender, IA, behavioral measures, or any other ERPs, |rs| <
.17, ps > .16. Additionally, correlations between IA, behavioral performance and ERPs did not
significantly differ for men and women, |Fisher's Zs| < 1.43, ps > .15, showing a similar pattern
to the sample as a whole.
Participant Engagement
As shown in Table S3, correlations were computed between participants' reported level of
engagement in the task (from the post-task questionnaire), IA, behavioral measures, and ERPs;
these correlations are given in Table S1. Participants' overall level of engagement was
significantly related to LD accuracy and ERN following SS errors and was related to SS N1 at a
trend level, indicating that participants who were more engaged in the task performed better
overall and processed SS errors to a greater extent. How hard participants tried to respond word
or non-word correctly was also significantly related to LD accuracy. Overall engagement and
how hard participants tried to respond word or non-word correctly were only related to IA at a
trend level. No measure of engagement was significantly related to FD, RT, SSD, or SSRT.
Lexical Decision Stop Signal (LDSS) Task Characteristics
RESPONSE MODULATION, PSYCHOPATHY, AND ERPS
S3
Although the lexical decision component of the LDSS task used in the current study
increased the complexity of the go task over more traditional letter discriminations (X vs. O), the
mean SSRTs found here did not differ significantly from those found by Wodushek and
Neumann (2003) in a sample of adults with ADHD, t(109) = 1.31, p = .19. Our high IA group
did not differ significantly from their high ADHD symptom group, t(54) = 1.17, p = .25, and our
low IA group did not differ significantly from their low ADHD symptom group, t(53) = 0.69, p =
.49. This indicates that the increased complexity of the go task did not have a significant effect
on the stopping process. Additionally, neither lexical status nor word valence significantly
influenced the relationship between IA and any behavioral or ERP measure (Heritage &
Benning, 2012). For example, across pleasant, neutral, aversive, and non-words, correlations
between IA and lexical decision accuracy ranged from -.21 to -.26. The same range of
correlations between IA and SSRTs in various conditions was -.29 to -.34.
ERP-IA Relationships Controlling for Behavioral Performance
Partial correlations were computed between IA and all reported ERP measures
controlling for LD accuracy and SS accuracy to determine if behavioral performance influenced
these relationships. IA remained significantly correlated with ERN amplitude following incorrect
LD, r(64) = .27, p = .030, and correct LD, r(64) = .26, p = .041, but not SS errors, r(64) = .15, p
= .225. IA also remained significantly correlated with SS N1, r(64) = .27, p = .031.
Prediction of Each ERN Amplitude from Other ERNs
To generate new variables that represented the unique variance associated with each
ERN, separate linear regressions were conducted with each ERN as the dependant variable and
the other two as predictors. The unstandardized residuals were saved from these analyses as a
measure of the unique variance in each ERN not accounted for by the other two ERNs. These
RESPONSE MODULATION, PSYCHOPATHY, AND ERPS
S4
residuals were then subjected to the meditational analyses displayed in the bottom half of Table
3. As displayed in Table S4, the SS error ERN significantly predicted each LD ERN, and the two
LD ERNs independently predicted SS ERN. IA was no longer significantly correlated with the
unique variance associated with incorrect, correct LD, or SS errors. FD was still not correlated
with any ERN amplitude.
However, it is still possible that despite a lack of a significant correlation between IA and
residualized ERNs, SS N1 amplitude may yet mediate the IA → ERN relationship (Kenny,
Kashy, & Bolger, 1998) because IA and ERN relate to the N1 in opposite ways. Consider that
the relationship between IA and ERN is such that higher scores on IA produce shallower ERN
amplitudes, but the relationship between N1 and ERN is such that larger N1 amplitude is
associated with larger ERN amplitude. In this case, though both paths involving the N1 are
significant, they are opposite in sign, and thus the path between IA and ERN may be nonsignificant. This situation gives rise to what MacKinnon, Fairchild, and Fritz (2007) call
inconsistent mediation, as the mediator (in this case, N1 amplitude) acts as a suppressor variable
on the IA → ERN relationship.
As shown in Table S5, only the residualized SS ERN correlated with the SS N1, which
allowed N1 amplitude to mediate the IA → SS ERN relationship, as shown in Table 3. Because
the residualized LD ERNs were not related to SS N1 amplitude, they would not be able to
mediate the IA → LD ERN relationships in the analyses reported in Table 3.
RESPONSE MODULATION, PSYCHOPATHY, AND ERPS
S5
References
Hajcak, G., Moser, J. S., Yeung, N., & Simons, R. F. (2005). On the ERN and the significance of
errors. Psychophysiology, 42(2), 151–160. doi:10.1111/j.1469-8986.2005.00270.x
Hajcak, G., & Simons, R. F. (2008). Oops!.. I did it again: An ERP and behavioral study of
double-errors. Brain and Cognition, 68(1), 15–21. doi:10.1016/j.bandc.2008.02.118
Heritage, A. J., & Benning, S. D. (2012). Stimulus processing and psychopathy in a lexical
decision - stop signal task. Manuscript in preparation.
Kenny, D. A., Kashy, D., & Bolger, N. (1998). Data analysis in social psychology. In D. Gilbert,
S. Fiske, and G. Lindzey (Eds.), Handbook of social psychology (4th ed., pp. 233-265).
New York: McGraw-Hill.
MacKinnon, D. P., Fairchild, A. J., & Fritz, M. S. (2007). Mediation analysis. Annual Review of
Psychology, 58, 593-614.
Näätänen, R., & Picton, T. W. (1987). The N1 wave of the human electric and magnetic response
to sound: A review and an analysis of the component structure. Psychophysiology, 24(4),
375-425.
Patrick, C. J. (2010). Triarchic psychopathy measure (TriPM). Retrieved from
https://www.phenxtoolkit.org/index.php?pageLink_browse.protocoldetails&id_121601
Patrick, C. J., Fowles, D. C., & Krueger, R. F. (2009). Triarchic conceptualization of
psychopathy: Developmental origins of disinhibition, boldness, and meanness.
Development and Psychopathology, 21(3), 913–938. doi:10.1017/S0954579409000492
Wodushek, T. R., & Neumann, C. S. (2003). Inhibitory capacity in adults with symptoms of
attention deficit/hyperactivity disorder (ADHD). Archives of Clinical Neuropsychology.
Vol 18(3), 317–330.
RESPONSE MODULATION, PSYCHOPATHY, AND ERPS
S6
Table S1
Correlations among Fearless Dominance, Impulsive Antisociality and Triarchic Psychopathy Measure Subscales
FD Screen
IA Screen
Boldness
Meanness
Disinhibition
FD Lab
(.92**)
-.12
.78**
.10
-.46**
IA Lab
-.17
(.83**)
-.25
.44**
.52**
Boldness
1
.13
-.41**
Meanness
-
Disinhibition
-
-
-
1
.27*
1
Note. * p < .05, ** p < .01. FD = fearless dominance, IA = impulsive antisociality. Correlations in parentheses represent test-retest
correlations between FD and IA obtained at screening and test. The Triarchic Psychopathy Measure (Patrick, 2010) was only
administered in the laboratory.
RESPONSE MODULATION, PSYCHOPATHY, AND ERPS
S7
Table S2
Means (And Standard Deviations) for ERP Measures in the Sample as a Whole and by Median Split on Impulsive Antisociality
Group
SS N1
Incorrect LD ERN
Correct LD ERN
SS Error ERN
Whole
Sample
Low IA
-14.1 (6.59)
-6.15 (5.26)
-2.95 (2.37)
-7.16 (3.70)
-16.2 (6.77)
-6.88 (5.88)
-3.48 (2.46)
-7.99 (3.30)
High IA
-12.0 (5.76)
-5.42 (4.53)
-2.42 (2.18)
-6.34 (3.93)
Note. SS = stop signal, LD = lexical decision. All values are peak amplitude measured in microvolts.
RESPONSE MODULATION, PSYCHOPATHY, AND ERPS
S8
Table S3
Correlations between Task Engagement and Fearless Dominance, Impulsive Antisociality, Behavioral Measures, and ERP Responses
Question
FD
IA
Overall
Engagement
Task
Importance
.13
-.21+
Behavioral Measures
LD
SS
SS
SSRT
Accuracy Accuracy Delay
-.03
.37**
.09
.05
-.11
.09
-.16
.11
.21+
-.08
.07
.00
.10
.01
-.06
-.02
LD Effort
-.18
-.22+
-.11
.46**
.02
-.04
-.05
-.12
.08
.00
-.01
SS Effort
-.10
-.14
.09
.14
.11
.05
.01
-.07
.05
.05
-.03
RT
Incorrect LD
ERN
-.15
ERP Responses
Correct SS Error
LD ERN
ERN
-.06
-.25*
SS N1
-.22+
Note. * p < .05, ** p < .01. LD = lexical decision, FD = fearless dominance, IA = impulsive antisociality, RT = reaction time, SS =
stop signal, SSRT = stop signal reaction time. Overall Engagement = “How engaged were you in this task?” Task Importance = “How
important did you think this task was?” LD Effort = “How hard did you try to respond word or non-word correctly?” SS Effort =
“How hard did you try to avoid making a mistake like responding when you shouldn't have?”
RESPONSE MODULATION, PSYCHOPATHY, AND ERPS
S9
Table S4
Summary of Regression Analysis Predicting ERN Amplitudes
Independent Variable
B
SE(B)
β
t
P
Correct LD ERN
SS Error ERN
.262
.517
Incorrect LD ERN
.278 .120 .942
.176 .374 2.93
Incorrect LD ERN
SS Error ERN
.049
.312
Correct LD ERN
.051 .106 .942
.071 .492 4.39
.349
.000
Incorrect LD ERN
Correct LD ERN
.214
.699
.073
.159
SS Error ERN
.296 2.93
.444 4.39
.005
.000
.349
.005
Note. LD = lexical decision, SS = stop signal. Unstandardized residuals from these analyses were used in mediation analyses as
indicators of the unique variance associated with each ERN.
RESPONSE MODULATION, PSYCHOPATHY, AND ERPS
S10
Table S5
Correlations among Fearless Dominance (FD), Impulsive Antisociality (IA), and the Unique Variance of Each ERN
Incorrect LD ERN
FD
IA
SS N1
.01
.17
.01
Correct LD ERN
SS Error ERN
.13
.15
.13
Note. LD = lexical decision, SS = stop signal. ** p < .01.
-.11
.10
.49**
RESPONSE MODULATION, PSYCHOPATHY, AND ERPS
S11
Figure S1. Histogram of fearless dominance scores obtained in the laboratory for the sample as a whole.
RESPONSE MODULATION, PSYCHOPATHY, AND ERPS
S12
Figure S2. Histogram of impulsive antisociality scores obtained in the laboratory for the sample as a whole.
RESPONSE MODULATION, PSYCHOPATHY, AND ERPS
S13
Figure S3. Grand average waveforms of the ERN following incorrect lexical decisions, correct lexical decisions and SS errors for the
sample as a whole shown here at all electrodes used.
RESPONSE MODULATION, PSYCHOPATHY, AND ERPS
S14
Figure S4. Grand average waveforms of the N1 following SS onset for the sample as a whole shown here at all electrodes used.