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 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
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 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 non-significant. 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.
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 S1
Table S1
Correlations among Fearless Dominance, Impulsive Antisociality and Triarchic Psychopathy Measure Subscales
FD Lab / IA Lab / Boldness / Meanness / DisinhibitionFD Screen / (.92**) / -.17 / - / - / -
IA Screen / -.12 / (.83**) / - / - / -
Boldness / .78** / -.25 / 1 / - / -
Meanness / .10 / .44** / .13 / 1
Disinhibition / -.46** / .52** / -.41** / .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.
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 ERNWhole Sample / -14.1 (6.59) / -6.15 (5.26) / -2.95 (2.37) / -7.16 (3.70)
Low IA / -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.
Table S3
Correlations between Task Engagement and Fearless Dominance, Impulsive Antisociality, Behavioral Measures, and ERP Responses
FD / IA / RT / LD Accuracy / SS Accuracy / SS Delay / SSRT / Incorrect LD ERN / Correct LD ERN / SS Error ERN / SS N1
Overall Engagement / .13 / -.21+ / -.03 / .37** / .09 / .05 / -.11 / -.15 / -.06 / -.25* / -.22+
Task Importance / .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
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?”
Table S4
Summary of Regression Analysis Predicting ERN Amplitudes
Independent Variable / B / SE(B) / β / t / PIncorrect LD ERN
Correct LD ERN / .262 / .278 / .120 / .942 / .349
SS Error ERN / .517 / .176 / .374 / 2.93 / .005
Correct LD ERN
Incorrect LD ERN / .049 / .051 / .106 / .942 / .349
SS Error ERN / .312 / .071 / .492 / 4.39 / .000
SS Error ERN
Incorrect LD ERN / .214 / .073 / .296 / 2.93 / .005
Correct LD ERN / .699 / .159 / .444 / 4.39 / .000
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.
Table S5
Correlations among Fearless Dominance (FD), Impulsive Antisociality (IA), and the Unique Variance of Each ERN
Incorrect LD ERN / Correct LD ERN / SS Error ERNFD / .01 / .13 / -.11
IA / .17 / .15 / .10
SS N1 / .01 / .13 / .49**
Note. LD = lexical decision, SS = stop signal. ** p < .01.
sociated With Each ERN response.nique Varience
Figure S1. Histogram of fearless dominance scores obtained in the laboratory for the sample as a whole.
Figure S2. Histogram of impulsive antisociality scores obtained in the laboratory for the sample as a whole.
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.
Figure S4. Grand average waveforms of the N1 following SS onset for the sample as a whole shown here at all electrodes used.