Experiment 2:
Response-related Processes and the Influence of Conscientiousness, Task Difficulty and Response Awareness: Evidence from a Four-choice Flanker Task
The results of Experiment 1 suggested that trait conscientiousness levels and task demands interact to modulate response-related components that are said to reflect response monitoring and evaluation. Whereas explanations of the ERN/Ne provide a sound framework for understanding response-related processes at a basic level (Falkenstein et al., 1991), the impact of individual differences and task-specific factors are not specifically accounted for within current theories. Experiment 2 was designed to investigate the impact of increasing task demands using a four-choice flanker task, conscientiousness and response awareness on response-related components.
An overall increase in difficulty of the standard arrowhead flanker task used in Experiment 1 was achieved by using identical stimuli to that task but requiring a more complex decision relating to those stimuli. This provided an avenue to explore specifically how differential task demands in a more difficult task might impact the separate and combined effects of response awareness and conscientiousness on response-related processes. Consistent with the findings of Experiment 1, overall error response-related activity was expected to be significantly larger than correct response-related activity for early negative early positive and late positive
components. The conscientiousness effects evident in Experiment 1 are consistent with the findings of a number of researchers who suggest that the motivational importance or salience of responses and underlying personality traits are
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fundamentally involved in response monitoring and evaluation (Hajcak et al., 2005; Pailing & Segalowitz, 2004a). Evidence from Experiment 1 indicates that task demands are likely to moderate this effect. Consequently, further examination of the impact of differing conscientiousness levels in a more demanding task was included in Experiment 2 to further clarify this effect. Consistent with explanations of error- related components being linked to motivational factors (Hajcak et al., 2005; Pailing & Segalowitz, 2004a), it was expected that variation according to conscientiousness would be evident in ERN/Ne and Pe effects only. Also, if task demands moderate motivational effects then it was predicted that, similar to effects found in Experiment 1, mean ERN/Ne would not be differentiated in terms of levels of congruency for high conscientiousness levels, whereas low conscientiousness participants would demonstrate larger mean ERN/Ne in incongruent conditions compared to congruent conditions. On the other hand, if the four-choice flanker task proved too demanding in the incongruent condition then differentiation of ERN/Ne may also become evident for high conscientious individuals in this condition.
As with Experiment 1, certainty of responses was measured directly, with the inclusion of a response awareness question in the task following responses to stimuli. This was again also included to investigate the error awareness hypothesis of Pe (Endrass et al., 2005; Endrass et al., 2007; Nieuwenhuis et al., 2001), with larger mean Pe amplitudes predicted to be associated with error responses when
participants were aware compared to when they were not aware of their errors.
Method Participants
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age= 20.29), were recruited from first year psychology students at the University of Tasmania. Participant exclusion criteria were similar to that outlined in Experiment 1. Data from two participants were excluded because an insufficient number of error responses were made, leaving 19 participants with a mean age of 20.47 years whose data were included in analyses. Participants were grouped according to
conscientiousness scores the NEO PI-R (Costa & McCrae, 1992) as per Experiment 1 with group numbers totalling: low conscientiousness (n = 11), and high
conscientiousness (n = 8).
Apparatus and ERP Recording
The tasks were completed and data collected using the same software and equipment as that used in Experiment 1.
Stimuli
Participants completed the same arrowhead version of the flanker task (Eriksen & Eriksen, 1974) as that used in Experiment 1 except that in this instance, participants were required to respond in terms of four alternate choices. They were instructed to indicate, on a four button response pad, the direction and congruency of the centre arrowhead.
Procedure
The procedure for Experiment 2 followed that of Experiment 1.
Design and Analysis
The design and analyses used in Experiment 2 were the same as that used in Experiment 1. As with Experiment 1 the analysis of data associated with response awareness was confined to error (n = 9) and correct (n = 3) related activity associated with incongruent stimuli only since there were insufficient participants who were
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unaware of their responses in the congruent condition. There were also insufficient trials to match correct and incorrect trials in both aware and unaware conditions for each participant, so Response Type was considered a between subjects variable for this analysis. The between subjects variable Conscientiousness was also excluded from this analysis because there were not enough high conscientious participants to create high and low conscientious groups within this sample.
Results Behavioural Analyses
The three-way ANOVA conducted on reaction time data indicated that mean reaction time on error trials (M = 516.20 ms, SE = 24.39 ms) was not significantly different from that on correct trials (M = 527.94 ms, SE = 16.86 ms), F(1, 17) = 0.48, MSE = 5270, p = .49, ηp2 = .03. No other main effects or interactions reached significance.
Error rates ranged from 2% to 44% across participants with a mean error rate of 13.2%. The three-way ANOVA conducted on accuracy data revealed a significant main effect of Response Type, F(1, 17) = 148.75, MSE = 5196, p <.001, ηp2 = .90 and a significant main effect of Congruency, F(1, 17) = 5.57, MSE = 40, p = .03, ηp2
= .25 which were modified by a significant Response Type × Congruency
interaction, F(1, 17) = 13.36, MSE = 2583, p =.001, ηp2 = .44 (see Figure 15). As can
be seen in Figure 12, and confirmed by Tukey post hoc tests, there were significantly more correct responses to congruent stimuli compared to errors to congruent and incongruent stimuli (ps <.001), and significantly more correct responses to
incongruent stimuli than errors to both congruent and incongruent stimuli (ps <.001). While no further comparison reached significance (ps >.05), Figure 12 indicates that there were more correct responses to congruent stimuli than to incongruent stimuli,
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but more errors to incongruent compared to errors to congruent stimuli. No
significant main effects or interactions involving levels of conscientiousness reached significance. Error Correct Response Type -50 0 50 100 150 200 250 300 M ea n nu mbe r o f r es po nse s Congruent Incongruent
Figure 12. Mean number of error and correct responses to congruent and incongruent
stimuli (vertical bars denote 95% confidence intervals).
Grand Mean Averages
Perusal of grand mean averages confirmed that ERN/Ne and CRN was maximal at frontal, and fronto-central midline sites (see Figure 13). This is similar to the findings of other researchers (e.g., Falkenstein et al., 1991; Falkenstein et al., 2000; Gehring et al., 1993; Hajcak et al., 2004; Yeung et al., 2004) and the findings of Experiment 1. Choice of epoch from which mean amplitude for the ERN/Ne and CRN
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Figure 13. Grand mean averages for correct and error responses for high and low
conscientious participants in congruent (top panel) and incongruent (bottom panel) conditions.
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Early positive activity was also noted frontally, again with correct and error response-related activity showing clear amplitude differences. An early positive peak occurring approximately 120 ms post correct responses and a further peak at
approximately 200 ms was associated with error responses. Since these peaks displayed a longer latency than those elicited during the two-choice flanker task (Experiment 1) the choice of measurement window for the early correct response- related positivity, and the early error response-related positivity was different, 50 – 200 ms and 120 – 300 ms, respectively. The correct response-related positivity displayed a clear reduction in amplitude compared to the error response-related positivity.
Perusal of the grand mean averages revealed a slow going wave that increased in negativity as the activity became more parietal in presentation, with error related activity appearing to be more positive in amplitude than correct related activity. As with Experiment 1, the epoch chosen to measure this activity was 300 – 600 ms post response.
In both congruent and incongruent conditions an early negative deflection is apparent at frontal and fronto-central sites. In the congruent condition (Figure 13, top panel) there appears to be a marked difference between error and correct response- related activity in later slower going activity, with correct response activity being considerably more negative than error related activity. This is not the case in the incongruent condition (Figure 13, bottom panel) with little difference apparent in activity across most sites. However, at Pz in the incongruent condition, error and correct response activity associated with high conscientiousness appears more positive than error and correct response-related activity associated with low conscientiousness.
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Electrophysiological Analyses
A comparison of mean amplitude was completed for ERN/Ne and CRN, early Pe and Pc, and late Pe and Pc, in order to determine whether overall error and correct
response-related activity were significantly different. In each case error response- related related activity was significantly larger than correct response-related activity (ps <.05).
The four-way ANOVA conducted on ERN/Ne and CRN mean amplitude data showed a significant main effect of Response Type, F(1, 17) = 7.02, MSE = 11.11, p = .02, ηp2 = .29 which was modified by a Response Type × Sagittal Site interaction, F(1, 17) = 5.18, MSE = 0.47, p = .04, ηp2 = .24 (see Figure 14). Tukey post hoc tests confirmed that while there were no significant differences in mean amplitude across sagittal sites for error responses (ps >.05), error responses elicited significantly larger negativity than correct responses at both Fz (p <.001) and FCz (p <.001), and this difference was larger at FCz than at Fz.
Figure 14. ERN/Ne and CRN mean amplitude for correct and error responses at Fz
and FCz (vertical bars denote 0.95 confidence intervals).
Fz FCz Sagittal Site -6 -5 -4 -3 -2 -1 0 1 2 M ea n A m pli tu de ( µV ) Correct Error
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The four-way ANOVA conducted on early Pe and Pc mean amplitude data also revealed a significant main effect of Response Type, F(1, 17) = 10.96, MSE = 19.68, p < .004, ηp2 = .39 which was modified by a Response Type × Sagittal Site
interaction, F(1, 17) = 20.89, MSE = 1.42, p < .001, ηp2 = .55 (see Figure 15). Tukey
post hoc tests indicated that there was no significant difference in mean amplitude across Fz and FCz for correct responses (p <.05), however error responses elicited significantly larger positive activity at both Fz and FCz than correct responses (ps <.001) and error response activity showed a significantly larger positivity at FCz compared to Fz (p <.001). FZ FCz Sagittal Site -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 M ea n Am pli tu de ( µV ) Correct Error
Figure 15. Early Pe and Pc mean amplitude for correct and error responses at Fz and
FCz (vertical bars denote 0.95 confidence intervals).
The four-way ANOVA conducted on late Pe and Pc amplitude data revealed a significant main effect of Response Type, F(1, 17) = 34.61, MSE = 33.03, p < .001, ηp2 = .67, which was modified by a significant Response Type × Congruency
interaction, F(1, 17) = 9.41, MSE = 43.97, p = .007, ηp2 = .36 (see Figure 16).Tukey post hoc tests indicated that mean amplitude was significantly more positive for error
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responses in the congruent condition compared to correct responses in the congruent and incongruent conditions (ps<.01). Error responses also elicited significantly larger mean positivity in the incongruent condition compared to correct responses in the congruent condition (p <.05) but were not significantly different to correct responses to congruent stimuli (p >.05). This four-way analysis also showed that overall mean amplitude was significantly more positive at Pz (M = -6.86, SE = 1.29) than at FPz (M = -8.08, SE = 1.44), F(1, 17) = 5.03, MSE = 11.09, p = .04, ηp2 = .23. No other main effects or interactions reached significance.
Congruent Incongruent Congruency -20 -15 -10 -5 0 5 10 Mea n Ampl itud e (µV ) Correct Error
Figure 16. Late Pe and Pc mean amplitude to congruent and incongruent stimuli
(vertical bars denote 0.95 confidence intervals).
Separate analyses of each response related component (ERN/Ne, CRN and early and late Pe and Pc) were undertaken and are presented below.
ERN/Ne
The three-way ANOVA conducted on ERN/Ne mean amplitude data showed no significant main effects or interactions.
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CRN
The three-way ANOVA conducted on CRN mean amplitude data revealed a significant Congruency × Conscientiousness interaction, F(1, 17)= 4.56, MSE = 6.44, p < .048, ηp2 = .21 (see Figure 17). Whereas post hoc tests indicated that no
individual comparison reached significance (ps>.05), Figure 17 shows that high conscientious participants to produced larger negative mean amplitudes in the incongruent condition compared to the congruent condition while there was little difference according to congruency for low conscientious participants. Whereas, incongruent stimuli elicited similar CRN mean amplitude irrespective of
conscientiousness, congruent stimuli elicited larger mean CRN amplitude for low compared to high conscientious participants. No further main effects or interactions reached significance. Low High Conscientiousness -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 M ea n A mp lit ud e (µV ) Congruent Incongruent
Figure 17. CRN mean amplitude to congruent and incongruent stimuli for low and
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Early Pe
The three-way ANOVA conducted on early Pe mean amplitude data revealed that overall mean amplitude was significantly more positive at FCz (M = 3.16, SE = 1.38) than at Fz (M = 1.08, SE = 1.03), F(1, 17) = 9.73, MSE = 8.05, p = .006, ηp2 =
.36. A trend approaching significance for a Congruency × Sagittal Site interaction was also evident, F(1, 17) = 3.79, MSE = 1.92, p = .07, ηp2 = .18 (see Figure 18). As
can be seen in Figure 18 and confirmed by Tukey post hoc tests, overall early Pe mean amplitude elicited by both congruent and incongruent stimuli was significantly more positive at FCz compared to Fz (ps <.001) and congruent stimuli elicited larger mean positivity than incongruent stimuli at FCz (p <.05) with no significant
difference at Fz (p >.05) Fz FCz Sagittal Site -4 -2 0 2 4 6 8 10 M ea n A m pl itude (µV ) Congruent Incongruent
Figure 18. Early Pe mean amplitude to congruent and incongruent stimuli at Fz and
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Early Pc
The three-way ANOVA conducted on early Pc mean amplitude data revealed a significant Congruency × Conscientiousness interaction, F(1, 17) = 4.83, MSE = 11.18, p = .04, ηp2 = .22 (see Figure 19). Tukey post hoc tests failed to reveal any
statistically significant differences between individual means (ps >.05), however Figure 19 shows that mean amplitude to incongruent stimuli was more positive for low conscientious than high conscientious participants and, in the congruent condition, high conscientious participants demonstrated more positive activity than low conscientious participants. Low conscientious participants demonstrated larger mean positivity in the incongruent condition than the congruent condition and conversely high conscientious participants displayed larger positivity in the congruent compared to the incongruent condition. No other main effects or interactions reached significance.
Low High Conscientiousness -8 -6 -4 -2 0 2 4 6 M ea n A m pl itu de (µV ) Congruent Incongruent
Figure 19. EarlyPc mean amplitude to congruent and incongruent stimuli for low
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Late Pe
The three-way ANOVA conducted on late Pe mean amplitude data showed that mean amplitude tended to be more positive at Pz (M = -4.01, SE = 1.50) compared to CPz (M = -5.38, SE = 1.64), F(1, 17) = 4.06, MSE = 8.54, p = .06, ηp2 = .19. No
other main effects or interactions reached significance.
Late Pc
The three-way ANOVA conducted on late Pc mean amplitude data indicated that incongruent stimuli(M = -8.15, SE = 1.17) elicited significantly larger mean positive activity than congruent stimuli (M = -12.34, SE = 1.56), F(1, 17) = 20.20, MSE = 16.11. p < .001, ηp2 = .54. A trend approaching significance was also evident for a main effect of Sagittal Site, F(1, 17) = 4.07, MSE = 5.35, p = .06, ηp2 = .19.
Mean amplitude tended to be more positive at Pz (M = -9.71, SE = 1.22) compared to CPz (M = -10.79, SE = 1.42).
Response Awareness
The analyses of data associated with response awareness are presented below. A separate analysis of data associated with incongruent stimuli only was conducted because there were insufficient responses where participants were unaware of their responses to congruent stimuli. The examination of the impact of conscientiousness within this analysis was also not possible because there were not enough high conscientious participants to create high and low conscientious groups within this sample.
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Behavioural analyses
The two-way ANOVA conducted on reaction time data within aware and unaware conditions showed that overall, reaction time to errors (M = 629.72, SE = 86.31) was not significantly different to correct responses (M = 771.90, SE =
149.49), F(1, 10) = 0.68, MSE = 134094, p = .43, ηp2 = .06. However, reaction time to stimuli when participants were aware of their response type was significantly faster (M = 582.78, SE = 118.56) than when participants were not aware of their response type (M = 818.84, SE = 76.15), F(1, 10) = 5.62, MSE = 44617, p = .04, ηp2
= .36. No other main effects or interactions reach significance.
The two-way ANOVA conducted on accuracy data revealed significant main effects of Response Type, F(1, 10) = 36.09, MSE = 506.31, p < .001, ηp2 = .78 and
Response Awareness, F(1, 10) = 72.31, MSE = 302.51, p < .001, ηp2 = .88 which were modified by a significant Response Type × Response Awareness interaction, F(1, 10) = 59.56, MSE = 302.51, p < .001, ηp2 = .86 (see Figure 20). As can be seen
in Figure 20, and confirmed by Tukey post hoc tests, there were significantly more aware correct responses than unaware correct and error responses (ps <.001) and significantly more aware correct responses than aware error responses (p <.001). There were no significant differences in the number of aware and unaware error responses and also no significant differences in the number of aware error and correct responses (ps >.05).
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Figure 20. Mean number of aware and unaware error and correct responses (vertical
bars denote 0.95 confidence intervals).
Grand mean averages
Grand mean average waveforms were obtained for correct and incorrect responses in the incongruent condition only, and these were broken down by levels of participant awareness to their response (aware/unaware). Figure 21 shows, as with the overall grand means, a clear negative deflection occurring early post response (approximately 50 ms). This is followed by an early positive deflection that appears as a larger positive peak for correct responses where participants were aware with little difference in appearance for activity associated with other response types. A later slow going wave that, for the most part is negative, is also evident. This late activity follows a similar pattern to that of the earlier activity.
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Figure 21. Grand mean average waveforms for error and correct responses to
incongruent stimuli when participants were aware and unaware of their responses.
Electrophysiological analyses
The three-way ANOVA conducted on ERN/Ne and CRN mean amplitude data revealed significant main effects of Response Type, F(1,10) = 7.77, MSE = 41.69, p = .02,ηp2 = .44,which was modified by a Response Awareness × Response Type
interaction trend, F(1, 10) = 4.30, MSE = 27.52, p = .06, ηp2 = .46 (see Figure 22). Tukey post hoc tests revealed that when participants were aware of both error and correct responses, they demonstrated a significantly larger mean negativity than when they were not aware of correct responses only (ps< .05). While no other
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comparisons reached significance (ps >.05), Figure 22 indicates that ERN/Ne and CRN mean amplitude are more differentiated in the unaware condition compared to the aware condition where there is little mean amplitude difference. Overall, mean amplitude tended to be more negative at Fz (M = 0.21, SE = 1.16) than at FCz (M = .92, SE = 1.00), F(1, 10) = 4.53, MSE = 1.01, p = .06, ηp2 = .31. No other main effects or interactions reach significance.
Aware Unaware Awareness -10 -5 0 5 10 15 20 25 Me an Am pli tu de (µV ) Error Correct
Figure 22. ERN/Ne and CRN mean amplitude in aware and unaware conditions
(vertical bars denote 0.95 confidence intervals).
The three-way ANOVA conducted on early Pe and Pc mean amplitude data revealed significant main effects of Response Type, F(1, 10) = 6.32, MSE = 39.72, p