This section reports on associations between measures of sustained attention (Section 4.1.1.) and an ADHD diagnosis as well as on associations between measures of behavioral inhibition and an ADHD diagnosis (Section 4.1.2.). All analyses control for age but not for ADHD medication, as medication did not improve task performance (see Table C1 in Appendix C). However, the prescription of medication is related to the diagnosis of ADHD. Hence, as medication did not improve task performance, controlling for medication would control for ADHD or ADHD symptoms rather than for treatment effects on task performance.
4.1.1. Associations between Sustained Attention and an ADHD Diagnosis
Descriptive statistics for all measures of sustained attention are displayed in Table 6. However, to increase reliability and to prevent alpha error accumulation only the sustained attention deficit factor score of omission errors and RTVs (see Section 3.5.2.) was used to test for a deficit in sustained attention in children with ADHD. An analysis of covariance (ANCOVA) with the sustained attention deficit factor score as a dependent variable, ADHD diagnosis as a between factor, and age as a centered covariate yielded a significant effect for ADHD diagnosis, F(1, 67) = 8.15, p = .006, ηp2 = .108, but no effect for age, demonstrating
that children with an ADHD diagnosis had higher scores on the sustained attention deficit factor (MADHD = 0.39, MControl = -0.26)2.
4.1.2. Associations between Behavioral Inhibition and an ADHD Diagnosis
Descriptive statistics for the measures of behavioral inhibition are displayed in Table 6. Table 6 also depicts descriptive statistics for measures of conflict monitoring, as deficits in behavioral inhibition might be partly due to deficits in conflict-monitoring (see Section 2.1.1.). Analyses are presented separately for the Go/No-Go task and the Flanker task.
Go/No-Go. To analyze whether children with an ADHD diagnosis committed more
inhibition errors than unaffected control children (MADHD = 6.18%, MControl = 5.68%, see Table 6), an ANCOVA was calculated with the inhibition error rate as dependent variable, ADHD diagnosis as a between factor and age as a centered covariate. No significant effects for age or ADHD diagnosis were found.
Flanker. To simultaneously investigate deficits in behavioral inhibition and conflict-
monitoring in children with ADHD, response times and error rates were separately entered into a 2 x 2 x 2 mixed within- and between-subjects ANCOVA with the within factor Flanker congruency (congruent vs. incongruent), the within factor Flanker congruency in the preceding trial (congruent vs. incongruent), the between factor diagnosis (ADHD vs. control), and age as a centered covariate.
For response times, significant main effects were observed for congruency, F(1, 78) = 36.29, p < .001, ηp2 = .318, and age, F(1, 78) = 16.11, p < .001, ηp2 = .171, indicating slower response times for incongruent trials than for congruent trials (502 ms vs. 476 ms, congruency effect = 26 ms) and for younger children. In addition, a significant three-way interaction of congruency, congruency in the preceding trial, and diagnosis, F(1, 78) = 4.01, p = .049, ηp2 = .049, indicated a reduced sequential congruency effect for children diagnosed with ADHD (difference between congruency effects if the preceding trial was congruent or incongruent was -12 ms) as compared to unaffected children (difference between congruency effects if the preceding trial was congruent or incongruent was 8 ms; see Figure 5) . No other main effects or interactions reached significance.
2 A multivariate analysis of variance (MANCOVA) with all sustained attention variables from Table 6 as dependent variables and ADHD and age as predictors yielded a significant overall effect for ADHD diagnosis, F(9, 76) = 3.73, p = .001, ηp2 = .307. For additional results regarding each single sustained attention measure, see Table C2 in Appendix C.
Table 6
Mean Performances (Standard Deviations in Parentheses) in the Cognitive and Behavioral Tasks for Children With ADHD and Control Children
Measures Control ADHD
Sustained Attention CPT OE, % 2.85 (4.72) 4.31 (5.00) Go/No-Go OE, % 3.54 (5.41) 6.39 (7.19) Flanker OE, % 5.45 (9.24) 7.87 (9.61) CPT OE ≥ 2, n 0.54 (1.25) 1.67 (2.88) Go/No-Go OE ≥ 2, n 1.23 (2.61) 3.06 (4.09) Flanker OE ≥ 2, n 2.06 (4.55) 3.76 (5.81) CPT RTV 0.34 (0.11) 0.41 (0.16) Go/No-Go RTV 0.26 (0.07) 0.33 (0.10) Flanker RTV 0.36 (0.17) 0.46 (0.19) Factor score -0.26 (0.78) 0.39 (1.25) Behavioral Inhibition Go/No-Go IE, % 5.68 (3.30) 6.18 (3.64) Flanker IFE, % 16.62 (12.01) 12.82 (10.95) Conflict Monitoring, Flanker PCS, ms 5.70 (18.33) 0.74 (29.29) Flanker PCE, % -2.21 (5.60) -0.48 (4.94) Flanker SCRT, ms 11.84 (42.51) -12.10 (59.28) Flanker SCE, % 6.98 (7.86) 6.41 (10.81) Risky Decision-Making GDT risky decision, n 6.96 (4.84) 10.43 (4.58) CCT, n cards 4.40 (1.13) 4.65 (1.10) NST, n dices 36.02 (12.62) 37.83 (13.73)
Note. IE = inhibition errors; IFE = interference for errors; OE = omission errors; OE ≥ 2 = at
least two omission errors in a row; PCE = post-conflict errors; PCS = post-conflict slowing; RTV = response time variability; SCE = sequential congruency effect for errors; SCRT = sequential congruency effect for response times.
For error rates significant main effects were observed for congruency, F(1, 78) = 125.10, p < .001, ηp2 = .616, and congruency in the preceding trial, F(1, 78) = 5.45,
p = .022, ηp2 = .065, indicating higher error rates for incongruent trials as compared to
congruent trials in general (37.65% vs. 22.58%, congruency effect = 15.07 percentage points) as well as lower error rates after incongruent trials as after congruent trials (30.89% vs. 29.34%, post-conflict error rate effect = 1.51 percentage points). A significant interaction between congruency and congruency in the preceding trial, F(1, 78) = 40.64, p < .001, ηp2 = .343, revealed a sequential congruency effect (difference in congruency effects if the preceding trial was congruent and if the preceding trial was incongruent was 6.81 percentage points). The marginally significant three-way interaction of congruency, congruency in the preceding trial, and age F(1, 78) = 2.82, p = .097, ηp2 = .035, indicated that this sequential congruency effect was reduced for younger children. No other main effects or interactions reached significance.
Figure 5. Flanker Effects for Response Times. Mean response times for congruent and
incongruent trials as a function of congruency in the preceding trial for control children and children with ADHD. While control children showed the typical sequential congruency effect as indicated by a reduced Flanker congruency effect after incongruent trials (left panel), no such an effect was found for children with ADHD. Effects are shown for a centered age value of agecent = 0.09 years.
4.2. Research Aim 2 – Associations between Risky Decision-Making and an ADHD