Table 3.
Means and Pairwise Comparisons for Neurocognitive Measures
| |
Mean (SD) |
|||
|---|---|---|---|---|
| Measure | Placebo | Low | Medium | High |
| Stroop–Interference1 | 55.24 (4.81)a | 54.24 (4.44)a | 55.52 (4.75)a | 56.05 (4.02)a |
| Combined | 55.23 (5.25) | 53.54 (3.33) | 54.38 (3.25) | 55.62 (4.86) |
| Inattentive | 55.25 (4.33) | 55.38 (5.90) | 57.38 (6.32) | 56.75 (2.19) |
| CPT–Index Score2 | 9.41 (4.74)a | 8.39 (6.03)a | 5.64 (6.21)b | 5.17 (6.33)b |
| Combined | 10.24 (5.61) | 8.95 (6.86) | 5.60 (5.99) | 6.56 (6.75) |
| Inattentive | 8.81 (2.54) | 9.13 (5.11) | 5.50 (6.65) | 4.11 (5.76) |
| CPT–Hit RT | 51.15 (17.33)a | 55.70 (12.75)a | 55.51 (10.87)a | 57.85 (12.88)b |
| Combined | 51.44 (19.94) | 56.15 (14.27) | 55.94 (12.17) | 59.66 (13.84) |
| Inattentive | 50.74 (13.81) | 55.05 (10.97) | 54.90 (9.35) | 55.24 (11.64) |
| CPT–Hit RT SE | 59.96 (14.15)a | 52.24 (13.40)b | 49.33 (14.13)b | 44.64 (13.40)c |
| Combined | 61.84 (15.40) | 51.32 (14.39) | 49.43 (16.85) | 42.35 (14.71) |
| Inattentive | 57.23 (12.48) | 53.57 (12.56) | 49.19 (9.89) | 47.93 (11.23) |
| CPT–Omission3 | 81.56 (17.85)a | 71.86 (29.48)a,b | 64.46 (32.91)b,c | 58.60 (25.28)c |
| Combined | 82.74 (13.29) | 67.01 (32.71) | 59.26 (33.47) | 55.67 (28.82) |
| Inattentive | 79.85 (23.80) | 78.87 (24.13) | 71.97 (32.50) | 61.39 (20.42) |
| CPT–Commission | 55.28 (10.69)a | 53.95 (11.03)a,b | 51.80 (10.28)b | 50.49 (12.92)b |
| Combined | 55.52 (9.88) | 54.79 (11.08) | 53.41 (6.82) | 49.99 (11.18) |
| Inattentive | 54.93 (12.38) | 52.74 (11.51) | 49.48 (14.05) | 51.36 (15.78) |
| CPT–Attentiveness (d') | 61.72 (10.96)a | 57.84 (9.20)b | 54.15 (8.77)c | 53.33 (11.59)b,c |
| Combined | 60.69 (8.43) | 57.40 (8.92) | 54.60 (4.95) | 52.05 (8.02) |
| Inattentive | 63.21 (14.31) | 58.48 (10.10) | 53.49 (12.83) | 55.18 (15.80) |
| CPT–Beta | 77.59 (22.42)a | 69.32 (21.71)a | 60.05 (17.86)b | 57.59 (16.60)b,c |
| Combined | 75.78 (21.64) | 66.03 (21.67) | 57.41 (17.98) | 55.10 (15.04) |
| Inattentive | 80.20 (24.59) | 74.07 (22.14) | 63.87 (18.03) | 61.18 (18.96) |
| CPT–RT ISI Change | 68.32 (15.36)a | 58.29 (14.96)b | 57.11 (13.33)b | 57.12 (10.63)b |
| Combined | 71.99 (17.70) | 56.64 (14.38) | 56.81 (14.82) | 56.67 (12.45) |
| Inattentive | 63.02 (9.81) | 60.69 (16.34) | 57.54 (11.68) | 57.76 (7.94) |
Results in boldface are for the total sample. Standard deviations are indicated in parentheses. Means with nonoverlapping letters are significantly different (p < 0.05). With the exceptions noted below, all scores are T-scores. For all CPT measures, a higher score indicates worse performance.
1
For the Stroop, a higher T-score indicates better performance.
2
The CPT–Index score is an absolute score.
3
CPT-Omission errors are expressed as percentiles in the normative population.
Abbreviations: SD = Standard deviation; CPT = Continuous Performance Test; RT = reaction time; SE = standard error; ISI = interstimulus interval.