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Supplementary Material and Methods
Supplementary analyses were performed to control for potential mediating factors and confirm
the validity of the manipulations: (a) ANOVA of accuracy rates for Go and Stop response to
Alcohol and Neutral words; (b) ANCOVA of Go RT and SSRT to Alcohol and Neutral words
controlling for response accuracy to these stimuli; (c) ANOVA of heart rate reactivity during test
sessions; and (d) ANOVA of drink strength ratings for the P-Beer Group.
Response Accuracy to Alcohol and Neutral words
Table 2 shows that the ANOVA of accuracy scores for Alcohol and Neutral words yielded two
four-way interactions. The first of these involved Drink Group. Go accuracy rates did not differ
significantly as a function of any factor, although accuracy was somewhat poorer for Alcohol
than Neutral words. In contrast, Stop accuracy was generally better for Alcohol than Neutral
words. This bias was significant in 3 of 4 conditions in the Alcohol group, which would appear
to account for the interaction involving Drink Group. The second four-way interaction involved
Treatment Condition. Table S1 (below) shows that, in the Alcohol group, the greatest difference
(Alcohol > Neutral) in Stop accuracy, 11.2%, occurred in the Separate/Stress Absent Condition
(i.e., Alcohol alone), whereas in the P-Beer group, the greatest difference was in the
Separate/Soft Drink Condition (i.e., Stress alone).
Go RT and SSRT to Alcohol and Neutral Words Controlling for Response Accuracy
To ensure that variation in accuracy rates to Alcohol and Neutral words did not mediate effects
observed in the ANOVA of RT to these words, Go RT and SSRT for these words were re-
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analyzed by ANCOVA, controlling for Go and Stop accuracy to words.
In line with the original analysis, the ANCOVA yielded a Stress x Word Type interaction, F (1,
33) = 6.27, p = .017. However, as indicated by the three-way interaction in Table 2, this effect
was moderated by Response Type (p = .019), in contrast to the original ANOVA. The covariateadjusted means are shown below the x-axis in Figure 2. Inspection of these scores reveals that
the adjusted means were very close to the raw means. Therefore, the emergence of the significant
three-way interaction in the ANCOVA would appear to reflect increased statistical power when
accuracy-related variance was extracted. As a result, the Word Type effect (Alcohol vs. Neutral)
for Go RT in the No-Stress condition achieved significance (p < .01), whereas the Word Type
effect for SSRT in the No-Stress condition remained non-significant, p > .10. Notably, the Word
Type effect for Go RT remained significantly greater in the presence of stress (p < .05) than in
the absence of stress. Thus, when variation in response accuracy was controlled, Go RT was
slower to Alcohol vs. Neutral words when stress was present or absent, and stress was still
associated with greater impairment in Go RT and SSRT to Alcohol vs. Neutral words.
Table 2 also shows that the ANCOVA yielded a Stress x Treatment Condition interaction that
was not moderated by other factors, p’s > .18. The interaction reflected the same pattern of
significant simple effects as in the original ANOVA, and the adjusted RT scores differed from
their corresponding raw RT scores by < 5 ms.
Physiological Effects
Table 2 shows that the ANOVA of Heart Rate (HR) scores yielded a significant Stress x Time x
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Drink Group interaction. HR declined from pre-test baseline (arrival) to pre-noise task in both
groups. In the Alcohol Group, HR increased from pre- to post-noise and declined from postnoise to post-drink in the active stress condition, 69.1  71.4  64.6 beats/min, and also in the
no-stress control condition, 66.1  67.8  65.4 beats/min. In contrast, in the P-Beer Group, HR
declined in the active stress condition, 67.1  65.0  65.3 beats/min, as well as in the no-stress
control condition, 65.6  62.8 63.4 beats/min. The different directional response to the noise
task in the two Drink Groups, and different degree of recovery from post-noise to post-drink
under the active stressor vs. no-stress control account for the three-way interaction. However, the
lack of moderating effect of Treatment Condition, p > .41, suggests that these effects were not
due to the Test Drink manipulation. Overall, the results indicate that heart rate is not a very
sensitive physiological index of stress in this paradigm, although assessment during rather than
after the noise task may have improved the opportunity to detect the stress effect.
Drink Strength Ratings
The ANOVA of Drink Strength ratings in the P-Beer Group yielded no significant effects of
experimental factors. However, the Intercept (Grand Mean) differed significantly from 0, mean
(SD) = 2.3 (1.5), p < .001 (Table 2). Thus, P-Beer subjects estimated the strength of their dose as
comparable to ~2 standard bottles of beer, supporting the credibility of the P-Beer manipulation.
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Table S1. Accuracy (%) for Go and Stop responses to Alcohol and Neutral words in 4
experimental conditions: Combined (Stress + Test Drink; No Stress + Soft Drink) or Separate
(Stress + Soft Drink; No Stress + Test Drink) in male problem drinkers who received Alcohol (n
= 18) or Placebo Beer (P-Beer; n = 20) as their Test Drink. Soft drink served as the control
beverage for all subjects.
Drink Group Treatment Condition
Alcohol
Stress
Word Type
Response Accuracy
Go
Stop
Combined; Drink = Alcohol
Present
Alcohol
Neutral
90.3
92.5
42.6
44.9
Separate; Drink = Soft Drink
Present
Alcohol
Neutral
94.3
95.7
47.7*
39.7
Combined: Drink = Soft Drink
Absent
Alcohol
Neutral
93.4
94.9
47.8*
38.8
Separate: Drink = Alcohol
Absent
Alcohol
Neutral
93.4
96.0
52.1*
40.9
Combined; Drink = P-Beer
Present
Alcohol
Neutral
92.7
93.3
47.1
48.4
Separate; Drink = Soft Drink
Present
Alcohol
Neutral
88.2
90.8
52.5*
43.6
Combined: Drink = Soft Drink
Absent
Alcohol
Neutral
88.6
89.6
51.8
46.8
Separate: Drink = P-Beer
Absent
Alcohol
Neutral
93.0
91.7
51.5
48.6
Mean Alcohol
91.7
49.1*
Mean Neutral
93.1
44.0
Grand Mean
* Simple effect of Word Type, p < .05.
92.4
46.6
P-Beer