Expecting to drink alcohol can change some ratings of hypothetical monetary gains and losses. In a randomized, three-group experiment involving 75 university students, both wine and an alcohol-cued placebo changed selected valuation ratings compared with an openly nonalcoholic drink. The study did not demonstrate that alcohol increased every measure of risk perception, and it cannot establish an impairment threshold at a measured blood alcohol concentration of 0.02%: the participants’ blood and breath alcohol concentrations were not measured during the main experiment.
The useful forensic question is therefore how expectations and study design affect the interpretation of a behavioral result. A calculated alcohol target, a rating on paper and an observed driving deficit represent different kinds of evidence.
What did the 75 participants receive?
Tsurugizawa and colleagues randomly assigned healthy, right-handed, nonsmoking university students to three separate groups. The wine group contained 23 participants: 14 men and nine women. The placebo group contained 23: 15 men and eight women. The control group contained 29: 18 men and 11 women. Participants reported drinking less than once per week. This was a comparison between groups, rather than a crossover in which every person received all three beverages.
The alcohol group drank red wine containing 14% alcohol. Individual beverage volumes were calculated from body weight and sex using a Widmark formula, aiming at an estimated BAC of 0.02 g/100 mL, equivalent to 0.02 g/dL. The paper reports a mean beverage volume of 89.3 ± 3.7 mL. That volume is not a dose in grams of ethanol and must not be relabeled as one.
The placebo and control drinks were alcohol-free, wine-flavored grape juice. An opened, labeled wine bottle supplied an alcohol cue for the wine and placebo groups, whose participants were not told the actual beverage identity. The control participants were told that their drink contained no alcohol. The authors report that the cued groups believed their beverage was wine.
Why was 0.02% a target rather than a measured result?
Breath testing was conducted in a preliminary study, but not in the main volunteers. The investigators wanted to avoid revealing the placebo condition through a breath-test result. They acknowledge that this decision leaves uncertainty about whether the intended alcohol concentration was actually achieved.
No participant-level whole-blood, serum, plasma, urine or breath ethanol series was provided for the main experiment. Consequently, the paper cannot connect a particular measured concentration to a particular participant’s response. Nor can it distinguish individual absorption and elimination profiles. A statement such as “the experiment proved impairment at 0.02% BAC” would turn a dosing assumption into an analytical measurement.
What was tested about 45 minutes after drinking?
Participants were instructed not to eat during the hour before the experiment. They consumed the beverage over approximately ten minutes before an MRI session lasting around 45 minutes, then completed paper-and-pencil tasks within about ten minutes. The published analysis addressed those behavioral tasks independently of the MRI experiments; its results are not reported brain-imaging findings.
For hypothetical gains and losses of 100,000 yen, participants rated subjective likelihood and waiting time at seven stated probabilities, from 0.05 to 0.95. They marked a 180-mm scale. A separate valuation task asked about happiness from gains and aversion to losses for ten hypothetical amounts ranging from 10,000 to 100,000 yen. These were ratings of imagined outcomes, not actual monetary losses, risky driving or observed harmful conduct.
Which findings were significant, and which were not?
Compared with the informed control, the wine group showed lower subjective valuation ratings for amounts from 10,000 through 50,000 yen. The alcohol-cued placebo also produced lower ratings for the two smallest amounts, 10,000 and 20,000 yen. Thus, a beverage-associated change in selected ratings did not require the active wine condition.
For the likelihood and waiting-time measures, the reported tables showed no significant beverage main effects at the tested probabilities. There were differences associated with gain versus loss and, for some likelihood comparisons, sex. Those differences should not be described as evidence that alcohol made women or men more impaired.
The investigators also fitted Stevens’ power functions to the ratings. Nonlinear models fitted the task data better than linear models. For the valuation exponent, placebo differed significantly from control, while wine did not show that significant contrast. This pattern does not, by itself, prove that placebo had a larger effect than wine. A significant result in one comparison and a nonsignificant result in another is not a direct statistical test of the difference between those effects.
What limits the interpretation?
The six sex-by-beverage subgroups were small and unequal, with eight to 18 participants each. The young, infrequently drinking university sample does not represent all drivers, patients or habitual drinkers. The study examined several outcomes, probabilities, monetary amounts and model parameters; its selective findings need to retain their particular endpoints rather than becoming a single claim about overall judgment.
The authors also acknowledge that using the same 180-mm scale does not establish that gain happiness and loss aversion are psychologically equivalent quantities. Hypothetical money may not elicit the same response as real consequences. The uncertain achieved ethanol concentrations further restrict any dose-response inference.
How should the study inform an expert opinion?
The experiment supports considering expectancy when interpreting subjective monetary valuation after a purported alcoholic drink. It does not establish a safe alcohol concentration, diagnose an individual’s impairment, quantify crash risk, determine legal capacity or explain why a disputed act occurred. Those conclusions would require evidence connecting the relevant person, timing, exposure and functional task.
Related research on this site examines alcohol-cued placebo effects on lightheadedness and motivation. That is a different endpoint from monetary valuation. Neither type of subjective response substitutes for a measured ethanol concentration or a validated assessment of the function at issue.
Primary study
Tsurugizawa T, Tokuda S, Harada T, Takahashi T, Sadato N. Pharmacological and Expectancy Effects of a Low Amount of Alcohol Drinking on Outcome Valuation and Risk Perception in Males and Females. PLoS ONE. 2016;11(4):e0154083. doi:10.1371/journal.pone.0154083.