In this study, the investigators will try to advance our understanding of the effects of mindset inductions for coping with motivational interventions in hazardously drinking students. In an earlier study, the investigators found an interactive effect of implemental mindsets with motivational interviewing on actual risk behavior but not risk perception. The investigators will target potential underlying processes (e.g., resistance to change, commitment), as well as compensation and generalization effects by including the assessment of consumption of alternative risky substances.

The investigators target consumption-related risks and address interactions between mindsets and motivational interviewing. Combining a mindset induction with a Screening and Brief Intervention tool in which the risk status of the individual was assessed, and the interventionist provided feedback, conducted a decisional balance exercise, and used techniques from motivational interviewing, the investigators found effects on risk taking but not risk perception. Neither general risk taking in the subscales of the Domain-Specific Risk-Taking Scale nor alcohol-related risk perception in a specific questionnaire was significantly affected by our manipulations. Still, participants in an implemental mindset managed to reduce their monthly alcohol consumption on average by about 7 to 8 standard units (equates to roughly five glasses of wine) while participants in a deliberative mindset actually increased their alcohol consumption by a similar amount. The investigators want to replicate the earlier findings while simultaneously enriching our research design with a) a control condition to test whether the implemental mindset decreased drinking, the deliberative mindset increased drinking, or both happened concurrently, b) test for compensation and/or generalization effects by including the assessment of another substance, namely Tetrahydrocannabinol (THC), to see if participants may compensate their reduced alcohol consumption by enhanced consumption of substitutes or if they can self-regulate the consumption of both, and c) to test whether the decisional balance element of the ASSIST-linked brief intervention is driving the differences between mindsets.

Design. The experiment follows a 3 between (Mindset: deliberative vs. implemental vs. control) x 2 between (Brief Intervention: short-form \[without decisional balance\] vs. long-form \[with decisional balance\]) factorial experimental design. Main dependent variables are the Timeline Followback (TLFB)-based self-reports of substance consumption, alcohol-related risk perception, and moderating/mediating variables related to the brief intervention itself (e.g., commitment, openness, resistance to change).

Hypotheses. In the control condition, the investigators expect to see similar results to earlier work on the effectiveness of motivational interviewing in reducing alcohol. In the deliberative and implemental mindset condition, however, the investigators expect to see a more nuanced picture, similar to our previous experiment. To better disentangle this, the investigators will include specific resistance and commitment ratings during the brief intervention session after the personalized feedback and after the decisional balance exercise that follows, the two subsequent parts of the brief intervention. The investigators hypothesize that deliberative mindset participants would show low resistance during personalized feedback but high resistance after the decisional balance exercise, and the opposite pattern for commitment. Implemental mindset participants, on the other hand, are expected to show the opposite pattern for resistance and commitment after the decisional balance exercise; it remains unclear, however, how this group will respond to the personalized feedback procedure. Furthermore, the investigators want to explore whether the reduction/increase in consumption is specific to the one substance that is addressed in the brief intervention or whether regulation of consumption also affects alternative substances in terms of generalization or compensation. The investigators use THC as a model substitute because of the high prevalence (e.g., 64% in an earlier study.

Procedure. The procedure will be very similar to our previous experiment. Participants will first be screened using an online questionnaire, and only at-risk drinking individuals (as indicated by the AUDIT) will be invited to the first lab session. Participants then receive the mindset manipulation. The investigators will ensure that the interventionist will be blind to the participants' mindset condition and that the mindset manipulation will involve a problem or project that is not related to substance use. Thereafter, the interventionist will assess the individuals' risk behavior regarding a set of substances (using the WHO's ASSIST manual) in an interview setting and will give the participants individualized feedback on their consumption (i.e., the first phase of the brief intervention). The interventionist will then conduct a motivational interview about the participants' personal alcohol consumption (i.e., the second phase of the brief intervention). Afterward, the interventionist will rate how resistant the participants behaved during the intervention. Thereafter participants report their alcohol and THC consumption for the last four weeks using the TLFB and fill out a series of questionnaires. Four weeks later, participants are back for a second lab session in which they again fill out the same battery of questionnaires to assess their (alcohol-specific) risk perception and to assess their alcohol and THC consumption, again using the TLFB.