The Role of Source Credibility in the Validation of Information Depends on the Degree of (Im-)Plausibility

Scientific facts improve cannabis perception and public opinion: results from Sinaloa, México

Cannabis, the most prevalent drug in Latin America, has long been associated with the state of Sinaloa, Mexico, known for its cultivation and distribution. Despite increasing global acceptance, cannabis use remains stigmatized in Mexican society, driven by perceptions of it as a highly psychoactive and addictive substance lacking medicinal or industrial value. This study investigates the impact of scientific information on societal perceptions of cannabis in Sinaloa. A large convenience sample of 3162 individuals from Sinaloa participated in this research, responding to a questionnaire on cannabis consumption and attitudes. Participants were then subjected to an intervention consisting of an informative briefing based on the documents "Using Evidence to Talk About Cannabis" and "State of the Evidence: cannabis use and regulation" by the International Centre for Science in Drug Policy. After the intervention, participants' attitudes were immediately reevaluated through the same questionnaire, allowing for a comparison of pre- and post-intervention responses. The results indicate that the intervention (providing scientific information) significantly influenced attitudes toward cannabis, with education and age playing prominent roles in its effectiveness. Notably, the intervention fostered more positive or more neutral attitudes, potentially reducing stigma and promoting a better-informed perspective on cannabis. This study highlights the pivotal role of evidence in shaping informed citizens' views, while underscoring the importance of countering misinformation for societal progress. These findings have significant implications for forthcoming cannabis policy modifications in Mexico, emphasizing the necessity of engaging knowledgeable individuals in policy decisions to address the violence and inequalities associated with the illicit drug trade, particularly in Sinaloa.

The differential effects of a governmental debunking campaign concerning COVID-19 vaccination misinformation

BACKGROUND

Throughout the ongoing COVID-19 pandemic debunking misinformation has been one of the most employed strategies used to address vaccine hesitancy. We investigated whether - and for whom - debunking is effective or even counterproductive in decreasing misinformation belief and vaccination hesitancy.

METHOD

We conducted a randomized controlled trial (N = 588) utilizing a real-world debunking campaign from the German Ministry of Health. We considered the condition (debunking vs. control) as between-subjects factor, assessed misinformation belief (pretest vs. posttest) as a repeated-measures factor and vaccination intention as a dependent variable. Preregistered subgroup analyses were conducted for different levels of a priori misinformation belief and general vaccination confidence.

RESULTS

The analyses revealed differential effects on misinformation belief and vaccination intention in participants with low, medium, and high a priori belief: A debunking effect on misinformation belief (d_RM = -0.80) was only found in participants with a medium a priori belief and did not extend to these participants' vaccination intentions. Among participants with a high a priori misinformation belief, explorative analysis revealed a small unintended backfiring effect on vaccination intentions (η_p² = 0.03).

CONCLUSIONS

Our findings suggest that debunking is an effective communication strategy to address moderate levels of misinformation beliefs, but it does not constitute a one-fits-all strategy to reduce vaccination hesitancy among the general public. Although countering misinformation should certainly be an integral part of public health communication, additional initiatives, which address individual concerns with targeted and authentic communication, should be taken to enhance the impact on hesitant populations and avoid backfiring effects.

General knowledge norms: Updated and expanded for German

The general knowledge questions introduced by Nelson and Narens (Journal of Verbal Learning and Verbal Behavior, 19(3), 338-368, 1980) have been a valuable research tool in various areas of cognitive research. We translated, updated, and expanded the set of questions for German. We present a total set of 356 general knowledge questions with their recall probability as well as metacognitive measures-confidence and peer judgments-based on a university student sample (N = 512). Furthermore, we present response latencies, pairwise correlations between recall probability and metacognitive judgments as well as the most common commission errors. These general knowledge questions can be used in studies with German speaking participants in a broad range of research fields, such as memory, illusory truth, misinformation, and metacognitive processes.

Story stimuli for instantiating true and false beliefs about the world

We offer short story (“vignette”) materials that have been developed and tested with the intention of influencing people’s true and false beliefs about the world. First, we present norming data on the baseline rates at which participants from both U.S.-census matched and general U.S. online samples were correctly able to classify a selected set of accurate (e.g., aerobic exercise strengthens your heart and lungs) and inaccurate (e.g., aerobic exercise weakens your heart and lungs) assertions as “True” or “False.” Next, we present data which validate that reading vignettes in which people discuss these accurate and inaccurate assertions influences participants’ subsequent judgments of the validity of the asserted claims. These vignettes are brief, easy-to-read, allow for flexible and accountable online data collection, and reflect realistic accurate and inaccurate claims that people routinely encounter (e.g., preventative health behaviors, use of alternative medicines and therapies, etc.). As intended, vignettes containing inaccurate assertions increased participants’ subsequent judgment errors, while vignettes containing accurate assertions decreased participants’ subsequent judgment errors, both relative to participants’ judgments after not reading related information. In an additional experiment, we used the vignette materials to replicate findings from Salovich et al. (2021), wherein participants reported lower confidence in correct judgments and higher confidence in incorrect judgments after having read inaccurate assertions. Overall, these materials are well suited for investigations on the consequences of exposures to accurate and inaccurate information, address limitations in currently available stimuli, and align with trends in research practice (e.g., online sampling) within psychological science.