ABSTRACT
A central aspect of scientific knowledge is scientific uncertainty. When scientists touch upon political issues, there are two contrary expectations: One is that scientists communicate in a straightforward manner and give a direct, concrete suggestion. The other is that they communicate in a way that carefully considers the pros and cons as well as the current state of (non-) knowledge. This 2x2 experimental study investigated how disclosing scientific uncertainty affects the perceived trustworthiness of a scientist when they express either their motive to inform or their motive to advocate. All participants (N = 503) read an interview with a scientist about the usefulness of further vaccinations against COVID-19. In the interview, uncertainty was explicitly addressed (vs. not). Furthermore, the scientist either disclosed their motive to advocate or their motive to merely inform about research results. Results showed that the scientist was perceived as more trustworthy (i. e., having more expertise, integrity, and benevolence) when they communicated uncertainty than when they did not. However, contrary to our expectations, the effect of the scientist's expressed motive to advocate (vs. to inform) on trustworthiness did not depend on whether uncertainty was explicitly addressed or not.