We selected familiar conspiracy theories (e.g., “The assassination of John F. Kennedy was not committed by the lone gunman, Lee Harvey Oswald, but was rather a detailed, organised conspiracy to kill the President,” answered from 1 = “Completely false” to 9 = “Completely true”). Hence, we reasoned that using this kind of scale increases the likelihood that people would recruit facts or information to answer.

Then, participants moved to Section 2 in which they completed the main dependent variable, namely perceived scarcity of the information that they may have used to answer the conspiracy belief scale. To measure this perception of scarcity (α = .74), we created a three-item scale (e.g., “The information I used to answer questions asked in the previous Section 1 are”:) that participants could answer by using a 9-point scale (1 = Disclosed to the public view to 9 = Hidden from public view).

Participants then indicated to what extent they relied on different potential sources of beliefs when they answered the conspiracy belief scale, on a 9-point scale (1 = Strongly disagree to 9 = Strongly agree). The choice of these potential sources of beliefs was based both on a pretest4 and the literature. Among these potential sources of beliefs,5 the two most relevant to our hypothesis were: (a) information obtained by others “Other people allowed me to acquire the information used to answer the questions asked in the first section (discussion with my friends, etc.)” and (b) information obtained by themselves “I got by myself the information used to answer the questions asked in the first section (e.g., media, reading, etc.)”. To avoid order effects, all the beliefs’ subjective sources were presented randomly. Finally, participants completed demographic information before being debriefed and thanked.