AI Insight
This study examined four widely-used short scales that measure general conspiracy mentality using a nationally representative U.S. sample and bifactor analysis. While all four scales share a common underlying conspiracy mentality factor that accounts for most variance, two scales contain additional problematic content: the GCB-5 includes paranormal beliefs and the GMC correlates with partisan political views. The GMC also measures the trait differently at extreme values, diverging by over one standard deviation from the common factor.
Why it matters
The findings challenge the common assumption that these conspiracy mentality scales are interchangeable in research. Researchers need to carefully select which scale to use and consider controlling for paranormal thinking or partisanship when using specific scales, as failing to do so may produce inflated or biased estimates of conspiracy belief.
Understand the Science
IntroductionConspiracy theory researchers increasingly rely on general measures of “conspiracy mentality” to explain belief in specific conspiracy theories. A growing consensus holds that the leading short-form scales are effectively interchangeable. This recommendation assumes that the scales measure the same underlying trait. We conduct a three-step test to determine whether four widely used measures are interchangeable in reflecting a single common conspiracy-mentality factor.MethodsUsing a nationally representative U.S. sample, we conducted a bifactor analysis partitioning the common and unique variance of the American Conspiracy Theories Scale (ACT), the Conspiracy Mentality Questionnaire (CMQ), the General Measure of Conspiracism (GMC), and the Generic Conspiracist Beliefs Scale (GCB-5). We compared the general and scale-specific factors on reliability and on structural, convergent, discriminant, and criterion validity, including prediction of belief in individual conspiracy theories.ResultsA single common factor accounted for most of the variance across all four short-form scales and evidenced comparable performance in terms of internal consistency, test–retest reliability, and in structural, convergent, discriminant, and criterion validity. The GCB-5 retained meaningful but apparently additional paranormal content even after controlling for the common factor of conspiracy mentality. The GMC’s unique residual correlated with partisan-coded beliefs about vaccines, SARS (COVID-19), climate change, and the Obama “birther” conspiracy. The GMC also tended to produce less extreme values than the other three scales at both ends of the trait, diverging from the common factor by over a standard deviation.DiscussionThe four short-form generic scales are not strictly interchangeable. While these scales share a common conspiracy mentality factor, two of them carry measurable, orthogonal content that inflates their associations with beliefs in specific conspiracy theories: paranormal content in the GCB-5, and partisan content in the GMC. The GMC also maps observed scores onto the common factor differently from the other three scales, particularly at the extremes of the trait. When measuring conspiracy thinking, researchers should treat the choice of scale as a deliberate decision and should not assume estimates obtained with different scales are equivalent. Further, we recommend that researchers consider controlling for paranormal thinking or partisanship when using the GCB-5 or the GMC, respectively.