The common factor of conspiracy mentality: a bifactor analysis of four short-form measures of general conspiracy thinking

For years, researchers investigating the psychology behind conspiracy theories have increasingly relied on brief, generalized questionnaires to measure what they term a "conspiracy mentality"—a foundational worldview that major world events are covertly orchestrated by hidden actors. A growing scholarly consensus has maintained that the leading short-form scales used to capture this trait are effectively interchangeable, assuming they tap into the same underlying psychological disposition. However, a comprehensive new study published in Frontiers in Psychology challenges this foundational assumption, revealing that while these popular scales share a common core, they also harbor distinct biases, unique residuals, and structural variances that prevent them from being treated as equivalent instruments.

Methodology and Analytical Framework

To test whether widely used short-form measures truly reflect a single, unified trait, researchers examined secondary data from a nationally representative U.S. sample originally gathered via the online research platform Prolific. The study evaluated four prominent scales: the American Conspiracy Theories (ACT) Scale, the Conspiracy Mentality Questionnaire (CMQ), the Generic Conspiracist Beliefs Scale (GCB-5), and the General Measure of Conspiracism (GMC).

The research team implemented a rigorous three-step statistical evaluation utilizing advanced bifactor modeling. This approach partitioned the variance of the items into a single overarching common factor—representing general conspiracy mentality—and orthogonal specific factors capturing the unique residual variance inherent to each individual scale. Furthermore, the researchers compared the measures across multiple dimensions of validity, including internal consistency, test-retest reliability, structural integrity, convergent and discriminant validity, and their capacity to predict endorsement of 21 specific conspiracy theories cataloged in the Belief in Conspiracy Theories Inventory (BCTI).

Findings on Shared Core Traits Versus Scale-Specific Residuals

The analysis confirmed that a single common factor accounted for the majority of the variance across all four short-form scales, demonstrating robust internal consistency and stability over a two-week test-retest interval. This core finding reassures researchers that the instruments successfully tap into a generalized, unidimensional worldview regarding secret plots and elite manipulation.

Despite this shared foundation, however, the study exposed significant divergences when evaluating the unique residual content of the individual scales. While the residuals for the ACT and CMQ demonstrated negligible influence on specific conspiracy endorsements once the common factor was controlled, the GCB-5 and the GMC retained meaningful, orthogonal content that systematically skewed their predictive relationships.

Specifically, the GCB-5 demonstrated a persistent association with paranormal and supernatural ideation, maintaining a strong predictive link with extraterrestrial cover-up theories even after researchers controlled for the general conspiracy mentality factor. Conversely, the GMC exhibited a distinct political slant. Its residual variance correlated positively with Republican party identification ($r = 0.28$) and predicted specific, politically polarized conspiracy narratives prominent in recent U.S. discourse—such as anti-vaccine claims, the origins of SARS as a biological weapon, climate change denial, and the "birther" conspiracy regarding former President Barack Obama. Additionally, the GMC produced non-linear scoring anomalies, assigning scores that diverged by more than a standard deviation at both the lower and upper extremes of the trait compared to the other three measures.

Implications for Psychological Research and Polling

The empirical findings carry substantial implications for behavioral scientists, political psychologists, and public opinion researchers. By demonstrating that the four short-form scales are not strictly interchangeable, the study cautions against treating estimates derived from different instruments as equivalent across academic literature or pooled datasets.

The presence of "content contamination"—such as paranormal themes embedded in the GCB-5 or partisan political leanings embedded in the GMC—suggests that researchers must exercise deliberate judgment when selecting measurement tools. The study’s authors recommend that academics explicitly justify their choice of scale based on the specific research question at hand. Furthermore, they advise that investigators utilizing the GCB-5 should control for paranormal or magical thinking, while those employing the GMC should account for political ideology and partisanship.

Broader Context and Future Directions

The debate over how best to quantify conspiracist ideation arrives at a time of heightened societal concern regarding misinformation, institutional distrust, and political polarization. As researchers continue to explore the psychological architecture connecting conspiracy beliefs to broader unwarranted epistemic worldviews—such as pseudoscience and magical thinking—clarifying the boundaries of the core latent trait remains paramount.

While the current research provides a vital empirical baseline, the study’s authors note several limitations, including its reliance on a single cross-sectional U.S. sample and the exclusive use of short-form measures rather than full-length item batteries. Future investigations will need to test the temporal invariance of these factor structures across diverse international cultures and political climates to determine whether the observed anomalies are universal features of the scales or artifacts of specific geopolitical contexts. Ultimately, the research underscores that measuring the human tendency to see secret plots is far more complex than previously assumed, requiring heightened methodological precision moving forward.