Abstract
Although uncertainty and ambiguity have been used interchangeably within the anxiety literature, no studies have directly compared the psychometric properties and predictive utility of two commonly used scales to assess these constructs, the Intolerance of Uncertainty Scale (IUS) and the Tolerance of Ambiguity Scale (TOA). Furthermore, previous findings of the individual scales have been inconsistent regarding their factor structure and potential clinical utility. Therefore, the current study aims to independently evaluate the factor structure of the IUS and TOA utilizing exploratory and confirmatory factor analysis. Additionally, predictive utility of the scales was evaluated with correlation and regression analyses. Data were collected across 3 studies. Results suggest two-factor solutions provide the best-fitting models for both scales; however, these findings differ from previous studies. The IUS and its subscales provide greater predictive utility for anxiety and related areas of psychopathology compared to the TOA, suggesting that the IUS and uncertainty may be more closely related to anxiety and related symptoms. Future studies should continue to examine the interconnected role of uncertainty and ambiguity within anxiety and other forms of psychopathology.