Development and initial validation of an abbreviated Spider Phobia Questionnaire using item response theory.

An abbreviated Spider Phobia Questionnaire (SPQ) was developed using methods based in item response theory. Fifteen of the 31 SPQ items that demonstrated good to excellent discrimination along the spider fear continuum were retained in Study 1 that consisted of 1,555 nonclinical and clinical participants. The SPQ-15 demonstrated good internal consistency and correlated highly with the full SPQ. Structural equation modeling revealed that the SPQ-15 demonstrated excellent convergent validity, with strong associations with small animal disgust and other phobic symptoms. Supportive evidence was also found for divergent validity in relation to panic-related symptoms. The SPQ-15 was uniquely predictive of avoidance behavior and fear and disgust responding towards spiders in nonclinical, analogue, and treatment-seeking samples in Studies 2, 3, and 4. Lastly, in Study 5, the SPQ-15 was sensitive to the effects of exposure-based treatment. These findings suggest that the SPQ-15 has considerable strengths, including decreased assessment and scoring time while retaining high reliability, validity, and sensitivity.