Psychometric evaluation of the Pinocchio Illusion Questionnaire.
Level 4 - case-series / case-control
Single-cohort psychometric validation study without a comparison group
PubMed 32185641 · doi:10.3758/s13414-020-02011-4
What was done
Researchers evaluated the psychometric properties of the Pinocchio Illusion Questionnaire (PIQ) in 60 participants. The Pinocchio Illusion (perceived nose elongation caused by bicep tendon vibration while touching the nose with eyes closed) was elicited across two trials. The authors assessed test-retest reliability, internal consistency, factor structure via Principal Component Analysis (PCA), open-ended free responses versus an 11-item questionnaire, and correlations with self-reported interoceptive awareness and schizotypal traits.
What was found
The PIQ showed strong test-retest reliability and internal consistency. However, PCA failed to identify a latent variable structure capable of distinguishing illusion-specific perceptual changes from unrelated or contradictory experiences. Open-ended spontaneous reports of illusion-specific aberrations occurred in only 5% of participants during the first elicitation and 8.3% during the second, whereas endorsement of illusion-specific items on the 11-item closed-ended scale ranged from 30% to 53.33% in the first trial and 31.67% to 46.67% in the second.
Why it matters
The large discrepancy between open-ended reports and rating scale items suggests closed-ended questionnaires for bodily illusions may be heavily inflated by demand characteristics. Researchers measuring somatic illusions need standardized elicitation protocols and more specific instruments to capture true perceptual changes.
Limits
The sample size was modest (N = 60), and participant demographics were not specified in the abstract. Correlation magnitudes with interoceptive awareness and schizotypal traits were not numerically reported in the abstract.