Psychometric evaluation of the Pinocchio Illusion Questionnaire

Perceived nose elongation resulting from vibratory stimulation to the bicep brachii tendon in the absence of visual input while the finger is touching the nose, known as the Pinocchio Illusion (PI), is used to investigate how afferent signals can contribute to aberrant top-down perception of body representation. The Pinocchio Illusion Questionnaire (PIQ) was developed to empirically quantify PI perception, allowing for external validation of the PI with psychologically relevant phenomenon. The current study (N = 60) examined the PIQ's test-retest reliability, internal consistency, factor structure, and correlations with self-reported interoceptive awareness and schizotypal traits. The PIQ demonstrated strong test-retest reliability and internal validity; however, a Principal Component Analysis did not yield a latent variable structure that distinguished PI-specific perceptual aberrations from unrelated or contradictory perceptual experiences. Additionally, decreased reports of PI-specific perceptual aberrations during two elicitations of the PI on the PIQ's open-ended free-response section (percent of sample endorsement = 5% (first elicitation); 8.3% (second elicitation)) compared to its 11-item section (endorsement of PI-specific items ranging 30-53.33% (first)]; 31.67-46.67% (second)) suggest that these responses may be heavily influenced by demand characteristics rather than accurately capturing PI perception. Therefore, further psychometric development of the PIQ and standardization of procedures to elicit the illusion are recommended.