Participatory Development and Psychometric Evaluation of the Introspective Predictive Processing Inventory: A Self-Report Measure for Autistic and Non-Autistic Adults.
Marik Roos, Hannah Storm, Lucie Zimmer and 1 others
A new 18-item self-report measure, developed with autistic adults, distinguishes autistic from non-autistic adults with high accuracy and captures their subjective experiences of sensory overwhelm, social miscommunication, and need for predictability.
It is not a diagnostic tool.
Key findings
1The 18-item IPPI discriminated between autistic and non-autistic adults with high accuracy (AUC = 0.97 in the online sample, 0.99 in the lab sample). Autistic adults scored substantially higher: mean 103.43 (SD 17.34) versus 49.08 (SD 19.26) in Sample 1, and 106.00 (SD 14.60) versus 45.00 (SD 18.36) in Sample 3.
2The measure has a two-factor structure: 'Prediction Integration and Interpretation' (12 items) and 'Prediction Error Sensitivity and Stability Needs' (6 items). This structure was confirmed in independent samples and showed measurement invariance between autistic and non-autistic groups.
3IPPI scores were independent of general cognitive ability. In a multiple regression controlling for group, verbal IQ (p = 0.111) and nonverbal IQ (p = 0.419) were non-significant predictors, while group membership was the strongest predictor (p < 0.001).
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What it does not show
Participants were recruited through convenience sampling (social media, online communities, autism organizations), which the authors note may have introduced selection bias including higher education levels, later age of diagnosis, and reversed sex ratios compared to population-based samples. No test-retest reliability was established, so it is unknown how stable scores are over time. No objective validation (neuroimaging, behavioral tasks) links IPPI scores to actual predictive processing mechanisms. The authors state the theoretical links between items and mechanisms remain hypothetical. No measurement invariance testing by gender was conducted, so the gender difference observed in Sample 1 (autistic females scoring higher) cannot be interpreted confidently. Dropout was higher in the autism group (34.4%) than the comparison group (19.4%), which the authors attribute to public sharing of survey links and the introspective nature of the questions. Sample size was determined by available financial and personnel resources rather than a power analysis.
Declared interests
The authors received no financial support and declared no conflicts of interest.
The easy way to misread this
Do not read a high IPPI score as confirmation that a person has predictive processing differences at a neural or mechanistic level. The authors state explicitly that the measure captures subjective experiences that are theoretically linked to predictive processing, not the mechanisms themselves. The theoretical links remain hypothetical and have not been validated against objective measures such as neuroimaging or behavioral tasks.
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