GAFS-8

GAFS-8 measures general alexithymia by providing a latent-trait score derived from an optimal eight-item subset of the Toronto Alexithymia Scale (TAS-20) to enable psychometrically robust comparisons across autistic and non-autistic populations.

Key Features:

• Item Reduction and Psychometric Robustness: Confirmatory factor analysis and item response theory applied to data from 743 cognitively able autistic adults and 721 general-population controls identified an eight-item subset that strongly indexes a general alexithymia factor with sound psychometric properties.
• Differential Item Functioning (I-DIF): Analysis of differential item functioning between autistic and non-autistic groups indicated practically ignorable I-DIF for the retained items.
• Nomological Validity: Correlational analyses show GAFS-8 scores predict autistic traits, repetitive behaviours, and depression symptoms, with associations remaining after controlling for trait neuroticism.
• Latent-Trait Scoring: Produces norm-referenced latent trait scores of alexithymia based on the selected TAS-20 items.

Scientific Applications:

• Autism Research: Quantifies alexithymia to investigate cognitive and emotional differences associated with autism.
• Trait Decomposition: Helps distinguish variance attributable to autism from variance attributable to co-occurring alexithymia.
• Mechanistic and Intervention Studies: Provides a psychometrically robust outcome for studies aiming to understand mechanisms of autism-related behaviours and to develop targeted interventions.

Methodology:

Confirmatory factor analysis, item response theory, differential item functioning analysis, and correlational analyses controlling for neuroticism were applied to samples of 743 cognitively able autistic adults and 721 general-population controls.