The Kiddie Formal Thought Disorder Rating Scale: clinical assessment, reliability, and validity.

The Kiddie Formal Thought Disorder Story Game and the Kiddie Formal Thought Disorder Scale were administered to schizophrenic, schizotypal, and normal children, aged 5 to 13 years. The story game elicited more elaborate speech samples than did a structural clinical interview focused on psychotic symptomatology. The sum of illogical thinking and loose associations was a reliable kappa = 0.77), sensitive (79%), and specific (90%) indicator of schizophrenia in this sample. It also demonstrated significant developmental changes in the schizophrenic and normal subjects. Incoherence and poverty of content of speech were infrequently rated in both schizophrenic and normal subjects.