ABSTRACT
Recognizing the complexity and continuum nature of thought disorder phenomena, Johnston and Holzman developed the Thought Disorder Index (TDI) as a summary measure of pathological thinking. First introduced in 1975 as part of an unpublished doctoral dissertation, the TDI later formed the basis of a book entitled Assessing Schizophrenic Thinking, which presented empirical support for the reliability and validity of the TDI. This chapter focuses on the empirical, conceptual, and clinical contributions and shortcomings of the TDI. Initially, Johnston and Holzman used the TDI to assess thought disorder on verbal subtests of the WAIS in addition to the Rorschach, believing that the less structured subtests of the WAIS and the Rorschach would be equally likely to provide a context for eliciting disordered thinking. Taking Rapaport's deviant verbalization categories on the Rorschach as a starting point, Johnston and Holzman looked for a way to quantify the assessment of schizophrenic thought disorder.
