Whitaker Index of Schizophrenic Thinking
Purpose: Designed to measure degrees of schizophrenic thinking
Population: Mental Patients 16 years and older with 8th grade education and IQ of 80
Score: Similarities, Word Pairs, New Inventions, Total
Time:. 20 minutes for each Form
Author: Leighton C. Whitaker
Publisher: Western Psychological Services
Description: The Whitaker Index of Schizophrenic Thinking (WIST) is offered as a measure of schizophrenic thinking, defined as thinking that is "illogical," "impaired," and "unwitting." The WIST has two main uses: to differentiate persons with schizophrenia from those without schizophrenia, and to serve as an objective measure of degree of thinking impairment. There are two nonequivalent alternate forms for the test: Form A which has item content designed to arouse emotion or anxiety and Form B has more neutral item content. Each form has twenty-five multiple-choice items, nine "similarities" items that require selecting the answer that is most similar to a given word, nine "word pair" items requiring selection of an answer that is most similar in meaning to a given pair of words, and seven "new inventions" items requiring selection of the most likely consequence of a new invention.
Scoring: Each item has a range of scores from 0 to 4 representing the degree of schizophrenic thinking. The score is the total of the weighted scores for each wrong answer. All individual scores are summed and recorded as the TOTAL The subscales for Similarities, Word Pairs and New Inventions are summed for the total WIST score. The time taken for the subject to respond is also recorded and summed to obtain the WIST Index.
Reliability: The manual contains evidence for reliability including internal consistency measures on an "early version of Form A" (not further specified) yielding a Kuder-Richardson Formula 20 reliability coefficient of .77 on unweighted scores. Hoyt reliability coefficients on Forms A and B were approximately .80 using unweighted scores. Forms A and B differ as described above, and are noted to be noncomparable for the purpose of reliability estimation. Test-retest reliability is considered impractical because the subject learns the correct answer during the inquiry. Additional evidence of WIST reliability would be desirable.
Validity: Analysis showed that use of the Index (Score plus Time) value and a cutoff of 20 on Form A, 17 on Form B produced maximum differentiation of diagnosed schizophrenics and non-schizophrenics, at approximately 80% efficiency, Such accuracy clearly makes the WIST useful for research applications, but presents difficulty if the WIST is used for clinical assessment and individual decision making. Although Whitaker argues the WIST measures a particular type of thinking disorder specific to schizophrenia, others argue that the WIST reflects generalized cognitive deficit. In another study, 20 schizophrenics (10 paranoid, 10 non-paranoid) and 10 non-schizophrenic patients were assessed, but the WIST Index did not differentiate well between schizophrenic and non-schizophrenic patients. However, the WIST Index had a significant negative correlation with the Shipley Institute of Living Scale, which measures general cognitive functioning. In a study with anti-psychotic drugs, no significant relationship between drug dosage level and cognitive performances were found.
Norms: The WIST standardization sample included 38 hospitalized acute and 44 chronic schizophrenic patients, 55 hospitalized non-schizophrenics, and a "normal" group of 50 including 26 maintenance workers and 24 college students. Careful patient selection is described.
Suggested use: The WIST can be useful in psychiatric emergency rooms, hospitals and clinics, community mental health center, college or university health centers and counseling centers, and recruitment centers for police or the military. The WIST can be used to evaluate symptomatic status of patients previously diagnosed as schizophrenic.