title: Use of methods from chaos theory to quantify a fundamental dysfunction in the behavioral organization of schizophrenic patients.
abstract: OBJECTIVE
  This study aimed to quantify the complexity of behavioral sequences of patients with schizophrenia and comparison subjects by using methods from nonlinear dynamical systems theory.
  
  
  METHODS
  A simple choice task consisting of predicting 500 random right or left appearances of a stimulus was used to obtain binary response sequences in 22 patients with schizophrenia and 16 comparison subjects. Dynamical entropy was measured and the fluctuation spectrum of local subsequence entropies calculated to quantify the degree of interdependency between consecutive responses of patients and comparison subjects.
  
  
  RESULTS
  The response sequences generated by the schizophrenic patients exhibited a higher degree of interdependency than those of comparison subjects. Moreover, schizophrenic patients exhibited significantly less consistency in their response selection and ordering, characterized by a greater contribution of both highly perseverative and highly unpredictable subsequences of responses within a test session.
  
  
  CONCLUSIONS
  The result of the biological abnormality underlying schizophrenia may not be a simple increase or decrease of neuropsychological or neurobiological functions. Instead, the observed abnormalities in behavioral patterns reflect a quantifiable dysregulation and disorganization of these functions.
authors.affiliation: Department of Psychiatry 0804, University of California, San Diego, La Jolla 92093-0804, USA.
authors.forename: M P
authors.initials: MP
authors.lastname: Paulus
authors.forename: M A
authors.initials: MA
authors.lastname: Geyer
authors.forename: D L
authors.initials: DL
authors.lastname: Braff
mesh_terms: D000328:Adult; D002755:Choice Behavior; D005260:Female; D005556:Form Perception; D006801:Humans; D008297:Male; D008960:Models, Psychological; D017711:Nonlinear Dynamics; D011569:Psychiatric Status Rating Scales; D012559:Schizophrenia / Q000175:diagnosis*; D012565:Schizophrenic Psychology