Exclusion criteria. Participants who meet any of the following will be excluded: (a) history of any of the following DSM IV diagnoses - Pervasive Developmental Disorders, Elective Mutism, Organic Mental Disorders (except Psychoactive Substance-Induced), Schizophrenia, Delusional (Paranoid) Disorder, Psychotic Disorder, and Bipolar Affective Disorder, (b) Any Substance Abuse or Dependence Disorder diagnosis (substance use that does not meet DSM IV diagnosis criteria will not excluded).