The Diagnostic and Statistical Manual of Mental Disorders (DSM-5; American Psychiatric Association, 2013) combined all previous autism diagnoses into a single diagnostic category, autism spectrum disorder (ASD). One critical issue with the DSM-5 ASD symptoms is that they overlap with behaviors consistent with introversion, a non- pathological tendency to be introspective, and the symptoms of schizoid personality disorder. The purpose of the present study was to determine whether an 84-item measure of the ASD DSM-5 criteria (Coolidge Autism Symptom Survey; CASS) could differentiate among extroverted and introverted children who were developing typically (DT), children with a diagnosis of schizoid personality disorder, and children diagnosed with mild, moderate, and severe levels of ASD. One-hundred forty-nine participants were recruited from University of Colorado, Colorado Springs undergraduate classes. Each respondent was asked to fill out the CASS about a child they knew, who matched one of these diagnoses, between the ages of 5-17 years old. Unfortunately, no children were found to meet the schizoid personality disorder criterion. It was found that there were no differences in overall CASS sums between extroverted DT and introverted DT children. However, as hypothesized both of those groups scored significantly lower on the CASS than children with mild ASD, moderate ASD, and severe ASD. The CASS scores on the latter two groups were not significantly different. Preliminary psychometric analyses of

the CASS support the two DSM-5 criteria categories (Deficits in Communication/Social Interactions and Restrictive/Repetitive Behaviors), and they support the preliminary reliability and validity of the CASS.