 Behavioral Measures Participants who are receiving intensive behavioral intervention services during the course of the study will have continuous measures of many aspects of performance recorded daily, as a part of their behavioral intervention services. Such measures will be customized to the behavioral education needs of each child, but are likely to include, at a minimum: 1 measure of adaptive behavior e.g., language; 2 measure of aberrant behavior e.g., tantrums, etc.; and 3 stereotyped behavior. All such continuous measures can be observed throughout the course of the participants involvement in the study. However, the consideration of any particular continuous measure as part of the current study would require inter-observer agreement data be collected on those measures for a minimum of 25 of the observed data. That is, a second, independent observer must record data on all behavioral clinical measures which will be included in the study. Participants who are not receiving intensive behavioral intervention services will receive only the behavioral measures described below. Participants who are receiving intensive behavioral intervention services during the course of the study will receive the measures described below, as well as any of their clinical behavioral measures for which adequate inter-observer agreement data are collected. 