The Autism Diagnostic Observation Schedule (ADOS) is a semi-structured assessment of communication, social interaction, and play (or imaginative use of materials) for individuals suspected of having autism or other pervasive developmental disorders. The ADOS consists of four modules, each of which is appropriate for children and adults of differing developmental and language levels, ranging from nonverbal to verbally-fluent.
The ADOS consists of standardized activities that allow the examiner to observe the occurrence or non-occurrence of behaviors that have been identified as important to the diagnosis of autism and other pervasive developmental disorders across developmental levels and chronological ages. The examiner selects the module that is most appropriate for a particular child or adult on the basis of his/her expressive language level and chronological age. Structured activities and materials, as well as less structured interactions, provide standardized contexts in which social, communicative and other behaviors relevant to pervasive developmental disorders are observed. Within each module, the participant's response to each activity is recorded. Overall ratings are made at the end of the schedule. These ratings can then be used to formulate a diagnosis through the use of a diagnostic algorithm for each module. In effect, the ADOS provides a 30- to 45-minute observation period during which the examiner presents the individual being assessed with numerous opportunities to exhibit behaviors of interest in the diagnosis of autism/PDD through standard 'presses' for communication and social interaction. 'Presses' consist of planned social occasions in which it has been determined in advance that a behavior of a particular type is likely to appear (Murray, 1938).
The modules provide social-communicative sequences that combine a series of unstructured and structured situations. Each situation provides a different combination of presses for particular social behaviors. Module 1 is intended for individuals who do not consistently use phrase speech (defined as non-echoed. three-word utterances that sometimes involve a verb and that are spontaneous, meaningful word combinations). Materials for Module 1 have been selected for young children, but materials from other modules may be substituted if desired. Module 2 is intended for individuals with some phrase speech who are not verbally fluent. Module 3 is intended for verbally fluent children for whom playing with toys is age-appropriate (usually up to 12 - 16 years of age). Verbal fluency is broadly defined as having the expressive language of a typical four-year-old child: producing a range of sentence types and grammatical forms, using language to provide information about events out of the context of the ADOS, and producing some logical connections within sentences (e.g., "but" or "though"). Module 4 includes the many of the tasks in Module 3 (some of which are optional), as well as additional interview items about daily living. It is intended for verbally-fluent adolescents and adults. The difference between Modules 3 and 4 lies primarily in whether information about social-communication is more appropriately acquired during play or a conversational interview.
The four modules overlap in activities, but together contain a variety of tasks ranging from observing how a young child requests that the examiner continue blowing up a balloon in Module 1 to a conversation about social relationships at school or work in Module 4. Modules 1 and 2 will often be conducted while moving among different places around a room, reflecting the interests and activity levels of young children or children with very limited language; Modules 3 and 4 take place sitting at a table and involve more conversation and language without a physical context. Though the superficial appearance of the different modules is quite varied, the general principles involving the deliberate variation of the examiner's behavior using a hierarchy of structured and unstructured social behaviors are the same.
Because the focus of the ADOS is on observation of social behavior and communication, the goal of the activities is to provide interesting, standardized contexts in which interactions occur. Standardization lies in the hierarchy of behavior employed by the examiner and the kinds of behaviors taken into account in each activity during the overall ratings. The activities serve to structure the interaction; they are not ends in themselves. The object is not to test specific cognitive abilities or other skills in the activities, but to have tasks that are sufficiently intriguing that the child or adult being assessed will want to participate.
In general, each module should stand on its own in providing a range of tasks and social presses. If in doubt as to which module to choose, it is better to err in choosing a module that requires fewer language skills than an individual possesses than to risk confounding language difficulties with the social demands of the instrument. The order of tasks, pacing and materials can be varied, depending on the needs of the individual being assessed.
Many of the ratings made at the end of each schedule are similar across modules, with some identical items and some that are relevant only for a subset of modules. Separate algorithms for the different modules have been generated and are presented at the end of each scoring booklet. Adequate inter-rater reliability for items has been established for all modules.
The ADOS offers clinicians and researchers the opportunity to observe social behavior and communication in standardized, well-documented contexts. These contexts are defined in terms of the degree to which the examiner's behavior structures the individual participant's response and social initiative. For purposes of diagnosis, use of this instrument should be accompanied by information from other sources, particularly a detailed history from parents whenever possible (see Lord, Rutter & Le Couteur, 1994). Its goal is to provide standardized contexts in which to observe the social-communicative behaviors of individuals across the life span in order to aid in the diagnosis of autism and other pervasive developmental disorders. For this reason, it may not be a good measure of response to treatment or developmental gains especially in the later modules. On the other hand, some items have been deliberately included across several modules, even though they have diagnostic utility only in one (e.g., response to joint attention). It may be that developmental or treatment gains will be measurable using these items. An alternative strategy to measure absolute gains is to re-administer the same modules over time, as well as administering the developmentally-appropriate module.
*Adapted from the ADOS Manual, Western Psychological Services, 2001.