About the ADOS-G

The Autism Diagnostic Observation Schedule -Generic (ADOS-G) 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 (PDD). It is a combination of two earlier instruments: the Autism Diagnostic Observation Schedule (ADOS: Lord et al., 1989), a schedule intended for adults and children with language skills at a minimum of the three-year-old level, and the Pre-Linguistic Autism Diagnostic Observation Scale (PL-ADOS: DiLavore, Lord & Rutter, 1995), a schedule intended for children with limited or no language, as well as additional items developed for verbally fluent, high-functioning adolescents and adults. The ADOS-G consists of four modules, each of which is appropriate for children and adults of differing developmental and language levels, ranging from no expressive or receptive language to verbally fluent adults. These modules are described in separate sections following this introduction. They are labeled with numerals 1 to 4, with each activity numbered within its module.

The ADOS-G consists of standard 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, and less structured interactions, provide standard 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-G 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, based on the PL-ADOS, 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 the child's 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 a combination of the ADOS and PL-ADOS and is intended for individuals with some phrase speech who are not verbally fluent. Module 3 is based on the ADOS and is intended for children for whom playing with toys is age- appropriate, (usually under 12 - 16 years of age) who are verbally fluent. Verbal fluency is broadly defined as having the expressive language of a typical four year-old child: producing 4. range of sentence types and grammatical forms, using language to provide information about events out of context and producing some logical connections within sentences ( e.g., "but" or "though"). There may be some continued grammatical errors. Module 4 includes the socioemotional questions of the ADOS as well as additional tasks and some 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 modules overlap in activities, but together contain a range of tasks 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-G is on observation of social behavior and communication, the goal of the activities is to provide interesting, standard 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. What the examiners do not do (such as deliberately waiting to see if the participant will initiate an interaction or try to maintain it) is often as important as what they do.

In general, each module should stand on its own in providing a range of tasks and social presses. However, an examiner may need to shift from one module to another if the language level of the individual is different than expected or, if for another reason, the tasks seem generally inappropriate. If in doubt, 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. As is discussed later within the four modules, 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 section. Adequate inter-rater reliability for items has been established. However, this work has been carried out in small samples; thus, replication from independent samples will be very important.

In the following pages, the manual is organized around the four modules. Within each module, there is a general introduction, a description of tasks, a list of the materials needed and guidelines for overall ratings. Separate coding sheets contain the ratings and provide a recording form for notes made during each activity. These sheets include a summary of the purpose of each activity and the focus of observations targeted during each task. Notes should be taken during administration of each schedule. All modules, even if videotaped, should be rated immediately after they are administered. Earlier research with the PL-ADOS and ADOS showed that ratings of items made after live administration of the scales were equal or greater in reliability (and never less) than ratings from videotapes because the ratings involve social nuances of behavior that are not always observable or interpretable on a screen (such as distinguishing appropriate eye contact from looking over one's shoulder). Within a clinic or research group, examiners should obtain inter-rater reliability with each other before using the instruments for research. Our recommendation has been for 80 percent agreement on individual items and mean kappas greater than .60 (when sample sizes and distributions permit) for raters for three consecutive joint scorings.

The examiner needs to be sufficiently familiar with the ratings and the activities that she can focus her attention on observation of the individual being assessed, rather than on administration of the tasks. This requires practice in administering the activities, scoring, and observation. Notes need to be sufficiently detailed to be interpretable but not so lengthy that they interfere with administration.

The ADOS-G 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.

For purposes of brevity, the examiner is referred to as "she" and the participant as "he."