There are a variety of methods used to identify the source of the behavior. One such method consists of interviewing the client and other persons who interact with him/her. Rating scales may also be used for this purpose. This is usually done at the beginning and serves as a basis for other, more reliable methods because interviews and rating scales alone do not result in a complete functional assessment. Observing the client behave in his or her everyday setting will allow for the discovery of the antecedents that set the stage for the behavior to occur and the consequences that immediately follow it. Consequently, this results in a more dependable method. One other method that may be used to identify the function of the behavior of interest, and that is perhaps even more reliable than the aforementioned, is controlling the environment it occurs in to learn what effects it may produce on the behavior. This is done by situating the client in dissimilar situations and observing changes in the behavior. Each technique alone will generate useful information, however, they can be combined and lead to a greater understanding. These methods should only be performed by someone who has been carefully trained because improper implementation can result in adverse consequences.
Functional assessment is a method used in the field of applied behavior analysis as a way to discover the function of behavior. An assortment of procedures is used in order to conclude what is maintaining the behavior. Once this is established an intervention will be generated to deal with the problem behavior and new, desirable behavior will be developed. A functional assessment is therefore, the primary step in the development
of a behavior support plan. However, the purpose of this procedure is not merely to define the undesirable behavior. It also allows for the understanding of the function of such behavior. This is significant for teaching and promoting alternative behaviors that are desirable. A functional assessment will garner a greater understanding of the particular influences of behavior by determining the relationship between the behavior and the environment it occurs in.
In order to conduct a comprehensive functional assessment, the behavior that is of interest should be defined clearly in a way that is observable and measurable. Certain elements should be included to aid in the definition process: frequency, latency, duration, intensity, setting events, and all of the other circumstances in which the behavior takes place.
Functional assessments are crucial in the development of behavioral interventions. An intervention that is created without first understanding the causes of a particular behavior may not be as successful as one which has been based on this.