1) behavioural assessment is used to depict, as validly, clearly, and objectively as possible, an individual's patterns of behavior. Specific measures are selected based on the behaviour and its context in order to depict clearly the target behaviour prior to, during, and after any systematic intervention or treatment. This information is used for the planning, execution, and evaluation of treatment. Though direct observation forms the core of behavioural assessment, indirect methods also are used at times to supplement information for guiding our selection of the most appropriate treatment strategy.

2) The attempt to (a) define the target behavior; (b) identify functional relations between the target behaviour and its antecedents and consequences; and (c) identify an effective intervention for changing the target behavior.