Why Function Matters
The cornerstone of applied behavior analysis is that interventions should be based on the function of behavior. Two topographically identical behaviors (e.g., hitting) may serve completely different functions (e.g., attention vs. escape), and effective treatment depends on matching the intervention to the function. FBA is the process of identifying that function.
Indirect Assessment
Indirect assessments collect information about behavior without directly observing it. Methods include structured interviews (e.g., Functional Assessment Interview, FAI), rating scales (e.g., Motivation Assessment Scale, MAS, Questions About Behavioral Function, QABF), and review of records. Advantages: easy to administer, inexpensive, can be completed quickly. Limitations: relies on others' recall, which may be inaccurate. Best used as a starting point to generate hypotheses about function.
Descriptive Assessment
Descriptive assessments involve direct observation of behavior in the natural environment. Methods include ABC (antecedent-behavior-consequence) recording and scatterplot analysis. ABC recording captures what happens before, during, and after each occurrence of the target behavior. Scatterplot analysis identifies temporal patterns (e.g., behavior occurs most during math class). Advantages: based on direct observation in natural settings. Limitations: correlational, not causal. Cannot definitively identify function.
Functional Analysis
Functional analysis is the gold standard for identifying behavior function. It involves systematic manipulation of environmental variables to test hypotheses about maintaining contingencies. Standard conditions: alone (automatic), attention, demand (escape), tangible, and control (play). The condition that produces the highest rates of behavior identifies the function. Advantages: experimental demonstration of function. Limitations: requires trained staff, controlled environment, and carries risks if behavior is dangerous.
Choosing the Right Method
Start with indirect assessment to generate hypotheses. Use descriptive assessment to refine hypotheses in the natural environment. Conduct a functional analysis when you need an experimental demonstration of function, when indirect and descriptive results are inconclusive, or when the behavior is severe enough to warrant the most precise assessment. Consider brief functional analyses for efficiency in clinical settings.