The Role of Assessment in ABA Practice
Assessment is the foundation of effective behavior-analytic service delivery. Before designing any intervention, a BCBA must conduct thorough assessments to identify the client's strengths, needs, preferences, and the environmental variables maintaining problem behavior. Using validated assessment tools ensures that treatment decisions are data-driven rather than based on intuition or convenience.
The BCBA exam tests your knowledge of a variety of assessment tools and your ability to select the appropriate assessment for a given clinical situation. This guide covers the major categories of assessment and the most commonly used instruments in each category.
Preference Assessments
Identifying effective reinforcers is essential for successful ABA programming. Preference assessments systematically evaluate an individual's preferences among a set of stimuli to identify potential reinforcers. Several validated methods exist, each with advantages for different clinical situations.
Multiple Stimulus Without Replacement (MSWO)
The MSWO procedure presents an array of stimuli (typically five to seven items) simultaneously. The individual selects one item, and that item is removed from the array. The remaining items are rearranged, and the individual selects again. This continues until all items have been selected or the individual stops engaging. The MSWO produces a ranked hierarchy of preferences and is one of the most efficient preference assessment methods for identifying a differentiated hierarchy.
Paired Stimulus (Fisher et al., 1992)
In a paired stimulus assessment, two items are presented at a time in all possible pairwise combinations. The individual selects one item from each pair, and the percentage of trials in which each item is selected is calculated. This method produces a clear ranking and is considered one of the most reliable preference assessment formats. However, it requires more time than the MSWO because every pair must be presented.
Free Operant Observation
Free operant observation involves providing the individual with free access to a variety of stimuli and recording the duration of engagement with each item. This method is useful for individuals who have difficulty making discrete choices, and it can identify stimuli that maintain engagement over time. It is less intrusive than structured formats and can be conducted during natural activities.
Single Stimulus Engagement
Each item is presented individually, and the individual's approach and engagement duration are recorded. This format is useful for individuals with limited scanning or selection skills. It requires less complex responding than paired or multiple stimulus formats, making it appropriate for individuals with significant developmental disabilities.
Skill Assessments
Skill assessments evaluate the individual's current repertoire across developmental and functional domains to identify intervention targets and track progress over time.
VB-MAPP (Verbal Behavior Milestones Assessment and Placement Program)
Developed by Mark Sundberg, the VB-MAPP assesses language and social skills based on Skinner's analysis of verbal behavior. It evaluates milestones across 170 developmental benchmarks organized into three levels (0 to 18 months, 18 to 30 months, and 30 to 48 months). The assessment covers mand, tact, listener responding, visual perceptual skills, play, social behavior, and other domains. The VB-MAPP also includes a barriers assessment that identifies 24 common barriers to learning and a transition assessment to guide placement decisions.
ABLLS-R (Assessment of Basic Language and Learning Skills, Revised)
The ABLLS-R is a criterion-referenced assessment tool that evaluates 544 skills across 25 domains including language, social interaction, self-help, academic, and motor skills. It provides a comprehensive picture of the individual's current abilities and generates targets for intervention. The ABLLS-R uses a task-analyzed format that breaks each skill into component steps, making it particularly useful for developing individualized treatment plans.
AFLS (Assessment of Functional Living Skills)
The AFLS assesses practical life skills needed for community living and independence. It covers areas such as basic living skills, home skills, community participation, school skills, vocational skills, and independent living skills. This assessment is particularly valuable for adolescent and adult clients, as it targets the functional skills needed for maximum independence.
Essentials for Living
Developed by Patrick McGreevy, Essentials for Living focuses on essential skills for individuals with significant disabilities. It includes 2,600 skills organized into eight categories and emphasizes functional communication, daily living, and community participation. The assessment also includes a section on essential behaviors to reduce, focusing on problem behaviors that interfere with learning and daily functioning.
Functional Behavior Assessment Methods
Functional behavior assessment (FBA) identifies the environmental variables that maintain problem behavior. The information gathered through FBA is used to design function-based interventions.
Indirect Assessment Methods
Indirect methods gather information from people who know the individual well. Common tools include the Functional Assessment Screening Tool (FAST), the Motivation Assessment Scale (MAS), and the Questions About Behavioral Function (QABF). These tools use interviews and rating scales to generate hypotheses about the function of behavior. While efficient and easy to administer, indirect methods have lower reliability than direct methods and should not be used as the sole basis for identifying function.
Descriptive Assessment (ABC Data)
Descriptive assessment involves direct observation of the individual in their natural environment. The observer records antecedent events, the target behavior, and the consequences that follow each occurrence. ABC (antecedent-behavior-consequence) data collection can reveal patterns in the environmental context of problem behavior. However, descriptive assessment has limitations because correlational data cannot definitively establish causal relationships between environmental events and behavior.
Functional Analysis
The functional analysis (Iwata et al., 1982/1994) is the gold standard for identifying the function of problem behavior. It involves systematically manipulating antecedent and consequence variables across test conditions (attention, demand/escape, tangible, and alone) and comparing rates of behavior to a control (play) condition. Elevated rates of behavior in a specific test condition indicate the maintaining variable. While the functional analysis provides the most definitive information about behavioral function, it requires trained personnel and careful safety protocols, especially when analyzing severe problem behavior.
Selecting the Right Assessment
Choosing the appropriate assessment depends on the referral question, the client's characteristics, the available resources, and the clinical context. For new clients, a combination of preference assessment, skill assessment, and functional behavior assessment typically provides the comprehensive information needed to develop an effective treatment plan. For the BCBA exam, be prepared to identify which assessment tool is most appropriate for a given scenario and explain why that tool is the best fit.