By: Jacob Papazian MS, BCBA – Regional Clinical Director

The Walt Disney company said it best in their iconic ride “Spaceship Earth”: “we are on the brink of a new communication renaissance.” Behavior Analysis is on one such brink. As a field we are expanding into new contexts and populations. As the ABA sector becomes more well known, resources are becoming more scarce (Harvey, Harvey, Kenkel & Russo, 2010). Analysts are charged with implementing services without compromising ethical integrity. One such area is the functional analysis. Although crucial to ethical treatment, analog assessments are time consuming, expensive, and can be dangerous to staff and students (Hanley, 2012).

What is Trial Based Functional Analysis (TBFA)?

The Trial Based Functional Analysis, a relatively new form of assessment, was created to combat these difficulties by offering a fast and inexpensive form of assessment that informs behavior plan implementation. Rather than requiring 20+ minute conditions per each individual condition, two minute conditions that rapidly alternate are implemented in a pairwise fashion that are used to evaluate the potential antecedents and consequences that contribute to the initiation and ongoing maintenance of a targeted behavior. Using a control-test-control-control format, each analogous “condition” takes approximately six minutes to complete resulting in approximately ten conditions per hour of direct analysis which could potentially result in an interpretable result. Conditions are terminated after a single instance of the target behavior following delivery of the reinforcer being assessed. These probe data are usually presented as percentage of trials with problem behavior but have recently been analyzed using equal interval graphs (Bloom et al., 2013).

The current literature has validated this assessment using the Litmus Test (i.e., using reduction in problem behavior when interventions are based on the function derived in the assessment) and by comparing results from analog assessments (Austin, Groves, Reynish, & Francis, 2015). These two forms of validation have resulted in very different conclusions. Comparing the TBFA to standard analog assessments has resulted in an approximate 60% match (Austin et al. 2015). Those validating using the Litmus Test have found a near 100% validation rate (Bloom, Labmert, Dayton & Samaha, 2013; Kodak, Fisher, Paden, & Dickens, 2013; Lambert, Bloom, & Irvin, 2012). Studies using the Litmus Test have incorporated multiple baseline across participant designs, which add to the internal validity of their claims, but do not account for this discrepancy.

Understanding the Current Limitations of TBFA

So that’s fantastic: when we build a behavior plan off of the TBFA it works. However, the discrepancy between analog and alternative methods exists in a fairly significant chasm. Very little literature has been conducted in an attempt to determine why this discrepancy exists. Hypotheses abound ranging from lack of experience or training with the assessment method to failure of conditional discrimination or that the TBFA is simply an inferior form of analysis when compared to the analog. The questions abound but with such limited data and research it is difficult to make proper assertions.

The problem here: we simply do not have the research yet to back up any claims! We have emerging evidence but nothing that truly compares apples to apples the differences between the assessment methods to make a truly informed decision regarding clinical utility. As the great Dylan Thomas once said: “do not go gentle into that good night.” Research on, my fellow nerds!


  • Austin, J. L., Groves, E. A., Reynish, L.C., & Francis, L. L. (2015). Validating Trial Based Functional Analyses in Mainstream Primary School Classrooms. Journal of Applied Behavior Analysis (48)2, 274-288.
  • Bloom., S. E., Lambert, J. M., Dayton, E., & Samaha, A.L. (2013). Teacher Conducted Trial- Based Functional Analyses as the Basis for Intervention. Journal of Applied Behavior Analysis 46(1), 208-218.
  • Hanley, G.P. (2012). Functional Assessment of Problem Behavior: Dispelling Myths, Overcoming Implementation Obstacles, and Developing New Lore. Behavior Analysis in Practice 5(1), 54-72.
  • Harvey, C.A., Harvey, M.T., Kenkel, M.B., & Russo, D. C. (2010). Funding of applied behavior analysis services: Current status and growing opportunities. Psychological Services, 7(3), 202-212.
  • Kodak, T., Fisher, W.W., Paden, A., & Dickes, N. (2013). Evaluation of the Utility of a Discrete Trial Functional Analysis in Early Intervention Classrooms. Journal of Applied Behavior Analysis 46(1), 301-306.
  • Lambert, J.M., Bloom, S.E., & Irvin, J. (2012). Trial-Based Functional Analysis and Functional Communication Training in an Early Childhood Setting. Journal of Applied Behavior Analysis 45(3), 579-584.


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