Trial-Based Functional Analysis has limited validity outside of defined clinical settings

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Functional analysis (FA) is an essential requirement within the practice of supporting individuals with a learning disability (intellectual disability or ID) with behaviours that challenge. The benefits of completing functional based assessments are outlined in current policy and best practice documents, including:

Challenging behaviour and learning disabilities: prevention and interventions for people with learning disabilities whose behaviour challenges’ NICE guideline, draft for consultation, December 2014 and ‘Positive and Proactive Care Dept of Health 2014.

This study aims to explore the validity of a variant of functional analysis assessment; trial-based functional assessment (TBFA). In the TBFA model, the subject is exposed to specific antecedents and consequences over time limited ‘trials’ within the context of ongoing routines and activities, with test and control settings.

So for example if the function of a behaviour is hypothesized as being ‘to escape’, the person is observed to see if they escape when presented with a particular antecedent or consequence. The aim is to systematically work out what triggers or maintains a behaviour and so verify its function.

The authors outline the prevalence of research into functional analysis procedures and its variants. They find there has been a growth in studies published, with the development of TBFA as a distinct variation of this assessment increasingly included in the published literature. The authors report the need to systematically review the evidence behind this and to identify future areas of research. 

Completing Functional Analysis has clear benefits in planning responses to chalenging behaviour

Completing Functional Analysis has clear benefits in planning responses to chalenging behaviour


The study is set within the traditional style of a psychological University based review of an area of research.  The methodology (the type of study) then focuses on detailing whether and how the selected studies will benefit research and practice.

The literature search follows a fairly standardised but rigorous practice, where electronic and manual searches based on key words are combined. There were a limited number of studies that met the requirements for inclusion, limited by the precise nature of the standardised TBFA procedure.  The review identified and detailed 13 studies. The rationale for inclusion, what data was included for consideration and how agreement was reached about these decisions is then detailed in the review.


The difficulties of conducting systematic reviews of types of assessment are made apparent within the article. Even when comparing a small number of studies, it is still difficult to completely control for the variation of conditions.

The variations that would impact on the results of the study are: the selection of the studies for the review, the choice of subjects, behaviours across studies, settings of studies, who conducted the TBFA trials, the TBFA procedure itself and the outcomes of the trials – successful in identifying behaviour function or not.

These variations reflect the complex nature of the task at hand, that of defining the function of individual behaviours in different subjects across different settings. They also reflect the complexity of the procedure.

The authors believe that the data from the identified studies hold validity in that they enable behavioural function to be identified. This then leads onto ‘effective and efficient interventions’.

The identified implications of this study rest on its stated benefits for research and for practice.

This review identifies the need to complete further TBFA research. This is principally to address the difficulties encountered in validly generalising benefits, from the many variables contained between the 13 studies reviewed. For example TBFA is used predominantly in educational settings with children with a developmental/ intellectual disability.

The studies selected had small subject numbers, and studies were not wholly controlled for randomisation of procedure – (Control and test). These variations may limit how generalisable TBFA is to an adult population in community settings, prompting the authors to point future research to evaluate the ‘social validity’ of TBFAs.

Practice benefits are limited by the complex methodology designed to enable functional assessments to be shortened and so be less resource intense. This raises the issue of training and whether the process would remain valid ‘outside of the field of behaviour analysis’.

Although TBFA is not considered ‘evidence based practice’ yet, within a defined educational setting, it does promise to have less impact on disrupting classroom routines and be less resource dependent. Lambert & Bloom in 2012 identified that TBFA may be especially useful for early childhood settings because it can be conducted in a format that allows for brief assessment trials.

The reviewers identified researchers found it difficult to control for variation

The reviewers identified researchers found it difficult to control for variation

Conclusion and Comment

Functional assessments are a means to an end in that they identify the function of behaviour so that interventions can be identified that support a reduction in ‘maintaining variables’ or triggers.

The authors find TBFA to be a promising assessment of challenging behaviour used in applied or educational settings with children, in that as an assessment it is less resource intense than traditional FA. Susan Bloom, an educational Psychologist and published proponent of TBFA, identifies that this assessment provides the benefits of experimental FA (that require extended resources and time) whilst remaining a practical and convenient way of obtaining valid results.

Other non-standard methods of FA were identified within this study. It was not stated whether they have been found to be as valid or not, although the need seek out ‘acceptable and feasible’ FA models is a recommendation.

Whilst the study adds to the research literature within this restricted sphere of study, it may also distract from the wider practical benefits of ensuring individuals receive thorough functional assessments paired with effective interventions in non-applied community settings.

Although it has been argued that the rigorous selection of cases, with limited subject numbers in distinct settings has limited the generalisability of findings. It can be equally argued that a strength of this study was that TBFA did successfully identify behavioural function, across 13 studies and their wide range of variabilities.

However, only 4 of the 13 studies went on to test for validity of these findings using function-based treatments. In addition, the rigorous selection of case studies may have excluded information and data salient to identifying alternative brief FA methods. It may be there are other brief FA methods with equal or increased validity.

A number of ethical issues have been raised by the use of this (as well as analog FA) methods due to the fact that the procedure directly reinforces the very behaviour being targeted for reduction.

It is recognised that the authors identify there is a need for further research particularly to ascertain if the process has social validity in terms of acceptability, feasibility and suitability.

Need for further research in acceptability, feasibility and suitability

Need for further research in acceptability, feasibility and suitability


A Systematic Review of Trial-Based Functional Analysis of Challenging Behavior Mandy Rispoli, Jennifer Ninci, Leslie Neely, Samar Zaini Journal of Developmental and Physical Disabilities
26, 3, 271-283 [abstract]

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Russell Woolgar

Russell is currently working as an independent Clinician/ Chair attending Care and Treatment reviews in secure services under Transforming care. Before this Russell was employed on a secondment to NHS England to support the transforming care agenda as a regional project manager. Prior to this he managed the Learning Disability Outreach team in Leicester. He has worked as a learning disability nurse for over 30 years, across residential and community services. He has a Masters degree in ‘Learning Disability –Quality of Life’ and has a passion for sharing knowledge to benefit others. His specific interests relate to his hands on experience of managing a ‘challenging needs team’. He used to chair the East Midlands Learning Disability Nurse Network.

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