Hierarchical task analysis: Developments, applications, and extensions

doi:10.1016/j.apergo.2005.06.003

Applied Ergonomics

Volume 37, Issue 1, January 2006, Pages 55-79

https://doi.org/10.1016/j.apergo.2005.06.003 Get rights and content

Abstract

Hierarchical task analysis (HTA) is a core ergonomics approach with a pedigree of over 30 years continuous use. At its heart, HTA is based upon a theory of performance and has only three governing principles. Originally developed as a means of determining training requirements, there was no way the initial pioneers of HTA could have foreseen the extent of its success. HTA has endured as a way of representing a system sub-goal hierarchy for extended analysis. It has been used for a range of applications, including interface design and evaluation, allocation of function, job aid design, error prediction, and workload assessment. Ergonomists are still developing new ways of using HTA which has assured the continued use of the approach for the foreseeable future.

Section snippets

Origins of task analysis

According to Kirwan and Ainsworth (1992), hierarchical task analysis (HTA) is the “best known task analysis technique” (p. 396). It is probably a special case in the ergonomics repertoire of methods. Since the first paper written on the specification for the method in 1967 by Annett and Duncan, the past 38 years have seen many developments in ergonomics research and methods but HTA has remained a central approach. It is fitting to review the current state of the art to help take stock of where

Development of HTA

In the original paper laying out the approach for conducting HTA, Annett et al. (1971) make it clear that the methodology is based upon a theory of human performance. They proposed three questions as a test for any task analysis method, namely: does it lead to any positive recommendations, does it apply to more than a limited range of tasks, and does it have any theoretical justifications? Perhaps part of the answer for the longevity of HTA is that the answer to each of these questions is

A framework for conducting HTA

There do seem to be many different conventions for expressing HTA that have developed from peoples’ own adaptation and mutations. It is difficult, therefore, to propose that there is one right way of doing this, although some have tried (Shepherd, 1989, Shepherd, 2001; Annett, 2004). This section will follow the examples of Stammers (1996) and Shepherd, 1998, Shepherd, 2001 to propose a framework within which HTA can be conducted, allowing for personal adaptation for the purpose at hand.

The

Some applications of HTA

Most, if not all, application areas in ergonomics require some form of task representation. Kirwan and Ainsworth (1992) claim that HTA may “be used in almost every circumstance” (p. 29), offering a major cost saving in a system design program, rather than continually re-analysing the task for every different type of application. Annett (2004, pers. commun.) has made the point that the form of the HTA could vary depending upon the application, so that the first or subsequent drafts of HTA might

Some extensions of HTA

The whole point of conducting HTA to analyse tasks, means that the HTA representation is the starting point for the analysis rather than the end point. The tabular format has enabled a mechanism for extending the analysis beyond the system description provided in the sub-goal hierarchy and plans. It is perhaps ironic that, whilst initial developments in HTA sought to simplify the tabular format, latter developments have sought to extend it. These extensions in HTA have enabled the analyst to

Future requirements for software support of HTA

Attempts have been made to develop software support for HTA, with varying degrees of success but none supports the full range of applications to which HTA may be put. The software tool of Bass et al. (1995) was only developed to prototype form, to simplify the production of the hierarchical diagrams and the tabular format by allowing direct manipulation of the data objects and easy editing of the analysis. Other examples have been developed for specific applications, such as error prediction or

Some general conclusions

The future for HTA seems assured, at least in the short to medium term. The variety of domains and applications that it has been used for is a testament to its usefulness. The developments and extensions of the approach suggest that it is likely to remain in the core repertoire for ergonomists. HTA should also serve as a benchmark for all other ergonomics methods and approaches. The key features of the approach are that it was not only developed on strong theoretical foundations but also

Acknowledgements

The author of this paper gratefully acknowledges the helpful comments from Professor John Annett, Dr. Don Harris and Dr. Karen Lane on an earlier version. This work from the Human Factors Integration Defence Technology Centre was part-funded by the Human Sciences Domain of the UK Ministry of Defence Scientific Research Programme. The report on which this paper is based was used to develop a software tool for HTA which is available free-of-charge from www.hfidtc.com.

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Hierarchical task analysis: Developments, applications, and extensions

Abstract

Section snippets

Origins of task analysis

Development of HTA

A framework for conducting HTA

Some applications of HTA

Some extensions of HTA

Future requirements for software support of HTA

Some general conclusions

Acknowledgements

Appl. Ergon.

Appl. Ergon.

Issues of quality and practicability in task analysis: preliminary results from two surveys

Ergonomics

Recent developments in hierarchical task analysis

Theoretical and pragmatic influences on task analysis methods