Assignment 2: Hierarchical task analysis

In this assignment, you will:

  • Conduct a hierarchical task analysis (HTA) for a task
  • Elicit a user's mental model about the same task 
  • Compare the mental model and the task structure

HTA was presented in this week's lecture. In addition to lecture slides, the following materials can be useful resources for you:

  • Benyon: Designing interactive systems, Chapter 11. Link
  • Ritter et al.: Foundations for Designing User-Centered Systems, Chapter 11. Link
  • Stanton: Hierarchical task analysis: Developments, applications, and extensions. Applied Ergonomics 37 (2006) 55–79. Link
  • Annett: Hierarchical task analysis. In E. Hollnagel (Ed.), Handbook of Cognitive Task Design. (pp. 17-35). Erlbaum. Link
  • Lane et al: Applying hierarchical task analysis to medication administration errors. Applied Ergonomics 37 (2006) 669–679. Link

Photo sharing task

Your task is to analyse photo sharing via email in a mobile phone. An efficient way of doing that is by going to a phone Photo Gallery, selecting the photos, and pressing a the Share symbol:

One way to share images from a phone

The picture shows one part of the entire series of actions that this task consists of. Your tasks in this Assignment are to 1. to do a HTA on this task, 2. examine how a user might represent this sharing task, and 3. to compare the user's mental model and the HTA's model of the same task.


Familiarize yourself with the task so that you can perform it, starting from the actions that are shown in the screenshots above.

Task 1: HTA

Analyse the task structure of the photo sharing task. Create a diagram about it using the notation that Lane et al (2006) use in their paper's Appendices and which is also shown below.

Source: (c) Adegboyega Akinsiku,


Note: it may be faster to first sketch the diagram with pen and paper, and use a textual representation of the task (see lecture slide for "Non-graphical HTA") before drawing the final diagram.

Task 2: Elicitation of a mental model

Find a friend and ask him/her to show how to share photos from a phone via email. Let the user explain the steps in that task. Do not seek to correct the user if the sequence of actions has errors, inefficiencies or if it deviates from the HTA that you created. If the user does not know how to perform this task, continue until you understand what the user is trying to do, and then show how the task can be performed.

Make notes while you observe and discuss. Once you think you know what the user's task structure is like, thank the user and prepare a new HTA that describes how the user understood the photo sharing task.

Task 3: Comparison of the two HTAs

Compare the two diagrams and identify the differences. Analyse the pros and cons of the task structures by their execution speed, vulnerability to mistakes, and simplicity.

How to return this assignment

Your submission must be returned as a PDF, and it must include 1) HTA diagram from Task 1, and 2) HTA diagram from Task 2, and 3) a comparison of the two.

This assignment is carried out independently.

Return your assignment by 23:55 on Sunday 23 September 2018 as a PDF via this page.