HTA as a framework for task analysis

Presenter: Hilary Ince, University of Idaho

IntroductionHierarchical Task Analysis (HTA): “explores tasks

through a hierarchy of goals indicating what a person is expected to do, and plans indicating the conditions when subordinate goals should be carried out”

Not often used for cognitive tasks, paper aims to change that

IntroductionThere is lack of agreement on nature and

purpose of task analysis“Task” can be human behavior, system goals, how

context constrains goal attainment, or a mix of these

“Task analysis” can be an investigatory tool or a method to model human behavior, can be specific and rigorous or just a guideline

IntroductionMiller’s definition of task: “a group of

discriminations, decisions, and effector activities related to each other by temporal proximity, immediate purpose, and a common man-machine output”

Not a great definition… temporal proximity is not always there, nor is immediate purpose

For this paper, task is a “problem facing an operator” (distinguishes from behavior)

Justification of HTAHierarchy can exert control, where higher levels

control lower ones

Can also be descriptive, describing sub-goals in relation to each other in terms of their purpose

HTA “relates to the strategy of examining a task within a practical project”

Strategy in Task AnalysisBox 1 – Setting Goals: Begin by identifying main

goal associated with the problem

Box 2 – Observing Constraints: Goals will have constraints to their attainment… recognize these

Box 3 – Calculating criticality: Only examine task elements deemed critical, either subjectively or with data

Strategy in Task AnalysisBox 4 – Ceasing Rediscription: If current

performance is acceptable, do not examine the goal further

Box 5 – Generating Hypotheses: If current performance is not acceptable, look for a cause of the problem by examining operator-system interaction

Box 6 – Cost-benefit analysis: Do the benefits outweigh the cost of the hypothesis?

Strategy in Task AnalysisBox 7 – Recording the analysis: If an acceptable

hypothesis is selected, show progress, hypotheses proposed, and hypotheses rejected for cost (the cost may prove worth it later)

Box 8 – Redescription: If an acceptable hypothesis hasn’t been selected, attempt to redescribe the goal

Strategy in Task AnalysisBox 9 – Challenging the contraints: If still unable

to establish a hypothesis, challenge contraints. Management may allow higher costs, requirements may be able to shift

Analyzing Cognition within the Task Analysis Context

Article suggests that instead of distinguishing between cognitive and non-cognitive TAs, should consider how general TA accommodates cognitive tasks

HTA is deliberately flexible, and can be used in many situations

“Task must first be understood to anticipate the demands placed on cognition”

ConclusionsTask is complementary, not synonymous, with

behavior

HTA is a general task analysis strategy, not a method for modeling behavior

Cognitive task analyses for decision centered design

and trainingPresenter: Hilary Ince, University of Idaho

IntroductionCognitive task analysis (CTA): “an approach that

‘determines the mental processes and skills required to perform a task at high proficiency levels and the changes that occur as skills develop’”

Critical decision method (CDM): “a retrospective interview strategy that applies a set of cognitive probes to actual nonroutine incidents that required expert judgment or decision making”

MethodCDM explores actual non-routine events, and

what decisions were made

Participants asked to recall such a case, and tell the story in detail

Cognitive probes used to get participants to think about their situational awareness and planning at the time of the event

Study 117 whitewater rafting guides with varying

experience interviewed

Asked to describe an incident when they had to make quick decisions

Timelines were created of each event, then summarized into situation assessment records (SAR)

A SAR is a breakdown of primary environmental cues, expectancies generated from cues, goals of the guides, and selected course of action

Study 1 Results and Discussion

17 critical incidents collected, 52 total decision points

88% of decisions made under 5 seconds

As expected, expert guides made decisions based on previous experiences

Results showed that mental simulation of the river ahead is helpful, could be a good training tool

Study 210 experienced GA pilots, average of 10,000

hours experience

Asked to recall a situation where an unusual or difficult situation was made regarding weather

Probed two weather situations: slowly deteriorating and thunderstorms

Study 2 Results and Discussion

High degree of consistency between experts regarding critical cues

Novices should be trained to recognize these cues

Can be taught to apply knowledge through training

Study 3Aim of the study was to determine requirements

for a computer system to replace manual ambulance dispatch system

5 dispatchers with 5-9 years of experience interviewed

Asked to describe a particularly unusual or difficult situation

Details randomly arranged on Post-its, then participants rearranged the details in orderOften remembered additional information

Study 3 Results and Discussion

Interviews coded as cues, situation assessments, goals, and courses of action

Goals were identified as:Obtain early, accurate picture of incidentMaintain situational awarenessMatch available resources to needs of situationGet help on the way within three minutesMaintain record of events

Study 3 Design Implications

Display shows available ambulances near event

Supports planning for major incidents

Evaluation of CDMKey feature of CDM is use of probes

Recreation of the timeline using Post-its was helpful

Results of CDM can be used to influence training programs, as shown in these Studies 1 and 2

Questions?