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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?