HTA As a Framework for Task Analysis

1. HTA As a Framework for Task Analysis A. Shepherd 1998 Brenda Crook

2. 2 Themes Justification of HTA as a framework for analyzing tasks rather than method for modeling behavior Treatment of cognitive task elements within this framework

3. Hierarchical Task Analysis (HTA) Process of exploring tasks through a hierarchy of goals and plans Task: problem facing an operator Goal: what a person is expected to do Plans: conditions when subordinate goals should be carried out Distinguishes between the task and the behavior recruited to carry out the task

4. HTA Task Analysis identifies strategies by which the operator can be facilitated to solve the problem Influenced by Systems Thinking System: any complex of inter-related parts Characteristics Functions – purpose the system serves in broad context System components/sub-components and their interaction Hierarchical description of structure of components

5. HTA: Systems Thinking Influence Hierarchical System Description Can Be: Just a description of system at some level of detail To imply degree of control in which higher levels in the hierarchy influence behavior of lower levels HTA supports Systems-Influenced model of human behavior through Concepts of Feedback and Control Pursuit of Goal through adaptive behavior Control of Behavior through Feedback

6. HTA: Feedback and Control Miller et al (1960) proposed TOTE Describes relationship between action and feedback in controlling performance T: Operator Tests environment against specified criterion O: if test is mismatch, Operates to affect change T: Tests again to check if discrepancy still exists E: Exits if match accomplished O: Operates again if match not accomplished

7. HTA: Feedback and Control Annett and Duncan (1967) proposed IAF Feedback and control in approach to task analysis I: Input A: Action F: Feedback Failure to carry out an operation successfully will be due to failure of handling I A or F

8. HTA: Production Systems TOTE and IAF can be compared to “production systems” used in cognitive modeling Production: condition-action statement Condition: T (in TOTE) or I or F (in IAF) Action: O (in TOTE) or A (in IAF) Production is triggered when circumstances match ‘condition’ When a ‘condition’ consistently ‘matches’ a specified pattern, the action should follow Feedback: different set of conditions warrants a different action Connection between task analysis and cognitive modeling

9. HTA: Analytical Strategy vs Model Systematic examination of tasks to establish hypotheses to enable goals to be attained HTA as model of behavior suggests Everyone organizes task data the same way Utilization information in pursuit of goals is consistent across all circumstances Doesn’t address changes in mental organization of task information as more or less skill is achieved

10. HTA Strategic Framework 9 Elements Relies upon other methods and perspectives to enable completion Systematic strategy important particularly in large multiple-activity tasks Hierarchical representation of task Ensures fit of task and behavior to system goals Identifies adjustments to task or task affordance to support behavior capabilities Identifies modifications in behavior to meet task demands

11. HTA Strategic Framework Setting Goals Identify main work goal associated with problem Observing Constraints Constraints associated with goal attainment Can be environmental, management, design Calculating Criticality Importance of goal and reliability of execution Can be subjective or data-based Only examine critical task elements

12. HTA Strategic Framework Ceasing Redescription Analysis stops for non-critical tasks identified in #3 Generating Hypotheses – if performance is not satisfactory Examine operator-system interaction Human error analysis, model behavior to determine weaknesses Make design suggestions Observe constraints throughout Cost-Benefit Analysis Hypotheses costs Changes as project/analysis progresses

13. HTA Strategic Framework Recording the Analysis Provides documentation of progress, how task was represented, proposed design solutions, rejected hypotheses Redescription May not have design hypotheses Re-examine task in terms of sub-systems/subordinate operations Challenging Constraints When no hypotheses can be established

14. HTA as Strategy vs Behavior Model Framework that relates various stages of decision making encountered in a task Generalized task analysis strategy that employs a variety of methods as part of task analysis vs. as a precursor Hierarchy of operations and plans and thus distinguishes ‘task’ from ‘behavior’

15. HTA and Cognition Analysis Preece et al (1994) distinction between HTA and Cognitive Task Analysis (CTA) HTA: establishes accurate description of steps required to complete a task CTA: represents knowledge that needed to complete the task Argument: successful performance in all tasks depends upon interaction between physical and cognitive elements

16. CTA in HTA Framework CTA methods can be utilized within HTA frame GOMS: Goals, Operations, Methods, Selection rules TAG: Task, Action, Grammar TAKD: Task Analysis for Knowledge Description Use within HTA frame economy of effort Ensures examination of task elements not done in vacuum

17. CTA in HTA Framework HTA supports recent approaches to cognitive modeling: “unitary theories of cognitive architecture” (Hjaer and Hansen 1995) Role of knowledge within processes of learning, inference, and decision making in producing behaviors Manner in which information is acquired, stored, organized and retrieved to account for decision making and performance across range of task elements Demonstrates need to account for behaviors that interact across task hierarchy Mapping cognitive task elements onto cognitive skills difficult Physical tasks are visible

18. CTA in HTA Framework HTA supports CTA through inferring cognitive task elements onto cognitive skills by stating plans Decision process can be inferred Different actions consistently carried out in different circumstances Monitoring can be inferred Operator jumps to action following period of inactivity Diagnosis, Rectification, Compensation, Recovery Carrying out tasks to maintain system status

19. HTA Advantages in CTA Can identify what is supposed to be achieved Task must first be understood to anticipate demands on cognition Cognitive task variation based on demands placed on individual Can establish interaction between cognition and action Can identify inter-relationships between cognitive skills underlying and interacting with different cognitive task elements

20. HTA Advantages in CTA Can Identify task elements in context Factors that influence performance of a cognitive task element Goal context – situational factors such as crisis Frequency, Predictability, and Coincidence Predictable events can be automated Determine unpredictable events and when they may occur together – increased cognitive demands may limit performance Priming – prompts to operator for next step Decision Outcome and Criticality

21. Survey Results in Quality and Practicability in Task Analysis Ainsworth and Marshall 1998

22. Quality and Practicality in Task Analysis Surveyed Defense and Nuclear Industries Purpose Examine ways in which TA’s were conducted Examine extent of variability between TA’s Examine suitability of different TA methods

23. Defense Industry Results 27 reports obtained Use of TA method Depended on purpose of TA Multiple methods often listed Ranged across eight different TA methods HTA, cognitive modeling, scenario-specific modeling, workload analysis, qualitative assessments, link analysis, functional flow analysis, taxonomies and error analysis

24. Defense Industry Results Data Collection Data sources not clearly defined – affects confidence of findings and recommendations Mostly used sequential task lists; little HTA for complex tasks order Good use in general of decomposition tables More detailed decomposition = detailed recommendations High reliance on subjective workload analysis to determine functional allocations – of limited use by itself

25. Defense Industry Results Graphical Techniques Not always used effectively Confusion about techniques Failures to exploit representations Inappropriate scales Too complex diagrams – trivial/missed relationships Data Presentation Analysts not identified/ SME background unknown ? Basis of recommendations – opinion vs. understanding

26. Defense Industry Results Data Presentation (cont.) Level of detail of analysis inconsistent Leads to difficulty in prioritizing recommendations/making alternate resolutions difficult Methodology for task timings not reported

27. Nuclear Industry Results 70 reports Each TA categorized by respondents into one of six phases of system life cycle Concept, feasibility, project definition, detailed design, acceptance/commissioning, in-service TA not used much during concept phase Defense industry tended to use TA earlier in design process Depth of analysis high when HF expertise used

28. Nuclear Industry Results TA Method HTA widely used Task plans with text vs flow diagrams Complex plans resulted in unclear diagrams Task decomposition in over half More complex decomposition = more detailed recs 12 TA’s were task descriptions from written procedures Task steps missed/unchecked Recs tended to be generic and without psychological insights

29. Nuclear Industry Results Data Collection Most popular were walk/talk-throughs, informal discussions Effective use and format Scenario specific focus Timelines used widely Use was good Basis for timing unclear in some Error analysis depth/scope varied Data Presentation Variable presentation of reports, some with no HTA diagrams No structured overview of task Model used by analyst not illustrated

30. Conclusions Over 100 TA’s examined in 2 surveys Provided useful insights into ways that TA’s are utilized by organizations Identified areas of improvement

31. Conclusions Differences between defense and nuclear industry use of TA’s Presentation of TA objectives not clear to defense analyst Depth of analysis/level of HF expertise was greater in the nuclear industry

32. Recommendations Define objectives of TA clearly Avoids superficial/costly study Report methods and data sources Enables user to assess weight of recommendations Ensure task analysis for complex tasks is accomplished by someone with psychological expertise Analysis more insightful Develop guidelines to address various stages of conducting a TA Advice should be systematic vs prescriptive/inflexible rules

33. Questions/Discussion?