Advantages and Disadvantages of Physiological Assessment For Next Generation Control Room Design

Transcription

1 Advantages and Disadvantages of Physiological Assessment For Next Generation Control Room Design Tuan Q. Tran, Ronald L. Boring, Donald D. Dudenhoeffer, Bruce P. Hallbert, M.David Keller*, and Tessa M. Anderson** Idaho National Laboratory, New Mexico State University*, & Idaho State University** IEEE HPRCT August 27-32st 2007

2 Introduction Next generation advanced energy systems have been conceptualized to be more computerized, intelligent, integrated, and automated Thus, it will inevitably present new information processing demands on the human operator leading to a high-level of workload High workload can severely diminish one s s ability to perceive, recognize, and respond to emergency or unanticipated events, thus, can place both the operator and system at risk

3 Physiological Measures and Workload Traditional workload measures in human factors include subjective self report and performance modeling. An alternative to self report exists in the form of physiological measures. Physiological measurements are not constrained to several limitations tions that are inherent in: Self-report questionnaires The inherent biases (e.g., social desirability) that comes with self- evaluation Task interruption or distraction effects on the subject Not be cognitive penetrable when self-assessing oneself Reliance on memory to remember task experience Performance modeling Modeler determines and assigns appropriate level of workload demand Over or under task decomposition Scripted-nature does not allow an inspection of emergent or unexpected behaviors

4 Physiological Measures and Workload In the physiological measurement approach, subjects are monitored by an array of physiological sensors some requiring contact with the subject s s body through electrolyte sensors (e.g., EEG) while others are standoff sensors (e.g., eye tracking device embedded in the physical system). EEG Eye Tracking (GSR)

5 Physiological Measures and Workload Physiological measures permit a more objective workload assessment and can provide real-time evaluation Thus, designer can quickly and accurately identify usability problems as they occur Moreover, it fosters the assessment of emergent behaviors allowing designers to detect novel design issues.

6 Possible Physiological Sensors to Assess Workload Physiological Sensors Eye Tracking Brief Descriptions Assess eye movements (scan patterns) and characteristics (eye-blinking, pupil dilation) Electroencephalograms Measure neurological activities by placing electro-skinsensors across various positions on the skull (currently the skin-sensors are embedded in a wearable headset) Body Posture Assess changes in automatic behavior (i.e., postural adjustment) which is assumed to correlate with changes in cognitive activity. For example, a decline in postural stability is correlated with an increase in mental activity Galvanic Skin Response Measures the autonomic nervous system (ANS) activity to gauge a person s arousal level Inter-Heart Beat Interval Measures the time between successive heartbeats in Image-Based Technology milliseconds Records changes in visual behaviors. Rests on foundation that a person s states can be exhibited in certain visual behaviors that are easily observable from changes in facial features such as the eyes, head, and face (e.g., yawning, sluggishness in facial expression, sagging posture).

7 Beyond Workload Assessment: Using Physiological Assessment to Extend Understanding of PSFs Performance Shaping Factors (PSFs) play a critical step in quantification for many current HRA methods Modifying nominal human error probability to produce an adjusted human error probability Performance Shaping Factors Nominal Human Error Probability Adjusted Human Error Probability

8 Using Physiological Assessment to Extend Understanding of PSFs Shortcoming to current HRA methods: Typically assess PSFs within a time-slice or event- based Adjusting failure rates does not consider changes in in PSF levels or performance that could be validated through physiological measures Thus, we currently have an inability in HRA to assess several PSF characteristics

9 Additional PSF Characteristics PSF Characteristics Brief Descriptions Example Latency Momentum Static Dynamic time duration of PSF effect propensity of PSF to change over time PSF that remains constant across the events or tasks in a scenario PSF evolves naturally across events or tasks in a scenario when an operator experiences high stress, how long will that stress linger until the operator recuperates and returns to a state of homeostasis stress progressively increases as it approaches the closing window of available time to perform an action poor fitness for duty due to lack of sleep the night before has a constant effect throughout an event during an unusually long work shift, fatigue a negative contributor to fitness for duty, would be expected to evolve and influence performance Initiator a PSF effect initiates another PSF effect limited time available initiates high stress and workload

10 Using Physiological Assessment to Extend Understanding of PSFs Advantages of physiological assessment for HRA can monitor/track PSFs characterization across time and single or multiple events physiological results can be time-stamped with behavioral data allowing finer precision in our ability to predict less and more successful task performance These advantages are important in dealing with the challenges of developing next generation control rooms such as: updating the crew staffing model defining shared resources between the automated system and human operators evaluating newly designed interfaces or novel system configurations

11 Limitations to Physiological Assessment Precision Overall, the precision of physiological assessment in assessing workload is improving. However, it is still not highly accurate [70-80% ] Thus, we propose that physiological assessment should be used jointly with traditional behavioral measures (e.g., workload questionnaire, observational methods, and protocol analysis).

12 Limitations to Physiological Assessment Practical Application technology has not reached the point in which it can be used in actual operational conditions for long periods of time Due to long-term usability and comfort issues (e.g., wearing a complete sensor laden suit or helmet for long periods of time is fatiguing) Simpler heart rate or GSR measures for a complete shift is possible. Data Analysis Bandwidth the amount of data collected from proposed physiological assessment methods might be overwhelming if collected over a long periods of time (complete shift). Development of smart data mining algorithms could be useful Researchers will have to determine what data is important and learn how to evaluate it.

13 Conclusion: Physiological Measures Can overcome some of the limitations/biases of current workload evaluation methods including self report and performance modeling Can be used to acquire useful information on PSF characteristics and human-system performance that, in turn, can improve the quality of HRA This information can be useful in: Evaluating crew staffing for new reactor designs, determining functional allocation between operators and intelligent systems, and in prototyping new interface designs Providing feedback regarding problematic design issues Identifying conditions where failure rates might be higher