Simulated Process Control Task Research Articles

Interruptions versus breaks: The role of cue utilisation in a simulated process control task

AbstractAlthough interruptions and breaks are similar insofar as they both offer a momentary recess from the primary task, the premise for the activity in which the operator engages differs. Interruptions impose the requirement to direct resources to complete a task, while breaks offer the opportunity for suspended goal rehearsal. The aim of this study was to investigate differences in resumption lags following “interruptions” and “breaks,” and whether cue utilisation moderates this relationship. Seventy‐nine university students completed an assessment of cue utilisation and managed scheduled and unscheduled interruptions and breaks during a 35‐min rail control simulation. The analyses revealed that participants who recorded higher cue utilisation recorded shorter resumption lags following scheduled, rather than unscheduled interruptions. Participants who recorded lower cue utilisation recorded shorter resumption lags following breaks compared to interruptions, irrespective of the administration. The results suggest that scheduled interruptions and breaks offer the opportunity for suspended goal rehearsal.

Retention of a standard operating procedure under the influence of social stress and refresher training in a simulated process control task

In a simulated process control task, we investigated the effects of refresher training and acute social stress on performing a standard operating procedure (SOP) containing a production and monitoring task and knowledge recall after a retention interval of two weeks. In a 2 × 2 between-group design (Factor 1: induced social stress, Factor 2: refresher training), 76 engineering students performed an SOP at t1 in week 1 and at t2 in week 3. A MANOVA in week three (t2) indicated a main effect of the refresher training for the SOP execution containing a production and a monitoring task and an impairing effect of stress on the monitoring task. That means that after a retention interval, stress mainly affects the SOP’s monitoring task. An additional correlational analysis showed that knowledge test performance is negatively associated with cortisol level and that retentivity is a strong predictor for knowledge test performance and production task performance, too.Practitioner Summary: We investigated effects of social stress and refresher training on performing a standard operating procedure (SOP) after a retention interval of two weeks. The impact of social stress reduced the monitoring task performance as part of the SOP, but not the production outcome. Without refresher training, performance is significantly worse.Abbreviation: SOP: Standard Operating Procedure; MANOVA: Multivariate Analysis of Variance; CSB: Chemical Safety and Hazard Investigation Board; TSST: Trierer Social Stress Test; P-TSST: Placebo Trierer Social Stress Test; WaTrSim: Water Treatment Simulation; HPA axis: hypothalamic pituitary adrenal axis; WIT-2: Wilde Intelligenztest – 2; SPSS: Statistical Package for the Social Sciences; ANOVA: Analysis of Variance.

Design of an Adaptive Human-Machine System Based on Dynamical Pattern Recognition of Cognitive Task-Load.

This paper developed a cognitive task-load (CTL) classification algorithm and allocation strategy to sustain the optimal operator CTL levels over time in safety-critical human-machine integrated systems. An adaptive human-machine system is designed based on a non-linear dynamic CTL classifier, which maps a set of electroencephalogram (EEG) and electrocardiogram (ECG) related features to a few CTL classes. The least-squares support vector machine (LSSVM) is used as dynamic pattern classifier. A series of electrophysiological and performance data acquisition experiments were performed on seven volunteer participants under a simulated process control task environment. The participant-specific dynamic LSSVM model is constructed to classify the instantaneous CTL into five classes at each time instant. The initial feature set, comprising 56 EEG and ECG related features, is reduced to a set of 12 salient features (including 11 EEG-related features) by using the locality preserving projection (LPP) technique. An overall correct classification rate of about 80% is achieved for the 5-class CTL classification problem. Then the predicted CTL is used to adaptively allocate the number of process control tasks between operator and computer-based controller. Simulation results showed that the overall performance of the human-machine system can be improved by using the adaptive automation strategy proposed.

Does skill retention benefit from retentivity and symbolic rehearsal? – two studies with a simulated process control task

Two experiments were designed to compare two symbolic rehearsal refresher interventions (imaginary practice, a hidden introspective process) and investigate the role of retentivity in skill retention. Retentivity is investigated as the ability to memorise and reproduce information and associations that were learned a short time ago. Both experiments comprised initial training (week 1), a symbolic rehearsal for the experimental group (week 2) and a retention assessment (week 3). In the first study, the experimental group received a symbolic rehearsal, while the control group received no rehearsal. In the second study, the experimental group received the same symbolic rehearsal used in study 1, enhanced with rehearsal tasks addressing human–computer interaction. The results showed that both symbolic rehearsal interventions were equally likely to mitigate skill decay. The retentivity showed medium to high correlations with skill retention in both studies, and the results suggest that subjects high in retentivity benefit more from a symbolic rehearsal refresher intervention. Practitioner Summary: Skill decay becomes a problem in situations in which jobs require the correct mastery of non-routine situations. Two experimental studies with simulated process control tasks showed that symbolic rehearsal and retentivity can significantly mitigate skill decay and that subjects higher in retentivity benefit more from refresher interventions.

System reliability, performance and trust in adaptable automation

The present study examined the effects of reduced system reliability on operator performance and automation management in an adaptable automation environment. 39 operators were randomly assigned to one of three experimental groups: low (60%), medium (80%), and high (100%) reliability of automation support. The support system provided five incremental levels of automation which operators could freely select according to their needs. After 3 h of training on a simulated process control task (AutoCAMS) in which the automation worked infallibly, operator performance and automation management were measured during a 2.5-h testing session. Trust and workload were also assessed through questionnaires. Results showed that although reduced system reliability resulted in lower levels of trust towards automation, there were no corresponding differences in the operators' reliance on automation. While operators showed overall a noteworthy ability to cope with automation failure, there were, however, decrements in diagnostic speed and prospective memory with lower reliability.

The effects of automation-induced complacency on fault diagnosis and management performance in process control

Operators of automated systems can develop complacency, impairing their ability to respond in a timely and appropriate fashion when automation fails. This study sought to examine the impact of an instructional manipulation of attentiveness, in terms of engagement and accountability, on fault diagnosis and fault management. Participants trained on the operation of a simulated process control task, with instructions varied to induce higher or lower attentiveness to the task. After several routine faults within the system, a fault occurred along with a failure of a previously available diagnostic and management aid, and shortly after a second failure occurred. The first failure was associated with significant impairment of diagnosis and management, but comparatively few differences between attentiveness groups. Results are discussed in terms of their implications for a model of human-automation interaction.

Predictive displays for a process-control schematic interface.

Our objective was to examine the extent to which increasing precision of predictive (rate of change) information in process control will improve performance on a simulated process-control task. Predictive displays have been found to be useful in process control (as well as aviation and maritime industries). However, authors of prior research have not examined the extent to which predictive value is increased by increasing predictor resolution, nor has such research tied potential improvements to changes in process control strategy. Fifty nonprofessional participants each controlled a simulated chemical mixture process (honey mixer simulation) that simulated the operations found in process control. Participants in each of five groups controlled with either no predictor or a predictor ranging in the resolution of prediction of the process. Increasing detail resolution generally increased the benefit of prediction over the control condition although not monotonically so. The best overall performance, combining quality and predictive ability, was obtained by the display of intermediate resolution. The two displays with the lowest resolution were clearly inferior. Predictors with higher resolution are of value but may trade off enhanced sensitivity to variable change (lower-resolution discrete state predictor) with smoother control action (higher-resolution continuous predictors). The research provides guidelines to the process-control industry regarding displays that can most improve operator performance.

Counteracting skill decay: four refresher interventions and their effect on skill and knowledge retention in a simulated process control task

In process automation, skill decay has not been investigated systematically. In two experimental studies, refresher interventions (RIs) were compared to support skill and knowledge retention of a start-up procedure on a simulated process control task. Based on theories of proceduralisation, the ‘testing-effect' and mental practice, four different RIs were designed. In Study 1 (N = 68), two experimental groups (EGs) received either an RI called ‘Practice' or an RI called ‘Skill Demonstration'. Both RIs support skill retention, but the Skill Demonstration-RI performed with a higher mental workload. In Study 2 (N = 68), two EGs received an RI called ‘Symbolic Rehearsal' or an RI called ‘Procedural Knowledge Test', and aimed at supporting knowledge retention. Both EGs supported knowledge retention but showed moderate skill decay. Results imply that RIs affect skill and knowledge retention differently and should be applied in accordance with the task requirements and their dependence on accurate skill or knowledge maintenance.

Customization of user interfaces to reduce errors and enhance user acceptance

Customization is assumed to reduce error and increase user acceptance in the human–machine relation. Reconfiguration gives the operator the option to customize a user interface according to his or her own preferences. An experimental study with 72 computer science students using a simulated process control task was conducted. The reconfiguration group (RG) interactively reconfigured their user interfaces and used the reconfigured user interface in the subsequent test whereas the control group (CG) used a default user interface. Results showed significantly lower error rates and higher acceptance of the RG compared to the CG while there were no significant differences between the groups regarding situation awareness and mental workload. Reconfiguration seems to be promising and therefore warrants further exploration.

Identifying Changes in Human Operator Mental Workload by Locally Linear Embedding and Support Vector Clustering Approaches

This paper describes a psychophysiological-signal-based clustering framework for detecting the changes in operator mental workload incurred by a simulated process control task. A combination of locally linear embedding and support vector clustering approaches is adopted. The unsupervised method is shown to be able to extract features from several channels of the electroencephalogram (EEG) data and to determine whether or not the level of mental workload changes. Simulation results have also demonstrated that a few data clusters can be derived to interpret the change in the operator workload.

“Being prepared for the infrequent”: A comparative study of two refresher training approaches and their effects on temporal and adaptive transfer in a process control task

Operators working with highly automated technical systems face the challenge of skill retention due to few opportunities to apply the skills they acquired during initial training. Therefore, the use of refresher training is common in many high-risk environments. However, so far, the design and effectiveness of refresher training has not been focused on in training and human factors related research. We compared two refresher training approaches–practice and symbolic rehearsal–to a control group without refresher training. Fifty-nine engineering students were trained for one hour on a simulated process control task. A week later, the practice group completed four trials with the simulated task and the symbolic rehearsal group underwent four trials in written form. The final testing session took place two weeks after initial training. Refresher training was effective for temporal transfer, with the practice refresher group performing significantly better than the symbolic rehearsal group.

Human Performance Consequences of Automated Decision Aids in States of Sleep Loss

The authors investigated how human performance consequences of automated decision aids are affected by the degree of automation and the operator's functional state. As research has shown, decision aids may not only improve performance but also lead to new sorts of risks.Whereas knowledge exists about the impact of system characteristics (e.g., reliability) on human performance, little is known about how these performance consequences are moderated by the functional state of operators. Participants performed a simulated supervisory process control task with one of two decision aids providing support for fault identification and management. One session took place during the day, and another one took place during the night after a prolonged waking phase of more than 20 hr. Results showed that decision aids can support humans effectively in maintaining high levels of performance, even in states of sleep loss, with more highly automated aids being more effective than less automated ones. Furthermore, participants suffering from sleep loss were found to be more careful in interaction with the aids, that is, less prone to effects of complacency and automation bias. However, cost effects arose that included a decline in secondary-task performance and an increased risk of return-to-manual performance decrements. Automation support can help protect performance after a period of extended wakefulness. In addition, operators suffering from sleep loss seem to compensate for their impaired functional state by reallocating resources and showing a more attentive behavior toward possible automation failures. Results of this research can inform the design of automation, especially decision aids.

Individual Differences in Complex Task Performance: Interaction Effects of Risk-Taking Behavior and Cognitive Variables

While individual differences and their influence on training and performance have been widely examined in fields such as industrial or educational psychology, they have not been a strong focus of human factors research. The present study aims to investigate the relationship between individual characteristics and complex task performance with special consideration of interaction effects. Fifty engineering students participated in a four-hour training session on a simulated process control task and a testing session one week later. Before the training session, the following individual characteristics were assessed: risk-taking behavior, general mental ability (GMA), and need for cognition (NFC). Interaction effects of risk-taking behavior and GMA, as well as of risk-taking behavior and NFC, on performance were found. Twenty to 30% of the variance in system control performance was accounted for by the individual characteristics and their interaction effects. Findings suggest that interaction effects should be systematically investigated in future research concerning individual differences in the context of human—system interaction.

Comparative study of three training methods for enhancing process control performance: Emphasis shift training, situation awareness training, and drill and practice

Three training methods to improve attention management skills in process control were compared. Forty students from technical disciplines participated in a five-hour module of emphasis shift training (EST), EST combined with situation awareness training (EST/SA), and drill and practice (D&P) on a simulated process control task. Participants were then tested three times for 45 min each (immediately after training, two weeks after training, and six weeks after training) for system control performance and diagnostic performance on familiar and nonfamiliar fault states. D&P led to superior diagnostic performance on familiar system faults. EST/SA training supported the diagnosis of novel system faults. EST was less effective than expected for system control performance. Implications for training design in process control are discussed.

Assessment of Structural Knowledge as a Training Outcome in Process Control Environments

The objective of the present studies was to apply a novel method for structural knowledge assessment to process control to assess the potential of its measures as a training outcome. Traditionally, knowledge is assessed by verbal achievement tests on the subject matter. However, traditional methods are regarded as limited in their ability to assess higher-order learning or understanding. Two experiments (Experiment 1, N= 41; Experiment 2, N= 50) were conducted in which participants were given a 4-hr training session on a simulated process control task. At a later testing session, participants worked on the task for 70 min and completed knowledge tests on declarative, procedural, and structural knowledge. Structural knowledge was measured with the computer-based Association Structure Test (AST), which combines an association task and Pathfinder network on the basis of relatedness ratings. In both studies, structural knowledge was significantly related to diagnostic performance, and evidence was found for internal consistency as well as convergent and predictive validity. Findings indicate that structural assessment with the AST shows promise as a training outcome in process control. Potential applications of this research include the improvement of training design, delivery, and evaluation.

Sensitivity of candidate markers of psychophysiological strain to cyclical changes in manual control load during simulated process control

Complex systems are vulnerable to unpredictable breakdowns in operator performance. Although primary task goals are typically protected by compensatory effort, such protection may break down under fatigue and high strain. Detection of strain states would enable prediction of increased operational risk through adaptive automation, triggering a switch of control from human to computer. A simulated process control task was used to identify markers of strain under a cyclic loading procedure, which forced performance breakdown through stepwise changes in control load. Four trained participants provided data on control performance and a range of candidate psychophysiological markers of strain (two EEG power ratios and HRV). Within-individual analyses showed the strongest sensitivity for ‘task load index’ (TLI), an EEG measure based on executive control activity in frontal brain areas, though all measures were sensitive for some participants. The implications of such findings for the development of a closed loop system for adaptive automation are discussed.

The predictive qualities of operator characteristics for process control performance: The influence of personality and cognitive variables

This article examines the relationship between operator characteristics and process control performance. Thirty-nine trainee operators participated in a 4-h training session of a simulated process control task and a testing session in which various system faults had to be managed. Cognitive ability, cognitive flexibility, self-efficacy and personality traits were measured as operator characteristics. Cognitive ability related positively to system control performance but not to diagnostic performance. Participants with low cognitive flexibility performed best on system control, whereas participants with high cognitive flexibility performed best on diagnostic performance. A hierarchical regression analysis revealed that cognitive ability, cognitive flexibility and declarative knowledge accounted for about 30% of the variability of system control. The findings suggest that consideration of cognitive ability and cognitive flexibility be increased in personnel selection for complex work environments.

An Evaluation of a "Time Tunnel" Display Format for the Presentation of Temporal Information

The time tunnel display design technique combines the benefits of configural displays (salient visual properties corresponding to critical domain semantics) with the benefits of temporal information (i.e., the value of variables and properties over time). In Experiment 1 a baseline configural display and a time tunnel display were evaluated using real-time measures of system control, fault detection, and state estimation in a simulated process control task. The results provided little evidence in support of the time tunnel format. In Experiment 2 access to the temporal context was limited: Participants performed the detection and estimation tasks with static "snapshots" of system states that had been generated in Experiment 1. The overall pattern of results indicates that the time tunnel display was more effective for state estimation tasks than was the baseline configural display and or a trend display. Issues in the design of temporal displays are discussed, including representational formats and the choice of temporal time frames. Issues in the evaluation of temporal displays are also discussed, including the role of temporal information and the critical nature of participants' access to this information. Actual or potential applications of this research include design techniques for improving graphical displays and methodological insights to guide future evaluations.

A preliminary investigation of the time tunnels display design technique

Two forms of decision support were evaluated using a simulated process control task environment. The time tunnel display design concept provides temporal (historical) information about the value of variables and relationships over time using perspective geometry and the depth plane. The compensated level variable is a quickened display that provides estimates of system state that is not confounded by counter-intuitive and time-delayed thermodynamic effects. These two forms of decision support were applied factorially (present, absent) to produce four experimental conditions. The results for system control and fault detection tasks indicate that display quickening improved performance significantly while the time tunnel displays did not. The results for data extraction tasks (reporting the values of system variables) were dependent upon the quality of the mapping between properties in the domain and visual features in the display. Methodological factors that may have influenced the results are considered and subsequent evaluations of the time tunnels design technique, using alternative methodologies, are discussed. It is concluded that the time tunnels display design concept has potential as a form of decision support and is worthy of additional research efforts.

Training Conditions and Strategic Aspects of Skill Transfer in a Simulated Process Control Task

In carrying out tasks, operators are at liberty to adopt a variety of strategies both at an operational level and at a more private psychological level, according to the affordances provided in the operational situation. Skill transfer between tasks is likely to be affected not only by common task elements but also by domain-specific strategic knowledge. The implication for training design thus would be to examine training methods that encourage learners to develop strategic knowledge to maximize transfer. Our focus has been on teaching knowledge of goal interactions and side effects as a means of enhancing domain-specific strategies. We describe an experiment to test predictions made through an operational classification of plans and to examine the extent to which transfer is facilitated by strategic knowledge. Participants were required to learn how to carry out the first stage in starting up a simulated distillation column, following instruction that varied in terms of degree of explicit procedural guidance and knowledge of goal interactions. The transfer task involved continuing the start-up process to achieve the final product targets. The results indicated that, although common task elements accounted for the majority of transfer effects, strategic knowledge also played a significant role in transfer.