Culture, politics and ergonomics.

The beginning of a new century is an appropriate moment to consider the role of ergonomics in relation to the problems facing society. To help solve these serious global problems, ergonomics needs to be open to new disciplines, particularly those in the social sciences. Also, it may be difficult to generalize research on human-centred sociotechnical design without taking into account national characteristics, economics and political constraints. Currently there is more interest than ever in what ergonomics has to offer, but to deliver its promise requires a much broader approach than is usual. By adopting such new approaches one may help solve both the problems of the overdeveloped postindustrial societies and those of the societies of the Third World, where a new approach to work and economics may provide an improved chance for development given the recent changes in global economic policy.

Adaptive automation, trust, and self-confidence in fault management of time-critical tasks.

An experiment on adaptive automation is described. Reliability of automated fault diagnosis, mode of fault management (manual vs. automated), and fault dynamics affect variables including root mean square error, avoidance of accidents and false shutdowns, subjective trust in the system, and operator self-confidence. Results are discussed in relation to levels of automation, models of trust and self-confidence, and theories of human-machine function allocation. Trust in automation but not self-confidence was strongly affected by automation reliability. Operators controlled a continuous process with difficulty only while performing fault management but could prevent unnecessary shutdowns. Final authority for decisions and action must be allocated to automation in time-critical situations.

Trust in automation. Part II. Experimental studies of trust and human intervention in a process control simulation.

Two experiments are reported which examined operators' trust in and use of the automation in a simulated supervisory process control task. Tests of the integrated model of human trust in machines proposed by Muir (1994) showed that models of interpersonal trust capture some important aspects of the nature and dynamics of human-machine trust. Results showed that operators' subjective ratings of trust in the automation were based mainly upon their perception of its competence. Trust was significantly reduced by any sign of incompetence in the automation, even one which had no effect on overall system performance. Operators' trust changed very little with experience, with a few notable exceptions. Distrust in one function of an automatic component spread to reduce trust in another function of the same component, but did not generalize to another independent automatic component in the same system, or to other systems. There was high positive correlation between operators' trust in and use of the automation; operators used automation they trusted and rejected automation they distrusted, preferring to do the control task manually. There was an inverse relationship between trust and monitoring of the automation. These results suggest that operators' subjective ratings of trust and the properties of the automation which determine their trust, can be used to predict and optimize the dynamic allocation of functions in automated systems.

Trust, control strategies and allocation of function in human-machine systems.

As automated controllers supplant human intervention in controlling complex systems, the operators' role often changes from that of an active controller to that of a supervisory controller. Acting as supervisors, operators can choose between automatic and manual control. Improperly allocating function between automatic and manual control can have negative consequences for the performance of a system. Previous research suggests that the decision to perform the job manually or automatically depends, in part, upon the trust the operators invest in the automatic controllers. This paper reports an experiment to characterize the changes in operators' trust during an interaction with a semi-automatic pasteurization plant, and investigates the relationship between changes in operators' control strategies and trust. A regression model identifies the causes of changes in trust, and a 'trust transfer function' is developed using time series analysis to describe the dynamics of trust. Based on a detailed analysis of operators' strategies in response to system faults we suggest a model for the choice between manual and automatic control, based on trust in automatic controllers and self-confidence in the ability to control the system manually.

Designing for transportation safety in the light of perception, attention, and mental models.

Most recent research on error has concentrated on errors of planning, judgement, and action. This paper is concerned with errors in the acquisition of information which are caused by perceptual and attentional mechanisms. Failures to schedule attentional sampling of the environment will lead to accidents. Theoretical models exist for attention and for data acquisition. These models suggest how designers might approach human-machine systems so as to reduce error. A brief summary of the author's feelings about probabilistic risk assessment and related attempts to predict error is provided.

A lattice theory approach to the structure of mental models.

Lattice theory is proposed to provide a formalism for the knowledge base used as a mental model by the operator of a complex system. The ordering relation 'greater than or equal to' is interpreted as 'is caused by', and the lattice becomes a representation of the operator's causal hypotheses about the system. A given system can be thought of causally in different ways (purposes, mechanics, physical form, etc.). Each gives rise to a separate lattice. These are related to each other and to an objective description of the structure and function of the physical system by homomorphic mappings. Errors arise when nodes on the mental lattices are not connected in the same way as the physical system lattice; when the latter changes so that the mental lattice no longer provides an accurate map, even as a homomorphism; or when inverse one-to-many mapping gives rise to ambiguities. Some suggestions are made about the design of displays and decision aids to reduce error.

Fault management in process control: eye movements and action.

Operators controlled a simulated thermal hydraulic system based on Crossman's waterbath task. They were required to keep the system at set points for temperature, level and flow rates. The system was subjected to disturbances and to failures, which the operators were required to manage. Behavioural data were collected in the form of keystroke commands, and in addition eye movements were measured. Evidence for 'cognitive lockup' and for a preference for serial fault management were found. Fixation durations do not change, but faulty subsystems are examined more frequently. During lockup other subsystems may be examined but action on them is delayed. Eye movements give considerable additional insight into the nature of process control information processing compared with traditional measures of operator performance.

Attention, practice, and semantic targets.

Observers detected letters in streams of digits under conditions of divided or selective attention for a period of 10 hr. There were marked practice effects both on the detectability of targets and on the response criteria used by observers. The detectability of targets and the response criteria were both strongly dependent on events in the contralateral channel. The same effects were observed in a second experiment in which the task was to detect animal names in streams of nouns. The data are similar to those obtained in recent experiments using pure tones, so that a unified theory of attention should be possible, valid alike for semantic and nonsemantic messages. Such a theory is outline.