Describes an approach to human performance based on economic concepts. It elaborates on the view that the human system employs utility considerations to decide on allocation of its limited resources. The efficiency of those resources for performing a task depends on parameters characterizing the task and the performer. This approach is used to discuss various models and interpretations for dual-task performance and their predictions, subject to the assumption that there is a single pool of resources. An expansion of this approach is then presented that hinges on the idea that the human-processing system incorporates a number of mechanisms, each having its own capacity. Those capacities can at any moment be allocated among several processes. Empirical evidence relevant to this idea and new interpretations for phenomena of dual-task performance suggested by it are presented. (3½ p ref)

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An experimental study was conducted to test the transfer of skills from a complex computer game to the flight performance of cadets in the Israeli Air Force flight school. The context relevance of the game to flight was argued on the basis of a skill-oriented task analysis, using the framework provided by contemporary models of the human processing system. The influence of two embedded training strategies was compared, one focusing on the specific skills involved in performing the game, the other designed to improve the general ability of trainees to cope with the high processing and response demands of the flight task and teach better strategies of attention control. Efficient control and management of attention under high task load are argued to be skills that can improve with proper training and generalize to new situations. Flight performance scores of two groups of cadets who received 10 h of training in the computer game were compared with those of a matched group without game experience. Both game groups performed significantly better than the no-game group in the subsequent test flights. The results are discussed with reference to the theoretical framework within which the context relevance of the game was supported. Also considered are the effects of the different training schedules and the significance of the data to the study of attention control. The game has now been incorporated into the regular training program of the Air Force.

The determinants and costs of control were studied in 6 experiments examining the performance costs of changing stimulus dimension (digit value/number of elements) or attention strategies (speed/accuracy) on the first trial after task transition. Costs were compared for task shift and reconsideration only. Preparation ability was studied by presenting all transition information at the beginning of a 2-part block or only prior to each part. Results showed pronounced first-trial transition costs. Different factors were associated with stop-start and task-switching requirements. Transition costs were separate from those of basic task performance. Costs were sensitive to global control considerations and were larger for task dimension changes than for attention strategy shifts. Costs involving task dimension change, but not strategy shifts, were reduced with advanced preparation. These results are discussed in relation to contemporary models of control. A new distinction is proposed between activation and execution of control strategies.

Psychophysical functions describe the relationship between variations in the amplitude of a defined physical quantity and the psychological perception of these changes. Examples are brightness, loudness, and pain. The regularities of these relationships have been formulated into psychophysical laws. The measurement methodology of psychophysical scaling has been refined by the Harvard group led by S. S. Stevens, who proposed a power function as a general form for such laws. The main argument of the present article is that a similar scaling approach can be adapted to the measurement of workload and task demands based upon subjective estimates. The rationale is that these estimates, like other psychophysical judgments, reflect the individual's perception of the amount of processing resources that the subject invests to meet the demand imposed by a task. This approach was successfully applied to the assessment of 21 experimental conditions given to a group of 60 subjects. The paper discusses the main results of this effort and their implications to theory and application in human performance.

Objectives: The purpose of this study was to investigate the nature and causes of human errors in the intensive care unit (ICU), adopting approaches proposed by human factors engineering. The basic assumption was that errors occur and follow a pattern that can be uncovered. Design: Concurrent incident study. Setting: Medical-surgical ICU of a university hospital. Measurements and main results: Two types of data were collected: errors reported by physicians and nurses immediately after an error discovery; and activity profiles based on 24-h records taken by observers with human engineering experience on a sample of patients. During the 4 months of data collection, a total of 554 human errors were reported by the medical staff. Errors were rated for severity and classified according to the body system and type of medical activity involved. There was an average of 178 activities per patient per day and an estimated number of 1.7 errors per patient per day. For the ICU as a whole, a severe or potentially detrimental error occurred on average twice a day. Physicians and nurses were about equal contributors to the number of errors, although nurses had many more activities per day. Conclusions: A significant number of dangerous human errors occur in the ICU. Many of these errors could be attributed to problems of communication between the physicians and nurses. Applying human factor engineering concepts to the study of the weak points of a specific ICU may help to reduce the number of errors. Errors should not be considered as an incurable disease, but rather as preventable phenomena.I nvestigations of the nature of human errors in hospitals are rare. It is human nature not to report errors, and the medical profession is no different from other professions. The importance of error prevention was recognized by anesthesiologists with the publication of error analysis and critical incidences in the operating theater. 1 (Anesthesiology is one of the few fields to publish such a study.) The paucity of published investigation in this area may be related, at least in part, to the fear of legal liability.Great efforts have been invested in the industrial sector in the analysis of job requirements and the design of workplaces, equipment, and the physical environment for the benefit of workers. In air traffic control, for instance, human factors have been studied extensively. 2 In contrast, almost no attention has been given to human factor considerations in the hospital setting. As malpractice premiums have increased, hospitals tend to spend more time preparing themselves against liability claims rather than actively trying to avoid errors. A recent review 3 concluded that "reducing the incidence of the events will require identification of their causes and developing methods to prevent errors or reduce their effect".Observations during routine daily activities in the intensive care unit (ICU) demonstrated that mistakes do occur, sometimes with severe consequences. 4 5 The present prospective study investigated the nature and c...

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