INTERACTION OF S-R COMPATIBILITY AND THE RATE OF GAIN OF INFORMATION

Four school children of different ages and grades responded vocally at three levels of stimulus uncertainty ( Hs) to visually presented Arabic numerals. S-R compatibility was greatest for the oldest child and least for the youngest. Reaction time ( RT) was influenced by both Hs and S-R compatibility; the effect of Hs on RT was greatest where S-R compatibility was lowest.

INDIVIDUAL AND SITUATIONAL VARIABLES AFFECTING HUMAN PERFORMANCE

Present methods of measuring and predicting operator performance are criticized because of their failure to consider individual and situational variables which mediate that performance.

IMPROVEMENTS NEEDED IN A CENTRAL STORE OF HUMAN PERFORMANCE DATA

A central data store represents an attempt to make quantitative information about human performance conveniently available for system planning, functions allocation, equipment design, selection and training, and evaluation. Major areas for future improvement of data store technology include establishment of a central function to integrate human performance data, quantification of meaningful categories of psychological processes, development of an error taxonomy, improved scaling of laboratory to operational performance, inclusion of new types of behavior, relating of conditions under which performance is accomplished to performance levels, and development of a basis for forecasting behavioral loading from early system information.

SOME PROBLEMS IN THE MEASUREMENT OF HUMAN PERFORMANCE IN MAN--MACHINE SYSTEMS

Quantification of human performance in man–machine systems is receiving more and more attention in human factors work. Obstacles to such quantification include: (1) complexity and subjectivity of available quantification methods, (2) grossness of assumptions behind these methods, and (3) resistance of some psychologists. Research is needed (1) to develop an improved human performance data bank, (2) to develop improved models and methods, and (3) to validate quantification data, models and methods. Some research is being done in these areas.

SIMULATION, MODELS, AND GAMES: SOURCES OF MEASUREMENT

Simulation, models and games are analogies. They resemble in some way something else about which information is desired. We may therefore measure on the analogy instead of the real world objects. Critical dimensions of analogies are the level of abstraction and the fidelity of simulation, however, if the objective is to measure the most critical aspect is the validity of measurement. Unfortunately, validity is not always a practical concept. Since the objective of measurement is to derive information, simulation studies are analyzed with respect to information objectives in the attempt to derive criteria for measure selection.

QUANTIFICATION IN MAN--MACHINE SYSTEMS

Quantification is defined as the pairing of elements of two sets. This definition and the characteristics of the sets in question is expanded, and the varieties and methods for quantifying in man-machine systems are described. Special attention is given to a brief overview of psychophysics and to probability theory as they relate to the problems of quantification in this area. Finally, guidelines are presented to aid in the search for adequate quantification.

FIELD MEASUREMENT OF HUMAN PERFORMANCE IN MAN--MACHINE SYSTEMS

Field evaluation of human performance is rapidly assuming a role of major importance in system measurement. However, the special conditions under which such ecological tests must be performed impose certain limitations upon the evaluator which must be recognized. These limitations involve restrictions on the opportunity to manipulate variables, which lead to greater use of subjectively-oriented data collection tools: e.g. the human observer, the interview and checklists. Factors to be considered in the planning of a field test are discussed.

METHODS OF PREDICTING HUMAN RELIABILITY IN MAN--MACHINE SYSTEMS

Four studies describing the development and application of a simple multiplicative probability model for human error prediction are reviewed and evaluated. The methodology is an elementaristic one that requires analysis of system operations to the task-element level. Estimates of human performance reliability are applied through the use of the Data Store, which is based on extrapolation of results from 164 experimental studies. The various possibilities of operator action are explored in detail through a “probability” tree; each branch of the tree represents an alternative contingency. Performance reliabilities for task elements are progressively combined through the use of the series product rule to yield reliability estimates for tasks, mission phases, and the overall system. The methodology has been applied in two contexts: the generation of reliability estimates through a computerized Monte Carlo program and by using experts' rating of operator performance.

ON THE PERFORMANCE OF A COMBINATION OF DETECTORS

The performance of a combination of two hypothetical detectors is first examined. It is shown that the performance of the combination may be as poor as the poorer detector alone when the inflation in false alarm rate of the combination of detectors is considered. Experimental tests were carried out in which listeners attempted to detect the presence or absence of a tonal signal in noise under two conditions: unaided by an external source of information (actually aided by a simulated machine detector set at chance performance); and aided by a simulated machine detector set at the same discriminability as the listener. While the performance of the aided listener was consistently superior to the unaided listener, the improvement in performance fell considerably short of an ideal combination. It is concluded that the gain in performance expected from combinations of detectors must be interpreted cautiously.

THE DEI TECHNIQUE FOR EVALUATING EQUIPMENT SYSTEMS FROM THE INFORMATION TRANSFER POINT OF VIEW

This paper describes and gives the basis for a Display Evaluative Index (DEI) technique, a calculational method for deriving a figure of merit of the effectiveness of displays of a particular equipment to transfer information to the operator and for the operator to act on that information and perform the appropriate control action. Reliability, validity, and discriminating power results are reported to be satisfactory.

SUBJECTIVE INFORMATION AS A FUNCTION OF SOURCE INFORMATION

Three experiments are reported in which subjective information, defined as the amount of information in judgments of number and frequency of events, was studied, Results suggest different phenomena according to whether judgments are made relative to the display or to the source from which the display is a sample. The results also suggested a variety of other phenomena regarding the effects of number of events at a time, redundancy and the rate time of information presentation on subjective information.

VISUAL AFTER-IMAGES AS A SOURCE OF INFORMATION

This report is concerned with the ability of observers to extract data from induced retinal after-images as a means of increasing the display exposure time in single glimpse situations. It was found that observers can use after-image data, and that the gain in reporting to be expected will be greatest for those situations where, without after-images, reporting is most difficult, that is, under conditions of high display load or very short exposure time. The benefit demonstrated was associated primarily with the positive after-image; however, the negative after-image was not ruled out as a persistent data source.

THE EFFECT OF RULE FLEXIBILITY ON SYSTEM ADAPTATION

A study was performed to test the effect of strict vs. flexible operating rules on a simulated terminal air traffic control system under a variety of traffic conditions with constant load. Twelve college students were trained in control procedures, were assigned to two crews, and operated the system in a sequence of 24 problem sessions in which the variables were arranged in factorial combination. Only the change to more flexible rules produced consistently significant performance changes. The differences in the way the two crews responded to the changes in the rules depended on the degree of crew cohesiveness. A theoretical formulation of system adaptation derived from earlier studies with an air defense system is discussed, and a new formulation is presented which is consistent with the findings in both the present and the earlier studies.