MAKING DISPLAYS INTO MENTAL MODELS

NEWSLETTER ARTICLE

System operators' responsibilities are going through radical changes with computerized control systems. No longer can an operator be only a good controller; they are expected to be decision makers and problem solvers as well. Operators who are trained only to control do not necessarily have a realistic mental model of the system they are controlling. Good display designs can improve operator problem solving abilities by improving their mental model of the system.

In the NAS-NRC (National Academy of Sciences-Nuclear Regulatory Commission) "Research Needs for Human Factors," (Committee on Human Factors, 1983), it stated that "incorrect operator models can lead to disastrous results...." Correct mental models, therefore, become essential to optimal system control.

Ray Eberts and Walter Schneider performed a series of experiments to analyze the concept of display augmentation on an operator's mental model (Human Factors Journal, 1985, 27(4) 371-393). The intent of the project was to identify predictors that may assist in mental mapping and, if so, if there is a difference in various methods of augmentation.

Display augmentation is the inclusion of predictors which can inform the operator of the outcome of his or her control actions prior to completion of the action. It an excellent means of enhancing the predictive abilities of operators, thereby allowing the operator to be a decision maker as well as controller. This anticipatory capability also enhances system efficiency and safety. Augmentation is commonly used in the control of systems that have slow dynamics (e.g. oil tankers, submarines, transport aircraft).

According to Eberts & Schneider, groups with limited augmentation lack the ability to correctly predict the outcome of their actions, due to incorrect mental models. "Without augmentation that appropriately represents display dynamics, controllers can have serious misconceptions of the control dynamics." Therefore, poor augmentation can cause errors to occur due to improper mental models formulated from the predictor.

These experiments have established the importance of correctly augmenting computer displays to assist in problem solving and decision making. Information in displays must be carefully selected to ensure the indicators are consistent with system dynamics. Also, the augmentation must eliminate any misconceptions by the operator.

If operators are trained with good displays and predictors, the operator will have better predictive capabilities even if no predictors are present.

Good display design also enhances operator effectiveness and reduces operator error; poor displays can contribute to system misinterpretation and error.

Copyright 1986 Beville Operator Performance Specialists, Inc., All Rights Reserved