Double trade-off curves with different cognitive processing combinations: testing the cancellation axiom of mental workload measurement theory.

The accomplishment model of average mental workload--a formal axiomatic measurement theory--was used as a basis for developing and testing secondary task indices of mental workload (H. A. Colle & G. B. Reid, 1997). Its cancellation axiom implies global sensitivity, which is an important theoretical and practical criterion for mental workload indices. Performance levels of different secondary tasks were empirically equated in mental workload and then used to test the cancellation axiom. Cognitive processing similarity--including orthographic, phonemic, and semantic processing of pairs of operator and secondary tasks--was manipulated in three experiments. Equivalencies between secondary tasks were independent of secondary-operator task similarity, consistent with the cancellation axiom and the global sensitivity of these secondary tasks. The results suggest that standardized secondary task techniques can be developed for the practical measurement of mental workload. Actual or potential applications of this research include the development of functionally useful and realistic secondary task measures of mental workload.

Context effects in subjective mental workload ratings.

The impact of performance context on subjective mental workload ratings was assessed with the Subjective Workload Assessment Technique (SWAT) and the NASA Task Load Index (TLX). In Experiment 1, a strong context effect was demonstrated. A low range of task difficulty produced considerably higher ratings on a common set of difficulty levels than did a high range of task difficulty. In Experiment 2, increasing the participants' range of experiences during practice eliminated the context effect. We recommend that methods for standardizing context, such as providing experience with the complete difficulty range, be developed for subjective mental workload evaluations. Actual or potential applications of this research include providing methodologies for controlling context effects in practical assessments of mental workload to increase the validity of subjective measures.

Multidimensional scaling analysis of simulated air combat maneuvering performance data.

This paper describes the decomposition of air combat maneuvering by means of multidimensional scaling (MDS). MDS analyses were applied to performance data obtained from expert and novice pilots during simulated air-to-air combat. The results of these analyses revealed that the performance of expert pilots is characterized by advantageous maneuverability and intelligent energy management. It is argued that MDS, unlike simpler metrics, permits the investigator to achieve greater insights into the underlying structure associated with performance of a complex task.

The subjective perception of workload in low-time private pilots: a preliminary study.

Control of pilot workload may prevent performance failure of VRF pilots in adverse weather. Measurement of workload and the prediction of performance failure are the first steps. Twelve low-time non-instrument rated pilots were progressively tasked with flight maneuvers under simulated instrument meteorological conditions to the point of performance failure. For each of 3 simulated flights, 14 maneuvers, presented in groups, were performed. Perceived workload was reported by the Subjective Workload Assessment Technique. We obtained 500 workload scores. Workload scores varied significantly between the groups of maneuvers. Instrument landing system approaches had the highest workloads, with descents the second highest. Workload scores were significantly higher when associated with performance failure. The Subjective Workload Assessment Technique proved to be a sensitive workload measure. It showed some promise as a predictor of performance breakdown.

Instructor pilot teaching behavior and student pilot stress in flight training.

The purpose of this study was to investigate the relationship between instructor pilot behavior and student pilot stress. Six instructor pilots and 12 undergraduate pilot training students served as subjects. Two students were assigned to each instructor. Ten categories of instructor pilot behavior were coded from audio cassette tapes made during four sorties from the initial instrument phase of undergraduate pilot training in the T-50 Instrument Flight Simulator. Behaviors were tallied and converted to a rate per minute; inter-recorder agreement was 87%. Instructors who relied heavily on acceptance and praise behaviors were placed in a positive group (N = 4), while those relying on criticism and scolding were placed in a negative group (N = 2). Student stress was estimated from timed urine samples used to quantify catecholamine excretion. Results indicated that missions in the T-50 Instrument Flight Simulator produced a significant stress response in the subjects and that the stress response was greater in lessons taught by the instructor pilots in the negative group.

Catecholamine excretion in A-10 pilots.

Catecholamine excretion was determined for 15 USAF pilots during surface attack training in the A-10 aircraft. Timed urine samples were used to determine excretion rates of epinephrine and norepinephrine during basal conditions, during five sorties performed in high-realism simulators, and during six actual flights. Catecholamine excretion was significantly elevated (p < 0.05) over basal rates during all 11 training sorties; therefore, it was concluded that A-10 conversion and surface attack training results in a significant stress response in the subjects. The stress response experienced in the simulator diminished across trials; the stress response from aircraft flights remained steady through all sorties monitored. The relative proportions of epinephrine and norepinephrine remained similar across all but the final sorties in both the simulator and the aircraft. These occasions were typified by increased norepinephrine and decreased epinephrine excretion rates.

Task-specific simulator pretraining and in-flight stress of student pilots.

Student pilots (n = 20) were assigned to experimental and control groups. The experimental group received 80 min of high-fidelity, task-specific simulation prior to exposure to the initial power-on stall and spin recovery lesson unit in T-37 pilot training. Both experimental and control groups received orientation simulator experience not related to the aircraft spin series. Catecholamine excretion patterns indicated that the initial power-on stall and spin recovery lesson unit resulted in a pronounced stress response in both groups. A statistically significant difference in the norepinephrine/epinephrine ratio was found to exist between the experimental and control groups. It was concluded that task-specific simulator pretraining resulted in an altered stress response characterized by lower arousal and greater mental work than was evidenced in the control group.