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When a dual tracking task consisting of two incoherent (uncorrelated) subtasks is partly integrated, such that it is characterized by incompatibility of similarity, or when axis similarity of subtasks is high, it may be difficult to map subtask stimuli to the proper responses. Especially for older adults, an increase in mapping demands may be a source of confusion (cross talk). In the present experiment this issue was addressed with a dual task consisting of two unrelated one-dimensional compensatory tracking tasks with position dynamics. Task performance was measured in terms of root mean square tracking error and cross-axial correlations. Tracking error data were consistent with the hypothesis that older subjects are penalized when there is incompatibility between control and display integration. In general, negative effects of incompatibility of integrality were the greatest when partial integration involved integration of the response component. Both performance measures indicated that with increasing incoherent similarity, task performance of the old subjects was more hampered than was that of their young counterparts.

Age-related differences in dual-task performance may be affected by factors such as skill integration and perceptual competition. Therefore these factors were examined in a dual-task experiment with young and older adults involving two one-dimensional compensatory tracking tasks. Single-task difficulty was individually adjusted for each subject. It was found that differences in pure dual-task performance between young and older subjects increase when the subtasks are coherent such that skills can be integrated. In addition, the degree to which integration reduces the effects of visual competition was larger for the young than for the older subjects. It is concluded that in dual tasks with coherent subtasks, older adults may show an impaired ability to perform the sub tasks in an integrated manner.

Three experiments including reaction time (RT) tasks and driving tasks were conducted to identify variables that may be sensitive to the effects of brain damage or aging and to determine how RT tasks relate to driving performance. In Experiment 1 mean RTs of the brain-damaged and older subjects disproportionately increased relative to those of controls, with increasing difference between subsequent compound stimuli. In Experiment 2 response accuracy of brain-damaged subjects deteriorated more than that of controls when the similarity of a task to actual driving increased. In Experiment 3 brain-damaged patients were slower and less accurate than the controls on all measures of a platoon car-following task, whereas the older subjects were only less accurate. Compared with those of the controls, brake RTs of neither the older subjects nor the patients were disproportionately affected by increasing task load. Performance on the platoon driving task could be successfully predicted by a laboratory RT task on time estimation only for the brain-damaged subjects.

The magnitude of age effects in single- and dual-tasks may be affected by the degree to which performance depends on well-learned skills that were previously developed. In addition, age-effects may be affected by the requirement to modify these skills and by attentional requirements emerging from the mutual relation of subtasks. Effects of skill modification and emergent attentional processes were examined in an experiment in which experienced subjects performed two perceptual-motor tasks, a vehicle steering task and car-following task in a driving simulator. Car-following was performed under two conditions of familiarity, determining whether or not a normal psychomotor routine had to be modified. In dual-task performance, the demand of sub tasks was constant or alternating in counterphase. In general, the older subjects' performance did not differ from that of their younger counterparts, except when the single- or dual-task involved routine modification in car-following. Dual-task costs were basically manifested in the car-following task. Post hoc interpretations of the data indicated that the results were not completely consistent with the complexity hypothesis.

The present study was conducted to gain insight into the effects of different forms of continuous haptic information (CHI) on operator performance with a moving unmanned platform. In a simulator experiment, participants tracked a moving target with a disturbed viewfinder (moving platform). While the participants performed this combined pursuit and compensatory tracking task, haptic information was provided to them concerning translatory disturbances of the platform. Two steering variables were manipulated between participants: presence or absence of CHI provided at the control device and automated or manual stabilization of the platform. The other factors were image degradation, motor task load, and visual task load. Haptic information was generated by movements of an active joystick that was used for steering the platform. It was shown that both CHI and platform stabilization substantially reduced tracking error. These effects were not additive; CHI improved tracking performance only when the platform was not stabilized, and it did not significantly degrade pursuit tracking performed with a stabilized viewfinder. The magnitude of the CHI effect was independent of image degradation, motor load, and visual load. CHI at the joystick improves tracking performance when it involves relevant control information; when it provides other information, tracking performance is only marginally degraded. Actual or potential applications of this research include performance of missions in environments that are difficult to access, potentially harmful to humans, or both, such as reconnaissance behind enemy lines, tracing of environmental pollution at sea, and assessment of damage in nuclear disaster areas.

To improve the efficiency of images presented in low-cost vehicle simulators, the virtual viewing direction (i.e., the direction in which the image is rendered) can be head-slaved, the display can be surrounded with a less detailed peripheral image, or both. Three simulator experiments were used to evaluate the effect of these techniques on lane-keeping performance and spatial orientation. In Experiment 1, vehicle references or a head-slaved display (HSD) provided feedback on the virtual viewing direction. Vehicle references improved lane-keeping performance somewhat with a standard 50° h x 50° v display. An HSD (50° h x 50° v) allowed better steering performance, but not to the levels obtained with a wide display (150° h x 50° v). Experiments 2a and 2b evaluated the effects of surrounding the HSD with a less detailed peripheral image and of moving the HSD discretely or continuously. With the peripheral image, lane-keeping performance (Experiment 2a) and spatial orientation (Experiment 2b) were similar to those with a wide display. In both experiments, performance with the discretely moving HSD was superior to that with the continuously moving HSD. The results show that low-cost driving simulators can be equipped with more efficient displays that are as effective as wide displays for lane-keeping and spatial orientation.