Synthesized auditory displays and speech recognizers were used in two experiments to develop guidelines for their implementation in military aircraft. In the first experiment, the competition between encoding and response modalities of concurrent tasks was examined. The memory search task was more susceptible to competition for visual encoding, whereas the tracking task bore the greater impact from shared manual responding. The second experiment examined competition between tasks for encoding and response modalities and the optimum assignment of modalities to a given task. A simulated flight task was performed concurrently with either a spatial task (target acquisition) or a verbal task (memory). Best performance and least interference with the flight task were obtained when the spatial task was displayed visually and responded to manually and also when the verbal task was displayed auditorily and responded to with speech.

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This report addresses two factors that potentially influence the use of auditory displays and speech responses in a time-sharing environment. (1) S-C-R compatibility is proposed as a condition of enhanced performance when a verbal task employs the auditory/speech (A/S) modes and a spatial task employs the visual/manual (V/M) modes of input and output. (2) Task interference is enhanced to the extent that tasks performed concurrently compete for common input and output modes. An experiment is described in which a tracking task (V/M) is time-shared with a Sternberg Memory Search Task employing all four i/o combinations. As predicted by factor (2), dual task interference increased as a function of shared modalities between tasks. An asymmetry of interference effects was observed such that tracking was most disrupted by common output channels while RT was disrupted by common input modes.