EFFECTS OF COGNITIVE WORKLOAD ON SPEECH PRODUCTION - ACOUSTIC ANALYSES AND PERCEPTUAL CONSEQUENCES

The present investigation examined the effects of cognitive workload o n speech production. Workload was manipulated by having talkers perfor m a compensatory visual tracking task while speaking test sentences of the form ''Say hVd again.'' Acoustic measurements were made to compar e utterances produced under workload with the same utterances produced in a control condition. In the workload condition, some talkers produ ced utterances with increased amplitude and amplitude variability, dec reased spectral tilt and F0 variability and increased speaking rate. N o changes in F1, F2, or F3 were observed across conditions for any of the talkers. These findings indicate both laryngeal and sublaryngeal a djustments in articulation, as well as modifications in the absolute t iming of articulatory gestures. The results of a perceptual identifica tion experiment paralleled the acoustic measurements. Small but signif icant advantages in intelligibility were observed for utterances produ ced under workload for talkers who showed robust changes in speech pro duction. Changes in amplitude and amplitude variability for utterances produced under workload appeared to be the major factor controlling i ntelligibility. The results of the present investigation support the a ssumptions of Lindblom's [''Explaining phonetic variation: A sketch of the H&H theory,'' in Speech Production and Speech Modeling (Klewer Ac ademic, The Netherlands, 1990)] H&H model: Talkers adapt their speech to suit the demands of the environment and these modifications are des igned to maximize intelligibility.