This study examined the influence of 3 different types of concurrent tasks on speech motor performance. The goal was to uncover potential differences in speech movements relating to the nature of the secondary task. Twenty young adults repeated sentences either with or without simultaneous distractor activities. These distractions included a motor task (putting together washers, nuts, and bolts), a linguistic task (generating verbs from nouns), and a cognitive task (performing mental arithmetic). Lip movement data collected during the experimental conditions revealed decreases in displacement and velocity during the motor task. The linguistic and cognitive tasks were associated with increased spatiotemporal variability and increases in the strength of the negative correlations between upper and lower lip displacements. These findings show that distractor tasks during speech can have a significant influence on several labial kinematic measures. This suggests that the balance of neural resources allocated to different aspects of human communication may shift according to situational demands.

Much of the research in human communication and its disorders has focused on speech and language separately. Few investigators have examined how language demands may influence the physical production of speech. In a recent article, Lieberman (2001) stressed the importance of the way speech and language are integrated, noting that “the neural bases of human language are intertwined with other aspects of cognition, motor control, and emotion”(p. 33). The authors of several studies have indicated the need for further research in the areas of linguistic and cognitive processes and their relationship to speech motor control in order to better understand the production of spoken language (Maner, Smith, & Grayson, 2000; Strand, 1992; Strand & McNeil, 1996).