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The effects of divided attention on speech kinematic, verbal fluency and manual motor performance
Christopher Dromey and Erin Hamblin

This study explored bidirectional interference between selected speech, language and manual motor activities in order to test aspects of the functional distance hypothesis, which predicts that similar activities are regulated by brain regions that lie in close anatomical proximity. Twenty young adults repeated a tongue-twister or generated a list of words in a verbal fluency task in isolation or while placing pegs and washers into holes with the right or left hand. Lip movement measures for the phrase repetition revealed decreases in displacement and velocity and increases in movement variability as well as in sound pressure level when speakers performed the manual task concurrently with speech. Manual dexterity declined when the participants were required to generate word lists, but not when they simply repeated the target utterance. The prediction that right-handed activities would interfere more with speech and language tasks (because they both rely on left hemisphere processing) was not unequivocally supported. Instead, use of the non-dominant hand for fine motor tasks may require sufficient attention that other demanding communication tasks are affected.

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