Effects of concurrent verbal and musical tasks on a unimanual skill.

Subjects balanced a dowel rod on the right or left index finger while speaking, while remaining silent, and while humming a melody. In males balancing times for the right hand decreased with concurrent verbalization. Verbalization had no effect on left hand performance in males, nor on either hand in females. Concurrent humming had no effect on performance of males or females. Poorer right hand performance by males when verbalizing is attributed to interference with right-sided motor control by the left hemisphere due to verbal activity programmed by the same hemisphere. Unimpaired right hand performance in verbalizing females suggests that the language function is less clearly lateralized in females than in males. The possibility that music may be shared by both hemispheres is discussed.