Prevalent direction of reflective lateral eye movements and ear asymmetries in a dichotic test of musical chords.

Subjects who consistently move their gaze either to the right or to the left while reflecting on visuo-spatial or verbal questions are usually called "lateral eye movers". This study evaluated auditory asymmetries to a dichotic test of musical chords in 23 right-handed females, selected through test-retest as reliable lateral eye movers; 12 were "left movers" (LMs) and 11 were "right movers" (RMs). During the assessment of the prevalent direction of gaze as well as during the dichotic test, the oculomotor activity was controlled through a video camera. The hypothesis was that the left ear advantage usually found with dichotic chords is enhanced in LMs and reduced in RMs, and that this effect is not due to the facilitating influence of lateral eye movements occurring during the task. Results show that: (a) left movers exhibit a marked advantage of the left ear while right movers do not exhibit any significant ear advantage; (b) despite the instruction to fix a central point, lateral movers tend to show unwarranted eye movements in their usual direction; (c) the effect of the prevalent direction of gaze on the dichotic advantage is not due to eye movements made during the dichotic test. These findings give further support to the hypothesis that the tendency to consistently shift the gaze to one side is related to hemispheric asymmetries as measured by lateralized tests.