Kinsbourne, M.: Direction of gaze and distribution of cerebral thought processes. Neuropsychologia Vol. 12pp. 279-281, 1974.

Abstract: During verbal thought, subjects look right, and during spatial thought they look up and to the left. This effect is weakened or abolished if subjects are asked to hold central fixation, if they are confronted by an experimenter or by the sound of his voice, or if they are set to respond other than straight ahead. If precautions are taken in these respects, the phenomenon is a useful index of cerebral lateralization of cognitive function.