Are lateral eye-movements a valid index of functional hemispheric asymmetries?

Lateral eye-movements (LEMs) to verbal and spatial questions are frequently used as an index of asymmetries in hemisphere activation and the concept of 'hemisphericity'. There have, however, been few attempts to validate LEMs using independent cognitive measures of hemisphere function. This study relates laterality indices of LEMs recorded in the dark using infrared recording techniques, and elicited by verbal and spatial questions, to other measures of left and right hemisphere functioning (verbal and non-verbal dichotic listening, block design, digit span) in 43 subjects. LEM laterality indices were unrelated to these validation measures. It is concluded that although appropriate question type-LEM relationships may reflect transient asymmetries in hemispheric activation, they are not a valid index of stable individual differences in hemisphere utilization.