The field dependence-independence cognitive style, that component of the psychological differentiation dimension which subsumes spatial ability and certain aspects of personality and social behavior, was found to be associated with variations between individuals in the extent of differenttion of EEG activity between the two hemispheres. Fluctuations over time in integrated EEG amplitudes recorded from the left and right hemispheres were more similar to each other (i.e., less differentiated) in individuals with a field dependent cognitive style than in those who were field independent. (10pp.)