ABSTRACT
This chapter discusses the generality of the bilateral effect and summarizes research on 13 possible hypotheses of the effect, leading to one as the most likely explanation. There are two major reasons why the bilateral effect is of importance in the study of hemispheric differences. First, the cause of the bilateral effect is itself of theoretical interest, because it is now known to reflect an interaction between the hemispheres in the processing of information. Second, on a purely empirical level, any method that increases the size of obtained asymmetries deserves attention as a means of increasing the power of experimental manipulations. The bilateral effect may be defined as the larger field asymmetries found using bilateral displays compared to unilateral displays. It has been argued that it generalizes across modalities, stimulus types, and dependent measures, thus representing one of the fundamental phenomena of lateralization research.
