To measure the relative role of left- or right-hemispheric processes involved both in creation of works of art and their perception, a procedure was derived based on calibrated expert estimations (of works or their authors). The resulting instrument for measurements consists of 7-10 scales and two sets of ‘contrastive objects’ (‘tuning forks,’ each containing 7-12 objects). The asymmetry is reflected by appropriate index which varies from –1 to +1 (‘pure’ right- and ‘pure’ left-hemispheric dominance, respectively). It occurs possible to eliminate subjectivity both of experts and researchers (compilers of the instrument). The method was used in evolutionary studies concerning 102 composers, 240 painters, etc.; the error of measurement was usually 3-5%. Evolutionary curves built on the basis of these indices, permitted to observe periodical switching between left and right styles in music, painting, theatre staging, and poetry.