Aticietit ntid tiiedieval scholars cotisidered toties related by sittiple (stiiall-iriteger) ratios to he tintiirally pleasitig, biit cotitetiiporaty scholars nttribiite the special perceptiinl statiis of siicli soiitids to exposirre. We itiwstigated the possibility of processitig predispositiotis for sotiie torie cotiihitintiotis by cr.nliiatirig itgatits' ability to detect siihtle ciiatiges to pattenis of sirtiiiltarieoiis atid seqiietitinl toiles. It gatits detected siicli chariges to pairs of piire toties (intervals) orily dieti the toties were related by simple freqireticy ratios. This was the CNSC for
9-ntotith-old it garits tested with harrnotiic (sittiiiltririeoiis) ititervals arid for 6-ttiotitli-old ittfnrits tested with ttielodic (seqiietitial) iritervals. These resirlts ore coilsisterit witli II biologicnl basis for the prevaletice of particirlar ititends historiccilly arid cross-ciiltiirally .The origin of the idea that consonant, or pleasant-sounding, combinations of musical tones have special numerical properties is generally attributed to Pythagoras (ca. 600 BC) (see Plomp & Levelt, 1965, for a review of historical accounts of consonance and dissonance). When Pythagoras partitioned a vibrating string into two sections whose lengths were related by simple (i.e., small-integer) ratios, such as 2:1, 3:2, and 4:3. he observed that the resulting combinations of tones sounded more consonant than did combinations for lengths related by more complex ratios. In the Middle Ages, beauty in general was considered to depend on numerical properties, music in particular being "number made audible" (Seay, 1975, p. 19). Indeed, the medieval philosopher Boethius considered music, arithmetic, geometry, and astronomy to be equal parts of the Quadrivium, the four essential disciplines of mathematics. The degree of beauty was believed to reflect the relative simplicity of the underlying numerical relations. In fact, musical intervals (combinations of two tones) with simple ratios were thought to mirror the beauty of God, the complex-ratio (45:32) interval known as the tritatie being the "devil in music" (Seay, 1975, p. 83).Renaissance scholars' discovery of the association between the pitch of a tone and its frequency of vibration (hertz, or cycles per second) provided a psychophysical rationale for Pythagorean ideas of consonance-subdividing a string into simple ratios based on length results in simple ratios based on frequency (see Hall, 1980, p. 442). According to Galileo (17th century) as well as some contemporary theorists (Bernstein, 1976; Boomsliter & Creel, 1961), tones related by simple frequency ratios are preferred because their vibrations generate more regular or pleasing neural patterns, a claim as yet uncor-