Rhythmic and melodic strutures in perceptual space

By asking a person to say how much or how little alike two musical forms are, one can infer the dimensional properties of that person's musical space. We asked musically trained listeners to rate the similarity of pairs of brief melodies on a 9-point scale. Each of four different melodies and their inversions was played in each of four duration patterns (anapestic, dactylic, iambic, and trochaic) for a total of 1024 pairs of patterns. Multi-dimensional scaling and cluster analyses of the similarity matrices showed that at least five dimensions were necessary for giving a good account of the perceptual space of these musical structures. Surprisingly, the major dimensions were rhythmic, thus (using INDSCAL): (i) accent early or late, (ii) duple or triple meter, (iii) iambic-dactylic versus anapestic-trochaic. Other dimensions were (iv) rising versus falling pitch and (v) number of pitch-interval reversals. Cluster analysis suggests that some spaces have duple and triple meter as main branches, while others have accent first and accent last as main branches. Decision times (DT) were an inverted-U function of similarity (S). The curve, when folded about S = 5, was well fit by the power function DT(ms) = 737S027, with a coefficient of determination R2 = 0.98.