Music moves us. Its kinetic power is the foundation of human behaviors as diverse as dance, romance, lullabies, and the military march. Despite its significance, the music-movement relationship is poorly understood. We present an empirical method for testing whether music and movement share a common structure that affords equivalent and universal emotional expressions. Our method uses a computer program that can generate matching examples of music and movement from a single set of features: rate, jitter (regularity of rate), direction, step size, and dissonance/visual spikiness. We applied our method in two experiments, one in the United States and another in an isolated tribal village in Cambodia. These experiments revealed three things: (i) each emotion was represented by a unique combination of features, (ii) each combination expressed the same emotion in both music and movement, and (iii) this common structure between music and movement was evident within and across cultures. M usic moves us, literally. All human cultures dance to music and music's kinetic faculty is exploited in everything from military marches and political rallies to social gatherings and romance. This cross-modal relationship is so fundamental that in many languages the words for music and dance are often interchangeable, if not the same (1). We speak of music "moving" us and we describe emotions themselves with music and movement words like "bouncy" and "upbeat" (2). Despite its centrality to human experience, an explanation for the music-movement link has been elusive. Here we offer empirical evidence that sheds new light on this ancient marriage: music and movement share a dynamic structure. A shared structure is consistent with several findings from research with infants. It is now well established that very young infants-even neonates (3)-are predisposed to group metrically regular, auditory events similarly to adults (4, 5). Moreover, infants also infer meter from movement. In one study, 7-mo-old infants were bounced in duple or triple meter while listening to an ambiguous rhythm pattern (6). When hearing the same pattern later without movement, infants preferred the pattern with intensity (auditory) accents that matched the particular metric pattern at which they were previously bounced. Thus, the perception of a "beat," established by movement or by music, transfers across modalities. Infant preferences suggest that perceptual correspondences between music and movement, at least for beat perception, are predisposed and therefore likely universal. By definition, however, infant studies do not examine whether such predispositions survive into adulthood after protracted exposure to culture-specific influences. For this reason, adult cross-cultural research provides important complimentary evidence for universality. Previous research suggests that several musical features are universal. Most of these features are low-level structural properties, such as the use of regular rhythms, preference for small-integer frequency ratios, hierarchical organization of pitches, and so on (7, 8) . We suggest music's capacity to imitate biological dynamics including emotive movement is also universal, and that this capacity is subserved by the fundamental dynamic similarity of the domains of music and movement. Imitation of human physiological responses would help explain, for example, why "angry" music is faster and more dissonant than "peaceful" music. This capacity may also help us understand music's inductive effects: for example, the soothing power of lullabies and the stimulating, synchronizing force of military marching rhythms. Here we present an empirical method for quantitatively comparing music and movement by leveraging the fact that both can express emotion. We used this method to test to what extent expressions of the same emotion in music and movement share the same structure; that is, whether they have the same dynamic features. We then tested whether this structure comes from biology or culture. That is, whether we are born with the predisposition to relate music and movement in particular ways, or whether these relationships are culturally transmitted. There is evidence that emotion expressed in music can be understood across cultures, despite dramatic cultural differences (9). There is also evidence that facial expressions and other emotional movements are crossculturally universal (10-12), as Darwin theorized (13). A natural predisposition to relate emotional expression in music and movement would explain why music often appears to be cross-culturally intelligible when other fundamental cultural practices (such as verbal language) are not (14). To determine how music and movement are related, and whether that relationship is peculiar to Western culture, we ran two experiments. First, we tested our common structure hypothesis in the United States. Then we conducted a similar experiment in L'ak, a culturally isolated tribal village in northeastern Cambodia. We compared the results from both cultures to determine whether the connection between music and movement is universal. Because many musical practices are culturally transmitted, we did not expect both experiments to have precisely identical results. Rather, we hypothesized results from both cultures would differ in their details yet share core dynamic features enabling cross-cultural legibility. We created a computer program capable of generating both music and movement; the former as simple, monophonic piano melodies, and the latter as an animated bouncing ball. Both were controlled by a single probabilistic model, ensuring there was an isomorphic relationship between the behavior of the music and the movement of the ball. This model represented both music and movement in terms of dynamic contour: how changes in the stimulus unfold over time. Our model for dynamic contour comprised five quantitative parameters controlled by on-screen slider bars. Stimuli were generated in real time, and manipulation of the slider bars resulted in immediate changes in the music being played or the animation being shown (Fig. 1) .
REF found further empirical evidence for a shared dynamic structure between music and movement in a study that leveraged a common feature between these modalities: the capacity to convey affective content.
Music and movement share a dynamic structure that supports universal expressions of emotion
Proceedings of the National Academy of Sciences of the United States of America
Proceedings of the National Academy of Sciences of the United States of America
Psychology Medicine