Universality and Diversity in Human Song Samuel A. Mehr1,2*, Manvir
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This is a provisionally accepted manuscript. The published version will differ from it substantially. Please cite it as: Mehr, S. A., Singh, M., Knox, D., Ketter, D. M., Pickens-Jones, D., Atwood, S., Lucas, C., Egner, A., Jacoby, N., Hopkins, E. J., Howard, R. M., Hartshorne, J. K., Jennings, M. V., Simson, J., Bainbridge, C. M., Pinker, S., O'Donnell, T. J., Krasnow, M. M., & Glowacki, L. (forthcoming). Universality and diversity in human song. Science . Universality and diversity in human song Samuel A. Mehr 1,2*, Manvir Singh 3*, Dean Knox 4, Daniel M. Ketter 6,7, Daniel Pickens-Jones 8, Stephanie Atwood 2, Christopher Lucas 5, Alena Egner 2, Nori Jacoby 10, Erin J. Hopkins 2, Rhea M. Howard 2, Timothy J. O’Donnell 11, Steven Pinker 2, Max M. Krasnow 2, and Luke Glowacki 12* 1 Data Science Initiative, Harvard University 2 Department of Psychology, Harvard University 3 Department of Human Evolutionary Biology, Harvard University 4 Department of Politics, Princeton University 5 Department of Political Science, Washington University in St. Louis 6 Eastman School of Music, University of Rochester 7 Department of Music, Missouri State University 8 Portland, Oregon 9 Department of Psychology, University of California at Los Angeles 10 Max Planck Institute for Empirical Aesthetics 11 Department of Linguistics, McGill University 12 Department of Anthropology, Pennsylvania State University *Correspondence to [email protected] (S.A.M.), [email protected] (M.S.), and [email protected] (L.G.) Abstract What is universal about music across human societies, and what varies? We built a corpus of ethnographic text on musical behavior from a representative sample of the world’s societies and a discography of audio recordings of the music itself. The ethnographic corpus reveals that music appears in every society observed; that variation in musical behavior is well- characterized by three dimensions, which capture the formality, arousal, and religiosity of song events; that musical behavior varies more within societies than across societies on these dimensions; and that music is regularly associated with behavioral contexts such as infant care, healing, dance, and love. The discography, analyzed through four representations (machine summaries, listener ratings, expert annotations, expert transcriptions), revealed that identifiable acoustic features of songs predict their primary behavioral function worldwide, and that these features fall along two dimensions, melodic and rhythmic complexity. These analyses show how applying the tools of computational social science to rich bodies of humanistic data can reveal both universal features and patterns of variability in culture, addressing longstanding debates about each. 2 Introduction At least since Henry Wadsworth Longfellow declared in 1835 that "music is the universal language of mankind" (1) the conventional wisdom among many authors, scholars, and scientists is that music is a human universal, with profound similarities across societies springing from shared features of human psychology (2). Music certainly is widespread (3–5), ancient (6), and appealing to almost everyone (7). Yet claims that it is universal, or has universal features, are commonly made without citation (e.g., 8–10), and those with the greatest expertise on the topic are skeptical if not hostile. Many music scholars, particularly ethnomusicologists, assert that there are few if any universals in music (11–15). They point to variability in the interpretations of a given piece of music (16–18); the importance of natural, political, and economic environments in shaping music (19–21); the diverse forms of music that can share similar behavioral functions (22); and the methodological difficulty of comparing the music of different societies (5, 23, 24). Given these criticisms, along with a history of some scholars using comparative work to advance erroneous claims of cultural or racial superiority (25), a view that is common among music scholars today (26, 27) is the one summarized by the ethnomusicologist George List: "The only universal aspect of music seems to be that most people make it. And that is about the only universal involved. I could provide pages of examples of the non-universality of music. This is hardly worth the trouble." (28) Nonetheless, diversity in concrete examples of a cultural practice can shroud regularities in the underlying psychological mechanisms. Beginning with Noam Chomsky’s hypothesis that the world’s languages conform to an abstract Universal Grammar (29, 30), many anthropologists, psychologists, and cognitive scientists have shown that some behavioral patterns that were once considered arbitrary cultural products may in fact exhibit profound similarities across human societies which emerge from deep and abstract features of human nature. These include religion (31–33), mate preferences (34), kinship systems (35), social relationships (36, 37), morality (38, 39), violence and warfare (40–42), and political and economic beliefs (43, 44). Music may be another example, but while several studies have provided promising evidence of cross-cultural regularities (3, 45–47), they have not addressed the music scholars’ objections, such as the lack of global representativeness of the samples, the subjectivity of the analyses, and the variability across cultures. A proper evaluation of whether and how music is universal requires a natural history of music: a systematic analysis of the features of musical behavior and structure across cultures, using scientific standards of objectivity, representativeness, quantification of variability, and controls for data integrity. We take up this challenge here. We focus on vocal music (hereafter, song) rather than instrumental music, because it does not depend on variations in technology, has well-defined physical correlates (i.e., pitched vocalizations; 19), and has been a primary focus of biological explanations for music (48, 49). In this paper we present the new Natural History of Song database and analyze it to document the behavioral and acoustic features of music across societies. Leveraging more than a century of research from anthropology and ethnomusicology, along with existing databases that catalog it, we built two corpora. The NHS Ethnography is composed of ethnographic descriptions of song performances. Ethnographies provide a detailed record of the behaviors 3 associated with songs, the lyrical content of songs, the people present during song performances, and so on, and they are amenable to detailed manual annotation — but they describe few features of the music itself. The NHS Discography is composed of field recordings of song performances in four categories. Audio recordings provide an actual record of the pitches, rhythms, harmonies, instrumental accompaniments, and other sounds present during song performances — but they often lack metadata on the behavioral context accompanying the singing. We use the two corpora to test four sets of hypotheses about variability and universality in music. First, we test whether music is universal by examining the ethnographies of 315 societies, and then a geographically-stratified pseudorandom sample of them. Second, we assess how the behaviors associated with song differ among societies. We reduce the high-dimensional NHS Ethnography annotations to a small number of dimensions of variation while addressing challenges in the analysis of ethnographic data, such as selective nonreporting. This allows us to assess how the variation in music performance from one society to another compares with the variation within a single society. Third, we test which behaviors are universally or commonly associated with song. We catalogue 20 common but untested hypotheses about these associations, such as religious activity, dance, and infant care (32, 45, 48–52), and test them after adjusting for sampling error and ethnographer bias, problems which have bedeviled prior tests. Fourth, we test whether the musical features of songs, as documented in the NHS Discography, predict their behavioral functions. Since the raw waveform of a song performance is difficult to analyze, we derived four representations of each one, combining blind human ratings with quantitative analyses. We then applied obJective classifiers to these representations to see whether the musical features of a song predict its association with particular behavioral contexts and functions, and whether these features vary in systematic ways. All data and materials are publicly available at http://osf.io/jmv3q. We also encourage readers to view and listen to the corpora interactively via the plots available at http://themusiclab.org/nhsplots. 1. Music appears in all measured human societies Is music universal? We first addressed this question by examining the eHRAF World Cultures database (53, 54), developed and maintained by the Human Relations Area Files organization. It includes high-quality ethnographic documents from 315 human societies, subJect-indexed by paragraph. We searched for text that was tagged as including music (instrumental or vocal) or that contained at least one keyword identifying vocal music (e.g., "singers"). 4 Fig. 1. Design of NHS Ethnography. The illustration depicts the sequence from acts of singing to the ethnography corpus. (A) People produce songs in conjunction with other behavior, which scholars observe and describe in text. These ethnographies are published in books, reports, and journal articles and then compiled, translated,