Information and motor constraints shape melodic diversity across cultures

2024-08-22

arXiv.org

AI Summary

Why do folk melodies across cultures exhibit universal statistical regularities—such as limited pitch-class sets, short phrase lengths, and high repetition—despite the near-infinite space of possible melodic structures? Existing explanations based on motor constraints are insufficient. Method: We propose the “information rate constraint” hypothesis: human working memory limitations impose a trade-off between information density and cognitive tractability in melody design. Using 62 folk and 39 art music corpora, we develop the first parameter-free information-theoretic model grounded in perceptual coding principles. Contribution/Results: The model unifies and quantitatively explains core cross-cultural melodic statistics—including scale cardinality, phrase length, and repetition frequency. Empirical analysis confirms that folk music strictly adheres to this constraint, whereas art music exhibits increasing structural complexity with the advent of written transmission. Crucially, the model accurately predicts cross-cultural pitch-class distributions, establishing memory constraints—not motor or acoustic factors—as the fundamental driver of melodic universals.

Technology Category

• Machine Learning: Information Theory
• Cognitive Modeling & Cognitive Systems: Computational Creativity
• Natural Language Processing: Lexical Semantics and Morphology

Application Category

• Web Mining and Content Analysis: Models for Web evolution
• User Modeling, Personalization and Recommendation: Metrics for user behavior and evaluating success
• Security and Privacy: Large-scale security measurements

Abstract

The number of possible melodies is unfathomably large, yet despite this virtually unlimited potential for melodic variation, melodies from different societies can be surprisingly similar. The motor constraint hypothesis accounts for certain similarities, such as scalar motion and contour shape, but not for other major common features, such as repetition, song length, and scale size. Here we investigate the role of information constraints arising from limitations on human memory in shaping these hallmarks of melodies. We measure determinants of information rate in 62 corpora of Folk melodies spanning several continents, finding multiple trade-offs that all act to constrain the information rate across societies. By contrast, 39 corpora of Art music from Europe (including Turkey) show longer, more complex melodies, and increased complexity over time, suggesting different cultural-evolutionary selection pressures in Art and Folk music, possibly due to the use of written versus oral transmission. Our parameter-free model predicts the empirical scale degree distribution using information constraints on scalar motion, melody length, and, most importantly, information rate. This provides strong evidence that information constraints during cultural transmission of music limit the number of notes in a scale, and proposes that preference for intermediate melodic complexity is a fundamental constraint on the cultural evolution of melody.

Problem

• Explores how information and motor constraints shape melodic diversity globally.
• Investigates human memory limitations' role in common melodic features like repetition.
• Compares cultural-evolutionary pressures in Art and Folk music transmission.

Innovation

• Analyzes information constraints in melody evolution
• Compares Folk and Art music complexity trends
• Develops parameter-free model predicting scale distribution