TY - JOUR

T1 - Multifractal analysis reveals music-like dynamic structure in songbird rhythms

AU - Roeske, Tina C.

AU - Kelty-Stephen, Damian

AU - Wallot, Sebastian

N1 - This work was funded by the Max Planck Society (T.R. and S.W.). D.K-S. did not receive any funding.

PY - 2018/12/1

Y1 - 2018/12/1

N2 - Music is thought to engage its listeners by driving feelings of surprise, tension, and relief through a dynamic mixture of predictable and unpredictable patterns, a property summarized here as "expressiveness". Birdsong shares with music the goal to attract its listeners' attention and might use similar strategies to achieve this. We here tested a thrush nightingale's (Luscinia luscinia) rhythm, as represented by song amplitude envelope (containing information on note timing, duration, and intensity), for evidence of expressiveness. We used multifractal analysis, which is designed to detect in a signal dynamic fluctuations between predictable and unpredictable states on multiple timescales (e.g. notes, subphrases, songs). Results show that rhythm is strongly multifractal, indicating fluctuations between predictable and unpredictable patterns. Moreover, comparing original songs with re-synthesized songs that lack all subtle deviations from the "standard" note envelopes, we find that deviations in note intensity and duration significantly contributed to multifractality. This suggests that birdsong is more dynamic due to subtle note timing patterns, often similar to musical operations like accelerando or crescendo. While different sources of these dynamics are conceivable, this study shows that multi-timescale rhythm fluctuations can be detected in birdsong, paving the path to studying mechanisms and function behind such patterns.

AB - Music is thought to engage its listeners by driving feelings of surprise, tension, and relief through a dynamic mixture of predictable and unpredictable patterns, a property summarized here as "expressiveness". Birdsong shares with music the goal to attract its listeners' attention and might use similar strategies to achieve this. We here tested a thrush nightingale's (Luscinia luscinia) rhythm, as represented by song amplitude envelope (containing information on note timing, duration, and intensity), for evidence of expressiveness. We used multifractal analysis, which is designed to detect in a signal dynamic fluctuations between predictable and unpredictable states on multiple timescales (e.g. notes, subphrases, songs). Results show that rhythm is strongly multifractal, indicating fluctuations between predictable and unpredictable patterns. Moreover, comparing original songs with re-synthesized songs that lack all subtle deviations from the "standard" note envelopes, we find that deviations in note intensity and duration significantly contributed to multifractality. This suggests that birdsong is more dynamic due to subtle note timing patterns, often similar to musical operations like accelerando or crescendo. While different sources of these dynamics are conceivable, this study shows that multi-timescale rhythm fluctuations can be detected in birdsong, paving the path to studying mechanisms and function behind such patterns.

KW - Empirical education research

KW - Psychology

UR - http://www.scopus.com/inward/record.url?scp=85044212181&partnerID=8YFLogxK

U2 - 10.1038/s41598-018-22933-2

DO - 10.1038/s41598-018-22933-2

M3 - Journal articles

C2 - 29545558

AN - SCOPUS:85044212181

VL - 8

JO - Scientific Reports

JF - Scientific Reports

SN - 2045-2322

IS - 1

M1 - 4570

ER -