Investigation of musicality in birdsong

Abstract

Songbirds spend much of their time learning, producing, and listening to complex vocal sequences we call songs. Songs are learned via cultural transmission, and singing, usually by males, has a strong impact on the behavioral state of the listeners, often promoting affiliation, pair bonding, or aggression. What is it in the acoustic structure of birdsong that makes it such a potent stimulus? We suggest that birdsong potency might be driven by principles similar to those that make music so effective in inducing emotional responses in humans: a combination of rhythms and pitches —and the transitions between acoustic states—affecting emotions through creating expectations, anticipations, tension, tension release, or surprise. Here we propose a framework for investigating how birdsong, like human music, employs the above “musical” features to affect the emotions of avian listeners. First we analyze songs of thrush nightingales (Luscinia luscinia) by examining their trajectories in terms of transitions in rhythm and pitch. These transitions show gradual escalations and graceful modifications, which are comparable to some aspects of human musicality. We then explore the feasibility of stripping such putative musical features from the songs and testing how this might affect patterns of auditory responses, focusing on fMRI data in songbirds that demonstrate the feasibility of such approaches. Finally, we explore ideas for investigating whether musical features of birdsong activate avian brains and affect avian behavior in manners comparable to music’s effects on humans. In conclusion, we suggest that birdsong research would benefit from current advances in music theory by attempting to identify structures that are designed to elicit listeners’ emotions and then testing for such effects experimentally. Birdsong research that takes into account the striking complexity of song structure in light of its more immediate function – to affect behavioral state in listeners – could provide a useful animal model for studying basic principles of music neuroscience in a system that is very accessible for investigation, and where developmental auditory and social experience can be tightly controlled.

Acoustic sequences in non‐human animals: a tutorial review and prospectus

“…Although it seems intuitively obvious that a sequence of such labels may contain information, this intuition arises from our own natural human dispensation to language and writing, and may not be particularly useful in identifying information in animal sequences. We appreciate that birdsong, for instance, can be described as a complex combination of notes, and we may be tempted to compare this animal vocalisation to human music (Baptista & Keister, 2005; Araya-Salas, 2012; Rothenberg et al, 2013). An anthropocentric approach, however, is not likely in all cases to identify structure relevant to animal communication.…”

Convergent evidence for the molecular basis of musical traits

“…Even birdsong is known to have musical features: it is a combination of rhythms, pitches, and transitions that induce emotional responses17 and vocal learning show similar features between songbirds and humans18. In zebra finches, vocal learning happens during sensitivity period from 25 to 65 dph (days post-hatch)19.…”

A Potential Metric of the Attractiveness of Bird Song to Humans

“…As far as we are aware, no one has previously tried to derive a metric that can be used to quantify variation in the attractiveness of bird song, for obvious reasons: not least, it is a subjective trait on whose elements no two people will exactly agree (Rothenberg et al. ). Nevertheless, it is clear that while people differ in what they find attractive, some bird songs are generally considered to be more aesthetically pleasing than others.…”

“…The fascination of scientists is but one manifestation of the wonder that the beauty and diversity of bird song evokes (Mynott 2009), which is expressed in art, and also in the desire to possess the singers that would appear to be a major driver of the international cage bird trade. As far as we are aware, no one has previously tried to derive a metric that can be used to quantify variation in the attractiveness of bird song, for obvious reasons: not least, it is a subjective trait on whose elements no two people will exactly agree (Rothenberg et al 2013). Nevertheless, it is clear that while people differ in what they find attractive, some bird songs are generally considered to be more aesthetically pleasing than others.…”