The sound of a horse's hooves in motion is all about rhythm
The sequence of a horse's hooves hitting the ground seems intuitively rhythmic, but is it really? A team of researchers led by Marco Gamba of the University of Turin and Andrea Ravignani of Sapienza University of Rome, funded by the ERC project The Origins of Human Rhythm (TOHR), has answered this question in two studies published in the Journal of Anatomy and Annals of the New York Academy of Sciences, highlighting the similarities between the rhythms of horse locomotion and musical rhythms. This connection could explain why the different equine gaits - stride, trot and gallop - are so rhythmic and recognisable.
Musical rhythm in many Western cultures is based on sequences of time intervals that follow ratios of integers, each of which defines a rhythmic category. A note, for example, may last as long as the previous one, or twice or three times as long. In recent years, studies on various animal species have already revealed that similar ratios are found in the vocalisations of other species, confirming the key role of these temporal structures in rhythm perception.
For the first time, researchers have shown that horses' gaits also share these same temporal structures: the intervals between successive hooves striking the ground are characterised by rhythmic categories. In particular, the horses' stride and trot are isochronous, as the ground is struck at regular intervals, like the ticking of a clock; the gallop, on the other hand, presents a sequence of three intervals in which the third one lasts twice as long as the other two, i.e. a 1:1:2 pattern, recalling the basic rhythm of the song “We Will Rock You” by Queen.
‘This 1:1:2 pattern is incidentally also found in the Overture of Rossini's William Tell. Perhaps this explains why this piece is often used as a soundtrack in films in which horses are seen galloping,' says Andrea Ravignani.
These studies continue a line of research in which our universities have joined forces to investigate the rhythmic characteristics of animal and human behaviour, trying to unearth similarities and differences that have yet to be interpreted in terms of their evolutionary significance,’ adds Marco Gamba.
In addition to rhythmic categories, ‘another fundamental element in distinguishing between horse gaits is tempo, i.e. the speed at which beats follow one another in any given rhythmic pattern, similar to what we observe between different musical genres,’ explains Teresa Raimondi, a postdoctoral fellow at Sapienza University of Rome. In particular, step and trot are easily distinguishable due to the longer duration of the intervals, and thus a slower rhythmic pattern in the trot than in the step.
‘The discovery of common rhythmic patterns between music, animal communication and locomotion reinforces the idea that locomotion and motor control may have played a crucial role in the evolution of rhythm, both in human communication and that of other species,’ concludes Lia Laffi, a PhD student at the University of Turin in collaboration with the Fondazione Zoom.
The results of the two studies quantitatively discriminate horse gaits based on rhythm, revealing surprising commonalities with human music and some animal communicative signals. Gait and vocal rhythmicity share key features, with the former probably predating the latter. Indeed, the ability to produce and recognise locomotion-related rhythms may have been a fundamental pre-adaptation for the development of more complex vocal rhythms at a later evolutionary stage. In particular, the perception of locomotor rhythmicity may have evolved in several species under the pressures of predator recognition and mating selection; it may subsequently have been adapted to rhythmic vocal communication.
Professors and researchers from the University of Veterinary Medicine in Vienna, the University of Copenhagen and the Italian Institute of Technology also participated in this international research effort.
References:
Laffi, L., Raimondi, T., Ferrante, C., Pagliara, E., Bertuglia, A., Briefer, E. F., Gamba, M., & Ravignani, A. (2024). “The rhythm of horse gaits”. Ann NY Acad Sci., 1–8. DOI: https://doi.org/10.1111/nyas.
Laffi, L., Bigand, F., Peham, C.,Novembre, G., Gamba, M. & Ravignani, A. (2024) “Rhythmic categories in horse gait kinematics”. Journal of Anatomy, 00,1–10. DOI: https://doi.org/10.1111/joa.
Further Information
Andrea Ravignani
Department of Human Neuroscience
Teresa Raimondi
Department of Human Neuroscience