Koen de Reus of VUB’s Artificial Intelligence Lab and the Comparative Bioacoustics Group at Max Planck Institute for Psycholinguistics in the Netherlands: “Failure of a non-human animal to synchronise in an experiment designed to test humans does not mean they are incapable of synchronising. It could also mean that the experiment was not appropriately designed to test a particular species.”
VUB researcher Koen de Reus is part of an international team exploring the best way to study how animals synchronise behaviours such as moving, vocalising, and breathing. In humans and other animals, these rhythmic behaviours occur in various contexts: during mating, locomotion, and social coordination, for example. Study design is frequently based on human norms, but to effectively study synchronisation abilities in other animals, investigators need to consider a species’ temporal, physical, perceptual, and motivational constraints, which could be similar to or different than those of humans.
The research team is now proposing that a set of “ecologically honest” design principles, which is specific to the animal and the context, would give a better picture of its synchronisation abilities. In reviewing the literature, the researchers found that anticipation and tempo flexibility have previously been recognised as critical features of synchrony, but their opinion piece published in the Philosophical Transactions of the Royal Society B is the first to acknowledge that an animal’s tempo flexibility is restricted to a specific range. This means scientists must first establish the natural range of tempi at which animals produce rhythmic behaviours, in order to study whether they can synchronise.
de Reus: “All animals are temporally constrained by the physical limits of their bodies, their perceptual systems, and their behavioural ecology. The interaction of these three components determines a species’ degree of tempo flexibility. Although all animals that synchronise demonstrate tempo flexibility, the degree of flexibility varies across species. A range of tempo differences have been observed in the behaviours of different animals. Some have very flexible ranges, like humans and geladas, while others are more restricted, like bonobos and fiddler crabs.”
Motivation is key
The team also found that it is crucial to consider which behaviour a synchronisation task should test, as some behaviours are more easily synchronised to a stimulus than others. Researchers should therefore consider the modality (acoustic, visual, tactile) to which an animal synchronises best. For example, humans synchronise best to sounds, but this might not be the case for other animals. Finally, an animal’s motivation to perform a specific behaviour is highly context dependent. An individual behaviour may only become apparent when individuals form groups and studying this behaviour under controlled laboratory conditions would therefore require several individuals.
Koen de Reus: “An animal will perceive and can synchronise to a stimulus only within a species-specific range of tempi. However, this does not necessarily mean that if a stimulus falls within that range an animal will synchronise to it. It needs to be motivated to do so, and this is very much dependent on the situational context.”
To improve understanding of synchronisation abilities across the animal kingdom, knowledge from both laboratory experiments and field studies should be integrated. Lab settings allow researchers to control a range of variables that can test the full extent of a species’ ability to synchronise. Meanwhile, field studies can increase understanding of why, when, and how animal species synchronise in their natural environments. Observational data allow scientists to identify the behaviours a species can naturally produce, which can then inform controlled laboratory experiments.
Henry Molly J., Cook Peter F., de Reus Koen, Nityananda Vivek, Rouse Andrew A. and Kotz Sonja A. 2021 An ecological approach to measuring synchronization abilities across the animal kingdom. Phil. Trans. R. Soc. B 376:20200336. http://doi.org/10.1098/rstb.2020.0336
Koen de Reus