Liao, Chun ChiehMagrath, Robert D.Manser, Marta B.Farine, Damien R.2025-05-302025-05-300962-8436PubMed:38768199WOS:001229124100003ORCID:/0000-0003-2208-7613/work/164937005http://www.scopus.com/inward/record.url?scp=85193994395&partnerID=8YFLogxKhttps://hdl.handle.net/1885/733755191To benefit from group living, individuals need to maintain cohesion and coordinate their activities. Effective communication thus becomes critical, facilitating rapid coordination of behaviours and reducing consensus costs when group members have differing needs and information. In many bird and mammal species, collective decisions rely on acoustic signals in some contexts but on movement cues in others. Yet, to date, there is no clear conceptual framework that predicts when decisions should evolve to be based on acoustic signals versus movement cues. Here, we first review how acoustic signals and movement cues are used for coordinating activities. We then outline how information masking, discrimination ability (Weber's Law) and encoding limitations, as well as trade-offs between these, can identify which types of collective behaviours likely rely on acoustic signals or movement cues. Specifically, our framework proposes that behaviours involving the timing of events or expression of specific actions should rely more on acoustic signals, whereas decisions involving complex choices with multiple options (e.g. direction and destination) should generally use movement cues because sounds are more vulnerable to information masking and Weber's Law effects. We then discuss potential future avenues of enquiry, including multimodal communication and collective decision-making by mixed-species animal groups.  This article is part of the theme issue 'The power of sound: unravelling how acoustic communication shapes group dynamic'.This study was funded by a grant from the European Research Council (ERC) under the European Union\u2019s Horizon 2020 research and innovation programme (grant agreement number 850859) and an Eccellenza Professorship Grant of the Swiss National Science Foundation (grant number PCEFP3_187058) awarded to D.R.F. C.-C.L. was funded by an RSB International PhD scholarship from the Australian National University (ANU). R.D.M. was funded by the Research School of Biology of the ANU and the Australian Research Council (grant number DP150102632). M.B.M. was funded by the University of Zurich. Acknowledgements14enPublisher Copyright: © 2024 The Authors.collective behaviourgroup cohesionmovementquorumvocal communicationQuorumGroup cohesionMovementVocal communicationCollective behaviour2024-05-2010.1098/rstb.2023.018485193994395