1
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Liao CC, Magrath RD, Manser MB, Farine DR. The relative contribution of acoustic signals versus movement cues in group coordination and collective decision-making. Philos Trans R Soc Lond B Biol Sci 2024; 379:20230184. [PMID: 38768199 PMCID: PMC11391321 DOI: 10.1098/rstb.2023.0184] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 01/30/2024] [Accepted: 03/04/2024] [Indexed: 05/22/2024] Open
Abstract
To 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'.
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Affiliation(s)
- Chun-Chieh Liao
- Division of Ecology and Evolution, Research School of Biology, Australian National University , Canberra, ACT , 2600, Australia
| | - Robert D Magrath
- Division of Ecology and Evolution, Research School of Biology, Australian National University , Canberra, ACT , 2600, Australia
| | - Marta B Manser
- Department of Evolutionary Biology and Environmental Studies, University of Zurich , Zürich , 8057, Switzerland
| | - Damien R Farine
- Division of Ecology and Evolution, Research School of Biology, Australian National University , Canberra, ACT , 2600, Australia
- Department of Evolutionary Biology and Environmental Studies, University of Zurich , Zürich , 8057, Switzerland
- Department of Collective Behavior, Max Planck Institute of Animal Behavior , Radolfzell , 78315, Germany
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2
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Goodale E, Magrath RD. Species diversity and interspecific information flow. Biol Rev Camb Philos Soc 2024; 99:999-1014. [PMID: 38279871 DOI: 10.1111/brv.13055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 01/14/2024] [Accepted: 01/15/2024] [Indexed: 01/29/2024]
Abstract
Interspecific information flow is known to affect individual fitness, population dynamics and community assembly, but there has been less study of how species diversity affects information flow and thereby ecosystem functioning and services. We address this question by first examining differences among species in the sensitivity, accuracy, transmissibility, detectability and value of the cues and signals they produce, and in how they receive, store and use information derived from heterospecifics. We then review how interspecific information flow occurs in communities, involving a diversity of species and sensory modes, and how this flow can affect ecosystem-level functions, such as decomposition, seed dispersal or algae removal on coral reefs. We highlight evidence that some keystone species are particularly critical as a source of information used by eavesdroppers, and so have a disproportionate effect on information flow. Such keystone species include community informants producing signals, particularly about predation risk, that influence other species' landscapes of fear, and aggregation initiators creating cues or signals about resources. We suggest that the presence of keystone species means that there will likely be a positive relationship in many communities between species diversity and information through a 'sampling effect', in which larger pools of species are more likely to include the keystone species by chance. We then consider whether the number and relative abundance of species, irrespective of the presence of keystone species, matter to interspecific information flow; on this issue, the theory is less developed, and the evidence scant and indirect. Higher diversity could increase the quantity or quality of information that is used by eavesdroppers because redundancy increases the reliability of information or because the species provide complementary information. Alternatively, there could be a lack of a relationship between species diversity and information if there is widespread information parasitism where users are not sources, or if information sourced from heterospecifics is of lower value than that gained personally or sourced from conspecifics. Recent research suggests that species diversity does have information-modulated community and ecosystem consequences, especially in birds, such as the diversity of species at feeders increasing resource exploitation, or the number of imitated species increasing responses to vocal mimics. A first step for future research includes comprehensive observations of information flow among different taxa and habitats. Then studies should investigate whether species diversity influences the cumulative quality or quantity of information at the community level, and consequently ecosystem-level processes. An applied objective is to conserve species in part for their value as sources of information for other species, including for humans.
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Affiliation(s)
- Eben Goodale
- Department of Health and Environmental Science, Xi'an Jiaotong-Liverpool University, Suzhou, 215123, China
| | - Robert D Magrath
- Division of Ecology and Evolution, Research School of Biology, Australian National University, Canberra, ACT, 2600, Australia
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3
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Murray MM, Middelmann NK, Federmeier KD. Animal cognition: Dogs build semantic expectations between spoken words and objects. Curr Biol 2024; 34:R348-R351. [PMID: 38714162 DOI: 10.1016/j.cub.2024.03.045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/09/2024]
Abstract
A recent study has used scalp-recorded electroencephalography to obtain evidence of semantic processing of human speech and objects by domesticated dogs. The results suggest that dogs do comprehend the meaning of familiar spoken words, in that a word can evoke the mental representation of the object to which it refers.
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Affiliation(s)
- Micah M Murray
- Department of Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland; The Sense Innovation and Research Center, Lausanne and Sion, Switzerland; Department of Hearing and Speech Sciences, Vanderbilt University, Nashville, TN 37232, USA.
| | - Naomi K Middelmann
- The Sense Innovation and Research Center, Lausanne and Sion, Switzerland; Pediopsychiatry Service, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Kara D Federmeier
- Department of Psychology, University of Illinois at Urbana-Champaign, Champaign, IL, USA; Departments of Linguistics and Kinesiology, University of Illinois at Urbana-Champaign, Champaign, IL, USA; Program in Neuroscience and the Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Champaign, IL, USA
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4
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Kamiloğlu RG, Sauter DA. Sounds like a fight: listeners can infer behavioural contexts from spontaneous nonverbal vocalisations. Cogn Emot 2024; 38:277-295. [PMID: 37997898 PMCID: PMC11057848 DOI: 10.1080/02699931.2023.2285854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 11/13/2023] [Indexed: 11/25/2023]
Abstract
When we hear another person laugh or scream, can we tell the kind of situation they are in - for example, whether they are playing or fighting? Nonverbal expressions are theorised to vary systematically across behavioural contexts. Perceivers might be sensitive to these putative systematic mappings and thereby correctly infer contexts from others' vocalisations. Here, in two pre-registered experiments, we test the prediction that listeners can accurately deduce production contexts (e.g. being tickled, discovering threat) from spontaneous nonverbal vocalisations, like sighs and grunts. In Experiment 1, listeners (total n = 3120) matched 200 nonverbal vocalisations to one of 10 contexts using yes/no response options. Using signal detection analysis, we show that listeners were accurate at matching vocalisations to nine of the contexts. In Experiment 2, listeners (n = 337) categorised the production contexts by selecting from 10 response options in a forced-choice task. By analysing unbiased hit rates, we show that participants categorised all 10 contexts at better-than-chance levels. Together, these results demonstrate that perceivers can infer contexts from nonverbal vocalisations at rates that exceed that of random selection, suggesting that listeners are sensitive to systematic mappings between acoustic structures in vocalisations and behavioural contexts.
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Affiliation(s)
- Roza G. Kamiloğlu
- Department of Psychology, University of Amsterdam, Amsterdam, the Netherlands
- Department of Experimental and Applied Psychology, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Disa A. Sauter
- Department of Psychology, University of Amsterdam, Amsterdam, the Netherlands
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5
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Pedretti G, Canori C, Costantini E, Palme R, Valsecchi P, Marshall-Pescini S. Intra and interspecific audience effect on domestic dogs' behavioural displays and facial expressions. Sci Rep 2024; 14:9546. [PMID: 38664496 PMCID: PMC11045831 DOI: 10.1038/s41598-024-58757-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Accepted: 04/02/2024] [Indexed: 04/28/2024] Open
Abstract
The aim of the current study was to investigate the influence of both intra- and interspecific audiences on dogs' facial expressions and behaviours. Forty-six dogs were exposed to three test conditions in which a food reward, initially available, was denied when in the presence of either a human (Human condition) or a dog audience (Dog condition), or in the absence of a visible audience (Non-social condition). Salivary cortisol was collected to evaluate the stress/arousal activation in the different conditions. Compared to the Non-social condition, the presence of a conspecific evoked more facial expressions, according to the DogFACS (Facial Action Coding System, an anatomically based tool to analyze facial expressions in domestic dogs), (EAD105-Ears downward), displacement behaviours (AD137-Nose licking, AD37-Lip wiping), tail wagging, whining, and panting (AD126). When facing a conspecific, dogs assumed a more avoidant attitude, keeping a distance and not looking at the stimuli, compared to when in the presence of the human partner. Dogs also exhibited more facial expressions (EAD102-Ears Adductor, EAD104-Ears Rotator), displacement behaviours (AD137-Nose licking, AD37-Lip wiping), panting (AD126) and whining when facing the conspecific than the human partner. Post-test cortisol was not influenced by any condition, and no association between pre-test cortisol and behavioural variables was found, thus strong differences in the levels of stress/arousal were unlikely to be responsible for differences in behavior between conditions. Considering the current results in the context of the available literature, we suggest that the higher displacement behaviors exhibited with the conspecifics were likely due to an increased level of uncertainty regarding the situations.
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Affiliation(s)
- Giulia Pedretti
- Department of Medicine and Surgery, University of Parma, Via Gramsci 14, 43126, Parma, Italy.
- Department of Chemistry, Life Science and Environmental Sustainability, University of Parma, Viale Delle Scienze 17/A, 43124, Parma, Italy.
| | - Chiara Canori
- Department of Chemistry, Life Science and Environmental Sustainability, University of Parma, Viale Delle Scienze 17/A, 43124, Parma, Italy
| | - Elisa Costantini
- Department of Chemistry, Life Science and Environmental Sustainability, University of Parma, Viale Delle Scienze 17/A, 43124, Parma, Italy
| | - Rupert Palme
- Unit of Physiology, Pathophysiology and Experimental Endocrinology, Department of Biomedical Sciences, University of Veterinary Medicine, Veterinärplatz 1, 1210, Vienna, Austria
| | - Paola Valsecchi
- Department of Medicine and Surgery, University of Parma, Via Gramsci 14, 43126, Parma, Italy
- Department of Chemistry, Life Science and Environmental Sustainability, University of Parma, Viale Delle Scienze 17/A, 43124, Parma, Italy
| | - Sarah Marshall-Pescini
- Domestication Lab, Konrad-Lorenz-Institute for Ethology, University of Veterinary Medicine, Veterinärplatz 1, 1210, Vienna, Austria.
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6
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Boros M, Magyari L, Morvai B, Hernández-Pérez R, Dror S, Andics A. Neural evidence for referential understanding of object words in dogs. Curr Biol 2024; 34:1750-1754.e4. [PMID: 38521063 DOI: 10.1016/j.cub.2024.02.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Revised: 01/17/2024] [Accepted: 02/14/2024] [Indexed: 03/25/2024]
Abstract
Using words to refer to objects in the environment is a core feature of the human language faculty. Referential understanding assumes the formation of mental representations of these words.1,2 Such understanding of object words has not yet been demonstrated as a general capacity in any non-human species,3 despite multiple behavior-based case reports.4,5,6,7,8,9,10 In human event-related potential (ERP) studies, object word knowledge is typically tested using the semantic violation paradigm, where words are presented either with their referent (match) or another object (mismatch).11,12 Such mismatch elicits an N400 effect, a well-established neural correlate of semantic processing.12,13 Reports of preverbal infant N400 evoked by semantic violations14 assert the use of this paradigm to probe mental representations of object words in nonverbal populations. Here, measuring dogs' (Canis familiaris) ERPs to objects primed with matching or mismatching object words, we found a mismatch effect at a frontal electrode, with a latency (206-606 ms) comparable to the human N400. A greater difference for words that dogs knew better, according to owner reports, further supported a semantic interpretation of this effect. Semantic expectations emerged irrespective of vocabulary size, demonstrating the prevalence of referential understanding in dogs. These results provide the first neural evidence for object word knowledge in a non-human animal. VIDEO ABSTRACT.
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Affiliation(s)
- Marianna Boros
- Neuroethology of Communication Lab, Department of Ethology, Eötvös Loránd University, Pázmány Péter sétány 1/C, 1117 Budapest, Hungary.
| | - Lilla Magyari
- Neuroethology of Communication Lab, Department of Ethology, Eötvös Loránd University, Pázmány Péter sétány 1/C, 1117 Budapest, Hungary; Norwegian Centre for Reading Education and Research, Faculty of Arts and Education, University of Stavanger, Professor Olav Hanssens vei 10, 4021 Stavanger, Norway; Department of Social Studies, Faculty of Social Sciences, University of Stavanger, Kjell Arholms gate 41, 4021 Stavanger, Norway.
| | - Boglárka Morvai
- Neuroethology of Communication Lab, Department of Ethology, Eötvös Loránd University, Pázmány Péter sétány 1/C, 1117 Budapest, Hungary
| | - Raúl Hernández-Pérez
- Neuroethology of Communication Lab, Department of Ethology, Eötvös Loránd University, Pázmány Péter sétány 1/C, 1117 Budapest, Hungary; ELTE NAP Canine Brain Research Group, Eötvös Loránd University, Pázmány Péter sétány 1/C, 1117 Budapest, Hungary
| | - Shany Dror
- Department of Ethology, Eötvös Loránd University, Pázmány Péter sétány 1/C, 1117 Budapest, Hungary; Doctoral School of Biology, Institute of Biology, ELTE Eötvös Loránd University, Pázmány Péter sétány 1/C, 1117 Budapest, Hungary
| | - Attila Andics
- Neuroethology of Communication Lab, Department of Ethology, Eötvös Loránd University, Pázmány Péter sétány 1/C, 1117 Budapest, Hungary; ELTE NAP Canine Brain Research Group, Eötvös Loránd University, Pázmány Péter sétány 1/C, 1117 Budapest, Hungary
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7
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Bao L, Rao J, Yu D, Zheng B, Yin B. Decoding the language of fear: Unveiling objective and subjective indicators in rodent models through a systematic review and meta-analysis. Neurosci Biobehav Rev 2024; 157:105537. [PMID: 38215801 DOI: 10.1016/j.neubiorev.2024.105537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 12/23/2023] [Accepted: 01/05/2024] [Indexed: 01/14/2024]
Abstract
While rodent models are vital for studying mental disorders, the underestimation of construct validity of fear indicators has led to limitations in translating to effective clinical treatments. Addressing this gap, we systematically reviewed 5054 articles from the 1960 s, understanding underlying theoretical advancement, and selected 68 articles with at least two fear indicators for a three-level meta-analysis. We hypothesized correlations between different indicators would elucidate similar functions, while magnitude differences could reveal distinct neural or behavioral mechanisms. Our findings reveal a shift towards using freezing behavior as the primary fear indicator in rodent models, and strong, moderate, and weak correlations between freezing and conditioned suppression ratios, 22-kHz ultrasonic vocalizations, and autonomic nervous system responses, respectively. Using freezing as a reference, moderator analysis shows treatment types and fear stages significantly influenced differences in magnitudes between two indicators. Our analysis supports a two-system model of fear in rodents, where objective and subjective fears could operate on a threshold-based mechanism.
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Affiliation(s)
- Lili Bao
- School of Psychology, Fujian Normal University, China; Key Laboratory for Learning and Behavioral Sciences, Fujian Normal University, China
| | - Jiaojiao Rao
- School of Psychology, Fujian Normal University, China; Key Laboratory for Learning and Behavioral Sciences, Fujian Normal University, China
| | - Delin Yu
- School of Psychology, Fujian Normal University, China; Key Laboratory for Learning and Behavioral Sciences, Fujian Normal University, China
| | - Benhuiyuan Zheng
- School of Psychology, Fujian Normal University, China; Key Laboratory for Learning and Behavioral Sciences, Fujian Normal University, China
| | - Bin Yin
- School of Psychology, Fujian Normal University, China; Key Laboratory for Learning and Behavioral Sciences, Fujian Normal University, China.
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8
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Friston KJ, Parr T, Heins C, Constant A, Friedman D, Isomura T, Fields C, Verbelen T, Ramstead M, Clippinger J, Frith CD. Federated inference and belief sharing. Neurosci Biobehav Rev 2024; 156:105500. [PMID: 38056542 PMCID: PMC11139662 DOI: 10.1016/j.neubiorev.2023.105500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 11/08/2023] [Accepted: 12/01/2023] [Indexed: 12/08/2023]
Abstract
This paper concerns the distributed intelligence or federated inference that emerges under belief-sharing among agents who share a common world-and world model. Imagine, for example, several animals keeping a lookout for predators. Their collective surveillance rests upon being able to communicate their beliefs-about what they see-among themselves. But, how is this possible? Here, we show how all the necessary components arise from minimising free energy. We use numerical studies to simulate the generation, acquisition and emergence of language in synthetic agents. Specifically, we consider inference, learning and selection as minimising the variational free energy of posterior (i.e., Bayesian) beliefs about the states, parameters and structure of generative models, respectively. The common theme-that attends these optimisation processes-is the selection of actions that minimise expected free energy, leading to active inference, learning and model selection (a.k.a., structure learning). We first illustrate the role of communication in resolving uncertainty about the latent states of a partially observed world, on which agents have complementary perspectives. We then consider the acquisition of the requisite language-entailed by a likelihood mapping from an agent's beliefs to their overt expression (e.g., speech)-showing that language can be transmitted across generations by active learning. Finally, we show that language is an emergent property of free energy minimisation, when agents operate within the same econiche. We conclude with a discussion of various perspectives on these phenomena; ranging from cultural niche construction, through federated learning, to the emergence of complexity in ensembles of self-organising systems.
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Affiliation(s)
- Karl J Friston
- Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, UK; VERSES AI Research Lab, Los Angeles, CA 90016, USA.
| | - Thomas Parr
- Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, UK
| | - Conor Heins
- VERSES AI Research Lab, Los Angeles, CA 90016, USA; Department of Collective Behaviour, Max Planck Institute of Animal Behavior, 78457 Konstanz, Germany; Centre for the Advanced Study of Collective Behaviour, 78457 Konstanz, Germany; Department of Biology, University of Konstanz, 78457 Konstanz, Germany
| | - Axel Constant
- VERSES AI Research Lab, Los Angeles, CA 90016, USA; School of Engineering and Informatics, The University of Sussex, Brighton, UK
| | - Daniel Friedman
- Department of Entomology and Nematology, University of California, Davis, Davis, CA, USA; Active Inference Institute, Davis, CA 95616, USA
| | - Takuya Isomura
- Brain Intelligence Theory Unit, RIKEN Center for Brain Science, Wako, Saitama 351-0198, Japan
| | - Chris Fields
- Allen Discovery Center at Tufts University, Medford, MA 02155, USA
| | - Tim Verbelen
- VERSES AI Research Lab, Los Angeles, CA 90016, USA
| | - Maxwell Ramstead
- Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, UK; VERSES AI Research Lab, Los Angeles, CA 90016, USA
| | | | - Christopher D Frith
- Institute of Philosophy, School of Advanced Studies, University of London, UK
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9
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Amphaeris J, Blumstein DT, Shannon G, Tenbrink T, Kershenbaum A. A multifaceted framework to establish the presence of meaning in non-human communication. Biol Rev Camb Philos Soc 2023; 98:1887-1909. [PMID: 37340613 DOI: 10.1111/brv.12989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 06/01/2023] [Accepted: 06/05/2023] [Indexed: 06/22/2023]
Abstract
Does non-human communication, like language, involve meaning? This question guides our focus through an interdisciplinary review of the theories and terminology used to study meaning across disciplines and species. Until now, it has been difficult to apply the concept of meaning to communication in non-humans. This is partly because of the varied approaches to the study of meaning. Additionally, while there is a scholarly acknowledgement of potential meaning in non-human cognition, there is also scepticism when the topic of communication arises. We organise some of the key literature into a coherent framework that can bridge disciplines and species, to ensure that aspects of meaning are accurately and fairly compared. We clarify the growing view in the literature that, rather than requiring multiple definitions or being split into different types, meaning is a multifaceted yet still unified concept. In so doing, we propose that meaning is an umbrella term. Meaning cannot be summed up with a short definition or list of features, but involves multiple complexities that are outlined in our framework. Specifically, three global facets are needed to describe meaning: a Signal Meaning Facet, an Interactant Meaning Facet, and a Resultant Meaning Facet. Most importantly, we show that such analyses are possible to apply as much to non-humans as to humans. We also emphasise that meaning nuances differ among non-human species, making a dichotomous approach to meaning questionable. Instead, we show that a multifaceted approach to meaning establishes how meaning appears within highly diverse examples of non-human communication, in ways consistent with the phenomenon's presence in human non-verbal communication and language(s). Therefore, without further recourse to 'functional' approaches that circumvent the critical question of whether any non-human meaning exists, we show that the concept of meaning is suitable for evolutionary biologists, behavioural ecologists, and others to study, to establish exactly which species exhibit meaning in their communication and in what ways.
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Affiliation(s)
- Jenny Amphaeris
- School of Arts, Culture, and Language, Bangor University, College Road, Bangor, LL57 2DG, UK
| | - Daniel T Blumstein
- Department of Ecology and Evolutionary Biology, University of California, 621 Young Drive South, Los Angeles, CA, 90095-1606, USA
| | - Graeme Shannon
- School of Natural Sciences, Bangor University, College Road, Bangor, LL57 2DG, UK
| | - Thora Tenbrink
- School of Arts, Culture, and Language, Bangor University, College Road, Bangor, LL57 2DG, UK
| | - Arik Kershenbaum
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK
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10
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Nunes S. Animal-friendly behavioral testing in field studies: examples from ground squirrels. Front Behav Neurosci 2023; 17:1239774. [PMID: 37681193 PMCID: PMC10480841 DOI: 10.3389/fnbeh.2023.1239774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 08/10/2023] [Indexed: 09/09/2023] Open
Abstract
Field studies of behavior provide insight into the expression of behavior in its natural ecological context and can serve as an important complement to behavioral studies conducted in the lab under controlled conditions. In addition to naturalistic observations, behavioral testing can be an important component of field studies of behavior. This mini review evaluates a sample of behavioral testing methods in field studies to identify ways in which behavioral testing can be animal-friendly and generate ethologically relevant data. Specific examples, primarily from studies of ground squirrels, are presented to illustrate ways in which principles of animal-friendly behavioral testing can be applied to and guide testing methods. Tests conducted with animals in their natural habitat and that elicit naturally occurring behavioral responses can minimize stress and disturbance for animals, as well as disruption of the larger ecosystem, and can have high ethological validity. When animals are trapped or handled as part of a study, behavioral testing can be incorporated into handling procedures to reduce overall disturbance. When behavior is evaluated in a testing arena, the arena can be designed to resemble natural conditions to increase the ethological relevance of the test. Efforts to minimize time spent in testing arenas can also reduce disturbance to animals. Adapting a behavioral test to a species or habitat conditions can facilitate reduced disruption to subjects and increased ethological relevance of the test.
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Affiliation(s)
- Scott Nunes
- Department of Biology, University of San Francisco, San Francisco, CA, United States
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11
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León J, Thiriau C, Crockford C, Zuberbühler K. Comprehension of own and other species' alarm calls in sooty mangabey vocal development. Behav Ecol Sociobiol 2023; 77:56. [PMID: 37234238 PMCID: PMC10205891 DOI: 10.1007/s00265-023-03318-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 03/26/2023] [Accepted: 03/30/2023] [Indexed: 05/27/2023]
Abstract
Abstract Primates understand the meaning of their own and other species' alarm calls, but little is known about how they acquire such knowledge. Here, we combined direct behavioural observations with playback experiments to investigate two key processes underlying vocal development: comprehension and usage. Especifically, we studied the development of con- and heterospecific alarm call recognition in free-ranging sooty mangabeys, Cercocebus atys, across three age groups: young juveniles (1-2y), old juveniles (3-4y) and adults (> 5y). We observed that, during natural predator encounters, juveniles alarm called to a significantly wider range of species than adults, with evidence of refinement during the first four years of life. In the experiments, we exposed subjects to leopard, eagle and snake alarm calls given by other group members or sympatric Diana monkeys. We found that young juveniles' locomotor and vocal responses were least appropriate and that they engaged in more social referencing (look at adults when hearing an alarm call) than older individuals, suggesting that vocal competence is obtained via social learning. In conclusion, our results suggest that alarm call comprehension is socially learned during the juvenile stage, with comprehension preceding appropriate usage but no difference between learning their own or other species' alarm calls. Significance statement Under natural conditions, animals do not just interact with members of their own species, but usually operate in a network of associated species. However, ontogenetic research on primate communication frequently ignores this significant element. We studied the development of con- and heterospecific alarm call recognition in wild sooty mangabeys. We found that communicative competence was acquired during the juvenile stages, with alarm call comprehension learning preceding appropriate vocal usage and with no clear difference in learning of con- and heterospecific signals. We also found that, during early stages of life, social referencing, a proactive form of social learning, was key in the acquisition of competent alarm call behaviour. Our results show that primates equally learn to interpret alarm calls from their own and other species during their early stages of life and that this learning process is refined as the animals mature. Supplementary Information The online version contains supplementary material available at 10.1007/s00265-023-03318-6.
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Affiliation(s)
- Julián León
- Institute of Biology, University of Neuchâtel, 2000 Neuchâtel, Switzerland
- Taï Monkey Project, Centre Suisse de Recherches Scientifiques, 01 BP1303 Abidjan 01, Côte d’Ivoire
| | - Constance Thiriau
- Taï Monkey Project, Centre Suisse de Recherches Scientifiques, 01 BP1303 Abidjan 01, Côte d’Ivoire
| | - Catherine Crockford
- Tai Chimpanzee Project, Centre Suisse de Recherches Scientifiques, 01 BP1303 Abidjan 01, Côte d’Ivoire
- Institute of Cognitive Sciences Marc Jeannerod, CNRS, 69330 Lyon, France
| | - Klaus Zuberbühler
- Institute of Biology, University of Neuchâtel, 2000 Neuchâtel, Switzerland
- Taï Monkey Project, Centre Suisse de Recherches Scientifiques, 01 BP1303 Abidjan 01, Côte d’Ivoire
- School of Psychology and Neuroscience, University of St. Andrews, Saint Andrews, KY16 9JP Scotland UK
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12
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Walsh SL, Engesser S, Townsend SW, Ridley AR. Multi-level combinatoriality in magpie non-song vocalizations. J R Soc Interface 2023; 20:20220679. [PMID: 36722171 PMCID: PMC9890321 DOI: 10.1098/rsif.2022.0679] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Comparative studies conducted over the past few decades have provided important insights into the capacity for animals to combine vocal segments at either one of two levels: within- or between-calls. There remains, however, a distinct gap in knowledge as to whether animal combinatoriality can extend beyond one level. Investigating this requires a comprehensive analysis of the combinatorial features characterizing a species' vocal system. Here, we used a nonlinear dimensionality reduction analysis and sequential transition analysis to quantitatively describe the non-song combinatorial repertoire of the Western Australian magpie (Gymnorhina tibicen dorsalis). We found that (i) magpies recombine four distinct acoustic segments to create a larger number of calls, and (ii) the resultant calls are further combined into larger call combinations. Our work demonstrates two levels in the combining of magpie vocal units. These results are incongruous with the notion that a capacity for multi-level combinatoriality is unique to human language, wherein the combining of meaningless sounds and meaningful words interactively occurs across different combinatorial levels. Our study thus provides novel insights into the combinatorial capacities of a non-human species, adding to the growing evidence of analogues of language-specific traits present in the animal kingdom.
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Affiliation(s)
- Sarah L. Walsh
- Centre for Evolutionary Biology, School of Biological Sciences, University of Western Australia, Crawley, WA 6009, Australia
| | - Sabrina Engesser
- Department of Biology, University of Copenhagen, 1165 København, Denmark
| | - Simon W. Townsend
- Department of Comparative Language Science, University of Zurich, Zurich 8006, Switzerland,Center for the Interdisciplinary Study of Language Evolution (ISLE), University of Zurich, Zurich 8006, Switzerland,Department of Psychology, University of Warwick, Coventry CV4 7AL, UK
| | - Amanda R. Ridley
- Centre for Evolutionary Biology, School of Biological Sciences, University of Western Australia, Crawley, WA 6009, Australia
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13
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Wilke C, Lahiff N, Badihi G, Donnellan E, Hobaiter C, Machanda Z, Mundry R, Pika S, Soldati A, Wrangham R, Zuberbűhler K, Slocombe K. Referential gestures are not ubiquitous in wild chimpanzees: alternative functions for exaggerated loud scratch gestures. Anim Behav 2022. [DOI: 10.1016/j.anbehav.2022.04.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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14
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Taylor D, Clay Z, Dahl CD, Zuberbühler K, Davila-Ross M, Dezecache G. Vocal functional flexibility: what it is and why it matters. Anim Behav 2022. [DOI: 10.1016/j.anbehav.2022.01.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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15
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Narbona Sabaté L, Mesbahi G, Dezecache G, Cäsar C, Zuberbühler K, Berthet M. Animal linguistics in the making: the Urgency Principle and titi monkeys’ alarm system. ETHOL ECOL EVOL 2022. [DOI: 10.1080/03949370.2021.2015452] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Lara Narbona Sabaté
- Institut Jean Nicod, Département d’Études Cognitives, ENS, EHESS, CNRS, PSL Research University, Paris 75005, France
| | | | | | | | - Klaus Zuberbühler
- School of Psychology & Neurosciences, University of St Andrews, Scotland, UK
- Institute of Biology, University of Neuchâtel, Rue Emile-Argand 11, Neuchâtel 2000, Switzerland
| | - Mélissa Berthet
- Institut Jean Nicod, Département d’Études Cognitives, ENS, EHESS, CNRS, PSL Research University, Paris 75005, France
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16
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Watzek J, Hauber ME, Jack KM, Murrell JR, Tecot SR, Brosnan SF. Modelling collective decision-making: Insights into collective anti-predator behaviors from an agent-based approach. Behav Processes 2021; 193:104530. [PMID: 34644659 DOI: 10.1016/j.beproc.2021.104530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 10/07/2021] [Accepted: 10/07/2021] [Indexed: 11/25/2022]
Abstract
Collective decision-making is a widespread phenomenon across organisms. Studying how animal societies make group decisions to the mutual benefit of group members, while avoiding exploitation by cheaters, can provide unique insights into the underlying cognitive mechanisms. As a step toward dissecting the proximate mechanisms that underpin collective decision-making across animals, we developed an agent-based model of antipredatory alarm signaling and mobbing during predator-prey encounters. Such collective behaviors occur in response to physical threats in many distantly related species with vastly different cognitive abilities, making it a broadly important model behavior. We systematically assessed under which quantitative contexts potential prey benefit from three basic strategies: predator detection, signaling about the predator (e.g., alarm calling), and retreating from vs. approaching the predator. Collective signaling increased survival rates over individual predator detection in several scenarios. Signaling sometimes led to fewer prey detecting the predator but this effect disappeared when prey animals that had seen the predator both signaled and approached it, as in mobbing. Critically, our results highlight that collective decision-making in response to a threat can emerge from simple rules without needing a central leader or needing to be under conscious control.
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Affiliation(s)
- Julia Watzek
- Department of Psychology, Language Research Center, Georgia State University, Atlanta, GA, USA
| | - Mark E Hauber
- Department of Evolution, Ecology, and Behavior, School of Integrative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
| | - Katharine M Jack
- Department of Anthropology, Tulane University, New Orleans, LA, USA
| | | | - Stacey R Tecot
- Laboratory for the Evolutionary Endocrinology of Primates, School of Anthropology, University of Arizona, Tucson, AZ, USA
| | - Sarah F Brosnan
- Department of Psychology, Language Research Center, Georgia State University, Atlanta, GA, USA; Department of Philosophy, Neuroscience Institute, Center for Behavioral Neuroscience, Georgia State University, Atlanta, GA, USA
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17
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Overlooked evidence for semantic compositionality and signal reduction in wild chimpanzees (Pan troglodytes). Anim Cogn 2021; 25:631-643. [PMID: 34822011 PMCID: PMC9107436 DOI: 10.1007/s10071-021-01584-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 11/16/2021] [Indexed: 11/11/2022]
Abstract
Recent discoveries of semantic compositionality in Japanese tits have enlivened the discussions on the presence of this phenomenon in wild animal communication. Data on semantic compositionality in wild apes are lacking, even though language experiments with captive apes have demonstrated they are capable of semantic compositionality. In this paper, I revisit the study by Boesch (Hum. Evol. 6:81–89, 1991) who investigated drumming sequences by an alpha male in a chimpanzee (Pan troglodytes) community in the Taï National Park, Côte d’Ivoire. A reanalysis of the data reveals that the alpha male produced semantically compositional combined messages of travel direction change and resting period initiation. Unlike the Japanese tits, the elements of the compositional expression were not simply juxtaposed but displayed structural reduction, while one of the two elements in the expression coded the meanings of both elements. These processes show relative resemblance to blending and fusion in human languages. Also unlike the tits, the elements of the compositional expression did not have a fixed order, although there was a fixed distribution of drumming events across the trees used for drumming. Because the elements of the expression appear to carry verb-like meanings, the compositional expression also resembles simple verb-verb constructions and short paratactic combinations of two clauses found across languages. In conclusion, the reanalysis suggests that semantic compositionality and phenomena resembling paratactic combinations of two clauses might have been present in the communication of the last common ancestor of chimpanzees and humans, not necessarily in the vocal modality.
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18
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Han S, Chen W, Elgar MA. An ambiguous function of an alarm pheromone in the collective displays of the Australian meat ant,
Iridomyrmex purpureus. Ethology 2021. [DOI: 10.1111/eth.13241] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Shaolin Han
- School of Biosciences University of Melbourne Melbourne Victoria Australia
| | - Wenman Chen
- School of Management Wuhan University of Technology Wuhan China
| | - Mark A. Elgar
- School of Biosciences University of Melbourne Melbourne Victoria Australia
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Pepperberg IM. Nonhuman and Nonhuman-Human Communication: Some Issues and Questions. Front Psychol 2021; 12:647841. [PMID: 34630194 PMCID: PMC8495326 DOI: 10.3389/fpsyg.2021.647841] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Accepted: 08/25/2021] [Indexed: 11/30/2022] Open
Abstract
Deciphering nonhuman communication – particularly nonhuman vocal communication – has been a longstanding human quest. We are, for example, fascinated by the songs of birds and whales, the grunts of apes, the barks of dogs, and the croaks of frogs; we wonder about their potential meaning and their relationship to human language. Do these utterances express little more than emotional states, or do they convey actual bits and bytes of concrete information? Humans’ numerous attempts to decipher nonhuman systems have, however, progressed slowly. We still wonder why only a small number of species are capable of vocal learning, a trait that, because it allows for innovation and adaptation, would seem to be a prerequisite for most language-like abilities. Humans have also attempted to teach nonhumans elements of our system, using both vocal and nonvocal systems. The rationale for such training is that the extent of success in instilling symbolic reference provides some evidence for, at the very least, the cognitive underpinnings of parallels between human and nonhuman communication systems. However, separating acquisition of reference from simple object-label association is not a simple matter, as reference begins with such associations, and the point at which true reference emerges is not always obvious. I begin by discussing these points and questions, predominantly from the viewpoint of someone studying avian abilities. I end by examining the question posed by Premack: do nonhumans that have achieved some level of symbolic reference then process information differently from those that have not? I suggest the answer is likely “yes,” giving examples from my research on Grey parrots (Psittacus erithacus).
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Affiliation(s)
- Irene M Pepperberg
- Department of Psychology, Harvard University, Cambridge, MA, United States
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20
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Evidence for vocal diversity during physical interference at the perch in sympatric Carollia species (Chiroptera: Phyllostomidae): a key to social organization and species coexistence? Zool J Linn Soc 2021. [DOI: 10.1093/zoolinnean/zlab040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
Vocal diversity might reflect the social organization and sustain the coexistence of cryptic species in sympatry. To test the extent to which vocal behaviour separates sympatric, cryptic species of a bat radiation, we compared vocalizations of genetically confirmed Carollia castanea, Carollia sowelli and Carollia perspicillata emitted by intraspecific dyads of identified individuals during corresponding physical interference interactions at the perch. Video analysis revealed a similar behaviour and interaction time across species. A sonagram-based visual classification of vocalization syllables of uninterrupted frequency–time contour discriminated 21 syllable classes. Class usage and distribution of the four shared classes differed across species. Carollia sowelli emitted the lowest number of classes in total and per interaction across species and displayed a limited number of syllable compositions in bouts. Discriminant analyses of syllables of a common, shared class provided evidence for species distinctiveness and individual-specific signatures. In general, sex did not account for data variability. The present vocalizations combine syllables reported from aggressive and submissive contexts in C. perspicillata and might express experienced ambivalence during interference at the perch. The diversity of vocal behaviour across congeners is discussed as arising from different ecological pressures during allopatric speciation and as an indicator of differences in species social organization.
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21
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Miglietta S, Bardino G, Sotto-Mayor A, Galli AS, Meulman E, Breuer T, Fuh T, Masi S. Absence of specific individuals and high food abundance elicit food calls in wild western gorillas. Behav Ecol Sociobiol 2021. [DOI: 10.1007/s00265-021-03027-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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22
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Affiliation(s)
- Sasha L. Winkler
- Department of Anthropology, University of California, Los Angeles, CA, USA
- UCLA Center for Behavior, Evolution, and Culture
| | - Gregory A. Bryant
- UCLA Center for Behavior, Evolution, and Culture
- Department of Communication, University of California, Los Angeles, CA, USA
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23
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Elgar MA, Riehl C. Editorial: Mechanisms of Communication and Recognition in Social Evolution. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2020.625831] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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24
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25
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Artiga M, Birch J, Martínez M. The meaning of biological signals. STUDIES IN HISTORY AND PHILOSOPHY OF BIOLOGICAL AND BIOMEDICAL SCIENCES 2020; 84:101348. [PMID: 32933851 DOI: 10.1016/j.shpsc.2020.101348] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We introduce the virtual special issue on content in signalling systems. The issue explores the uses and limits of ideas from evolutionary game theory and information theory for explaining the content of biological signals. We explain the basic idea of the Lewis-Skyrms sender-receiver framework, and we highlight three key themes of the issue: (i) the challenge of accounting for deception, misinformation and false content, (ii) the relevance of partial or total common interest to the evolution of meaningful signals, and (iii) how the sender-receiver framework relates to teleosemantics.
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Affiliation(s)
- Marc Artiga
- Department of Philosophy, Universitat de València, Av. Blasco Ibáñez 30, 46010, Valencia, Spain
| | - Jonathan Birch
- Department of Philosophy, Logic and Scientific Method, London School of Economics and Political Science, Houghton Street, London, WC2A 2AE, UK.
| | - Manolo Martínez
- Department of Philosophy, Universitat de Barcelona, Montalegre 6, 08001, Barcelona, Spain
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26
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Forget the audience: tadpoles release similar disturbance cues regardless of kinship or familiarity. Behav Ecol Sociobiol 2020. [DOI: 10.1007/s00265-020-02936-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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27
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Emotional expressions in human and non-human great apes. Neurosci Biobehav Rev 2020; 115:378-395. [DOI: 10.1016/j.neubiorev.2020.01.027] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2019] [Revised: 01/17/2020] [Accepted: 01/22/2020] [Indexed: 11/23/2022]
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28
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Ischer G, Zuberbühler K, Fedurek P. The relationship between food calling and agonistic behaviour in wild chimpanzees. Behav Processes 2020; 178:104182. [PMID: 32561234 DOI: 10.1016/j.beproc.2020.104182] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Revised: 05/27/2020] [Accepted: 06/15/2020] [Indexed: 01/03/2023]
Abstract
A number of social animals produce food-associated calls, which have been interpreted as informative and referential about the quality or quantity of food accessed by the caller. In chimpanzees, however, some behavioural patterns have remained unexplained by this model, suggesting that food-associated calls have a more generalized social function beyond attracting others to food, such as promoting tolerance between co-feeding individuals. In this study, we investigated how wild chimpanzees (Pan troglodytes schweinfurthii) of Budongo Forest, Uganda, use food associated-calls in situations when social tolerance is low, i.e., during agonistic interactions. We found a positive relationship between food calling and agonistic behaviours during a feeding event, independent of the number of males on the feeding patch. Moreover, food calling followed rather than preceded agonistic interactions, suggesting that aggression can trigger food call production. These results support the view that chimpanzee food-associated calls can act as social tools mediating competitive or aggressive interactions.
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Affiliation(s)
- Géraldine Ischer
- University of Neuchâtel, Department of Comparative Cognition, Neuchâtel, Switzerland
| | - Klaus Zuberbühler
- University of Neuchâtel, Department of Comparative Cognition, Neuchâtel, Switzerland; School of Psychology and Neuroscience, University of St Andrews, St Andrews, UK
| | - Pawel Fedurek
- Division of Psychology, Faculty of Natural Sciences, University of Stirling, Stirling, UK.
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29
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30
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Tegtman NT, Magrath RD. Discriminating between similar alarm calls of contrasting function. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190474. [PMID: 32420849 DOI: 10.1098/rstb.2019.0474] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In a pioneering study of signal design, Marler (Marler 1955 Nature 176, 6-8. (doi:10.1038/176006a0); Marler 1957 Behaviour 11, 13-37. (doi:10.1163/156853956X00066)) argued that the contrasting acoustic design of hawk (seet) and mobbing alarm calls of European passerines reflected their contrasting function. Hawk alarms were high-frequency tones, warning conspecifics to flee but making localization difficult for predators, while mobbing calls were broadband and harsh, allowing easy localization and approach. Contrasting signal features are also consistent with signal detection theory. Discriminating these calls quickly is critical for survival, because hawk alarms require immediate escape. These signals should therefore be selected to be easy to discriminate, reducing the trade-off between immediate fleeing to hawk alarms and unnecessary fleeing to mobbing alarms. Despite these expectations, hawk and mobbing alarm calls of superb fairy-wrens, Malurus cyaneus, are surprisingly similar, raising the question of discriminability without contextual cues. We synthesized these calls on computer, made intermediates and used playbacks to test whether calls can be discriminated acoustically, and if so by what features. We found that birds used multiple acoustic features when discriminating calls, allowing fast discrimination despite overlap in individual parameters. We speculate that the similarity of fairy-wren alarm calls could enhance detectability of both signals, while multiple subtle acoustic differences reduce a trade-off with discriminability. This article is part of the theme issue 'Signal detection theory in recognition systems: from evolving models to experimental tests'.
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Affiliation(s)
- Natalie T Tegtman
- Division of Ecology and Evolution, Research School of Biology, Australian National University, Canberra 2601, Australia
| | - Robert D Magrath
- Division of Ecology and Evolution, Research School of Biology, Australian National University, Canberra 2601, Australia
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31
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Smith K. How Culture and Biology Interact to Shape Language and the Language Faculty. Top Cogn Sci 2020; 12:690-712. [PMID: 30182526 PMCID: PMC7379493 DOI: 10.1111/tops.12377] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2018] [Revised: 08/08/2018] [Accepted: 08/08/2018] [Indexed: 11/28/2022]
Abstract
Recent work suggests that linguistic structure develops through cultural evolution, as a consequence of the repeated cycle of learning and use by which languages persist. This work has important implications for our understanding of the evolution of the cognitive basis for language; in particular, human language and the cognitive capacities underpinning it are likely to have been shaped by co-evolutionary processes, where the cultural evolution of linguistic systems is shaped by and in turn shapes the biological evolution of the capacities underpinning language learning. I review several models of this co-evolutionary process, which suggest that the precise relationship between evolved biases in individuals and the structure of linguistic systems depends on the extent to which cultural evolution masks or unmasks individual-level cognitive biases from selection. I finish by discussing how these co-evolutionary models might be extended to cases where the biases involved in learning are themselves shaped by experience, as is the case for language.
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Affiliation(s)
- Kenny Smith
- Centre for Language EvolutionUniversity of Edinburgh
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32
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Zhang L, Liu J, Gao Z, Zhang L, Wan D, Liang W, Møller AP. Comparative analysis of hissing calls in five tit species. Behav Processes 2020; 171:104029. [DOI: 10.1016/j.beproc.2019.104029] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2019] [Revised: 12/26/2019] [Accepted: 12/26/2019] [Indexed: 11/29/2022]
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33
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34
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Fischer J, Hammerschmidt K. Towards a new taxonomy of primate vocal production learning. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190045. [PMID: 31735147 PMCID: PMC6895554 DOI: 10.1098/rstb.2019.0045] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/18/2019] [Indexed: 11/12/2022] Open
Abstract
The extent to which vocal learning can be found in nonhuman primates is key to reconstructing the evolution of speech. Regarding the adjustment of vocal output in relation to auditory experience (vocal production learning in the narrow sense), effects on the ontogenetic trajectory of vocal development as well as adjustment to group-specific call features have been found. Yet, a comparison of the vocalizations of different primate genera revealed striking similarities in the structure of calls and repertoires in different species of the same genus, indicating that the structure of nonhuman primate vocalizations is highly conserved. Thus, modifications in relation to experience only appear to be possible within relatively tight species-specific constraints. By contrast, comprehension learning may be extremely rapid and open-ended. In conjunction, these findings corroborate the idea of an ancestral independence of vocal production and auditory comprehension learning. To overcome the futile debate about whether or not vocal production learning can be found in nonhuman primates, we suggest putting the focus on the different mechanisms that may mediate the adjustment of vocal output in response to experience; these mechanisms may include auditory facilitation and learning from success. This article is part of the theme issue 'What can animal communication teach us about human language?'
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Affiliation(s)
- Julia Fischer
- Cognitive Ethology Laboratory, German Primate Center, Kellnerweg 4, Göttingen, Niedersachsen 37077, Germany
- Department of Primate Cognition, Georg August University Göttingen, Göttingen, Niedersachsen, Germany
- Leibniz Science Campus Primate Cognition, Göttingen, Germany
| | - Kurt Hammerschmidt
- Cognitive Ethology Laboratory, German Primate Center, Kellnerweg 4, Göttingen, Niedersachsen 37077, Germany
- Leibniz Science Campus Primate Cognition, Göttingen, Germany
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35
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Zhang K, Liu T, Liu M, Li A, Xiao Y, Metzner W, Liu Y. Comparing context-dependent call sequences employing machine learning methods: an indication of syntactic structure of greater horseshoe bats. ACTA ACUST UNITED AC 2019; 222:jeb.214072. [PMID: 31753908 DOI: 10.1242/jeb.214072] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 11/14/2019] [Indexed: 12/20/2022]
Abstract
For analysis of vocal syntax, accurate classification of call sequence structures in different behavioural contexts is essential. However, an effective, intelligent program for classifying call sequences from numerous recorded sound files is still lacking. Here, we employed three machine learning algorithms (logistic regression, support vector machine and decision trees) to classify call sequences of social vocalizations of greater horseshoe bats (Rhinolophus ferrumequinum) in aggressive and distress contexts. The three machine learning algorithms obtained highly accurate classification rates (logistic regression 98%, support vector machine 97% and decision trees 96%). The algorithms also extracted three of the most important features for the classification: the transition between two adjacent syllables, the probability of occurrences of syllables in each position of a sequence, and the characteristics of a sequence. The results of statistical analysis also supported the classification of the algorithms. The study provides the first efficient method for data mining of call sequences and the possibility of linguistic parameters in animal communication. It suggests the presence of song-like syntax in the social vocalizations emitted within a non-breeding context in a bat species.
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Affiliation(s)
- Kangkang Zhang
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, No. 2555, Street Jingyue, Northeast Normal University, Changchun 130117, China
| | - Tong Liu
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, No. 2555, Street Jingyue, Northeast Normal University, Changchun 130117, China
| | - Muxun Liu
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, No. 2555, Street Jingyue, Northeast Normal University, Changchun 130117, China
| | - Aoqiang Li
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, No. 2555, Street Jingyue, Northeast Normal University, Changchun 130117, China
| | - Yanhong Xiao
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, No. 2555, Street Jingyue, Northeast Normal University, Changchun 130117, China
| | - Walter Metzner
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Ying Liu
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, No. 2555, Street Jingyue, Northeast Normal University, Changchun 130117, China
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36
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Méndez C, Sandoval L. Frequency and synchronisation features of a highly overlapped duet changes according to the context. BIOACOUSTICS 2019. [DOI: 10.1080/09524622.2019.1682672] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Carolina Méndez
- Escuela de Biología, Universidad de Costa Rica, San Pedro, Costa Rica
| | - Luis Sandoval
- Escuela de Biología, Universidad de Costa Rica, San Pedro, Costa Rica
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37
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Kalb N, Anger F, Randler C. Great tits encode contextual information in their food and mobbing calls. ROYAL SOCIETY OPEN SCIENCE 2019; 6:191210. [PMID: 31827857 PMCID: PMC6894574 DOI: 10.1098/rsos.191210] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Accepted: 10/01/2019] [Indexed: 06/10/2023]
Abstract
The calling behaviour of Paridae species (i.e. titmice, tits and chickadees) in a predator-related context is well-studied. Parid species are known to alter call types, note composition or call duration according to predation risk. However, how these species encode information about a non-threatening context, such as food sources, has been subject to only few studies. Studies in Carolina chickadees (Poecile carolinensis) have shown that this species alters the ratio of C and D notes to encode information about the presence of food and/or the flight behaviour of the signaller. This suggests that parids also use graded signals to encode information about non-predatory contexts. No study to date has directly compared the calls of a feeding context with those of a predation (i.e. mobbing) context. Hence, the aim of this study was to compare the calling behaviour of these two situations in great tits (Parus major). Calls uttered at a feeder were recorded, analysed and compared with calls uttered in front of taxidermy mounts of sparrowhawks (Accipiter nisus). In the food context, great tits reduced the number of D notes and increased the number of B, C and E notes compared with the mobbing context. Furthermore, tits produced calls with longer D notes and shorter intervals between D notes than in the mobbing context. This indicates that great tits use two mechanisms of graded signals (i.e. note type and acoustic structure of D calls) to inform conspecifics about the nature of a situation.
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Affiliation(s)
- Nadine Kalb
- Department of Biology, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 24, 72076 Tübingen, Germany
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Miyagawa S, Clarke E. Systems Underlying Human and Old World Monkey Communication: One, Two, or Infinite. Front Psychol 2019; 10:1911. [PMID: 31551849 PMCID: PMC6734162 DOI: 10.3389/fpsyg.2019.01911] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 08/05/2019] [Indexed: 11/13/2022] Open
Abstract
Using artificially synthesized stimuli, previous research has shown that cotton-top tamarin monkeys easily learn simple AB grammar sequences, but not the more complex AnBn sequences that require hierarchical structure. Humans have no trouble learning AnBn combinations. A more recent study, using similar artificially created stimuli, showed that there is a neuroanatomical difference in the brain between these two kinds of arrays. While the simpler AB sequences recruit the frontal operculum, the AnBn array recruits the phylogenetically newer Broca's area. We propose that on close inspection, reported vocal repertoires of Old World Monkeys show that these nonhuman primates are capable of calls that have two items in them, but never more than two. These are simple AB sequences, as predicted by previous research. In addition, we suggest the two-item call cannot be the result of a combinatorial operation that we see in human language, where the recursive operation of Merge allows for a potentially infinite array of structures. In our view, the two-item calls of nonhuman primates result from a dual-compartment frame into which each of the calls can fit without having to be combined by an operation such as Merge.
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Affiliation(s)
- Shigeru Miyagawa
- Linguistics and Philosophy, Massachusetts Institute of Technology, Cambridge, MA, United States
- Office of Open Learning, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Esther Clarke
- Linguistics and Philosophy, Massachusetts Institute of Technology, Cambridge, MA, United States
- Behavioral Ecology and Evolution Research (BEER) Group, Durham University, Durham, United Kingdom
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Abstract
Language is a cornerstone of human culture, yet the evolution of this cognitive-demanding ability is shrouded in mystery. Studying how different species demonstrate this trait can provide clues for its evolutionary route. Indeed, recent decades saw ample scientific attempts to compare human speech, the prominent behavioral manifestation of language, with other animals' vocalizations. Diligent studies have found only elementary parallels to speech in other animals, fortifying the belief that language is uniquely human. But have we really tested this uniqueness claim? Surprisingly, a true impartial comparison between human speech and other animals' vocalizations has hardly ever been conducted. Here, I illustrate how treating humans as an equal species in vocal-communication research is expected to provide us with no evidence for human superiority in this realm. Thus, novel balanced and unbiased comparative studies are vital for identifying any unique component of human speech and language.
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Affiliation(s)
- Yosef Prat
- School of Zoology, Faculty of Life Sciences, Tel-Aviv University
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Teixeira D, Maron M, Rensburg BJ. Bioacoustic monitoring of animal vocal behavior for conservation. CONSERVATION SCIENCE AND PRACTICE 2019. [DOI: 10.1111/csp2.72] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Affiliation(s)
- Daniella Teixeira
- School of Biological SciencesThe University of Queensland Brisbane Queensland Australia
| | - Martine Maron
- School of Earth and Environmental SciencesThe University of Queensland Brisbane Queensland Australia
| | - Berndt J. Rensburg
- School of Biological SciencesThe University of Queensland Brisbane Queensland Australia
- Department of Zoology, DST‐NRF Centre for Invasion BiologyUniversity of Johannesburg Johannesburg South Africa
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Wegdell F, Hammerschmidt K, Fischer J. Conserved alarm calls but rapid auditory learning in monkey responses to novel flying objects. Nat Ecol Evol 2019; 3:1039-1042. [PMID: 31133723 DOI: 10.1038/s41559-019-0903-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 04/16/2019] [Indexed: 11/09/2022]
Abstract
To evaluate the flexibility in vocal production and comprehension in a non-human primate, we presented a drone to West African green monkeys, Chlorocebus sabaeus. Calls given in response to the drone were clearly distinct from those given to other predators, but highly similar to the aerial alarm calls of the East African vervet monkey, Chlorocebus pygerythrus, suggesting that call structure is conserved. To probe how rapidly the animals attached meaning to the sound of the drone, we played back the drone sound after one to three exposures. Subjects immediately scanned the sky and ran for cover. In contrast to vocal production, comprehension learning was rapid and open-ended.
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Affiliation(s)
- Franziska Wegdell
- Cognitive Ethology Laboratory, German Primate Center, Göttingen, Germany
| | - Kurt Hammerschmidt
- Cognitive Ethology Laboratory, German Primate Center, Göttingen, Germany
| | - Julia Fischer
- Cognitive Ethology Laboratory, German Primate Center, Göttingen, Germany. .,Department for Primate Cognition, Georg-August-University Göttingen, Göttingen, Germany. .,Leibniz ScienceCampus Primate Cognition, Göttingen, Germany.
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Bairos-Novak KR, Ferrari MCO, Chivers DP. A novel alarm signal in aquatic prey: Familiar minnows coordinate group defences against predators through chemical disturbance cues. J Anim Ecol 2019; 88:1281-1290. [PMID: 30997683 DOI: 10.1111/1365-2656.12986] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 02/15/2019] [Indexed: 12/01/2022]
Abstract
Animal signalling systems outside the realm of human perception remain largely understudied. These systems consist of four main components: a signalling context, a voluntary signal, receiver responses and resulting fitness benefits to both the signaller and receiver(s). It is often most difficult to determine incidental cues from voluntary signals. One example is chemical disturbance cues released by aquatic prey during predator encounters that may serve to alert conspecifics of nearby risk and initiate tighter shoaling. We aimed to test whether disturbance cues are released incidentally (i.e. as a cue) or are produced voluntarily depending on a specific signalling context such as the audience surrounding the individual, and thus constitute a signal. We hypothesized that if receivers use disturbance cues to communicate risk among themselves, they would produce more (or more potent) disturbance cues when present in a group of conspecifics rather than when they are isolated (presence/absence of an audience) and use disturbance cues more when present alongside familiar rather than unfamiliar conspecifics (audience composition effect). We placed fathead minnows (Pimephales promelas) in groups with familiar fish, unfamiliar fish or as isolated individuals with no audience present, and then simulated a predator chase to evoke disturbance cues. We used bioassays with independent receivers to assess whether the disturbance cues produced differed depending on the signallers' audience. We found evidence of voluntary signalling, as minnows responded to disturbance cues from groups of fish with tighter shoaling while disturbance cues from isolated minnows did not evoke a significant shoaling response (presence/absence audience effect). Receivers also increased shoaling, freezing and dashing more in response to disturbance cues from familiar groups compared to disturbance cues from unfamiliar groups or isolated minnows (audience composition effect). Together, these findings support our hypothesis that disturbance cues are used as an antipredator signal to initiate coordinated group defences among familiar conspecifics involving shoaling, freezing and dashing. This study represents the strongest evidence to date that chemicals released by aquatic prey upon disturbance by predators serve as voluntary signals rather than simply cues that prey have evolved to detect when assessing their risk of predation.
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Affiliation(s)
- Kevin R Bairos-Novak
- Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.,Marine Biology and Aquaculture & ARC Centre of Excellence for Coral Reef Studies, James Cook University, Qld, Australia
| | - Maud C O Ferrari
- Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Douglas P Chivers
- Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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Martin MJ, Elwen SH, Kassanjee R, Gridley T. To buzz or burst-pulse? The functional role of Heaviside's dolphin, Cephalorhynchus heavisidii, rapidly pulsed signals. Anim Behav 2019. [DOI: 10.1016/j.anbehav.2019.01.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Loughry W, Oeser M, Anderson CD, Hoogland JL. The importance of individual variation in the alarm calls of Gunnison's prairie dogs. Anim Behav 2019. [DOI: 10.1016/j.anbehav.2019.01.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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Engesser S, Townsend SW. Combinatoriality in the vocal systems of nonhuman animals. WILEY INTERDISCIPLINARY REVIEWS. COGNITIVE SCIENCE 2019; 10:e1493. [PMID: 30724476 DOI: 10.1002/wcs.1493] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 01/03/2019] [Accepted: 01/09/2019] [Indexed: 12/27/2022]
Abstract
A key challenge in the field of human language evolution is the identification of the selective conditions that gave rise to language's generative nature. Comparative data on nonhuman animals provides a powerful tool to investigate similarities and differences among nonhuman and human communication systems and to reveal convergent evolutionary mechanisms. In this article, we provide an overview of the current evidence for combinatorial structures found in the vocal system of diverse species. We show that considerable structural diversity exits across and within species in the forms of combinatorial structures used. Based on this we suggest that a fine-grained classification and differentiation of combinatoriality is a useful approach permitting systematic comparisons across animals. Specifically, this will help to identify factors that might promote the emergence of combinatoriality and, crucially, whether differences in combinatorial mechanisms might be driven by variations in social and ecological conditions or cognitive capacities. This article is categorized under: Cognitive Biology > Evolutionary Roots of Cognition Linguistics > Evolution of Language.
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Affiliation(s)
- Sabrina Engesser
- Department of Comparative Linguistics, University of Zurich, Zurich, Switzerland
| | - Simon W Townsend
- Department of Comparative Linguistics, University of Zurich, Zurich, Switzerland.,Department of Psychology, University of Warwick, Coventry, UK
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Lameira AR, Call J. Time-space-displaced responses in the orangutan vocal system. SCIENCE ADVANCES 2018; 4:eaau3401. [PMID: 30443595 PMCID: PMC6235548 DOI: 10.1126/sciadv.aau3401] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 10/18/2018] [Indexed: 06/09/2023]
Abstract
One of the defining features of language is displaced reference-the capacity to transmit information about something that is not present or about a past or future event. It is very rare in nature and has not been shown in any nonhuman primate, confounding, as such, any understanding of its precursors and evolution in the human lineage. Here, we describe a vocal phenomenon in a wild great ape with unparalleled affinities with displaced reference. When exposed to predator models, Sumatran orangutan mothers temporarily suppressed alarm calls up to 20 min until the model was out of sight. Subjects delayed their vocal responses in function of perceived danger for themselves, but four major predictions for stress-based mechanisms were not met. Conversely, vocal delay was also a function of perceived danger for another-an infant-suggesting high-order cognition. Our findings suggest that displaced reference in language is likely to have originally piggybacked on akin behaviors in an ancestral hominid.
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Schamberg I, Wittig RM, Crockford C. Call type signals caller goal: a new take on ultimate and proximate influences in vocal production. Biol Rev Camb Philos Soc 2018; 93:2071-2082. [PMID: 29896860 DOI: 10.1111/brv.12437] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 05/22/2018] [Accepted: 05/23/2018] [Indexed: 11/27/2022]
Abstract
After 40 years of debate it remains unclear whether signallers produce vocalizations in order to provide receivers with information about call context or external stimuli. This has led some researchers to propose that call production is arousal- or affect-based. Although arousal influences certain acoustic parameters within a call type, we argue that it cannot explain why individuals across vertebrates produce different call types. Given emerging evidence that calls are goal-based, we argue that call type is a signal of a caller's goal to elicit a change in receiver behaviour. Using chimpanzees (Pan troglodytes) and vervet monkeys (Cercopithecus aethiops) as case studies, we demonstrate the two benefits of viewing call production as signalling both caller goal (which determines call type) and caller arousal (which affects within-call-type variation). Such a framework can explain first, why a single class of calls is apparently given in multiple contexts, and, second, why some species have larger call repertoires than others. Previous studies have noted links between sociality and repertoire size, but have not specified exactly why animals living in societies that are more complex might require a greater number of differentiated signals. The caller-goal framework potentially clarifies how social complexity might favour call diversification. As social complexity increases, callers may need to elicit a larger number of distinct behaviours from a wider range of distinct audiences.
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Affiliation(s)
- Isaac Schamberg
- Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Roman M Wittig
- Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.,Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan 01, Côte D'ivoire
| | - Catherine Crockford
- Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.,Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan 01, Côte D'ivoire
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