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Számadó S, Zachar I, Czégel D, Penn DJ. Honesty in signalling games is maintained by trade-offs rather than costs. BMC Biol 2023; 21:4. [PMID: 36617556 PMCID: PMC9827650 DOI: 10.1186/s12915-022-01496-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Accepted: 12/06/2022] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Signal reliability poses a central problem for explaining the evolution of communication. According to Zahavi's Handicap Principle, signals are honest only if they are costly at the evolutionary equilibrium; otherwise, deception becomes common and communication breaks down. Theoretical signalling games have proved to be useful for understanding the logic of signalling interactions. Theoretical evaluations of the Handicap Principle are difficult, however, because finding the equilibrium cost function in such signalling games is notoriously complicated. Here, we provide a general solution to this problem and show how cost functions can be calculated for any arbitrary, pairwise asymmetric signalling game at the evolutionary equilibrium. RESULTS Our model clarifies the relationship between signalling costs at equilibrium and the conditions for reliable signalling. It shows that these two terms are independent in both additive and multiplicative models, and that the cost of signalling at honest equilibrium has no effect on the stability of communication. Moreover, it demonstrates that honest signals at the equilibrium can have any cost value, even negative, being beneficial for the signaller independently of the receiver's response at equilibrium and without requiring further constraints. Our results are general and we show how they apply to seminal signalling models, including Grafen's model of sexual selection and Godfray's model of parent-offspring communication. CONCLUSIONS Our results refute the claim that signals must be costly at the evolutionary equilibrium to be reliable, as predicted by the Handicap Principle and so-called 'costly signalling' theory. Thus, our results raise serious concerns about the handicap paradigm. We argue that the evolution of reliable signalling is better understood within a Darwinian life-history framework, and that the conditions for honest signalling are more clearly stated and understood by evaluating their trade-offs rather than their costs per se. We discuss potential shortcomings of equilibrium models and we provide testable predictions to help advance the field and establish a better explanation for honest signals. Last but not least, our results highlight why signals are expected to be efficient rather than wasteful.
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Affiliation(s)
- Szabolcs Számadó
- Department of Sociology and Communication, Budapest University of Technology and Economics, Egry J. u. 1, Budapest, H-1111, Hungary.
- CSS-RECENS "Lendület" Research Group, MTA Centre for Social Science, Tóth Kálmán u. 4, Budapest, H-1097, Hungary.
| | - István Zachar
- Institute of Evolution, MTA Centre for Ecological Research, Konkoly-Thege Miklós út 29-33, Budapest, H-1121, Hungary
- Department of Plant Systematics, Ecology and Theoretical Biology, Biology Institute, ELTE University, Pázmány P. sétány 1/C, Budapest, 1117, Hungary
| | - Dániel Czégel
- Institute of Evolution, MTA Centre for Ecological Research, Konkoly-Thege Miklós út 29-33, Budapest, H-1121, Hungary
- Department of Plant Systematics, Ecology and Theoretical Biology, Biology Institute, ELTE University, Pázmány P. sétány 1/C, Budapest, 1117, Hungary
- Doctoral School of Biology, Institute of Biology, Eötvös Loránd University, Pázmány Péter sétány 1/C, Budapest, H-1117, Hungary
- BEYOND Center for Fundamental Concepts in Science, Arizona State University, AZ 85287-0506, Tempe, AZ, USA
| | - Dustin J Penn
- Department of Interdisciplinary Life Sciences, Konrad Lorenz Institute of Ethology, University of Veterinary Medicine, Vienna, Savoynestrasse 1a, 1160, Vienna, Austria
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Számadó S, Samu F, Takács K. Condition-dependent trade-offs maintain honest signalling. ROYAL SOCIETY OPEN SCIENCE 2022. [PMID: 36249330 DOI: 10.6084/m9.figshare.c.6214769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
How and why animals and humans signal reliably is a key issue in biology and social sciences that needs to be understood to explain the evolution of communication. In situations in which the receiver needs to differentiate between low- and high-quality signallers, once a ruling paradigm, the Handicap Principle has claimed that honest signals have to be costly to produce. Subsequent game theoretical models, however, highlighted that honest signals are not necessarily costly. Honesty is maintained by the potential cost of cheating: by the difference in the marginal benefit to marginal cost for low versus high-quality signallers; i.e. by differential trade-offs. Owing to the difficulties of manipulating signal costs and benefits, there is lack of empirical tests of these predictions. We present the results of a laboratory decision-making experiment with human participants to test the role of equilibrium signal cost and signalling trade-offs for the development of honest communication. We found that the trade-off manipulation had a much higher influence on the reliability of communication than the manipulation of the equilibrium cost of signal. Contrary to the predictions of the Handicap Principle, negative production cost promoted honesty at a very high level in the differential trade-off condition.
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Affiliation(s)
- Szabolcs Számadó
- Department of Sociology and Communication, Budapest University of Technology and Economics, Egry J. u. 1. H-1111, Budapest, Hungary
- CSS-RECENS, CSS-RECENS, Centre for Social Sciences, Tóth Kálmán u. 4, H-1097, Budapest, Hungary
| | - Flóra Samu
- CSS-RECENS, CSS-RECENS, Centre for Social Sciences, Tóth Kálmán u. 4, H-1097, Budapest, Hungary
- Agglomeration and Social Networks Lendület Research Group, Centre for Economic-and Regional Studies, CSS-RECENS, Centre for Social Sciences, Tóth Kálmán u. 4, H-1097, Budapest, Hungary
- Corvinus University of Budapest, Doctoral School of Sociology, Fővám tér. 8, H-1093, Budapest, Hungary
| | - Károly Takács
- The Institute for Analytical Sociology, Linköping University, S-601 74 Norrköping, Sweden
- CSS-RECENS, CSS-RECENS, Centre for Social Sciences, Tóth Kálmán u. 4, H-1097, Budapest, Hungary
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Számadó S, Samu F, Takács K. Condition-dependent trade-offs maintain honest signalling. ROYAL SOCIETY OPEN SCIENCE 2022; 9:220335. [PMID: 36249330 PMCID: PMC9532995 DOI: 10.1098/rsos.220335] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Accepted: 09/07/2022] [Indexed: 06/16/2023]
Abstract
How and why animals and humans signal reliably is a key issue in biology and social sciences that needs to be understood to explain the evolution of communication. In situations in which the receiver needs to differentiate between low- and high-quality signallers, once a ruling paradigm, the Handicap Principle has claimed that honest signals have to be costly to produce. Subsequent game theoretical models, however, highlighted that honest signals are not necessarily costly. Honesty is maintained by the potential cost of cheating: by the difference in the marginal benefit to marginal cost for low versus high-quality signallers; i.e. by differential trade-offs. Owing to the difficulties of manipulating signal costs and benefits, there is lack of empirical tests of these predictions. We present the results of a laboratory decision-making experiment with human participants to test the role of equilibrium signal cost and signalling trade-offs for the development of honest communication. We found that the trade-off manipulation had a much higher influence on the reliability of communication than the manipulation of the equilibrium cost of signal. Contrary to the predictions of the Handicap Principle, negative production cost promoted honesty at a very high level in the differential trade-off condition.
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Affiliation(s)
- Szabolcs Számadó
- Department of Sociology and Communication, Budapest University of Technology and Economics, Egry J. u. 1. H-1111, Budapest, Hungary
- CSS-RECENS, CSS-RECENS, Centre for Social Sciences, Tóth Kálmán u. 4, H-1097, Budapest, Hungary
| | - Flóra Samu
- CSS-RECENS, CSS-RECENS, Centre for Social Sciences, Tóth Kálmán u. 4, H-1097, Budapest, Hungary
- Agglomeration and Social Networks Lendület Research Group, Centre for Economic-and Regional Studies, CSS-RECENS, Centre for Social Sciences, Tóth Kálmán u. 4, H-1097, Budapest, Hungary
- Corvinus University of Budapest, Doctoral School of Sociology, Fővám tér. 8, H-1093, Budapest, Hungary
| | - Károly Takács
- CSS-RECENS, CSS-RECENS, Centre for Social Sciences, Tóth Kálmán u. 4, H-1097, Budapest, Hungary
- The Institute for Analytical Sociology, Linköping University, S-601 74 Norrköping, Sweden
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Guimarães M, Correa DT, Gaiarsa MP, Kéry M. Full-annual demography and seasonal cycles in a resident vertebrate. PeerJ 2020; 8:e8658. [PMID: 32140310 PMCID: PMC7047866 DOI: 10.7717/peerj.8658] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Accepted: 01/29/2020] [Indexed: 12/25/2022] Open
Abstract
Wildlife demography is typically studied at a single point in time within a year when species, often during the reproductive season, are more active and therefore easier to find. However, this provides only a low-resolution glimpse into demographic temporal patterns over time and may hamper a more complete understanding of the population dynamics of a species over the full annual cycle. The full annual cycle is often influenced by environmental seasonality, which induces a cyclic behavior in many species. However, cycles have rarely been explicitly included in models for demographic parameters, and most information on full annual cycle demography is restricted to migratory species. Here we used a high-resolution capture-recapture study of a resident tropical lizard to assess the full intra-annual demography and within-year periodicity in survival, temporary emigration and recapture probabilities. We found important variation over the annual cycle and up to 92% of the total monthly variation explained by cycles. Fine-scale demographic studies and assessments on the importance of cycles within parameters may be a powerful way to achieve a better understanding of population persistence over time.
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Affiliation(s)
- Murilo Guimarães
- Departamento de Zoologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brasil
| | - Decio T Correa
- Department of Integrative Biology, University of Texas, Austin, TX, United States of America
| | | | - Marc Kéry
- Swiss Ornithological Institute, Sempach, Switzerland
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Penn DJ, Számadó S. The Handicap Principle: how an erroneous hypothesis became a scientific principle. Biol Rev Camb Philos Soc 2020; 95:267-290. [PMID: 31642592 PMCID: PMC7004190 DOI: 10.1111/brv.12563] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 09/24/2019] [Accepted: 09/26/2019] [Indexed: 01/24/2023]
Abstract
The most widely cited explanation for the evolution of reliable signals is Zahavi's so-called Handicap Principle, which proposes that signals are honest because they are costly to produce. Here we provide a critical review of the Handicap Principle and its theoretical development. We explain why this idea is erroneous, and how it nevertheless became widely accepted as the leading explanation for honest signalling. In 1975, Zahavi proposed that elaborate secondary sexual characters impose 'handicaps' on male survival, not due to inadvertent signalling trade-offs, but as a mechanism that functions to demonstrate males' genetic quality to potential mates. His handicap hypothesis received many criticisms, and in response, Zahavi clarified his hypothesis and explained that it assumes that signals are wasteful as well as costly, and that they evolve because wastefulness enforces honesty. He proposed that signals evolve under 'signal selection', a non-Darwinian type of selection that favours waste rather than efficiency. He maintained that the handicap hypothesis provides a general principle to explain the evolution of all types of signalling systems, i.e. the Handicap Principle. In 1977, Zahavi proposed a second hypothesis for honest signalling, which received many different labels and interpretations, although it was assumed to be another example of handicap signalling. In 1990, Grafen published models that he claimed vindicated Zahavi's Handicap Principle. His conclusions were widely accepted and the Handicap Principle subsequently became the dominant paradigm for explaining the evolution of honest signalling in the biological and social sciences. Researchers have subsequently focused on testing predications of the Handicap Principle, such as measuring the absolute costs of honest signals (and using energetic and other proximate costs as proxies for fitness), but very few have attempted to test Grafen's models. We show that Grafen's models do not support the handicap hypothesis, although they do support Zahavi's second hypothesis, which proposes that males adjust their investment into the expression of their sexual signals according to their condition and ability to bear the costs (and risks to their survival). Rather than being wasteful over-investments, honest signals evolve in this scenario because selection favours efficient and optimal investment into signal expression and minimizes signalling costs. This idea is very different from the handicap hypothesis, but it has been widely misinterpreted and equated to the Handicap Principle. Theoretical studies have since shown that signalling costs paid at the equilibrium are neither sufficient nor necessary to maintain signal honesty, and that honesty can evolve through differential benefits, as well as differential costs. There have been increasing criticisms of the Handicap Principle, but they have focused on the limitations of Grafen's model and overlooked the fact that it is not a handicap model. This model is better understood within a Darwinian framework of adaptive signalling trade-offs, without the added burden and confusing logic of the Handicap Principle. There is no theoretical or empirical support for the Handicap Principle and the time is long overdue to usher this idea into an 'honorable retirement'.
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Affiliation(s)
- Dustin J. Penn
- Konrad Lorenz Institute of EthologyUniversity of Veterinary MedicineViennaAustria
| | - Szabolcs Számadó
- Department of Sociology and CommunicationBudapest University of Technology and EconomicsBudapestHungary,CSS‐ RECENSMTA Centre for Social SciencesBudapestHungary,Evolutionary Systems Research GroupMTA Centre for Ecological ResearchTihanyHungary
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Oxidative stress resistance in a short-lived Neotropical annual killifish. Biogerontology 2019; 21:217-229. [DOI: 10.1007/s10522-019-09855-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Accepted: 12/11/2019] [Indexed: 12/11/2022]
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Reichard M, Lanés LEK, Polačik M, Blažek R, Vrtílek M, Godoy RS, Maltchik L. Avian predation mediates size-specific survival in a Neotropical annual fish: a field experiment. Biol J Linn Soc Lond 2018. [DOI: 10.1093/biolinnean/bly022] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Martin Reichard
- The Czech Academy of Science, Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, Květná, Brno, Czech Republic
| | - Luis E K Lanés
- Laboratório de Ecologia e Conservação de Ecossistemas Aquáticos, Universidade do Vale do Rio dos Sinos, Bairro Cristo Rei, São Leopoldo, Rio Grande do Sul, Brazil
- Instituto Pró-Pampa – IPPAMPA, Bairro Centro, Pelotas, Rio Grande do Sul, Brazil
| | - Matej Polačik
- The Czech Academy of Science, Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, Květná, Brno, Czech Republic
| | - Radim Blažek
- The Czech Academy of Science, Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, Květná, Brno, Czech Republic
| | - Milan Vrtílek
- The Czech Academy of Science, Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, Květná, Brno, Czech Republic
| | - Robson S Godoy
- Laboratório de Ecologia e Conservação de Ecossistemas Aquáticos, Universidade do Vale do Rio dos Sinos, Bairro Cristo Rei, São Leopoldo, Rio Grande do Sul, Brazil
| | - Leonardo Maltchik
- Laboratório de Ecologia e Conservação de Ecossistemas Aquáticos, Universidade do Vale do Rio dos Sinos, Bairro Cristo Rei, São Leopoldo, Rio Grande do Sul, Brazil
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