One of the core features of human speech is that words cause listeners to retrieve corresponding visual mental images. However, whether vocalizations similarly evoke mental images in animal ...communication systems is surprisingly unknown. Japanese tits (Parus minor) produce specific alarm calls when and only when encountering a predatory snake. Here, I show that simply hearing these calls causes tits to become more visually perceptive to objects resembling snakes. During playback of snake-specific alarm calls, tits approach a wooden stick being moved in a snake-like fashion. However, tits do not respond to the same stick when hearing other call types or if the stick’s movement is dissimilar to that of a snake. Thus, before detecting a real snake, tits retrieve its visual image from snake-specific alarm calls and use this to search out snakes. This study provides evidence for a call-evoked visual search image in a nonhuman animal, offering a paradigm to explore the cognitive basis for animal vocal communication in the wild.
Many animals use variation in their alarm calls to warn conspecifics about different predatory threats. Information about predators can be encoded by producing discrete types of alarm calls and/or ...through graded variation in a single call type (i.e. calling rate or note repetitions). Another way to encode predator information is to combine different types of calls or notes into longer structured sequences. However, few studies have examined how individuals use discrete, graded and combinatorial variation in alarm calls to denote specific risks. I investigated the acoustic structure and information content of alarm calls in Japanese great tits, Parus major minor, by exposing their nests to three predator species (snakes, crows and martens) and a nonpredator species (doves). Great tits produced acoustically discrete alarm calls for the different nest predators: ‘jar’ calls for snakes and ‘chicka’ calls for crows and martens. The adults further discriminated between crows and martens by altering the calling rate and note number of the ‘chicka’ calls. A total of 175 types of note combinations were observed in the ‘chicka’ calls, and the tits used these combination types differently for the crows and martens. These results provide the first demonstration that birds can encode information about predator type by using production specificity, graded features and note combinations of discrete alarm calls. Previous studies have shown that parent and nestling Japanese great tits can respond in different, adaptive ways to discrete alarm calls. However, further playback studies are required to determine whether and how conspecifics can extract predator information from graded and combinatorial variation in alarm calls.
•I investigated alarm calls of Japanese great tits for different nest predators.•Great tits produced ‘jar’ calls for snakes, ‘chicka’ calls for crows and martens.•The number of notes in ‘chicka’ calls varied between crows and martens.•The note combination types of ‘chicka’ calls varied between crows and martens.
Human language can express limitless meanings from a finite set of words based on combinatorial rules (i.e., compositional syntax). Although animal vocalizations may be comprised of different basic ...elements (notes), it remains unknown whether compositional syntax has also evolved in animals. Here we report the first experimental evidence for compositional syntax in a wild animal species, the Japanese great tit (Parus minor). Tits have over ten different notes in their vocal repertoire and use them either solely or in combination with other notes. Experiments reveal that receivers extract different meanings from 'ABC' (scan for danger) and 'D' notes (approach the caller), and a compound meaning from 'ABC-D' combinations. However, receivers rarely scan and approach when note ordering is artificially reversed ('D-ABC'). Thus, compositional syntax is not unique to human language but may have evolved independently in animals as one of the basic mechanisms of information transmission.
Many animals produce vocal alarm signals when they detect a predator, and heterospecific species sharing predators often eavesdrop on and respond to these calls 1. Despite the widespread occurrence ...of interspecific eavesdropping in animals, its underlying cognitive process remains to be elucidated. If alarm calls, like human referential words, denote a specific predator type (e.g., “snake!”), then receivers may retrieve a mental image of the predator when hearing these calls 2–4. Here, using a recently developed experimental paradigm 5, I test whether heterospecific alarm calls evoke a predator-specific visual search image in wild birds. During playback of snake-specific alarm calls produced by Japanese tits (Parus minor), coal tits (Periparus ater) approach a wooden stick being moved in a snake-like manner. However, coal tits do not approach the same stick when hearing other call types or if the stick’s movement is dissimilar to that of a snake. Thus, Japanese tit snake alarms cause coal tits to specifically enhance visual attention to snakelike objects. These results provide experimental evidence for the evocation of visual search images by heterospecific alarm calls, highlighting the importance of integrating cross-modal information in interspecific eavesdropping.
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•Many animals eavesdrop on and respond to alarm calls produced by other species•I tested if other species’ alarm calls evoke a search image of a predator in birds•Coal tits approached snake-like objects when hearing Japanese tit snake alarm calls•Other species’ alarm calls can evoke a visual search image of a specific predator
Eavesdropping on other species’ alarm calls is widespread in animals, but its underlying cognitive process is unclear. Suzuki shows that a wild bird species enhances visual attention to snake-like objects when hearing snake-specific alarm calls of other species, providing evidence for call-evoked visual search images in interspecific eavesdropping.
Syntax is the set of rules for combining words into phrases, providing the basis for the generative power of linguistic expressions. In human language, the principle of compositionality governs how ...words are combined into a larger unit, the meaning of which depends on both the meanings of the words and the way in which they are combined. This linguistic capability, i.e., compositional syntax, has long been considered a trait unique to human language. Here, we review recent studies on call combinations in a passerine bird, the Japanese tit (Parus minor), that provide the first firm evidence for compositional syntax in a nonhuman animal. While it has been suggested that the findings of these studies fail to provide evidence for compositionality in Japanese tits, this criticism is based on misunderstanding of experimental design, misrepresentation of the importance of word order in human syntax, and necessitating linguistic capabilities beyond those given by the standard definition of compositionality. We argue that research on avian call combinations has provided the first steps in elucidating how compositional expressions could have emerged in animal communication systems.
Animal communication signals can contain surprisingly complex information, which plays a vital role in a variety of social interactions. For example, many species of birds and mammals produce vocal ...alarm signals when encountering a predator 1,2, and these calls often serve to communicate the type of predator and/or the degree of danger to members of a social group 3–5. Similarly, signals used in parent–offspring interactions can encode sophisticated information such as the type and immediacy of threat to the offspring 6–8. Here, I show that differential use of parental alarm calls in great tits (Parus major) functions to elicit different predator-avoidance behaviors in altricial nestlings: great tit parents produce acoustically distinctive alarm calls for the two main nest predators, the jungle crow (Corvus macrorhynchos) and the Japanese rat snake (Elaphe climacophora). Nestlings crouched down inside their nest cavity in response to alarm calls given for a crow, while they fled the cavity in response to alarm calls given for a snake. The two responses help nestlings to selectively evade those predators, because crows snatch nestlings from the nest entrance, whereas snakes invade the nest cavity. While chicks of some species have been shown to recognize and respond appropriately to parental alarm calls 7–10, the present findings demonstrate that nest predation by multiple predator species can drive evolution of complex parent–offspring communication in altricial species.
What do animal signals mean? This is a central question in studies on animal communication. Research into the semantics of animal signals began in 1980, with evidence that alarm calls of a non-human ...primate designated predators as external referents. These studies have challenged the historical assumption that such referential signaling is a unique feature of human language and produced a paradigm shift in animal communication research. Over the past two decades, an increasing number of field studies have revealed similar complexity in anti-predator communication of birds. The acoustic structures of avian alarm calls show a high degree of variation in pitch, duration, shape, and repetition rate. In addition to such distinct and graded variations, several birds combine discrete types of notes or calls into higher complex sequences. These variations in alarm calls are typically associated with the predator’s attributes, such as predator type and distance, and receivers respond to them with appropriate anti-predator behaviors. Although alarm calls of several bird species, as well as those of monkeys, appear to denote predator attributes, almost nothing is known about the cognitive processes that underlie the production and perception of these signals. In this review, I explore the existing evidence for referential signaling in birds and highlight the importance of the cognitive approach to animal communication research. I hope this review will promote further investigations of alarm-calling behavior in birds and will help enhance our understanding of the ecology and evolution of semantic communication.
Large-scale integrated quantum photonic technologies will require on-chip integration of identical photon sources with reconfigurable waveguide circuits. Relatively complex quantum circuits have been ...demonstrated already, but few studies acknowledge the pressing need to integrate photon sources and waveguide circuits together on-chip. A key step towards such large-scale quantum technologies is the integration of just two individual photon sources within a waveguide circuit, and the demonstration of high-visibility quantum interference between them. Here, we report a silicon-on-insulator device that combines two four-wave mixing sources in an interferometer with a reconfigurable phase shifter. We configured the device to create and manipulate two-colour (non-degenerate) or same-colour (degenerate) path-entangled or path-unentangled photon pairs. We observed up to 100.0 ± 0.4% visibility quantum interference on-chip, and up to 95 ± 4% off-chip. Our device removes the need for external photon sources, provides a path to increasing the complexity of quantum photonic circuits and is a first step towards fully integrated quantum technologies.
Parents of many bird species produce alarm calls when they approach and deter a nest predator in order to defend their offspring. Alarm calls have been shown to warn nestlings about predatory ...threats, but parents also face a similar risk of predation when incubating eggs in their nests. Here, I show that incubating female Japanese great tits, Parus minor, assess predation risk by conspecific alarm calls given outside the nest cavity. Tits produce acoustically discrete alarm calls for different nest predators: "jar" calls for snakes and "chicka" calls for other predators such as crows and martens. Playback experiments revealed that incubating females responded to "jar" calls by leaving their nest, whereas they responded to "chicka" calls by looking out of the nest entrance. Since snakes invade the nest cavity, escaping from the nest helps females avoid snake predation. In contrast, "chicka" calls are used for a variety of predator types, and therefore, looking out of the nest entrance helps females gather information about the type and location of approaching predators. These results show that incubating females derive information about predator type from different types of alarm calls, providing a novel example of functionally referential communication.
The syntax-semantics interface in animal vocal communication Suzuki, Toshitaka N; Wheatcroft, David; Griesser, Michael
Philosophical transactions of the Royal Society of London. Series B. Biological sciences,
01/2020, Volume:
375, Issue:
1789
Journal Article
Peer reviewed
Open access
Syntax (rules for combining words or elements) and semantics (meaning of expressions) are two pivotal features of human language, and interaction between them allows us to generate a limitless number ...of meaningful expressions. While both features were traditionally thought to be unique to human language, research over the past four decades has revealed intriguing parallels in animal communication systems. Many birds and mammals produce specific calls with distinct meanings, and some species combine multiple meaningful calls into syntactically ordered sequences. However, it remains largely unclear whether, like phrases or sentences in human language, the meaning of these call sequences depends on both the meanings of the component calls and their syntactic order. Here, leveraging recently demonstrated examples of meaningful call combinations, we introduce a framework for exploring the interaction between syntax and semantics (i.e. the syntax-semantic interface) in animal vocal sequences. We outline methods to test the cognitive mechanisms underlying the production and perception of animal vocal sequences and suggest potential evolutionary scenarios for syntactic communication. We hope that this review will stimulate phenomenological studies on animal vocal sequences as well as experimental studies on the cognitive processes, which promise to provide further insights into the evolution of language. This article is part of the theme issue 'What can animal communication teach us about human language?'
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