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Lessons learned in animal acoustic cognition through comparisons with humans. Anim Cogn 2023; 26:97-116. [PMID: 36574158 PMCID: PMC9877085 DOI: 10.1007/s10071-022-01735-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 11/21/2022] [Accepted: 12/06/2022] [Indexed: 12/28/2022]
Abstract
Humans are an interesting subject of study in comparative cognition. While humans have a lot of anecdotal and subjective knowledge about their own minds and behaviors, researchers tend not to study humans the way they study other species. Instead, comparisons between humans and other animals tend to be based on either assumptions about human behavior and cognition, or very different testing methods. Here we emphasize the importance of using insider knowledge about humans to form interesting research questions about animal cognition while simultaneously stepping back and treating humans like just another species as if one were an alien researcher. This perspective is extremely helpful to identify what aspects of cognitive processes may be interesting and relevant across the animal kingdom. Here we outline some examples of how this objective human-centric approach has helped us to move forward knowledge in several areas of animal acoustic cognition (rhythm, harmonicity, and vocal units). We describe how this approach works, what kind of benefits we obtain, and how it can be applied to other areas of animal cognition. While an objective human-centric approach is not useful when studying traits that do not occur in humans (e.g., magnetic spatial navigation), it can be extremely helpful when studying traits that are relevant to humans (e.g., communication). Overall, we hope to entice more people working in animal cognition to use a similar approach to maximize the benefits of being part of the animal kingdom while maintaining a detached and scientific perspective on the human species.
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Calcari C, Pilenga C, Baciadonna L, Gamba M, Favaro L. Long-term stability of vocal individuality cues in a territorial and monogamous seabird. Anim Cogn 2021; 24:1165-1169. [PMID: 33973095 DOI: 10.1007/s10071-021-01518-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 04/06/2021] [Accepted: 04/24/2021] [Indexed: 11/26/2022]
Abstract
The stability of individual acoustic features is fundamental in social species, and more importantly in monogamous and territorial species, showing long-term fidelity both to the partner and the breeding site. In this study, the stability over time of two discrete vocal types was investigated in the African penguin (Spheniscus demersus), a monogamous and territorial seabird. Contact calls and ecstatic display songs were recorded from an ex situ colony in 2017 and in 2020. For each vocalisation, we measured 14 spectral and temporal acoustic parameters related to both source and filter components. Two separate leave-one-out cross-validated Discriminant Function Analyses (DFA) were then performed, generating the discriminant functions from the vocalisations collected in 2017 to classify those recorded in 2020. The DFA correctly classified 62% of the contact calls (10 subjects) and 80.9% of the ecstatic display songs (seven subjects) according to the correct emitter, showing that acoustic cues to individuality encoded in both vocal types remained unchanged over four consecutive breeding seasons. We suggest that, in this monogamous and territorial bird species, individual acoustic stability could be selected for to identify groupmates and neighbours over the years and to help couples to reunite in consecutive breeding seasons, increasing individual fitness.
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Affiliation(s)
- Chiara Calcari
- Department of Environmental Biology, Sapienza University of Rome, Rome, Italy
- Department of Life Sciences and Systems Biology, University of Turin, Turin, Italy
| | | | - Luigi Baciadonna
- Department of Life Sciences and Systems Biology, University of Turin, Turin, Italy
| | - Marco Gamba
- Department of Life Sciences and Systems Biology, University of Turin, Turin, Italy
| | - Livio Favaro
- Department of Life Sciences and Systems Biology, University of Turin, Turin, Italy.
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3
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Leliveld LMC, Düpjan S, Tuchscherer A, Puppe B. Hemispheric Specialization for Processing the Communicative and Emotional Content of Vocal Communication in a Social Mammal, the Domestic Pig. Front Behav Neurosci 2020; 14:596758. [PMID: 33328923 PMCID: PMC7714956 DOI: 10.3389/fnbeh.2020.596758] [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: 08/20/2020] [Accepted: 10/26/2020] [Indexed: 11/13/2022] Open
Abstract
In humans, speech perception is lateralized, with the left hemisphere of the brain dominant in processing the communicative content and the right hemisphere dominant in processing the emotional content. However, still little is known about such a division of tasks in other species. We therefore investigated lateralized processing of communicative and emotionally relevant calls in a social mammal, the pig (Sus scrofa). Based on the contralateral connection between ears and hemispheres, we compared the behavioural and cardiac responses of 36 young male pigs during binaural and monaural (left or right) playback to the same sounds. The playback stimuli were calls of social isolation and physical restraint, whose communicative and emotional relevance, respectively, were validated prior to the test by acoustic analyses and during binaural playbacks. There were indications of lateralized processing mainly in the initial detection (left head-turn bias, indicating right hemispheric dominance) of the more emotionally relevant restraint calls. Conversely, there were indications of lateralized processing only in the appraisal (increased attention during playback to the right ear) of the more communicative relevant isolation calls. This implies differential involvement of the hemispheres in the auditory processing of vocalizations in pigs and thereby hints at similarities in the auditory processing of vocal communication in non-human animals and speech in humans. Therefore, these findings provide interesting new insight in the evolution of human language and auditory lateralization.
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Affiliation(s)
- Lisette M C Leliveld
- Institute of Behavioural Physiology, Leibniz Institute for Farm Animal Biology (FBN), Dummerstorf, Germany
| | - Sandra Düpjan
- Institute of Behavioural Physiology, Leibniz Institute for Farm Animal Biology (FBN), Dummerstorf, Germany
| | - Armin Tuchscherer
- Institute of Genetics and Biometry, Leibniz Institute for Farm Animal Biology (FBN), Dummerstorf, Germany
| | - Birger Puppe
- Institute of Behavioural Physiology, Leibniz Institute for Farm Animal Biology (FBN), Dummerstorf, Germany.,Behavioural Sciences, Faculty of Agricultural and Environmental Sciences, University of Rostock, Rostock, Germany
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Parker AN, Wallis GM, Obergrussberger R, Siebeck UE. Categorical face perception in fish: How a fish brain warps reality to dissociate "same" from "different". J Comp Neurol 2020; 528:2919-2928. [PMID: 32406088 DOI: 10.1002/cne.24947] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 04/14/2020] [Accepted: 04/28/2020] [Indexed: 11/07/2022]
Abstract
Categorical perception (CP) is the phenomenon by which a smoothly varying stimulus property undergoes a nonlinear transformation during processing in the brain. Consequently, the stimuli are perceived as belonging to distinct categories separated by a sharp boundary. Originally thought to be largely innate, the discovery of CP in tasks such as novel image discrimination has piqued the interest of cognitive scientists because it provides compelling evidence that learning can shape a category's perceptual boundaries. CP has been particularly closely studied in human face perception. In nonprimates, there is evidence for CP for sound and color discrimination, but not for image or face discrimination. Here, we investigate the potential for learned CP in a lower vertebrate, the damselfish Pomacentrus amboinensis. Specifically, we tested whether the ability of these fish to discriminate complex facial patterns tracked categorical rather than metric differences in the stimuli. We first trained the fish to discriminate sets of two facial patterns. Next, we morphed between these patterns and determined the just noticeable difference (JND) between a morph and original image. Finally, we tested for CP by analyzing the discrimination ability of the fish for pairs of JND stimuli along the spectrum of morphs between two original images. Discrimination performance was significant for the image pair straddling the boundary between categories, and chance for equivalent stimulus pairs on either side, thus producing the classic "category boundary" effect. Our results reveal how perception can be influenced in a top-down manner even in the absence of a visual cortex.
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Affiliation(s)
- Amira N Parker
- School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Guy M Wallis
- School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Rainer Obergrussberger
- School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Ulrike E Siebeck
- School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, Australia
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Huskey S, Tegge SM, Anderson CV, Smith ME, Barnett K. Gular pouch diversity in the Chamaeleonidae. Anat Rec (Hoboken) 2019; 303:2248-2261. [PMID: 31680478 DOI: 10.1002/ar.24313] [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: 12/10/2018] [Revised: 10/03/2019] [Accepted: 10/16/2019] [Indexed: 11/05/2022]
Abstract
Numerous chameleon species possess an out-pocketing of the trachea known as the gular pouch. After surveying more than 250 specimens, representing nine genera and 44 species, we describe two different morphs of the gular pouch. Species of the genera Bradypodion and Chamaeleo, as well as Trioceros goetzei, all possess a single gular pouch (morph one) formed from ventral expansion of soft tissue where the larynx and trachea meet. Furcifer oustaleti and Furcifer verrucosus possess from one to four gular pouches (morph two) formed by the expansion of soft tissue between sequential hyaline cartilage rings of the trachea. In Trioceros melleri, examples of both morphs of the gular pouch were observed. Morphometric data are presented for 100 animals representing eight species previously known to possess a gular pouch and two additional species, Bradypodion thamnobates and Bradypodion transvaalense. In the species with the absolutely and relatively largest gular pouch, Chamaeleo calyptratus, a significant difference was found between sexes in its width and volume, but not its length. In C. calyptratus, we show that an inflated gular pouch is in contact with numerous hyoid muscles and the tongue. Coupled with the knowledge that C. calyptratus generates vibrations from the throat region, we posit that the tongue (M. accelerator linguae and M. hyoglossus) and supporting hyoid muscles (i.e., Mm. sternohyoideus profundus et superficialis and Mm. mandibulohyoideus) are involved in the production of vibrations to produce biotremors that are amplified by the inflated gular pouch and used in substrate-borne communication.
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Affiliation(s)
- Steve Huskey
- Department of Biology, Western Kentucky University, Bowling Green, Kentucky
| | - Samuel M Tegge
- Department of Biology, Western Kentucky University, Bowling Green, Kentucky
| | | | - Michael E Smith
- Department of Biology, Western Kentucky University, Bowling Green, Kentucky
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O'Reilly C, Analuddin K, Kelly DJ, Harte N. Measuring vocal difference in bird population pairs. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2018; 143:1658. [PMID: 29604681 DOI: 10.1121/1.5027244] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Over time, a bird population's acoustic and morphological features can diverge from the parent species. A quantitative measure of difference between two populations of species/subspecies is extremely useful to zoologists. Work in this paper takes a dialect difference system first developed for speech and refines it to automatically measure vocalisation difference between bird populations by extracting pitch contours. The pitch contours are transposed into pitch codes. A variety of codebook schemes are proposed to represent the contour structure, including a vector quantization approach. The measure, called Bird Vocalisation Difference, is applied to bird populations with calls that are considered very similar, very different, and between these two extremes. Initial results are very promising, with the behaviour of the metric consistent with accepted levels of similarity for the populations tested to date. The influence of data size on the measure is investigated by using reduced datasets. Results of species pair classification using Gaussian mixture models with Mel-frequency cepstral coefficients is also given as a baseline indicator of class confusability.
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Affiliation(s)
- Colm O'Reilly
- Sigmedia Group, School of Engineering, Trinity College Dublin, Dublin, Ireland
| | - Kangkuso Analuddin
- Department of Biology and Biotechnology, Halu Oleo University, Southeast Sulawesi, Indonesia
| | - David J Kelly
- Department of Zoology, School of Natural Sciences, Trinity College Dublin, Dublin, Ireland
| | - Naomi Harte
- Sigmedia Group, School of Engineering, Trinity College Dublin, Dublin, Ireland
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Garcia SM, Kopuchian C, Mindlin GB, Fuxjager MJ, Tubaro PL, Goller F. Evolution of Vocal Diversity through Morphological Adaptation without Vocal Learning or Complex Neural Control. Curr Biol 2017; 27:2677-2683.e3. [PMID: 28867206 DOI: 10.1016/j.cub.2017.07.059] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 06/15/2017] [Accepted: 07/26/2017] [Indexed: 11/25/2022]
Abstract
The evolution of complex behavior is driven by the interplay of morphological specializations and neuromuscular control mechanisms [1-3], and it is often difficult to tease apart their respective contributions. Avian vocal learning and associated neural adaptations are thought to have played a major role in bird diversification [4-8], whereas functional significance of substantial morphological diversity of the vocal organ remains largely unexplored. Within the most species-rich order, Passeriformes, "tracheophones" are a suboscine group that, unlike their oscine sister taxon, does not exhibit vocal learning [9] and is thought to phonate with tracheal membranes [10, 11] instead of the two independent sources found in other passerines [12-14]. Here we show tracheophones possess three sound sources, two oscine-like labial pairs and the unique tracheal membranes, which collectively represent the largest described number of sound sources for a vocal organ. Birds with experimentally disabled tracheal membranes were still able to phonate. Instead of the main sound source, the tracheal membranes constitute a morphological specialization, which, through interaction with bronchial labia, contributes to different acoustic features such as spectral complexity, amplitude modulation, and enhanced sound amplitude. In contrast, these same features arise in oscines from neuromuscular control of two labial sources [15-17]. These findings are supported by a modeling approach and provide a clear example for how a morphological adaptation of the tracheophone vocal organ can generate specific, complex sound features. Morphological specialization therefore constitutes an alternative path in the evolution of acoustic diversity to that of oscine vocal learning and complex neural control.
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Affiliation(s)
- Sarah M Garcia
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112, USA.
| | - Cecilia Kopuchian
- CECOAL (Centro de Ecología Aplicada del Litoral) CONICET, Corrientes, Argentina; División Ornitología, Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" MACN-CONICET, Avenida Ángel Gallardo 470, Ciudad Autónoma de Buenos Aires, Argentina
| | - Gabriel B Mindlin
- Depto. Física, FCEyN, Universidad de Buenos Aires, C. Universitaria, Pab I, Buenos Aires, Argentina
| | - Matthew J Fuxjager
- Department of Biology, Wake Forest University, Winston-Salem, NC 27109, USA
| | - Pablo L Tubaro
- División Ornitología, Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" MACN-CONICET, Avenida Ángel Gallardo 470, Ciudad Autónoma de Buenos Aires, Argentina
| | - Franz Goller
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112, USA
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Favaro L, Gamba M, Alfieri C, Pessani D, McElligott AG. Vocal individuality cues in the African penguin (Spheniscus demersus): a source-filter theory approach. Sci Rep 2015; 5:17255. [PMID: 26602001 PMCID: PMC4658557 DOI: 10.1038/srep17255] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 10/26/2015] [Indexed: 11/29/2022] Open
Abstract
The African penguin is a nesting seabird endemic to southern Africa. In penguins of the genus Spheniscus vocalisations are important for social recognition. However, it is not clear which acoustic features of calls can encode individual identity information. We recorded contact calls and ecstatic display songs of 12 adult birds from a captive colony. For each vocalisation, we measured 31 spectral and temporal acoustic parameters related to both source and filter components of calls. For each parameter, we calculated the Potential of Individual Coding (PIC). The acoustic parameters showing PIC ≥ 1.1 were used to perform a stepwise cross-validated discriminant function analysis (DFA). The DFA correctly classified 66.1% of the contact calls and 62.5% of display songs to the correct individual. The DFA also resulted in the further selection of 10 acoustic features for contact calls and 9 for display songs that were important for vocal individuality. Our results suggest that studying the anatomical constraints that influence nesting penguin vocalisations from a source-filter perspective, can lead to a much better understanding of the acoustic cues of individuality contained in their calls. This approach could be further extended to study and understand vocal communication in other bird species.
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Affiliation(s)
- Livio Favaro
- Department of Life Sciences and Systems Biology, University of Turin, Via Accademia Albertina 13, 10123 Turin, Italy
| | - Marco Gamba
- Department of Life Sciences and Systems Biology, University of Turin, Via Accademia Albertina 13, 10123 Turin, Italy
| | - Chiara Alfieri
- Department of Life Sciences and Systems Biology, University of Turin, Via Accademia Albertina 13, 10123 Turin, Italy
| | - Daniela Pessani
- Department of Life Sciences and Systems Biology, University of Turin, Via Accademia Albertina 13, 10123 Turin, Italy
| | - Alan G. McElligott
- Biological and Experimental Psychology, School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
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Kriengwatana B, Escudero P, ten Cate C. Revisiting vocal perception in non-human animals: a review of vowel discrimination, speaker voice recognition, and speaker normalization. Front Psychol 2015; 5:1543. [PMID: 25628583 PMCID: PMC4292401 DOI: 10.3389/fpsyg.2014.01543] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Accepted: 12/12/2014] [Indexed: 12/03/2022] Open
Abstract
The extent to which human speech perception evolved by taking advantage of predispositions and pre-existing features of vertebrate auditory and cognitive systems remains a central question in the evolution of speech. This paper reviews asymmetries in vowel perception, speaker voice recognition, and speaker normalization in non-human animals - topics that have not been thoroughly discussed in relation to the abilities of non-human animals, but are nonetheless important aspects of vocal perception. Throughout this paper we demonstrate that addressing these issues in non-human animals is relevant and worthwhile because many non-human animals must deal with similar issues in their natural environment. That is, they must also discriminate between similar-sounding vocalizations, determine signaler identity from vocalizations, and resolve signaler-dependent variation in vocalizations from conspecifics. Overall, we find that, although plausible, the current evidence is insufficiently strong to conclude that directional asymmetries in vowel perception are specific to humans, or that non-human animals can use voice characteristics to recognize human individuals. However, we do find some indication that non-human animals can normalize speaker differences. Accordingly, we identify avenues for future research that would greatly improve and advance our understanding of these topics.
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Affiliation(s)
- Buddhamas Kriengwatana
- Behavioural Biology, Institute for Biology Leiden, Leiden UniversityLeiden, Netherlands
- Leiden Institute for Brain and Cognition, Leiden UniversityLeiden, Netherlands
| | - Paola Escudero
- The MARCS Institute, University of Western SydneySydney, NSW, Australia
| | - Carel ten Cate
- Behavioural Biology, Institute for Biology Leiden, Leiden UniversityLeiden, Netherlands
- Leiden Institute for Brain and Cognition, Leiden UniversityLeiden, Netherlands
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ten Cate C. On the phonetic and syntactic processing abilities of birds: from songs to speech and artificial grammars. Curr Opin Neurobiol 2014; 28:157-64. [PMID: 25078891 DOI: 10.1016/j.conb.2014.07.019] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2014] [Revised: 07/10/2014] [Accepted: 07/11/2014] [Indexed: 11/25/2022]
Abstract
Like speech and language, the songs of many songbirds consist of learned, rapidly produced, structured sequences of distinct vocal units, originating from an interplay between experience and learning biases. Songs are species specific, but also show considerable within species variation in elements or element sequencing. This variation implies that birds possess mechanisms to identify, categorize and combine sounds. I review the abilities for speech sound perception and categorization, as well as for grammatical rule learning by birds. Speech sound perception in birds is in many ways comparable to human speech perception. Birds can also detect and generalize patterns underlying artificially arranged strings of vocal elements. However, there is a need for more comparative studies to examine the limits of their rule learning abilities and how they relate to those of humans.
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Affiliation(s)
- Carel ten Cate
- Leiden Institute of Biology and Leiden Institute for Brain and Cognition, Leiden University, PO Box 9505, 2300 RA Leiden, The Netherlands.
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Defects in ultrasonic vocalization of cadherin-6 knockout mice. PLoS One 2012; 7:e49233. [PMID: 23173049 PMCID: PMC3500271 DOI: 10.1371/journal.pone.0049233] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Accepted: 10/07/2012] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND Although some molecules have been identified as responsible for human language disorders, there is still little information about what molecular mechanisms establish the faculty of human language. Since mice, like songbirds, produce complex ultrasonic vocalizations for intraspecific communication in several social contexts, they can be good mammalian models for studying the molecular basis of human language. Having found that cadherins are involved in the vocal development of the Bengalese finch, a songbird, we expected cadherins to also be involved in mouse vocalizations. METHODOLOGY/PRINCIPAL FINDINGS To examine whether similar molecular mechanisms underlie the vocalizations of songbirds and mammals, we categorized behavioral deficits including vocalization in cadherin-6 knockout mice. Comparing the ultrasonic vocalizations of cadherin-6 knockout mice with those of wild-type controls, we found that the peak frequency and variations of syllables were differed between the mutant and wild-type mice in both pup-isolation and adult-courtship contexts. Vocalizations during male-male aggression behavior, in contrast, did not differ between mutant and wild-type mice. Open-field tests revealed differences in locomotors activity in both heterozygote and homozygote animals and no difference in anxiety behavior. CONCLUSIONS/SIGNIFICANCE Our results suggest that cadherin-6 plays essential roles in locomotor activity and ultrasonic vocalization. These findings also support the idea that different species share some of the molecular mechanisms underlying vocal behavior.
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Ohms VR, Beckers GJL, ten Cate C, Suthers RA. Vocal tract articulation revisited: the case of the monk parakeet. ACTA ACUST UNITED AC 2012; 215:85-92. [PMID: 22162856 DOI: 10.1242/jeb.064717] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Birdsong and human speech share many features with respect to vocal learning and development. However, the vocal production mechanisms have long been considered to be distinct. The vocal organ of songbirds is more complex than the human larynx, leading to the hypothesis that vocal variation in birdsong originates mainly at the sound source, while in humans it is primarily due to vocal tract filtering. However, several recent studies have indicated the importance of vocal tract articulators such as the beak and oropharyngeal-esophageal cavity. In contrast to most other bird groups, parrots have a prominent tongue, raising the possibility that tongue movements may also be of significant importance in vocal production in parrots, but evidence is rare and observations often anecdotal. In the current study we used X-ray cinematographic imaging of naturally vocalizing monk parakeets (Myiopsitta monachus) to assess which articulators are possibly involved in vocal tract filtering in this species. We observed prominent tongue height changes, beak opening movements and tracheal length changes, which suggests that all of these components play an important role in modulating vocal tract resonance. Moreover, the observation of tracheal shortening as a vocal articulator in live birds has to our knowledge not been described before. We also found strong positive correlations between beak opening and amplitude as well as changes in tongue height and amplitude in several types of vocalization. Our results suggest considerable differences between parrot and songbird vocal production while at the same time the parrot's vocal articulation might more closely resemble human speech production in the sense that both make extensive use of the tongue as a vocal articulator.
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Affiliation(s)
- Verena R Ohms
- Behavioural Biology, Institute of Biology Leiden, Sylvius Laboratory, PO Box 9505, 2300 RA Leiden, The Netherlands.
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