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At least 811 records · Page 45Linked to original sources
PubMed2002

Atlantic bottlenose dolphin (Tursiops truncatus) hearing threshold for brief broadband signals.

The hearing sensitivity of an Atlantic bottlenose dolphin (Tursiops truncatus) to both pure tones and broadband signals simulating echoes from a 7.62-cm water-filled sphere was measured. Pure tones with frequencies between 40 and 140 kHz in increments of 20 kHz were measured along with broadband thresholds using a stimulus with a center frequency of 97.3 kHz and 88.2 kHz. The pure-tone thresholds were compared with the broadband thresholds by converting the pure-tone threshold intensity to energy flux density. The results indicated that dolphins can detect broadband signals slightly better than a pure-tone signal. The broadband results suggest that an echolocating bottlenose dolphin should be able to detect a 7.62-cm diameter water-filled sphere out to a range of 178 m in a quiet environment.

Animals↗
PubMed2002

Using information theory to assess the diversity, complexity, and development of communicative repertoires.

The application of quantitative and comparative measures from information theory on animal communication can provide novel insights into the ecological, environmental, social, and contextual properties that shape the structure, organization, and function of signal repertoires. Using 2 phylogenetically different mammalian species that share similar ecological and social constraints as examples, the authors quantitatively examined the internal structure and development of a subsystem of these species' vocal repertoires in comparison with that of human language and illustrated that these species exhibit convergent developmental processes. The authors also discussed how predictions on the structure and organization of animal communication systems can be made from this new application of information theoretic measures with respect to behavioral ecology.

Age Factors↗
PubMed2002

The presumption of sociality: social learning in diverse contexts in brown-headed cowbirds (Molothrus ater).

Data are presented on social and vocal learning in cowbirds (Molothrus ater) housed in large aviaries and given more degrees of freedom than in conventional experimental studies. The studies show that social and vocal outcomes are facultative responses to social contexts. Several findings are reviewed: First, cowbirds quickly self-organize into groups by age and sex; second, opportunities to interact across age and sex do exist and affect courtship competence; third, female cowbirds organize themselves differently in the presence and absence of male competition; and fourth, young, naive cowbirds show rapid and differential sensitivity to group dynamics. Taken as a whole, the data show that social Umwelten are dynamic, developmental ecologies.

Age Factors↗
PubMed2002

Multiple environmental contexts and communication in pygmy marmosets (Cebuella pygmaea).

There are multiple components to the concept of Umwelt experienced by an organism that may constrain the type and structure of communication signals as well as the usefulness of these signals. To illustrate the impact of these multiple environmental components, the authors used signals of the pygmy marmoset (Cebuella pygmaea), a small primate from the western Amazon. The authors summarize studies to show how the physical effects of the habitat; effects of other species, both predators and nonpredators; anthropogenic effects on the communication environment; within-group and between-groups influences other pygmy marmosets exert; and ontogeny influence the structure and usage of vocal signals. Communication within a species can be understood only in consideration of each of these contexts.

Animal Communication↗
PubMed2002

A new perspective on barking in dogs (Canis familiaris).

The disparity in bark frequency and context between dogs (Canis familiaris) and wolves (Canis lupus) has led some researchers to conclude that barking in the domestic dog is nonfunctional. This conclusion attributes the differences primarily to genetic variation caused by domestication rather than to the influence of social environment on ontogeny. Other researchers, however, have concluded that vocal usage and response to vocalizations in mammals are strongly guided by social interactions. Closer evaluation of dog vocalizations with respect to social environment reveals developmental factors that lead to both frequent barking and barking in many contexts. Additionally, spectrographic analysis indicates that bark structure varies predictably with context, suggesting that barks can be divided into contextual subtypes and may be a more complex form of communication than given credit.

Animal Communication↗
PubMed2002

The rattling sound of rattlesnakes (Crotalus viridis) as a communicative resource for ground squirrels (Spermophilus beecheyi) and burrowing owls (Athene cunicularia).

Animal communication involves very dynamic processes that can generate new uses and functions for established communicative activities. In this article, the authors describe how an aposematic signal, the rattling sound of rattlesnakes (Crotalus viridis), has been exploited by 2 ecological associates of rattlesnakes: (a) California ground squirrels (Spermophilus beecheyi) use incidental acoustic cues in rattling sounds to assess the danger posed by the rattling snake, and (b) burrowing owls (Athene cunicularia) defend themselves against mammalian predators by mimicking the sound of rattling. The remarkable similarity between the burrowing owl's defensive hiss and the rattlesnake's rattling reflects both exaptation and adaptation. Such exploitation of the rattling sound has favored alternations in both the structure and the deployment of rattling by rattlesnakes.

Animal Communication↗
PubMed2002

Species identity and the temporal characteristics of fish acoustic signals.

Analyses of the acoustic signals of fish show that fine-scale temporal patterns of signals are what vary among species. A growing body of research addressing the topic of species differences in fish acoustic signals suggests that these differences are related to mate choice or species isolation. However, little behavioral work has been done to determine whether these temporal differences are actually used in discriminating conspecific sounds from interspecific sounds. In this article, the authors review three cases--Centrachids, Mormyrids, and Pomancentrids--for which species specificity in both signal production and differential response to acoustic signals have been demonstrated. Work done on damselfish (Dascyllus albisella) is an especially good example and thus may serve as a model for future work.

Animal Communication↗
PubMed2003

Hearing and vocalizations in the orange-fronted conure (Aratinga canicularis).

The auditory sensitivities of the orange-fronted conure (Aratinga canicularis) were examined in relation to the spectral characteristics of its vocalizations. Absolute thresholds, masked thresholds, frequency difference limens, and intensity difference limens for pure tones were obtained using psychoacoustic techniques. In general, hearing abilities are similar to those found in many avian auditory generalists. One exception is the unusually low critical ratio (masked threshold) between 2.0 and 4.0 kHz, similar to that previously found in the budgerigar (Melopsittacus undulatus). These auditory sensitivities were compared with average spectra for (a) contact calls and (b) a general sample of vocalizations recorded from wild birds. The spectral regions of both greatest vocal energy and best auditory sensitivity were between 2.0 and 5.0 kHz.

Animals↗
PubMed2003

Open-ended categorization of chick-a-dee calls by black-capped chickadees (Poecile atricapilla).

The authors trained black-capped chickadees (Poecile atricapilla) in an operant discrimination with exemplars of black-capped and Carolina chick-a-dee calls, with the goal of determining whether the birds memorized the calls of conspecifics and heterospecifics or classified the calls by species. Black-capped calls served as both rewarded (S+) and unrewarded (S-) stimuli (the within-category discrimination), whereas Carolina chick-a-dee calls served as S-s (the between-category discrimination) in the black-capped chick-a-dee call S+ group. The Carolina call S+ group had Carolina calls as S+s and S-s (within-category) and black-capped calls as S-s (between-category). Both groups discriminated between call categories faster than within a call category. In 2 subsequent experiments, both S+ groups showed transfer to novel calls and propagation back to between-category calls. The results favor the hypothesis that the acoustically similar social calls of the 2 species constitute separate open-ended categories.

Animal Communication↗
PubMed2003

Salience of caller identity in rhesus monkey (Macaca mulatta) coos and screams: perceptual experiments with human (Homo sapiens) listeners.

Recent evidence from acoustic analysis and playback experiments indicates that adult female rhesus monkey (Macaca mulatta) coos are individually distinctive but their screams are not. In this study, the authors compared discrimination of individual identity in these sounds by naive human listeners who judged whether 2 sounds had been produced by the same monkey or 2 monkeys. Each of 3 experiments using this same-different design showed significantly better discrimination of vocalizer identity from coos than from screams. Experiment 1 demonstrated the basic finding. Experiment 2 also tested the effect of non-identity-related scream variation, and Experiment 3 added a comparison with human vowel sounds. Outcomes suggest that acoustic structural differences in coos and screams influence salience of caller-identity cues, with significant implications for understanding the functions of these calls.

Acoustics↗
PubMed2004

Perceptual and acoustic evidence for species-level differences in meow vocalizations by domestic cats (Felis catus) and African wild cats (Felis silvestris lybica).

To test for possible anthropogenic selection effects on meows in domestic felids, vocalizations by domestic cats (Felis catus) were compared with cries by their closest wild relative, the African wild cat (Felis silvestris lybica). Comparisons included analysis of acoustic characteristics and perceptual studies with human (Homo sapiens) listeners. The perceptual studies obtained human listener ratings of call pleasantness. Both the acoustic and perceptual comparisons revealed clear species-level differences: The domestic cat meows were significantly shorter in mean duration than the wild cat meows, showed higher mean formant frequencies, and exhibited higher mean fundamental frequencies. Human listeners at all levels of experience and affinity for cats rated domestic cat meows as far more pleasant sounding than wild cat vocalizations. These results are consistent with a model of cat domestication that posits selective pressure on meows based on human perceptual biases.

Acoustics↗
PubMed2005

Human listeners are able to classify dog (Canis familiaris) barks recorded in different situations.

The authors investigated whether human listeners could categorize played-back dog (Canis familiaris) barks recorded in various situations and associate them with emotional ratings. Prerecorded barks of a Hungarian herding dog breed (Mudi) provided the sample. Human listeners were asked to rate emotionality of the vocalization and to categorize the situations on the basis of alternative situations provided on a questionnaire. The authors found almost no effect of previous experience with the given dog breed or of owning a dog. Listeners were able to categorize bark situations high above chance level. Emotionality ratings for particular bark samples correlated with peak and fundamental frequency and interbark intervals. The authors did not find a significant effect of tonality (harmonic-to-noise ratio) on either the emotionality rating or situation categorization of the human listeners. Humans' ability to recognize meaning suggests that barks could serve as an effective means of communication between dog and human.

Adult↗
PubMed2005

Socially meaningful vocal plasticity in adult Campbell's monkeys (Cercopithecus campbelli).

Campbell's monkeys (Cercopithecus campbelli) frequently exchange vocalizations, the combined-harmonic calls, with individuals responding to one another's calls. Previous work has shown that these calls can be grouped into several structural variants. Adult females differ in their variant repertoires, which may change during their adult life, particularly after changes in the group composition. Playback of females' currently produced variants triggered vocal responses from other group members, whereas the same females' former, no longer used variants and those of stranger females never did. In contrast, former variants caused long-term cessation of vocal behavior, whereas stranger variants had no effect. Data showed that monkeys were able to distinguish between the different types of variants, indicating that these calls form part of a long-term social memory.

Age Factors↗
PubMed2006

Frequency-range discriminations and absolute pitch in black-capped chickadees (Poecile atricapillus), mountain chickadees (Poecile gambeli), and zebra finches (Taeniopygia guttata).

The acoustic frequency ranges in birdsongs provide important absolute pitch cues for the recognition of conspecifics. Black-capped chickadees (Poecile atricapillus), mountain chickadees (Poecile gambeli), and zebra finches (Taeniopygia guttata) were trained to sort tones contiguous in frequency into 8 ranges on the basis of associations between response to the tones in each range and reward. All 3 species acquired accurate frequency-range discriminations, but zebra finches acquired the discrimination in fewer trials and to a higher standard than black-capped or mountain chickadees, which did not differ appreciably in the discrimination. Chickadees' relatively poorer accuracy was traced to poorer discrimination of tones in the higher frequency ranges. During transfer tests, the discrimination generalized to novel tones when the training tones were included, but not when they were omitted.

Animal Communication↗
PubMed2006

The discrimination of temporal fine structure in call-like harmonic sounds by birds.

Thresholds for discriminating changes in the temporal fine structure of call-like, harmonic sounds were measured in zebra finches (Taeniopygia guttata) and budgerigars (Melopsittacus undulatus). Birds could detect changes in periods as short as 1.225 ms at near 100% accuracy even when spectral and envelope cues were identical, as in time-reversed stimuli. Humans performed poorly on such stimuli, paralleling results from previous studies. Bird thresholds were in the range of those reported in neurophysiological studies of the songbird high vocal center (HVC) to temporally modified conspecific songs. Taken together, these results show that birds can hear differences in temporal fine structure in their natural vocalizations that go beyond human capabilities, but whether these abilities have communicative relevance remains to be seen.

Adolescent↗
PubMed1997

Free-field binaural unmasking in budgerigars (Melopsittacus undulatus).

The detection of signals in noise is important for understanding both the mechanisms of hearing and how the auditory system functions under more natural conditions. In humans, the auditory system gains some improvement if the signal and noise are separated in space (binaural masking release). Birds with small heads are at a disadvantage in separating noise and signal sources relative to large mammals, because interaural time differences are much smaller. Two binaural phenomena in budgerigars related to the detection of tones in noise were examined. Budgerigars show 8 dB of free-field binaural masking release when signal and noise are presented to their right side and correlated noise is presented to their left side. Budgerigars also show a spatial masking release of 9 dB when a signal and noise are separated in azimuth by 90 degrees. These results are similar to those found in humans and other mammals with much larger heads.

Animals↗
PubMed2004

Hemispheric specialization in the primary auditory area of awake and anesthetized starlings (Sturnus vulgaris).

Although evidence exists for a lateralization of song production, few studies have focused on the perceptual aspect of lateralization in songbirds. In the present study, the authors recorded neuronal responses to a variety of species-specific and artificial, nonspecific stimuli in both hemispheres of awake and anesthetized male starlings (Sturnus vulgaris). Recordings were made in the primary auditory area of the songbird brain, the Field L complex. The right hemisphere exhibited significantly more responsive units than the left hemisphere in awake birds, and this difference was significantly reduced in anesthetized birds. Furthermore, clear hemispheric specialization toward categories of behaviorally relevant stimuli and precise parameters of these stimuli were found. The main auditory area of the starling's brain thus appears to show some degree of lateralization.

Acoustic Stimulation↗
PubMed2001

Impact of intended emotion intensity on cue utilization and decoding accuracy in vocal expression of emotion.

Actors vocally portrayed happiness, sadness, anger, fear, and disgust with weak and strong emotion intensity while reading brief verbal phrases aloud. The portrayals were recorded and analyzed according to 20 acoustic cues. Listeners decoded each portrayal by using forced-choice or quantitative ratings. The results showed that (a) portrayals with strong emotion intensity yielded higher decoding accuracy than portrayals with weak intensity, (b) listeners were able to decode the intensity of portrayals, (c) portrayals of the same emotion with different intensity yielded different patterns of acoustic cues, and (d) certain acoustic cues (e.g., fundamental frequency, high-frequency energy) were highly predictive of listeners' ratings of emotion intensity. It is argued that lack of control for emotion intensity may account for some of the inconsistencies in cue utilization reported in the literature.

Adult↗