http://content.apa.org/journals/com The Journal of Comparative Psychology publishes original empirical and theoretical research from a comparative perspective on the behavior, cognition, perception, and social relationships of diverse species. en-us Copyright 2008 American Psychological Association Gordon M. Burghardt, PhD 07357036 Mon, 17 Nov 2008 01:12:52 EST http://journals.apa.org/toc/journal/journal-com.jpg 77 http://content.apa.org/journals/com Business/Publishing and Printing/Publishing/Academic and Technical/Science Health/Mental Health Science/Social Sciences/Psychology/Journals and Publications http://blogs.law.harvard.edu/tech/rss http://content.apa.org/journals/com/122/3/231 http://content.apa.org/journals/com/122/3/231 It has long been known that individuals of many species vocally communicate with one another in noisy environments and in rich contexts of social interaction. It has recently become clear that researchers interested in understanding acoustic communication in animal groups must study vocal signaling in these noisy and socially complex settings. Furthermore, recent methodological advances have made it increasingly clear that the authors can tackle these more complex questions effectively. The articles in this Special Issue stem from a Symposium held at the June 2006 meeting of the Acoustical Society of America, and illustrate some of the taxonomic and methodological diversity in studies aimed at understanding how acoustic communication functions in social grouping. This introduction to the Special Issue provides a brief overview of the articles and key ideas in this field of inquiry, and suggests some future directions to take the field to help us understand how social pressures in animal groups may influence, and be influenced by, acoustic signals. (PsycINFO Database Record (c) 2008 APA, all rights reserved) Journal of Comparative Psychology - Vol 122, Iss 3 2008 Schwartz, Joshua J.; Freeberg, Todd M. American Psychological Association 10.1037/0735-7036.122.3.231 http://content.apa.org/journals/com/122/3/235 http://content.apa.org/journals/com/122/3/235 Animals often use acoustic signals to communicate in groups or social aggregations in which multiple individuals signal within a receiver's hearing range. Consequently, receivers face challenges related to acoustic interference and auditory masking that are not unlike the human cocktail party problem, which refers to the problem of perceiving speech in noisy social settings. Understanding the sensory solutions to the cocktail party problem has been a goal of research on human hearing and speech communication for several decades. Despite a general interest in acoustic signaling in groups, animal behaviorists have devoted comparatively less attention toward understanding how animals solve problems equivalent to the human cocktail party problem. After illustrating how humans and nonhuman animals experience and overcome similar perceptual challenges in cocktail-party-like social environments, this article reviews previous psychophysical and physiological studies of humans and nonhuman animals to describe how the cocktail party problem can be solved. This review also outlines several basic and applied benefits that could result from studies of the cocktail party problem in the context of animal acoustic communication. (PsycINFO Database Record (c) 2008 APA, all rights reserved) Journal of Comparative Psychology - Vol 122, Iss 3 2008 Bee, Mark A.; Micheyl, Christophe American Psychological Association 10.1037/0735-7036.122.3.235 http://content.apa.org/journals/com/122/3/252 http://content.apa.org/journals/com/122/3/252 A characteristic feature of hearing systems is their ability to resolve both fast and subtle amplitude modulations of acoustic signals. This applies also to grasshoppers, which for mate identification rely mainly on the characteristic temporal patterns of their communication signals. Usually the signals arriving at a receiver are contaminated by various kinds of noise. In addition to extrinsic noise, intrinsic noise caused by stochastic processes within the nervous system contributes to making signal recognition a difficult task. The authors asked to what degree intrinsic noise affects temporal resolution and, particularly, the discrimination of similar acoustic signals. This study aims at exploring the neuronal basis for sexual selection, which depends on exploiting subtle differences between basically similar signals. Applying a metric, by which the similarities of spike trains can be assessed, the authors investigated how well the communication signals of different individuals of the same species could be discriminated and correctly classified based on the responses of auditory neurons. This spike train metric yields clues to the optimal temporal resolution with which spike trains should be evaluated. (PsycINFO Database Record (c) 2008 APA, all rights reserved) Journal of Comparative Psychology - Vol 122, Iss 3 2008 Ronacher, Bernhard; Wohlgemuth, Sandra; Vogel, Astrid; Krahe, Rüdiger American Psychological Association 10.1037/0735-7036.122.3.252 http://content.apa.org/journals/com/122/3/264 http://content.apa.org/journals/com/122/3/264 This study investigated the cues used by female barking treefrogs, Hyla gratiosa, to assess distances to potential mates. Eight-speaker playback experiments were used to demonstrate that distance affects female choice in complex acoustic environments and to test 3 possible cues that females might use to assess distance: (a) degradation in spectral and temporal cues of calls, (b) relative call amplitude at the female's location, and (c) the rate at which the amplitude of calls increases as a female approaches a calling male. All 3 hypotheses were refuted, suggesting that females use a more complex mechanism, such as triangulation, to assess distance. Females preferred speakers with greater source amplitudes even when they had to travel further to reach those speakers. Determination of source amplitude is possible only if females can assess independently both the distance to sound sources and the amplitude of calls at the females' location. Hence, anuran amphibians may possess greater cognitive abilities than are generally attributed to them. (PsycINFO Database Record (c) 2008 APA, all rights reserved) Journal of Comparative Psychology - Vol 122, Iss 3 2008 Murphy, Christopher G. American Psychological Association 10.1037/0735-7036.122.3.264 http://content.apa.org/journals/com/122/3/274 http://content.apa.org/journals/com/122/3/274 Analysis of acoustic interactions between animals in active choruses is complex because of the large numbers of individuals present, their high calling rates, and the considerable numbers of vocalizations that either overlap or show close temporal alternation. The authors describe a methodology for recording chorus activity in bullfrogs (Rana catesbeiana) using multiple, closely spaced acoustic sensors that provide simultaneous estimates of sound direction and sound characteristics. This method provides estimates of location of individual callers, even under conditions of call overlap. This is a useful technique for understanding the complexity of the acoustic scene faced by animals vocalizing in groups. (PsycINFO Database Record (c) 2008 APA, all rights reserved) Journal of Comparative Psychology - Vol 122, Iss 3 2008 Megela Simmons, Andrea; Simmons, James A.; Bates, Mary E. American Psychological Association 10.1037/0735-7036.122.3.274 http://content.apa.org/journals/com/122/3/283 http://content.apa.org/journals/com/122/3/283 Male gray treefrogs call to attract females under challenging acoustic conditions. At higher chorus densities, there is considerable background noise and a good chance that a male's calls will often be overlapped by calls of other individuals. Call overlap may reduce the probability of mating because females prefer calls with internal pulse structure that is not obscured. With increases in acoustic stimulation, males lengthen call duration while simultaneously reducing call rate such that "pulse effort" changes little. In our study, we tested the "interference risk hypothesis." This proposes that males change call duration so that, on average, there will be a sufficient number of pulses and interpulse intervals clear of acoustic interference per call to attract a female. However, female choice experiments employing call alternatives of different durations, rates, intensity levels, and degrees of call overlap refuted this hypothesis. Our results leave open the possibilities that the dynamic shift in the two components of pulse effort are related to the problem of call detection in a noisy environment or are responses by males to the perceived threat of competition for females. (PsycINFO Database Record (c) 2008 APA, all rights reserved) Journal of Comparative Psychology - Vol 122, Iss 3 2008 Schwartz, Joshua J.; Brown, Robert; Turner, Sarah; Dushaj, Kola; Castano, Marisol American Psychological Association 10.1037/0735-7036.122.3.283 http://content.apa.org/journals/com/122/3/289 http://content.apa.org/journals/com/122/3/289 Synchronous interactions arise in various animal species that rhythmically broadcast acoustic, vibratory, and visual signals. These interactions are characterized by a coincidence in both rate and phase of the rhythms of neighboring signalers. Theory predicts several ways in which synchronized rhythms may specifically benefit the interacting signalers. However, synchrony may also arise as an emergent property, a default phenomenon that is neither preferred by conspecific receivers evaluating the signals nor advantageous to the signalers themselves. Here, we examine several well-studied cases of acoustic synchrony in Neoconocephalus katydids (Orthoptera: Tettigoniidae), a New World genus wherein males broadcast loud advertisement songs. We report that call synchrony found in N. spiza and N. nebrascensis results from two rather different mechanisms of rhythm adjustment. Moreover, synchrony in the former species appears to represent an incidental byproduct of signal competition between evenly matched males, whereas in the latter species synchrony functions as a specific adaptation in which cooperating males ensure that critical call features can be perceived by females. We discuss the separate evolutionary trajectories that may have led to similar outcomes, synchronous chorusing by advertising males, in these closely related species. (PsycINFO Database Record (c) 2008 APA, all rights reserved) Journal of Comparative Psychology - Vol 122, Iss 3 2008 Greenfield, Michael D.; Schul, Johannes American Psychological Association 10.1037/0735-7036.122.3.289 http://content.apa.org/journals/com/122/3/298 http://content.apa.org/journals/com/122/3/298 Studies of acoustic interactions in animal groups, such as chorusing insects, anurans, and birds, have been invaluable in showing how cooperation and competition shape signal structure and use. The begging calls of nestling birds are ideal for such studies, because they function both as a cooperative signals of the brood's needs and as competitive signals for parental allocation within the brood. Nonetheless, studies of acoustic interactions among nestlings are rare. Here we review our work on acoustic interactions in nestling tree swallows (Tachycineta bicolor), especially how calls are used in competition for parental feedings. Nestlings attracted parental attention and responded to acoustic interference mainly by increasing call output. However, nestlings also gave more similar calls when they called together and decreased their call bandwidth when exposed to elevated noise. We suggest that these competitive uses of calls might intensify the cooperative brood signal, affecting both parental provisioning and vocal development. Given their tremendous variation across species, begging calls offer promising opportunities for developmental and comparative studies of acoustic signaling. (PsycINFO Database Record (c) 2008 APA, all rights reserved) Journal of Comparative Psychology - Vol 122, Iss 3 2008 Horn, Andrew G.; Leonard, Marty L. American Psychological Association 10.1037/0735-7036.122.3.298 http://content.apa.org/journals/com/122/3/305 http://content.apa.org/journals/com/122/3/305 In large social groups acoustic communication signals are prone to signal masking by conspecific sounds. Bottlenose dolphins (Tursiops truncatus) use highly distinctive signature whistles that counter masking effects. However, they can be found in very large groups where masking by conspecific sounds may become unavoidable. In this study we used passive acoustic localization to investigate how whistle rates of wild bottlenose dolphins change in relation to group size and behavioral context. We found that individual whistle rates decreased when group sizes got larger. Dolphins displayed higher whistle rates in contexts when group members were more dispersed as in socializing and in nonpolarized movement than during coordinated surface travel. Using acoustic localization showed that many whistles were produced by groups nearby and not by our focal group. Thus, previous studies based on single hydrophone recordings may have been overestimating whistle rates. Our results show that although bottlenose dolphins whistle more in social situations they also decrease vocal output in large groups where the potential for signal masking by other dolphin whistles increases. (PsycINFO Database Record (c) 2008 APA, all rights reserved) Journal of Comparative Psychology - Vol 122, Iss 3 2008 Quick, Nicola J.; Janik, Vincent M. American Psychological Association 10.1037/0735-7036.122.3.305 http://content.apa.org/journals/com/122/3/312 http://content.apa.org/journals/com/122/3/312 The complexity of a social group may influence the vocal behavior of group members. Recent evidence in Carolina chickadees, Poecile carolinensis, indicated that one component of social complexity, group size, influenced the complexity of the "chick-a-dee" call, a vocalization functioning in social cohesion. Individuals in larger social groups used calls with greater information than did individuals in smaller social groups. Here, the authors review this earlier work, and describe a recent study indicating that social interactions between females and males within female-male pairs of chickadees were associated with rates of chick-a-dee call production in the males. Together, these studies suggest that the nature and complexity of social interactions among members of chickadee social groups influence chick-a-dee calling behavior. (PsycINFO Database Record (c) 2008 APA, all rights reserved) Journal of Comparative Psychology - Vol 122, Iss 3 2008 Freeberg, Todd M.; Harvey, Ellen M. American Psychological Association 10.1037/0735-7036.122.3.312 http://content.apa.org/journals/com/122/3/319 http://content.apa.org/journals/com/122/3/319 The classic evidence for vocal production learning involves imitation of novel, often anthropogenic sounds. Among mammals, this has been reported for dolphins, elephants, harbor seals, and humans. A broader taxonomic distribution has been reported for vocal convergence, where the acoustic properties of calls from different individuals converge when they are housed together in captivity or form social bonds in the wild. Vocal convergence has been demonstrated for animals as diverse as songbirds, parakeets, hummingbirds, bats, elephants, cetaceans, and primates. For most species, call convergence is thought to reflect a group-distinctive identifier, with shared calls reflecting and strengthening social bonds. A ubiquitous function for vocal production learning that is starting to receive attention involves modifying signals to improve communication in a noisy channel. Pooling data on vocal imitation, vocal convergence, and compensation for noise suggests a wider taxonomic distribution of vocal production learning among mammals than has been generally appreciated. The wide taxonomic distribution of this evidence for vocal production learning suggests that perhaps more of the neural underpinnings for vocal production learning are in place in mammals than is usually recognized. (PsycINFO Database Record (c) 2008 APA, all rights reserved) Journal of Comparative Psychology - Vol 122, Iss 3 2008 Tyack, Peter L. American Psychological Association 10.1037/a0013087 http://content.apa.org/journals/com/122/3/332 http://content.apa.org/journals/com/122/3/332 The study of communication in all its forms has come a long way conceptually and methodologically in the last decade, and this is more true of auditory communication than of the other sensory modalities. In considering the issues involved in communication, it is clear that simple dyadic considerations leave out too many important issues. Background noise, eavesdropping, and deception represent important neglected factors driving the evolution of the mechanisms, development, and ecological adaptiveness of communicatory processes in natural environments. (PsycINFO Database Record (c) 2008 APA, all rights reserved) Journal of Comparative Psychology - Vol 122, Iss 3 2008 Burghardt, Gordon M. American Psychological Association 10.1037/a0013124