Comparative perspectives on primate and human communication have been marked by two equally unten... more Comparative perspectives on primate and human communication have been marked by two equally untenable extremes: either language is special, without significant evolutionary precedent, or it is not: it is continuous in most aspects with animal communication systems. In this article we outline fertile common ground and point towards synthetic approaches that can unify the study of human and animal communication. First, we suggest that humans have a large suite of perceptual biases that introduce a pressure for languages to be 'functionally deployable'. We suggest that human languages are shaped by this pressure, along with previously established pressures to be both learnable and compressible, and domain-general constraints like memory. Collectively, we suggest that non-arbitrary structure-function relationships are crucial for the deployment of language and communication systems more generally.
Liveright) famously reported a bias in people's choice of nonsense words as labels for novel obje... more Liveright) famously reported a bias in people's choice of nonsense words as labels for novel objects, pointing to possible naïve expectations about language structure. Two accounts have been offered to explain this bias, one focusing on the visuomotor effects of different vowel forms and the other focusing on variation in the acoustic structure and perceptual quality of different consonants. To date, evidence in support of both effects is mixed. Moreover, the veracity of either effect has often been doubted due to perceived limitations in methodologies and stimulus materials. A novel word-construction experiment is presented to test both proposed effects using randomized word-and image-generation techniques to address previous methodological concerns. Results show that participants are sensitive to both vowel and consonant content, constructing novel words of relatively sonorant consonants and rounded vowels to label curved object images, and of relatively plosive consonants and nonrounded vowels to label jagged object images. Results point to additional influences on word construction potentially related to the articulatory affordances or constraints accompanying different word forms.
Researchers typically define animal signaling as morphology or behavior specialized for transmitt... more Researchers typically define animal signaling as morphology or behavior specialized for transmitting encoded information from a signaler to a perceiver. Although intuitively appealing, this conception is inherently metaphorical and leaves concepts of both information and encoding undefined. To justify relying on the information construct, theorists often appeal to Shannon and Weaver's quantitative definition. The two approaches are, however, fundamentally at odds. The predominant definition of animal signaling is thus untenable, which has a number of undesirable consequences for both theory and practice in the field. Theoretical problems include conceptual circularity and running afoul of fundamental evolutionary principles. Problems in empirical work include that research is often grounded in abstractions such as signal honesty and semanticity, and thereby distracted from more basic and concrete factors shaping communication. A revised definition is therefore proposed, making influence rather than transmission of encoded information the central function of animal signaling. This definition is conceptually sound, empirically testable, and inclusive, yet bounded. Implications are considered in both theoretical and empirical domains.
The willingness to utilise caves as shelters is held to have been important to early humans but d... more The willingness to utilise caves as shelters is held to have been important to early humans but dependent on pyrotechnology. Despite anecdotal evidence that non-human primates will also exploit caves there has as yet been no detailed account of such exploitation or of the reasons underlying it. Here we provide the first such data, on the frequency and patterning of the use of an underground cave system by baboons (Papio hamadryas)-and show that usage is determined, at least in part, by above-ground temperatures.
Philosophical Transactions of The Royal Society B: Biological Sciences, 2007
The social brain hypothesis is a well-accepted and well-supported evolutionary theory of enlarged... more The social brain hypothesis is a well-accepted and well-supported evolutionary theory of enlarged brain size in the non-human primates. Nevertheless, it tends to emphasize an anthropocentric view of social life and cognition. This often leads to confusion between ultimate and proximate mechanisms, and an over-reliance on a Cartesian, narratively structured view of the mind and social life, which in turn lead to views of social complexity that are congenial to our views of ourselves, rather than necessarily representative of primate social worlds. In this paper, we argue for greater attention to embodied and distributed theories of cognition, which get us away from current fixations on 'theory of mind' and other high-level anthropocentric constructions, and allow for the generation of testable hypotheses that combine neurobiology, psychology and behaviour in a mutually reinforcing manner.
Contact" calls are widespread in social mammals and birds, but the proximate factors that motivat... more Contact" calls are widespread in social mammals and birds, but the proximate factors that motivate call production and mediate their contact function remain poorly specified. Field study of chacma baboons (Papio cynocephalus ursinus) revealed that contact barks in adult females were motivated by separation both from the group at large and from their dependent infants. A variety of social and ecological factors affect the probability of separation from either one or both. Results of simultaneous observations and a playback experiment indicate that the contact function of calling between mothers and infants was mediated by occasional maternal retrieval rather than coordinated call exchange. Mothers recognized the contact barks of their own infants and often were strongly motivated to locate them. However, mothers did not produce contact barks in reply unless they themselves were at risk of becoming separated from the group.
Journal of The Acoustical Society of America, 2004
This study quantifies sex differences in the acoustic structure of vowel-like grunt vocalizations... more This study quantifies sex differences in the acoustic structure of vowel-like grunt vocalizations in baboons Í‘Papio spp.Í’ and tests the basic perceptual discriminability of these differences to baboon listeners. Acoustic analyses were performed on 1028 grunts recorded from 27 adult baboons Í‘11 males and 16 femalesÍ’ in southern Africa, focusing specifically on the fundamental frequency (F 0 ) and formant frequencies. The mean F 0 and the mean frequencies of the first three formants were all significantly lower in males than they were in females, more dramatically so for F 0 . Experiments using standard psychophysical procedures subsequently tested the discriminability of adult male and adult female grunts. After learning to discriminate the grunt of one male from that of one female, five baboon subjects subsequently generalized this discrimination both to new call tokens from the same individuals and to grunts from novel males and females. These results are discussed in the context of both the possible vocal anatomical basis for sex differences in call structure and the potential perceptual mechanisms involved in their processing by listeners, particularly as these relate to analogous issues in human speech production and perception.
His interests are in the intersection and evolution of social behavior, communication, and cognit... more His interests are in the intersection and evolution of social behavior, communication, and cognition. He combines detailed acoustic analyses with field tests of specific hypotheses about signal structure and function. His current research is focused on the vocal communication of baboons.
Journal of The Acoustical Society of America, 1998
The importance of individual identity and kinship has been demonstrated in the social behavior of... more The importance of individual identity and kinship has been demonstrated in the social behavior of many nonhuman primates, with some evidence suggesting that individually distinctive acoustic features are present in their vocalizations as well. In order to systematically test whether acoustic cues to identity are reliably present across the vocal repertoire of rhesus monkeys (Macaca mulatta), we examined coos, grunts, and noisy screams produced by adult females of two free-ranging groups. First, acoustic analyses were used to characterize spectral patterning, the fundamental frequency, and temporal characteristics of these three distinct call types. Vocalizations were then classified by caller identity, based on discriminant function analyses. Results showed that coos (rich, harmonically structured sounds) were markedly more distinctive by caller than were either grunts or noisy screams, and that spectral-patterning measures related to vocal tract filtering effects were the most reliable markers of individual identity. Grunts (pulsed, noisy calls) were classified at lower, but above-chance rates and spectral patterning cues were again critical in this sorting. Noisy screams (continuous, broadband noise bursts that could include a high-frequency, periodic component) could not be reliably sorted by caller. Playback experiments conducted with the screams showed no response differences when listening animals heard vocalizations produced by kin or nonkin individuals. This result was strikingly different from the corresponding outcome of a previous test with coo calls, but consistent with the acoustic analysis. Implications of these findings for vocal production mechanisms in nonhuman primates and previous studies of rhesus monkey vocalizations are discussed.
We present results of a 10-year study of free-ranging gray-footed chacma baboons (Papio ursinus g... more We present results of a 10-year study of free-ranging gray-footed chacma baboons (Papio ursinus griseipes) in the Okavango Delta of Botswana. The majority of deaths among adult females and juveniles were due to predation, while infants were more likely to die of infanticide. There were strong seasonal effects on birth and mortality, with the majority of conceptions occurring during the period of highest rainfall. Mortality due to predation and infanticide was highest during the 3-mo period when flooding was at its peak, when the group was more scattered and constrained to move along predictable routes.
There have been several previous studies of the loud, long-distance call of chimpanzees, termed a... more There have been several previous studies of the loud, long-distance call of chimpanzees, termed a 'pant hoot'. Some have explored the possibility that there are acoustically distinct subtypes of pant hoots that communicate to distant listeners different information about the caller's behaviour, or ecological and social circumstances. However, results to date have been either inconclusive or conflicting. To help resolve these issues, we undertook research on pant hoots produced by wild chimpanzees, Pan troglodytes schwienfurthii, living in the Budongo Forest, Uganda. In this paper, we report the results of acoustic analysis of 201 pant hoot series produced by seven adult males. Principal components analysis (PCA) was used to identify key dimensions of structural variation in the calls, which were then related to a large set of behavioural, social and ecological variables associated with call production. Although there was little evidence for distinctive pant hoot subtypes according to many of the social and ecological dimensions traditionally recognized, a number of significant patterns were identified. Specifically, pant hoots were produced with higher probability at abundant food sources, and they were more likely to contain a 'letdown' phase when produced in specific behavioural contexts, such as travelling and upon arrival at a food source. In addition, pant hoots produced while travelling along the ground in small parties prior to joining-up with other community members were consistently different from all other pant hoots, varying reliably in the fundamental frequency of their build-up elements, the tonal quality of climax elements and in the presence of a let-down phase. We discuss the possible mechanistic bases for these differences in the pattern of calling and detailed spectral structure of the calls and consider the implications for referential communication.
Predation, food competition, and infanticide all negatively impact female reproductive success. F... more Predation, food competition, and infanticide all negatively impact female reproductive success. Female dominance rank may mitigate these effects, if competitive exclusion allows high-ranking females to gain priority of access to critical food resources. It may also exacerbate them, if low-ranking females are forced to feed or rest in marginal habitats where they are at increased risk. In this chapter, we present data on reproduction, mortality, and female reproductive success from a 10-year study of free-ranging chacma baboons (Papio hamadryas ursinus) in the Okavango Delta of Botswana and examine the influence of predation, infanticide, and dominance rank on female reproductive success. Predation appeared to be the cause of most deaths among adult females and juveniles, whereas infanticide was the most likely cause of deaths among infants. Seasonality strongly affected both births and mortality: The majority of conceptions occurred during the period of highest rainfall. Mortality due to predation and infanticide was highest during the 3-month period when flooding was at its peak, most likely because the group was more constrained to move along predictable routes during this time. Those reproductive parameters most likely to be associated with superior competitive ability-interbirth interval and infant growth rates-conferred a slight fitness advantage on high-ranking females. This fitness advantage was counterbalanced, however, by the effects of infanticide and predation. Infanticide affected high- and low-ranking females more than middle-ranking females, while predation affected females of all ranks relatively equally. As a result, there were few rank-related differences in estimated female lifetime reproductive success.
Recent evidence from acoustic analysis and playback experiments indicates that adult female rhesu... more 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.
animal communication animal signals information information transmission language manipulation me... more animal communication animal signals information information transmission language manipulation meaning sensory exploitation sexual selection Animal communication studies often use analogies to human language and related constructs such as information encoding and transfer. This commonality is evident even when research goals are very different, for example when primate vocalizations are proposed to have word-like meaning, or sexually selected signals are proposed to convey information about a signaller's underlying quality. We consider some of the ambiguities and limitations inherent in such informational approaches to animal communication as background to advocating alternatives. The alternatives eschew language-based metaphors and broader informational constructs and focus instead on concrete details of signal design as they reflect and interact with established sensory, physiological and psychological processes that support signalling and responding in listeners. The alternatives we advocate also explicitly acknowledge the different roles and often divergent interests of signallers and perceivers that can yield fundamental asymmetries in signalling interactions, and they therefore shift the focus of interpretations of animal communication from informing others to influencing others. Ó
Mammalian females are strongly attracted to infants and interact regularly with them. Female babo... more Mammalian females are strongly attracted to infants and interact regularly with them. Female baboons make persistent attempts to touch, nuzzle, smell and inspect other females' infants, but do not hold them for long periods, carry them, or provide other kinds of care for them. Mothers generally tolerate these interactions, but never initiate them. The function of these brief alloparental interactions is not well understood. Infant handling might be a form of reproductive competition if females' interest in infants causes distress to mothers or harm to their infants. Alternatively, infant handling might be the product of selection for appropriate maternal care if females who are highly responsive to infants are the most successful mothers. We test several predictions derived from these hypotheses with data collected in a free-ranging group of baboons (Papio cynocephalus ursinus) in the Moremi Reserve of Botswana. Infants were most attractive when they were very young. Mothers of young infants were approached by other adult females on average once every 6 min, and other females attempted to handle their infants approximately once every 9 min. By the time infants were a year old, their mothers were being approached only once every 30 min and infants were being handled only once every 5 h. Females were more strongly attracted to other females' infants when they had young infants of their own, and their interest in other females' infants declined as their own infants matured. Females seemed to be equally attracted to all infants, but had greater access to offspring of their relatives and subordinate females. Females nearly always grunted as they handled infants. As in other contexts grunts are a reliable predictive signal that non-aggressive behavior will follow, the use of grunts before handling suggests that these interactions were not a form of deliberate harassment.
Comparative perspectives on primate and human communication have been marked by two equally unten... more Comparative perspectives on primate and human communication have been marked by two equally untenable extremes: either language is special, without significant evolutionary precedent, or it is not: it is continuous in most aspects with animal communication systems. In this article we outline fertile common ground and point towards synthetic approaches that can unify the study of human and animal communication. First, we suggest that humans have a large suite of perceptual biases that introduce a pressure for languages to be 'functionally deployable'. We suggest that human languages are shaped by this pressure, along with previously established pressures to be both learnable and compressible, and domain-general constraints like memory. Collectively, we suggest that non-arbitrary structure-function relationships are crucial for the deployment of language and communication systems more generally.
Liveright) famously reported a bias in people's choice of nonsense words as labels for novel obje... more Liveright) famously reported a bias in people's choice of nonsense words as labels for novel objects, pointing to possible naïve expectations about language structure. Two accounts have been offered to explain this bias, one focusing on the visuomotor effects of different vowel forms and the other focusing on variation in the acoustic structure and perceptual quality of different consonants. To date, evidence in support of both effects is mixed. Moreover, the veracity of either effect has often been doubted due to perceived limitations in methodologies and stimulus materials. A novel word-construction experiment is presented to test both proposed effects using randomized word-and image-generation techniques to address previous methodological concerns. Results show that participants are sensitive to both vowel and consonant content, constructing novel words of relatively sonorant consonants and rounded vowels to label curved object images, and of relatively plosive consonants and nonrounded vowels to label jagged object images. Results point to additional influences on word construction potentially related to the articulatory affordances or constraints accompanying different word forms.
Researchers typically define animal signaling as morphology or behavior specialized for transmitt... more Researchers typically define animal signaling as morphology or behavior specialized for transmitting encoded information from a signaler to a perceiver. Although intuitively appealing, this conception is inherently metaphorical and leaves concepts of both information and encoding undefined. To justify relying on the information construct, theorists often appeal to Shannon and Weaver's quantitative definition. The two approaches are, however, fundamentally at odds. The predominant definition of animal signaling is thus untenable, which has a number of undesirable consequences for both theory and practice in the field. Theoretical problems include conceptual circularity and running afoul of fundamental evolutionary principles. Problems in empirical work include that research is often grounded in abstractions such as signal honesty and semanticity, and thereby distracted from more basic and concrete factors shaping communication. A revised definition is therefore proposed, making influence rather than transmission of encoded information the central function of animal signaling. This definition is conceptually sound, empirically testable, and inclusive, yet bounded. Implications are considered in both theoretical and empirical domains.
The willingness to utilise caves as shelters is held to have been important to early humans but d... more The willingness to utilise caves as shelters is held to have been important to early humans but dependent on pyrotechnology. Despite anecdotal evidence that non-human primates will also exploit caves there has as yet been no detailed account of such exploitation or of the reasons underlying it. Here we provide the first such data, on the frequency and patterning of the use of an underground cave system by baboons (Papio hamadryas)-and show that usage is determined, at least in part, by above-ground temperatures.
Philosophical Transactions of The Royal Society B: Biological Sciences, 2007
The social brain hypothesis is a well-accepted and well-supported evolutionary theory of enlarged... more The social brain hypothesis is a well-accepted and well-supported evolutionary theory of enlarged brain size in the non-human primates. Nevertheless, it tends to emphasize an anthropocentric view of social life and cognition. This often leads to confusion between ultimate and proximate mechanisms, and an over-reliance on a Cartesian, narratively structured view of the mind and social life, which in turn lead to views of social complexity that are congenial to our views of ourselves, rather than necessarily representative of primate social worlds. In this paper, we argue for greater attention to embodied and distributed theories of cognition, which get us away from current fixations on 'theory of mind' and other high-level anthropocentric constructions, and allow for the generation of testable hypotheses that combine neurobiology, psychology and behaviour in a mutually reinforcing manner.
Contact" calls are widespread in social mammals and birds, but the proximate factors that motivat... more Contact" calls are widespread in social mammals and birds, but the proximate factors that motivate call production and mediate their contact function remain poorly specified. Field study of chacma baboons (Papio cynocephalus ursinus) revealed that contact barks in adult females were motivated by separation both from the group at large and from their dependent infants. A variety of social and ecological factors affect the probability of separation from either one or both. Results of simultaneous observations and a playback experiment indicate that the contact function of calling between mothers and infants was mediated by occasional maternal retrieval rather than coordinated call exchange. Mothers recognized the contact barks of their own infants and often were strongly motivated to locate them. However, mothers did not produce contact barks in reply unless they themselves were at risk of becoming separated from the group.
Journal of The Acoustical Society of America, 2004
This study quantifies sex differences in the acoustic structure of vowel-like grunt vocalizations... more This study quantifies sex differences in the acoustic structure of vowel-like grunt vocalizations in baboons Í‘Papio spp.Í’ and tests the basic perceptual discriminability of these differences to baboon listeners. Acoustic analyses were performed on 1028 grunts recorded from 27 adult baboons Í‘11 males and 16 femalesÍ’ in southern Africa, focusing specifically on the fundamental frequency (F 0 ) and formant frequencies. The mean F 0 and the mean frequencies of the first three formants were all significantly lower in males than they were in females, more dramatically so for F 0 . Experiments using standard psychophysical procedures subsequently tested the discriminability of adult male and adult female grunts. After learning to discriminate the grunt of one male from that of one female, five baboon subjects subsequently generalized this discrimination both to new call tokens from the same individuals and to grunts from novel males and females. These results are discussed in the context of both the possible vocal anatomical basis for sex differences in call structure and the potential perceptual mechanisms involved in their processing by listeners, particularly as these relate to analogous issues in human speech production and perception.
His interests are in the intersection and evolution of social behavior, communication, and cognit... more His interests are in the intersection and evolution of social behavior, communication, and cognition. He combines detailed acoustic analyses with field tests of specific hypotheses about signal structure and function. His current research is focused on the vocal communication of baboons.
Journal of The Acoustical Society of America, 1998
The importance of individual identity and kinship has been demonstrated in the social behavior of... more The importance of individual identity and kinship has been demonstrated in the social behavior of many nonhuman primates, with some evidence suggesting that individually distinctive acoustic features are present in their vocalizations as well. In order to systematically test whether acoustic cues to identity are reliably present across the vocal repertoire of rhesus monkeys (Macaca mulatta), we examined coos, grunts, and noisy screams produced by adult females of two free-ranging groups. First, acoustic analyses were used to characterize spectral patterning, the fundamental frequency, and temporal characteristics of these three distinct call types. Vocalizations were then classified by caller identity, based on discriminant function analyses. Results showed that coos (rich, harmonically structured sounds) were markedly more distinctive by caller than were either grunts or noisy screams, and that spectral-patterning measures related to vocal tract filtering effects were the most reliable markers of individual identity. Grunts (pulsed, noisy calls) were classified at lower, but above-chance rates and spectral patterning cues were again critical in this sorting. Noisy screams (continuous, broadband noise bursts that could include a high-frequency, periodic component) could not be reliably sorted by caller. Playback experiments conducted with the screams showed no response differences when listening animals heard vocalizations produced by kin or nonkin individuals. This result was strikingly different from the corresponding outcome of a previous test with coo calls, but consistent with the acoustic analysis. Implications of these findings for vocal production mechanisms in nonhuman primates and previous studies of rhesus monkey vocalizations are discussed.
We present results of a 10-year study of free-ranging gray-footed chacma baboons (Papio ursinus g... more We present results of a 10-year study of free-ranging gray-footed chacma baboons (Papio ursinus griseipes) in the Okavango Delta of Botswana. The majority of deaths among adult females and juveniles were due to predation, while infants were more likely to die of infanticide. There were strong seasonal effects on birth and mortality, with the majority of conceptions occurring during the period of highest rainfall. Mortality due to predation and infanticide was highest during the 3-mo period when flooding was at its peak, when the group was more scattered and constrained to move along predictable routes.
There have been several previous studies of the loud, long-distance call of chimpanzees, termed a... more There have been several previous studies of the loud, long-distance call of chimpanzees, termed a 'pant hoot'. Some have explored the possibility that there are acoustically distinct subtypes of pant hoots that communicate to distant listeners different information about the caller's behaviour, or ecological and social circumstances. However, results to date have been either inconclusive or conflicting. To help resolve these issues, we undertook research on pant hoots produced by wild chimpanzees, Pan troglodytes schwienfurthii, living in the Budongo Forest, Uganda. In this paper, we report the results of acoustic analysis of 201 pant hoot series produced by seven adult males. Principal components analysis (PCA) was used to identify key dimensions of structural variation in the calls, which were then related to a large set of behavioural, social and ecological variables associated with call production. Although there was little evidence for distinctive pant hoot subtypes according to many of the social and ecological dimensions traditionally recognized, a number of significant patterns were identified. Specifically, pant hoots were produced with higher probability at abundant food sources, and they were more likely to contain a 'letdown' phase when produced in specific behavioural contexts, such as travelling and upon arrival at a food source. In addition, pant hoots produced while travelling along the ground in small parties prior to joining-up with other community members were consistently different from all other pant hoots, varying reliably in the fundamental frequency of their build-up elements, the tonal quality of climax elements and in the presence of a let-down phase. We discuss the possible mechanistic bases for these differences in the pattern of calling and detailed spectral structure of the calls and consider the implications for referential communication.
Predation, food competition, and infanticide all negatively impact female reproductive success. F... more Predation, food competition, and infanticide all negatively impact female reproductive success. Female dominance rank may mitigate these effects, if competitive exclusion allows high-ranking females to gain priority of access to critical food resources. It may also exacerbate them, if low-ranking females are forced to feed or rest in marginal habitats where they are at increased risk. In this chapter, we present data on reproduction, mortality, and female reproductive success from a 10-year study of free-ranging chacma baboons (Papio hamadryas ursinus) in the Okavango Delta of Botswana and examine the influence of predation, infanticide, and dominance rank on female reproductive success. Predation appeared to be the cause of most deaths among adult females and juveniles, whereas infanticide was the most likely cause of deaths among infants. Seasonality strongly affected both births and mortality: The majority of conceptions occurred during the period of highest rainfall. Mortality due to predation and infanticide was highest during the 3-month period when flooding was at its peak, most likely because the group was more constrained to move along predictable routes during this time. Those reproductive parameters most likely to be associated with superior competitive ability-interbirth interval and infant growth rates-conferred a slight fitness advantage on high-ranking females. This fitness advantage was counterbalanced, however, by the effects of infanticide and predation. Infanticide affected high- and low-ranking females more than middle-ranking females, while predation affected females of all ranks relatively equally. As a result, there were few rank-related differences in estimated female lifetime reproductive success.
Recent evidence from acoustic analysis and playback experiments indicates that adult female rhesu... more 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.
animal communication animal signals information information transmission language manipulation me... more animal communication animal signals information information transmission language manipulation meaning sensory exploitation sexual selection Animal communication studies often use analogies to human language and related constructs such as information encoding and transfer. This commonality is evident even when research goals are very different, for example when primate vocalizations are proposed to have word-like meaning, or sexually selected signals are proposed to convey information about a signaller's underlying quality. We consider some of the ambiguities and limitations inherent in such informational approaches to animal communication as background to advocating alternatives. The alternatives eschew language-based metaphors and broader informational constructs and focus instead on concrete details of signal design as they reflect and interact with established sensory, physiological and psychological processes that support signalling and responding in listeners. The alternatives we advocate also explicitly acknowledge the different roles and often divergent interests of signallers and perceivers that can yield fundamental asymmetries in signalling interactions, and they therefore shift the focus of interpretations of animal communication from informing others to influencing others. Ó
Mammalian females are strongly attracted to infants and interact regularly with them. Female babo... more Mammalian females are strongly attracted to infants and interact regularly with them. Female baboons make persistent attempts to touch, nuzzle, smell and inspect other females' infants, but do not hold them for long periods, carry them, or provide other kinds of care for them. Mothers generally tolerate these interactions, but never initiate them. The function of these brief alloparental interactions is not well understood. Infant handling might be a form of reproductive competition if females' interest in infants causes distress to mothers or harm to their infants. Alternatively, infant handling might be the product of selection for appropriate maternal care if females who are highly responsive to infants are the most successful mothers. We test several predictions derived from these hypotheses with data collected in a free-ranging group of baboons (Papio cynocephalus ursinus) in the Moremi Reserve of Botswana. Infants were most attractive when they were very young. Mothers of young infants were approached by other adult females on average once every 6 min, and other females attempted to handle their infants approximately once every 9 min. By the time infants were a year old, their mothers were being approached only once every 30 min and infants were being handled only once every 5 h. Females were more strongly attracted to other females' infants when they had young infants of their own, and their interest in other females' infants declined as their own infants matured. Females seemed to be equally attracted to all infants, but had greater access to offspring of their relatives and subordinate females. Females nearly always grunted as they handled infants. As in other contexts grunts are a reliable predictive signal that non-aggressive behavior will follow, the use of grunts before handling suggests that these interactions were not a form of deliberate harassment.
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Papers by Drew Rendall