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The complex human environment results in a hard-to-bridge gap between human and animal studies on general cognitive abilities (g; colloquially often referred to as “intelligence”). Pet dogs are adapted to our environment, but a convincing demonstration ofgis missing. Exploratory and confirmatory factor analyses on seven tasks revealed a hierarchical structure with two cognitive domains (problem solving, learning) and an overarchingcanine g. Age did not affect the structure.Canine gwas negatively linked to age, height, and the owner’s emotional attitude but positively to training level, activity/excitability trait, experienced trauma and normal body condition. The longitudinal analyses over three years differentiated three main trajectory clusters: declining, stable, improving. The diversity of ageing phenotypes supports dogs’ translational value ingfactor and ageing research.One-Sentence SummaryThecanine gfactor is linked to age, height, training level, personality, body condition, and owner’s attitude.

Separation related disorder in dogs is a multi-faceted phenomenon. Dogs can react to the absence of their owner due to different inner states such as fear, panic or frustration. We hypothesized that dogs that are prone to frustration or fearfulness in other contexts would show a different behavioral response to separation from the owner. We investigated the association between inner states in different contexts and separation behaviors by combining a questionnaire with a separation test. Fear-related questionnaire components were rather associated with whining and the absence of barking. Dogs that received higher scores in the demanding component of the questionnaire, which might be in association of the frustration threshold of the dog, barked more and were more likely to scratch the door. Finally, dogs that were more prone to phobic reactions whined somewhat more and tried to escape. We provide empirical support for the assumption that separation-related behavioral responses of dogs might be triggered by different emotions.

Dogs, similarly to infants, have been shown to be sensitive to human speech especially when it is directed to them. However, what essential acoustic, paralinguistic and lexical features of dog-directed speech are responsible for this preference in dogs is largely unknown. In the present study, generalized dog (DDS)-, infant (IDS)- and adult (ADS)-directed speech stimuli were created by using prerecorded sentences of multiple female speakers and these composite (averaged) stimuli were then manipulated to control for linguistic content as well as to equalize their mean fundamental frequency (F0) value. All three possible pairwise combinations of these acoustic stimuli were then presented to adult dogs in a two-way choice task where two identical target objects were used to indicate the sound sources. We found a significant preference towards the target object associated with DDS in the DDS versus ADS condition and suggest that, for dogs, mean F0 difference is not essential for DDS–ADS discrimination. However, we did not find evidence of selection bias when IDS was simultaneously presented either with DDS or ADS. Interestingly, our results also showed that dogs were more willing to approach the ‘more prosodic’ location (i.e. DDS or IDS versus ADS) when the prosodically more prominent sound stimulus was presented on their left side which suggests right-hemispheric specialization for neural processing of prosodic sounds in this domestic species. We also found that dogs made their choice faster when the ‘more prosodic’ stimulus was given first which suggests that they can perceive the difference not only between DDS and ADS, but also between IDS and ADS and between IDS and DDS. In conclusion, the composite DDS, IDS and ADS stimuli in the present study proved to be an effective technique in exploring the acoustic determinants of dog-directed speech preference in dogs.

Emotionally expressive non-verbal vocalizations can play a major role in human-robot interactions. Humans can assess the intensity and emotional valence of animal vocalizations based on simple acoustic features such as call length and fundamental frequency. These simple encoding rules are suggested to be general across terrestrial vertebrates. To test the degree of this generalizability, our aim was to synthesize a set of artificial sounds by systematically changing the call length and fundamental frequency, and examine how emotional valence and intensity is attributed to them by humans. Based on sine wave sounds, we generated sound samples in seven categories by increasing complexity via incorporating different characteristics of animal vocalizations. We used an online questionnaire to measure the perceived emotional valence and intensity of the sounds in a two-dimensional model of emotions. The results show that sounds with low fundamental frequency and shorter call lengths were considered to have a more positive valence, and samples with high fundamental frequency were rated as more intense across all categories, regardless of the sound complexity. We conclude that applying the basic rules of vocal emotion encoding can be a good starting point for the development of novel non-verbal vocalizations for artificial agents.

Speech carries identity-diagnostic acoustic cues that help individuals recognize each other during vocal–social interactions. In humans, fundamental frequency, formant dispersion and harmonics-to-noise ratio serve as characteristics along which speakers can be reliably separated. The ability to infer a speaker’s identity is also adaptive for members of other species (like companion animals) for whom humans (as owners) are relevant. The acoustic bases of speaker recognition in non-humans are unknown. Here, we tested whether dogs can recognize their owner’s voice and whether they rely on the same acoustic parameters for such recognition as humans use to discriminate speakers. Stimuli were pre-recorded sentences spoken by the owner and control persons, played through loudspeakers placed behind two non-transparent screens (with each screen hiding a person). We investigated the association between acoustic distance of speakers (examined along several dimensions relevant in intraspecific voice identification) and dogs’ behavior. Dogs chose their owner’s voice more often than that of control persons’, suggesting that they can identify it. Choosing success and time spent looking in the direction of the owner’s voice were positively associated, showing that looking time is an index of the ease of choice. Acoustic distance of speakers in mean fundamental frequency and jitter were positively associated with looking time, indicating that the shorter the acoustic distance between speakers with regard to these parameters, the harder the decision. So, dogs use these cues to discriminate their owner’s voice from unfamiliar voices. These findings reveal that dogs use some but probably not all acoustic parameters that humans use to identify speakers. Although dogs can detect fine changes in speech, their perceptual system may not be fully attuned to identity-diagnostic cues in the human voice.

With very few exceptions, no coherent model of representing the self exists for nonhuman species. According to our hypothesis, understanding of the Self as an object’ can also be found in a wide range of animals including the dog, a fast-moving terrestrial predator/scavenger, with highly developed senses and complex cognitive capacity. We tested companion dogs in three experiments in which they faced three different variations of the same physical challenge: passing through an opening in a wall. We predicted that if dogs are capable of representing their own body size, they will react differently when faced with adequate or too small openings. We found that dogs started to move towards and approached the too small openings with significantly longer latencies than the suitable ones; and upon reaching it, they did not try to get through the too small openings. In another experiment, the medium-size (still large enough) opening was approached with latencies that fell between the latencies measured in the cases of the very large or the too small openings. Having discussed the potential underlying mechanisms, we concluded that our results convincingly assume that dogs can represent their own body size in novel contexts. Electronic supplementary material The online version of this article (10.1007/s10071-019-01337-3) contains supplementary material, which is available to authorized users.

When separated, young offspring produce separation calls to attract their mother's attention, reduce distance between them and receive maternal care. Previous studies suggest that these calls arouse the caregiver's attention because of their special acoustic structure. Furthermore, under specific conditions separation calls can elicit an approach response even from heterospecific mothers and nonparent conspecifics depending on their sex and parental experience and the species' parental care system. Dogs, Canis familiaris, are good models because we can easily test the effects of a wide range of individual characteristics such as sex, sexual state, age, breed and behaviour traits due to a diverse dog population. Here, we assessed the reaction of sexually mature, intact and neutered dogs to strange 4- and 11-day-old dog pup separation calls, presented from a hidden speaker. We recorded the reactions of former mothers, inexperienced intact females and males and inexperienced neutered females and males to six different repeated playbacks of pup separation call bouts. We tested the effect of sex, sexual state, parental experience and age of the dogs, the fundamental frequency, call length, jitter and nonlinear phenomena ratio of the playbacks and the habituation effect of repeated playbacks. We found a positive correlation between the jitter level of the sound and the dogs' attention, while the fundamental frequency negatively affected the dogs' orientation to the speaker and the door leading to the speaker. The sex, sexual state and parental experience of the dogs did not affect their reactions towards pup separation calls. Based on these results, it seems that dogs' reactions are affected mostly by the acoustics of the separation calls, not their own individual characteristics.

Background and aimsConspecific individual recognition using vocal cues has been shown in a wide range of species but there is no published evidence that dogs are able to recognize their owner based on his/her voice alone (interspecific individual recognition).MethodsIn our test, dogs had to rely on vocal cues to find their hidden owner in a two-way choice task. From behind an opaque screen, both the owner and a control person uttered neutral speech (reading sentences from a receipt) before the dogs were allowed to make their choice. Correct choices were reinforced by food and by verbal praise.ResultsDuring the six-choice trials, dogs chose their owner?s voice significantly more often than the control person?s voice. There was no effect of learning throughout the trials, and dogs did not show side preference.DiscussionThus, dogs are able to discriminate interspecific voices, suggesting that they are able to identify their owner based on vocal cues alone. This experimental design allows exploration of the role of individual acoustic parameters (such as fundamental frequency) in voice discrimination.

Companion cats often occupy the same anthropogenic niche as dogs in human families. Still, cat cognition remains an underrepresented research subject in ethology. Our goal was to examine whether two components that are crucial in dog-human communicative interactions (sensitivity to ostensive signals; gaze following) are also present in cats. In a two-object choice task, we used dynamic and momentary gazing in ostensive and non-ostensive communicative situations. We tested 41 cats at their owner's home. Cats on the group level achieved a 70% overall success rate, showing that they are capable of following human gaze as a referential cue. Cats' success rate was unaffected both by the type of gazing and the presence/absence of ostensive communication, showing that the subjects followed readily even the more difficult momentary cues. We found a trend (p = 0.085), showing that young cats (max. 1 year old) may achieve higher success rate than adult animals. Ostension had a significant effect on the latency of eye contact, which was the shortest when the experimenter called the cat's attention with ostensive signals (p = 0.006). Our results are the first that prove cats' ability to follow human gaze, which is considered to be one of the more difficult visual referential signals given during human-animal interactions. Although ostension did not affect the success rate of cats, we found ostensive human signals to be a more effective attention elicitor compared to non-ostensive vocalizations. Our study therefore provided the first insight to the existence of sensitivity to human ostension in another non-human species besides dogs. These results emphasize the possible relevance of the domestication process and responsiveness to socialization in the development of human-compatible socio-cognitive skills even in such animals as the cat, where the ancestor was not a highly social species.

Separation related disorder (SRD) is a common behavioural problem in dogs, characterised by severe physiological and behavioural signs which occur during the absence of their owner and significantly affects the dogs’ welfare. Dogs show similar attachment behaviour toward their owner, as children show toward their parents. While children’s separation anxiety is known to be associated with their own and their parents’ attachment style, in dogs it is yet to be investigated in a data-driven way, how SRD and attachment styles in dogs are related to owners’ attachment and caregiving styles. We collected data about dogs’ behaviour during separation and reunion and their owners’ feelings regarding separation using, an online questionnaire. We performed a principal component analysis and a two-step cluster analysis to form distinct groups based on the questionnaire items. We found four different clusters that differed in dogs’ behavioural and physiological signs of separation stress, their greeting behaviour, and their owners’ concern. These identified clusters accommodated well to the secure, insecure-anxious and insecure-avoidant attachment types, but secure dogs were found in two clusters that differed only in their owners’ concern. Dogs with owner reported SRD fit mainly to the insecure-anxious cluster, whose owners were not highly concerned on separation, suggesting a lower responsiveness and avoidant attachment style. Our study supports the theory that owners’ attachment and caregiving style might affect the dogs’ attachment style and SRD status. Our results also shed light on those behavioural, physiological signs and greeting behaviours which can diverge and were found to be of unequal importance for owners in the attribution of SRD and in their level of concern. This has important implications for diagnosis of SRD raising serious welfare concerns.

An original experiment by Pongrácz et al. (2005) showed that Hungarian listeners were able to categorize recordings of dog barks recorded in various contexts above chance level and assessed the barking dogs’ emotional state in accordance with these contexts. The present study sought to replicate this experiment in a Portuguese sample. Similar to Hungarians, Portuguese dog owners and non-owners rated the barks in accordance with their specific social contexts (e.g., a dog left alone is most probably in fearful state instead of a playful one), and correctly categorized territorial and separation barks above chance level. Similar error patterns were observed across subjects from the two countries. The Portuguese participants, however, were less successful in categorizing barks than the Hungarians. Additionally, results showed both sex and dog ownership effects. Women from both countries tended to attribute higher levels of despair to all bark recordings. Moreover, within the Portuguese sample, dog-owners were generally more accurate in categorizing the recordings than non-owners. Overall, the results of our replication study, besides supporting the universality of vocal emotion recognition in mammals, calls attention to the possibility of country/culture- and also individual-specific effects on human perception and understanding of nonhuman vocalizations.

Dogs live in 45% of households, integrated into various human groups in various societies. This is certainly not true for wolves. We suggest that dogs’ increased tractability (meant as individual dogs being easier to control, handle and direct by humans, in contrast to trainability defined as performance increase due to training) makes a crucial contribution to this fundamental difference. In this study, we assessed the development of tractability in hand-raised wolves and similarly raised dogs. We combined a variety of behavioural tests: fetching, calling, obeying a sit signal, hair brushing and walking in a muzzle. Wolf (N = 16) and dog (N = 11) pups were tested repeatedly, between the ages of 3–24 weeks. In addition to hand-raised wolves and dogs, we also tested mother-raised family dogs (N = 12) for fetching and calling. Our results show that despite intensive socialization, wolves remained less tractable than dogs, especially in contexts involving access to a resource. Dogs’ tractability appeared to be less context dependent, as they followed human initiation of action in more contexts than wolves. We found no evidence that different rearing conditions (i.e. intensive socialization vs. mother rearing) would affect tractability in dogs. This suggests that during domestication dogs might have been selected for increased tractability, although based on the current data we cannot exclude that the differential speed of development of dogs and wolves or the earlier relocation of wolves to live as a group explains some of the differences we found.

Separation related problems (SRP) caused by distress associated with separation from the preferred member of the social group, can be characterised by their symptoms e.g., excessive vocalisation. In dogs’ separation whines, nonlinear phenomena (NLP) (abrupt changes in the resonance of the vocal folds) might occur, which could be adaptive in communicating aroused inner states. Previously, using a separation test we found that more dogs that were classified as having SRP by their owner have NLP in their whines than nonaffected dogs and that NLP ratio increases with age, which suggests that separation stress might intensify with age. We repeated the separation test 21.19 ± 9.37 months later with 32 dogs from the previous study to investigate longitudinally how separation behaviour and vocalisations change with age. Beside behaviour, we measured the acoustic structure of the whines (jitter - small-scale irregularity of the pitch, entropy - vocal harshness, call length, pitch (f0) related parameters, and the spectral components) and calculated the NLP ratio. We formed clusters based on the dogs’ behaviour changes from the first test to the second, to see individual ageing patterns. Finally, we compared the dogs’ behaviour and the acoustic structure of their whines in the two occasions. We found that dogs could be clustered by the changes in their separation behaviour. 41 % of the dogs were stable over time, 38 % improved, and 16 % showed an increase in their separation behaviours. 3 % switched from barking to whining. Interestingly, SRP dogs were stable, some of them even showed improvement in their separation behaviour. On the contrary, we also found that SRP dogs tended to have an increased NLP ratio with age from test 1 to test 2 (p = 0.09), showed less escape-related behaviour (p = 0.01), but tended to spend more time passively whining at the door through which the owner left the room (p = 0.05), than non-SRP dogs. The behavioural and vocal results suggest elevated stress levels in SRP dogs with age, although they did not decline but mostly stayed stable in their separation behaviour, confirming that there could be a connection between SRP status, age, and NLP. However, together with the results of the clustering that showed that there are different patterns in dogs’ separation behaviour, we emphasise the importance of individual level longitudinal investigations in order to facilitate the early diagnosis of SRP and to provide a solid basis for the development of individualised treatment plan for SRP dogs.

Emotional contagion, a basic component of empathy defined as emotional state-matching between individuals, has previously been shown in dogs even upon solely hearing negative emotional sounds of humans or conspecifics. The current investigation further sheds light on this phenomenon by directly contrasting emotional sounds of both species (humans and dogs) as well as opposed valences (positive and negative) to gain insights into intra- and interspecies empathy as well as differences between positively and negatively valenced sounds. Different types of sounds were played back to measure the influence of three dimensions on the dogs' behavioural response. We found that dogs behaved differently after hearing non-emotional sounds of their environment compared to emotional sounds of humans and conspecifics ("Emotionality" dimension), but the subjects responded similarly to human and conspecific sounds ("Species" dimension). However, dogs expressed more freezing behaviour after conspecific sounds, independent of the valence. Comparing positively with negatively valenced sounds of both species ("Valence" dimension), we found that, independent of the species from which the sound originated, dogs expressed more behavioural indicators for arousal and negatively valenced states after hearing negative emotional sounds. This response pattern indicates emotional state-matching or emotional contagion for negative sounds of humans and conspecifics. It furthermore indicates that dogs recognized the different valences of the emotional sounds, which is a promising finding for future studies on empathy for positive emotional states in dogs.

In the human speech signal, cues of speech sounds and voice identities are conflated, but they are processed separately in the human brain. The processing of speech sounds and voice identities is typically performed by non-primary auditory regions in humans and non-human primates. Additionally, these processes exhibit functional asymmetry in humans, indicating the involvement of distinct mechanisms. Behavioural studies indicate analogue side biases in dogs, but neural evidence for this functional dissociation is missing. In two experiments, using an fMRI adaptation paradigm, we presented awake dogs with natural human speech that either varied in segmental (change in speech sound) or suprasegmental (change in voice identity) content. In auditory regions, we found a repetition enhancement effect for voice identity processing in a secondary auditory region – the caudal ectosylvian gyrus. The same region did not show repetition effects for speech sounds, nor did the primary auditory cortex exhibit sensitivity to changes either in the segmental or in the suprasegmental content. Furthermore, we did not find evidence for functional asymmetry neither in the processing of speech sounds or voice identities. Our results in dogs corroborate former human and non-human primate evidence on the role of secondary auditory regions in the processing of suprasegmental cues, suggesting similar neural sensitivity to the identity of the vocalizer across the mammalian order.

During separation, infants of various species often produce a special call type, the separation cry, which elicits instant response from the caregiver. Ignoring this stimulus might be costly; hence, adults have evolved a sensitivity to infant cries. As the acoustic structure and function of these vocalizations are conserved across mammals, adults might react similarly to heterospecific and conspecific separation calls. The domestic dog, Canis familiaris, is an excellent model to study reactions to heterospecific vocalizations due to their special niche in the human social environment. Through domestication, they have become especially sensitive to human communicative signals, including baby cries. Furthermore, they can share their natural environment with other species such as other pets and livestock, which could also affect their responsiveness towards heterospecific calls. Taking advantage of this potential cross-species sensitivity, we aimed to examine dogs' reactions to infant separation calls of humans and domestic cats, Felis catus, compared to conspecific calls. To explore the effect of novelty and specific acoustic features we also used synthesized cries, which allowed us to look for general rules behind dogs' reactions to heterospecific calls and general acoustic effects functioning across species. After testing 100 dogs with pup cries in a previous study, here we tested another 118 dogs in three groups based on the presented sounds' origin. All stimuli were analysed acoustically; then we tested the effects of the species and acoustic features on the dogs’ behaviours. Dogs reacted to pup and artificial cries the fastest, and baby cries the slowest, while responses to kitten sounds were intermediate. We also found general acoustic effects: tonality-related parameters extensively affected the reactions. Higher noisiness caused faster speaker and owner orientation, but it seems that species-specific cues might overwrite the general acoustic rules that appear across mammal separation calls.

Excessive dog barking is among the leading sources of noise pollution world-wide; however, the reasons for the annoyance of barking to people remained uninvestigated. Our questions were: is the annoyance rating affected by the acoustic parameters of barks; does the attributed inner state of the dog and the nuisance caused by its barks correlate; does the gender and country of origin affect the subjects’ sensitivity to barking. Participants from Hungary (N = 100) and Brazil (N = 60) were tested with sets of 27 artificial bark sequences. Subjects rated each bark according to the inner state of the dog and the annoyance caused by the particular bark. Subjects from both countries found high-pitched barks the most annoying: however, harsh, fast-pulsing, low-pitched barks were also unpleasant. Men found high-pitched barks more annoying than the women did. Annoyance ratings showed positive correlation with assumed negative inner states of the dog, positive emotional ratings showed negative correlation with the annoyance level. This is the first indication that acoustic features that were selected for effective vocal signalling may be annoying for human listeners. Among the explanations for this effect the role of affective communication and similar bioacoustics of particular animal vocalizations and baby cries are discussed.

In social robotics it has been a crucial issue to determine the minimal set of relevant behaviour actions that humans interpret as social competencies. As a potential alternative of mimicking human abilities, it has been proposed to use a non-human animal, the dog as a natural model for developing simple, non-linguistic emotional expressions for non-humanoid social robots. In the present study human participants were presented with short video sequences in which a PeopleBot robot and a dog displayed behaviours that corresponded to five emotional states (joy, fear, anger, sadness, and neutral) in a neutral environment. The actions of the robot were developed on the basis of dog expressive behaviours that had been described in previous studies of dog-human interactions. In their answers to open-ended questions, participants spontaneously attributed emotional states to both the robot and the dog. They could also successfully match all dog videos and all robot videos with the correct emotional state. We conclude that our bottom up approach (starting from a simpler animal signalling system, rather than decomposing complex human signalling systems) can be used as a promising model for developing believable and easily recognisable emotional displays for non-humanoid social robots. Humans spontaneously attribute emotions to an ethologically inspired robot.Dog emotional videos prime the attribution of emotions to robot videos.Participants were able to match both dog and robot videos to the corresponding emotions.Experience with dogs does not help identify dog and robot emotions.

Acoustic communication can play an important part in mother-young recognition in many mammals. This, however, has still only been investigated in a small range mainly of herd- or colony-living species. Here we report on the behavioral response of kittens of the domestic cat, a typically solitary carnivore, to playbacks of "greeting chirps" and "meows" from their own versus alien mothers. We found significantly stronger responses to the chirps from kittens' own mother than to her meows or to the chirps or meows of alien mothers. Acoustic analysis revealed greater variation between vocalizations from different mothers than for vocalizations from the same mother. We conclude that chirps emitted by mother cats at the nest represent a specific form of vocal communication with their young, and that kittens learn and respond positively to these and distinguish them from chirps of other mothers and from other cat vocalizations while still in the nest. © 2016 Wiley Periodicals, Inc. Dev Psychobiol 58: 568-577, 2016.

Dog barks represent a major source of noise pollution worldwide. However, the exact reasons why dog barks annoy people and why particular people show stronger reactions to dog barks than other nois...

This chapter provides a wide comparative perspective on the behavioural and neural capacities for vocalization processing in general, and for cross-species voice processing in particular. Vocal communication usually takes place among conspecifics, but in certain cases heterospecific vocalizations can also help optimize behaviour. Vocal anatomy and the neurophysiological processes of voice production are highly conserved across vertebrates, and the perception of basic biological meanings from vocalizations is thus based on auditory cues that are not species-specific. This chapter suggests that these similarities, and also the general ability to learn about vocal sounds, provide a good basis to assume that specific cues in heterospecific vocalizations may be efficiently processed. The chapter reviews the anatomical, behavioural, and neuroscientific evidence suggesting that heterospecific vocalization processing may work efficiently across a wide range of taxa, and shares the neural substrates involved in the processing of conspecific communication sounds.

Family dogs successfully follow human-given cues in a two-object choice test. However, whether this ability has any roots in dog–dog visual communication, has been seldom investigated. We designed a test where a video-projected, life-sized dog ‘demonstrator’ provided directional cues for the subjects by turning its head toward one of the two plates containing food. To avoid pseudo-replication, videos of 28 different dogs were recorded as ‘demonstrators’. N = 60 subjects were tested with a larger, smaller, or equally sized ‘demonstrator’, using a momentary head-and-gaze turn, while N = 15 subjects were tested using sustained demonstrative cues. Social status of the subjects, based on a questionnaire (single-kept, dominant or subordinate), was also taken into account. Our results showed that dogs did not choose between the plates by relying on the momentary head turns of the projected demonstrator (p = 0.35). Social rank did not have any effect on their choices either, however, ‘single’ dogs showed a left-side preference in their choices (p = 0.03). In the case of momentary gazing, all dogs developed strong side bias depending on their first choices (p

There is growing evidence that dog-directed and infant-directed speech have similar acoustic characteristics, like high overall pitch, wide pitch range, and attention-getting devices. However, it is still unclear whether dog- and infant-directed speech have gender or context-dependent acoustic features. In the present study, we collected comparable infant-, dog-, and adult directed speech samples (IDS, DDS, and ADS) in four different speech situations (Storytelling, Task solving, Teaching, and Fixed sentences situations); we obtained the samples from parents whose infants were younger than 30 months of age and also had pet dog at home. We found that ADS was different from IDS and DDS, independently of the speakers’ gender and the given situation. Higher overall pitch in DDS than in IDS during free situations was also found. Our results show that both parents hyperarticulate their vowels when talking to children but not when addressing dogs: this result is consistent with the goal of hyperspeech in language tutoring. Mothers, however, exaggerate their vowels for their infants under 18 months more than fathers do. Our findings suggest that IDS and DDS have context-dependent features and support the notion that people adapt their prosodic features to the acoustic preferences and emotional needs of their audience.

Barking is perhaps the most characteristic form of vocalization in dogs; however, very little is known about its role in the intraspecific communication of this species. Besides the obvious need for ethological research, both in the field and in the laboratory, the possible information content of barks can also be explored by computerized acoustic analyses. This study compares four different supervised learning methods (naive Bayes, classification trees, $$k$$ -nearest neighbors and logistic regression) combined with three strategies for selecting variables (all variables, filter and wrapper feature subset selections) to classify Mudi dogs by sex, age, context and individual from their barks. The classification accuracy of the models obtained was estimated by means of $$K$$ -fold cross-validation. Percentages of correct classifications were 85.13 % for determining sex, 80.25 % for predicting age (recodified as young, adult and old), 55.50 % for classifying contexts (seven situations) and 67.63 % for recognizing individuals (8 dogs), so the results are encouraging. The best-performing method was $$k$$ -nearest neighbors following a wrapper feature selection approach. The results for classifying contexts and recognizing individual dogs were better with this method than they were for other approaches reported in the specialized literature. This is the first time that the sex and age of domestic dogs have been predicted with the help of sound analysis. This study shows that dog barks carry ample information regarding the caller’s indexical features. Our computerized analysis provides indirect proof that barks may serve as an important source of information for dogs as well.

It is essential for social robots to fit in the human society. In order to facilitate this process we propose to use the family dog’s social behaviour shown towards humans as an inspiration. In this study we explored dogs’ low level social monitoring in dog-human interactions and extracted individually consistent and context dependent behaviours in simple everyday social scenarios. We found that proximity seeking and tail wagging were most individually distinctive in dogs, while activity, orientation towards the owner, and exploration were dependent on the context and/or the activity of the owner. The functional analogues of these dog behaviours can be implemented in social robots of different embodiments in order to make them acceptable and more believable for humans. Keywords: dog-owner interaction; social robotics; low-level social monitoring; greeting behaviour; individually distinctive behaviours

Nonhuman animals often use specific signals to initiate playful interactions. There is evidence also for different forms of play-maintenance. Playful encounters include out-of-context and exaggerated behavioural sequences. Scientists have already collected knowledge about virtual size modification via acoustic signalling in particular animal species during competitive/agonistic interactions, but the same was unknown in playful encounters. Using the cross-modal matching paradigm, we tested whether dogs prefer to look at the picture of a matching size dog when they are offered two differently sized projected pictures simultaneously with a playback of a playful or a food-guarding growl. We found that dogs looked at the matching picture when they heard the food-guarding growl, but they looked at rather the larger than the matching size dog when play growls were played back. These are the first results to show that dogs may communicate an exaggerated body size by the means of their growls during play, which may help in maintaining or enhancing the playful interaction. As agonistic dog growls were proven to be honest regarding their referential and size-related information content, our results gave evidence that exaggeration may work as play signal in the case of animal vocalizations.

Vocal expressions of emotions follow simple rules to encode the inner state of the caller into acoustic parameters, not just within species, but also in cross-species communication. Humans use these structural rules to attribute emotions to dog vocalizations, especially to barks, which match with their contexts. In contrast, humans were found to be unable to differentiate between playful and threatening growls, probably because single growls' aggression level was assessed based on acoustic size cues. To resolve this contradiction, we played back natural growl bouts from three social contexts (food guarding, threatening and playing) to humans, who had to rate the emotional load and guess the context of the playbacks. Listeners attributed emotions to growls according to their social contexts. Within threatening and playful contexts, bouts with shorter, slower pulsing growls and showing smaller apparent body size were rated to be less aggressive and fearful, but more playful and happy. Participants associated the correct contexts with the growls above chance. Moreover, women and participants experienced with dogs scored higher in this task. Our results indicate that dogs may communicate honestly their size and inner state in a serious contest situation, while manipulatively in more uncertain defensive and playful contexts.

Separation-related disorder (SRD) is one of the most common behavioral problems of companion dogs, causing inconvenience and stress for dog owners and others living close by, as well as being considered as a major contributor to poor animal welfare. Although excessive vocalization is considered as one of the typical symptoms of SRD, until now there were no attempts to analyze and compare the vocal output of affected and non-affected dogs in a systematic, empirical test. In a three-stage outdoor separation experiment we investigated the vocal response of 25 family dogs with, and 20 family dogs without, owner-reported SRD symptoms to the (1) departure; (2) absence; and (3) return of the owner. After the analysis of the occurrence and onset latency of barks and whines, we found that contrary to the commonly held view of excessive barking being one of the trademarks of SRD, dogs with owner-reported SRD symptoms can be reliably characterized by the early onset and high occurrence of whines during the departure and 2 min long absence of the owner, while barks were affected mainly by the age of the dogs. Breed and neuter status may modify the vocal reaction to separation, we found that more purebred dogs barked sooner, while breed and neutering status affected the whines only during the departure of the owner, showing that more mixed breeds and intact dogs whined in this phase. This is the first study that targeted directly the vocal response of family dogs to separation from the owner, and according to the results, whines and barks reflect potentially different motivational/inner states of dogs during a short isolation episode. Although the effect of other factors, such as sex, neuter status and breed cannot be ignored, the owner reported SRD status of dogs showed a high coincidence with the early onset of whining, which in turn proved to be a good indicator of high stress levels of dogs in this situation.

The visual sense of dogs is in many aspects different than that of humans. Unfortunately, authors do not explicitly take into consideration dog-human differences in visual perception when designing their experiments. With an image manipulation program we altered stationary images, according to the present knowledge about dog-vision. Besides the effect of dogs’ dichromatic vision, the software shows the effect of the lower visual acuity and brightness discrimination, too. Fifty adult humans were tested with pictures showing a female experimenter pointing, gazing or glancing to the left or right side. Half of the pictures were shown after they were altered to a setting that approximated dog vision. Participants had difficulty to find out the direction of glancing when the pictures were in dog-vision mode. Glances in dog-vision setting were followed less correctly and with a slower response time than other cues. Our results are the first that show the visual performance of humans under circumstances that model how dogs’ weaker vision would affect their responses in an ethological experiment. We urge researchers to take into consideration the differences between perceptual abilities of dogs and humans, by developing visual stimuli that fit more appropriately to dogs’ visual capabilities.

During speech processing, human listeners can separately analyze lexical and intonational cues to arrive at a unified representation of communicative content. The evolution of this capacity can be best investigated by comparative studies. Using functional magnetic resonance imaging, we explored whether and how dog brains segregate and integrate lexical and intonational information. We found a hemispheric bias for processing meaningful words, independently of intonation; an auditory brain region for distinguishing intonationally marked and unmarked words; and increased activity in primary reward regions only when both lexical and intonational information were consistent with praise. Neural mechanisms to separately analyze and integrate word meaning and intonation in dogs suggest that this capacity can evolve in the absence of language.