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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.

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.

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.

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.

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.

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...

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.

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.

This study shows that the small GTPase Rab11 is required for both autophagosome and endosome maturation. The authors demonstrate a novel cross-talk mechanism through which autophagy can orchestrate endosomal maturation events to ensure the required endolysosomal input for autophagosome maturation., During autophagy, double-membrane autophagosomes deliver sequestered cytoplasmic content to late endosomes and lysosomes for degradation. The molecular mechanism of autophagosome maturation is still poorly characterized. The small GTPase Rab11 regulates endosomal traffic and is thought to function at the level of recycling endosomes. We show that loss of Rab11 leads to accumulation of autophagosomes and late endosomes in Drosophila melanogaster. Rab11 translocates from recycling endosomes to autophagosomes in response to autophagy induction and physically interacts with Hook, a negative regulator of endosome maturation. Hook anchors endosomes to microtubules, and we show that Rab11 facilitates the fusion of endosomes and autophagosomes by removing Hook from mature late endosomes and inhibiting its homodimerization. Thus induction of autophagy appears to promote autophagic flux by increased convergence with the endosomal pathway.

In this paper we propose the application of evolutionary principles in studying technological devices and processes. First we introduce the concepts of Darwinian evolution, which we use to draw an analogy with technology and show how human-made devices can be treated as evolving artificial agents. After explaining the methodology of reconstructing evolutionary history, we apply successfully the delineated principles and methodology to an info-communication system: cellphones. By modeling a possible phylogenetic tree of mobile phones and exploring technological changes through time, we are able to show evolutionary trends and parallels with biological processes.

Humans excel at assessing conspecific emotional valence and intensity, based solely on non-verbal vocal bursts that are also common in other mammals. It is not known, however, whether human listeners rely on similar acoustic cues to assess emotional content in conspecific and heterospecific vocalizations, and which acoustical parameters affect their performance. Here, for the first time, we directly compared the emotional valence and intensity perception of dog and human non-verbal vocalizations. We revealed similar relationships between acoustic features and emotional valence and intensity ratings of human and dog vocalizations: those with shorter call lengths were rated as more positive, whereas those with a higher pitch were rated as more intense. Our findings demonstrate that humans rate conspecific emotional vocalizations along basic acoustic rules, and that they apply similar rules when processing dog vocal expressions. This suggests that humans may utilize similar mental mechanisms for recognizing human and heterospecific vocal emotions.