We have successfully measured the sleep electroencephalogram (EEG) of 12 family cats during an afternoon nap using a completely noninvasive methodology originally developed and validated for family dogs. Extracting both macrostructural and spectral sleep variables from the acquired data, we: (1) provided a descriptive analysis of sleep structure in cats and the power spectral density (PSD) distribution considering 3 sleep stages-drowsiness, non-rapid eye movement (NREM), and rapid eye movement (REM) sleep; and (2) compared the results to those obtained in family dogs measured under the same conditions and using the same methodology. Importantly, our description of sleep structure and PSD distribution in cats proved to be comparable to those of earlier invasive studies, highlighting that appropriate noninvasive methodologies may provide a viable alternative to those that are invasive in some cases. While no macrostructural differences were found between the sleep of cats and dogs, and the characteristic PSDs were mostly similar across sleep stages within the 2 species, the high-frequency resolution comparison of PSD distributions revealed differences between the 2 species in all sleep stages (concerning the delta, theta, alpha, sigma, and beta bands in drowsiness and NREM sleep; and the delta, alpha, and sigma bands in REM sleep). Potential factors underlying these differences are discussed, including differences in circadian rhythms, sleep homeostatic regulation, experienced stress, or even differential attitudes toward owners-highlighting important links between sleep characteristics and often more complex neural and behavioral features. In the present study, our aim was to measure sleep in family cats using a completely noninvasive electroencephalogram (EEG) measurement methodology, originally developed and validated for family dogs. We have successfully collected the sleep EEG of 12 family cats during an afternoon nap, providing a descriptive analysis of sleep characteristics in the species, as well as compared it to those acquired from dogs using the same noninvasive methodology. The sleep macrostructure showed no differences between the 2 species and the dominant power spectral densities were also similar across different sleep stages (drowsiness, non-rapid eye movement [NREM], rapid eye movement [REM]). However, the detailed analysis of power spectral densities revealed differences in all sleep stages of the 2 species (drowsiness, NREM, REM), across all frequency bands.

Recent advances in the field of canine neuro-cognition allow for the non-invasive research of brain mechanisms in family dogs. Considering the striking similarities between dog's and human (infant)'s socio-cognition at the behavioural level, both similarities and differences in neural background can be of particular relevance. The current study investigates brain responses of n = 17 family dogs to human and conspecific emotional vocalizations using a fully non-invasive event-related potential (ERP) paradigm. We found that similarly to humans, dogs show a differential ERP response depending on the species of the caller, demonstrated by a more positive ERP response to human vocalizations compared to dog vocalizations in a time window between 250 and 650 ms after stimulus onset. A later time window between 800 and 900 ms also revealed a valence-sensitive ERP response in interaction with the species of the caller. Our results are, to our knowledge, the first ERP evidence to show the species sensitivity of vocal neural processing in dogs along with indications of valence sensitive processes in later post-stimulus time periods.

Sleep research greatly benefits from comparative studies to understand the underlying physiological and environmental factors affecting the different features of sleep, also informing us about the possible evolutionary changes shaping them. Recently, the domestic dog became an exceedingly valuable model species in sleep studies, as the use of non-invasive polysomnography methodologies enables direct comparison with human sleep data. In this study, we applied the same polysomnography protocol to record the sleep of dog’s closest wild relative, the wolf. We measured the sleep of seven captive (six young and one senior), extensively socialized wolves using a fully non-invasive sleep EEG methodology, originally developed for family dogs. We provide the first descriptive analysis of the sleep macrostructure and NREM spectral power density of wolves using a completely non-invasive methodology. For (non-statistical) comparison, we included the same sleep data of similarly aged dogs. Although our sample size was inadequate to perform statistical analyses, we suggest that it may form the basis of an international, multi-site collection of similar samples using our methodology, allowing for generalizable, unbiased conclusions. As we managed to register both macrostructural and spectral sleep data, our procedure appears to be suitable for collecting valid data in other species too, increasing the comparability of non-invasive sleep studies.

Voice-sensitivity in the auditory cortex of a range of mammals has been proposed to be determined primarily by tuning to conspecific auditory stimuli, but recent human findings indicate a role for a more general tuning to voicelikeness. Vocal emotional valence, a central characteristic of vocalisations, has been linked to the same basic acoustic parameters across species. Comparative neuroimaging revealed that during voice perception, such acoustic parameters modulate emotional valence-sensitivity in auditory cortical regions in both family dogs and humans. To explore the role of voicelikeness in auditory emotional valence-sensitivity across species, here we constructed artificial emotional sounds in two sound categories: voice-like vs. sine-wave sounds, parametrically modulating two main acoustic parameters, f0 and call length. We hypothesised that if mammalian auditory systems are characterised by a general tuning to voicelikeness, voice-like sounds will be processed preferentially, and acoustic parameters for voice-like sounds will be processed differently than for sine-wave sounds - both in dogs and humans. We found cortical areas in both species that responded stronger to voice-like than to sine-wave stimuli, while there were no regions responding stronger to sine-wave sounds in either species. Additionally, we found that in bilateral primary and emotional valence-sensitive auditory regions of both species, the processing of voice-like and sine-wave sounds are modulated by f0 in opposite ways. These results reveal functional similarities between evolutionarily distant mammals for processing voicelikeness and its effect on processing basic acoustic cues of vocal emotions.

The dog rhinarium (naked and often moist skin on the nose-tip) is prominent and richly innervated, suggesting a sensory function. Compared to nose-tips of herbivorous artio- and perissodactyla, carnivoran rhinaria are considerably colder. We hypothesized that this coldness makes the dog rhinarium particularly sensitive to radiating heat. We trained three dogs to distinguish between two distant objects based on radiating heat; the neutral object was about ambient temperature, the warm object was about the same surface temperature as a furry mammal. In addition, we employed functional magnetic resonance imaging on 13 awake dogs, comparing the responses to heat stimuli of about the same temperatures as in the behavioural experiment. The warm stimulus elicited increased neural response in the left somatosensory association cortex. Our results demonstrate a hitherto undiscovered sensory modality in a carnivoran species.

The sleeping activity of family dogs has been studied increasingly in the past years. Recently, a validated, non-invasive polysomnographic method has been developed for dogs, enabling the parallel recording of several neurophysiological signals on non-anesthetized family dogs, including brain activity (EEG), eye movements (EOG), cardiac (ECG), and respiratory activity (PNG). In this study, we examined the ECG (N = 30) and respiratory signals (N = 19) of dogs during a 3-h sleep period in the afternoon, under laboratory conditions. We calculated four time-domain heart rate variables [mean heart rate (HR), SDNN, RMSSD, and pNN50] from the ECG and the estimated average respiratory frequency from the respiratory signal. We analyzed how these variables are affected by the different sleep-wake phases (wakefulness, drowsiness, NREM, and REM) as well as the dogs’ sex, age and weight. We have found that the sleep-wake phase had a significant effect on all measured cardiac parameters. In the wake phase, the mean HR was higher than in all other phases, while SDNN, RMSSD, and pNN50 were lower than in all other sleep phases. In drowsiness, mean HR was higher compared to NREM and REM phases, while SDNN and RMSSD was lower compared to NREM and REM phases. In REM, SDNN, and RMSSD was higher than in NREM. However, the sleep-wake phase had no effect on the estimated average respiratory frequency of dogs. The dogs’ sex, age and weight had no effect on any of the investigated variables. This study represents a detailed analysis of the cardiac and respiratory activity of dogs during sleep. Since variations in these physiological signals reflect the dynamics of autonomic functions, a more detailed understanding of their changes may help us to gain a better understanding of the internal/emotional processes of dogs in response to different conditions of external stimuli. As such, our results are important since they are directly comparable to human findings and may also serve as a potential basis for future studies on dogs.

Excessive aggression is a common behaviour problem in dogs that can have various destructive effects on the affected people and the implicated dog. Aggressive behaviour directed towards the owner or other family members is one of the most frequently occurring aggressive phenotypes. Here, we examine the reliability of a short questionnaire assessing aggressive behaviours by two, contextually different behavioural tests: ‘take away bone’ and ‘roll over’. Based on dogs' behaviour in the tests, we sorted dogs ( N = 93) in two groups for each test, namely a less and a more disobedient/resistant group. The two principal components obtained in our questionnaire—‘obedient’ and ‘aggressive towards owner’—showed significant differences between the behaviour groups. While dogs in the less disobedient/resistant groups had significantly higher ‘obedient’ and significantly lower ‘aggressive towards owner’ scores, dogs in the more disobedient/resistant groups had significantly higher ‘aggressive towards owner’ and significantly lower ‘obedient’ scores. Dogs' age, sex and neuter/spay status expressed their effect through interactions. Males, young dogs and intact dogs were less ‘obedient’ than older ones, while resistant spayed/neutered dogs were more aggressive towards the owner. The questionnaire used is a safe, easy to deploy and time-efficient tool to reliably assess certain owner-directed aggressive tendencies of family dogs.

One major challenge in human behavior and brain sciences is to understand how we can rewire already existing perceptual, motor, cognitive, and social skills or habits. Here we aimed to characterize one aspect of rewiring, namely, how we can update our knowledge of sequential/statistical regularities when they change. The dynamics of rewiring was explored from learning to consolidation using a unique experimental design which is suitable to capture the effect of implicit and explicit processing and the proactive and retroactive interference. Our results indicate that humans can rewire their knowledge of such regularities incidentally, and consolidation has a critical role in this process. Moreover, old and new knowledge can coexist, leading to effective adaptivity of the human mind in the changing environment, although the execution of the recently acquired knowledge may be more fluent than the execution of the previously learned one. These findings can contribute to a better understanding of the cognitive processes underlying behavior change, and can provide insights into how we can boost behavior change in various contexts, such as sports, educational settings or psychotherapy.

Body size is an important feature that affects fighting ability; however, size-related parameters of agonistic vocalizations are difficult to manipulate because of anatomical constraints within the vocal production system. Rare examples of acoustic size modulation are due to specific features that enable the sender to steadily communicate exaggerated body size. However, one could argue that it would be more adaptive if senders could adjust their signaling behavior to the fighting potential of their actual opponent. So far there has been no experimental evidence for this possibility. We tested this hypothesis by exposing family dogs (Canis familiaris) to humans with potentially different fighting ability. In a within-subject experiment, 64 dogs of various breeds consecutively faced two threateningly approaching humans, either two men or two women of different stature, or a man and a woman of similar or different stature. We found that the dogs’ vocal responses were affected by the gender of the threatening stranger and the dog owner’s gender. Dogs with a female owner, or those dogs which came from a household where both genders were present, reacted with growls of lower values of the Pitch–Formant component (including deeper fundamental frequency and lower formant dispersion) to threatening men. Our results are the first to show that non-human animals react with dynamic alteration of acoustic parameters related to their individual indexical features (body size), depending on the level of threat in an agonistic encounter.

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 < 0.001). However, when the projected demonstrator performed sustained gazing, subjects avoided the indicated plate (p = 0.027). This is the first study showing that dogs do not follow the head turn cues given by another dog, but rather avoid the food that the other dog gazes at. This finding gives support to the theory that good performance of dogs in case of human-given cues may not have a direct predecessor in dog-dog communication, but rather relies on dogs' specific attention to humans and/or the plentiful opportunity to associate human directional gestures with food reward during the ontogeny. (C) 2015 Elsevier B.V. All rights reserved.

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.

The several boundlessly shattered pages of “Story” by Edmond Jabès introduce one of his most embittered ideas. It is namely the acknowledgement of the impossibility of writing „precisely” a story through the separation of a couple and the parceling of a landscape. Nevertheless, the author does not give way to a confused and gloomy poetry but by recognizing the incommunicable he contemplates and then perceives emptiness in order to exhibit it to us in the purest possible way. Over and above unlimited space, what will therefore be presented is the eternal departure.

Experiments that use human pointing gestures in two-way object choice tests are popular for studying visual communication and referential understanding but results may be influenced by involuntary cues from handlers or experimenters (i.e., ‘Clever Hans Effects’). In this paper we investigated whether such cues from a dog’s owner affected performance of dogs during momentary distal pointing trials. Dogs were tested in four groups. In the ‘Blindfolded Owner’ group, the owners did not see the experimenter’s pointing gestures because they wore opaque glasses. In the ‘Passive Clever Hans’ group, owners were told before the test that if their dogs performed without error, they would receive a gift and their dog would be recorded in the ‘smartest dogs registry’. In the ‘Active Clever Hans’ group, owners were instructed to help their dogs to the correct side by pushing them gently in the correct direction. The fourth group served as a control and owners did not wear a blindfold or receive any specific information. We found no influence of cues from the owners in any of the experimental groups. In contrast to studies based on olfactory cues, this suggests that momentary pointing gestures from a human experimenter can be a reliable communicative cue for adult companion dogs, even when dog owners are present and provide additional voluntary or involuntary cues. We suggest that for short-term studies of visual communication, where individual dogs have little opportunity to learn their owners’ cues in the experimental context, the presence of owners may not necessarily distort results.

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.