Similarity between an unfamiliar human and the owner affects dogs' preference for human partner when responding to an unsolvable problem.

This study investigates whether dogs are able to differentiate between people according to whether or not they show similarities to their owners. We hypothesized that dogs would show a preference for the "similar" partner when interacting with unfamiliar humans. After having familiarized with two experimenters displaying different degrees of similarity to their owners, dogs (N = 36) participated in a situation where the desired toy object was made inaccessible in order to find out whether they initiate interaction with the two partners differently. Two different types of "similarity cues" were used (either alone or combined with each other): (1) persistent behavioral characteristics (i.e., familiar vs. strange motion pattern and language usage) and (2) an unfamiliar arbitrary group marker (i.e., one of the potential helpers was wearing clothing similar to that worn by the owner). Results show that although dogs payed equal attention to the human partners displaying various types of similarity to their owners during familiarization, they exhibited a visual attention preference for the human whose motion pattern and language usage were similar to their owner's in the inaccessible-toy task. However, there was weak evidence of discrimination based on the arbitrary group marker (clothing). Although dogs' different tendencies to interact with the potential helpers do not necessarily imply an underlying ability to create social categories based on the degree of similarity between the owner and unfamiliar people, these results suggest that functionally human infant-analogue forms of social categorization may have emerged in dogs.

Sleep macrostructure is modulated by positive and negative social experience in adult pet dogs.

The effects of emotionally valenced events on sleep physiology are well studied in humans and laboratory rodents. However, little is known about these effects in other species, despite the fact that several sleep characteristics differ across species and thus limit the generalizability of such findings. Here we studied the effect of positive and negative social experiences on sleep macrostructure in dogs, a species proven to be a good model of human social cognition. A non-invasive polysomnography method was used to collect data from pet dogs (n = 16) participating in 3-hour-long sleep occasions. Before sleep, dogs were exposed to emotionally positive or negative social interactions (PSI or NSI) in a within-subject design. PSI consisted of petting and ball play, while NSI was a mixture of separation, threatening approach and still face test. Sleep macrostructure was markedly different between pre-treatment conditions, with a shorter sleep latency after NSI and a redistribution of the time spent in the different sleep stages. Dogs' behaviour during pre-treatments was related to the macrostructural difference between the two occasions, and was further modulated by individual variability in personality. This result provides the first direct evidence that emotional stimuli affect subsequent sleep physiology in dogs.

The effect of oxytocin on human-directed social behaviour in dogs (Canis familiaris).

The oxytocin system has recently received increasing attention due to its effect on complex human behaviours. In parallel to this, over the past couple of decades, the human-analogue social behaviour of dogs has been intensively studied. Combining these two lines of research (e.g. studying the relationship between dog social behaviour and the oxytocin system) is a promising new research area. The present paper reviews the existing literature on how oxytocin is related to different aspects of human-directed social behaviour in dogs.

Interacting effect of two social factors on 18-month-old infants' imitative behavior: Communicative cues and demonstrator presence.

Certain aspects of a demonstration have been shown to influence infants' interpretation of an observational situation and result in selective imitation. Studying social factors that trigger selective imitation may improve our understanding of how infants encode certain situations. However, only a few studies have investigated the possible interactions among these factors. In our study, 18-month-old infants (N=54) observed an adult demonstrator retrieve a toy from under an opaque ("baited") container by manipulating another transparent empty one. Infants were assigned to one of four conditions representing all combinations of two social factors: ostensive communication during demonstration (Communicative vs. Non-communicative) and presence of the demonstrator during reenactment (D-present vs. D-not present). Results suggest that infants' choice behavior was formed in two steps: during the demonstration and during the test phase. Furthermore, an interaction between the effects of the two levels was observed. Communication during the demonstration triggered imitative learning. Infants tended to copy the observed manipulation to learn the communicatively assigned way to reach the goal. This choice behavior was not influenced later by the presence or absence of the demonstrator. The non-communicative demonstration, however, did not elicit a particular learning mechanism. Therefore, in this situation, infants' choice behavior was affected by the demonstrator's presence or absence. Infants developed an individual solution and chose the baited container in the D-not present condition, indicative of emulation. In the D-present situation, they were more likely to reproduce the observed manipulation, which can be interpreted as a tendency to communicate with or conform to the demonstrator.

Dogs Identify Agents in Third-Party Interactions on the Basis of the Observed Degree of Contingency.

To investigate whether dogs could recognize contingent reactivity as a marker of agents' interaction, we performed an experiment in which dogs were presented with third-party contingent events. In the perfect-contingency condition, dogs were shown an unfamiliar self-propelled agent (SPA) that performed actions corresponding to audio clips of verbal commands played by a computer. In the high-but-imperfect-contingency condition, the SPA responded to the verbal commands on only two thirds of the trials; in the low-contingency condition, the SPA responded to the commands on only one third of the trials. In the test phase, the SPA approached one of two tennis balls, and then the dog was allowed to choose one of the balls. The proportion of trials on which a dog chose the object indicated by the SPA increased with the degree of contingency: Dogs chose the target object significantly above chance level only in the perfect-contingency condition. This finding suggests that dogs may use the degree of temporal contingency observed in third-party interactions as a cue to identify agents.

Dogs (Canis familiaris) adjust their social behaviour to the differential role of inanimate interactive agents.

Dogs are able to flexibly adjust their social behaviour to situation-specific characteristics of their human partner's behaviour in problem situations. However, dogs do not necessarily detect the specific role played by the human in a particular situation: they may form expectations about their partners' behaviour based on previous experiences with them. Utilising inanimate objects (UMO-unidentified moving object) as interacting agents offers new possibilities for investigating social behaviour, because in this way we can remove or control the influence of previous experience with the partner. The aim of the present study was to investigate whether dogs are able to recognise the different roles of two UMOs and are able to adjust their communicative behaviour towards them. In the learning phase of the experiment, dogs were presented with a two-way food-retrieval problem in which two UMOs, which differed in their physical appearance and abilities, helped the dog obtain a piece of food in their own particular manner. After a short experience with both UMOs, dogs in the test phase faced one of the problems in the presence of both inanimate agents. Overall, dogs displayed similar levels of gazing behaviour towards the UMOs, but in the first test they looked, approached and touched the relevant partner first. This rapid adjustment of social behaviour towards UMOs suggests that dogs may generalise their experiences with humans to unfamiliar agents and are able to select the appropriate partner when facing a problem situation.

The effect of oxytocin on biological motion perception in dogs (Canis familiaris).

Recent studies have shown that the neuropeptide oxytocin is involved in the regulation of several complex human social behaviours. There is, however, little research on the effect of oxytocin on basic mechanisms underlying human sociality, such as the perception of biological motion. In the present study, we investigated the effect of oxytocin on biological motion perception in dogs (Canis familiaris), a species adapted to the human social environment and thus widely used to model many aspects of human social behaviour. In a within-subjects design, dogs (N = 39), after having received either oxytocin or placebo treatment, were presented with 2D projection of a moving point-light human figure and the inverted and scrambled version of the same movie. Heart rate (HR) and heart rate variability (HRV) were measured as physiological responses, and behavioural response was evaluated by observing dogs' looking time. Subjects were also rated on the personality traits of Neuroticism and Agreeableness by their owners. As expected, placebo-pretreated (control) dogs showed a spontaneous preference for the biological motion pattern; however, there was no such preference after oxytocin pretreatment. Furthermore, following the oxytocin pretreatment female subjects looked more at the moving point-light figure than males. The individual variations along the dimensions of Agreeableness and Neuroticism also modulated dogs' behaviour. Furthermore, HR and HRV measures were affected by oxytocin treatment and in turn played a role in subjects' looking behaviour. We discuss how these findings contribute to our understanding of the neurohormonal regulatory mechanisms of human (and non-human) social skills.

Oxytocin induces positive expectations about ambivalent stimuli (cognitive bias) in dogs.

Expectancy bias towards positive outcomes is a potential key to subjective well-being, and has been widely investigated in different species. Here we test whether oxytocin, suggested to play a role in human optimism and emotional processing, influences how dogs judge ambivalent situations (in a cognitive bias paradigm). Subjects first learned in a location discrimination task that a bowl either contained food (at the 'positive' location) or was empty (at the 'negative' location). Then, after receiving oxytocin or placebo nasal spray, they were presented with the bowl located halfway between the positive and negative positions in communicative or non-communicative contexts (N=4×16). A Positive Expectancy Score was calculated for each subject using the latency to approach this ambivalent location. Compared to placebo groups, subjects that received oxytocin pretreatment showed a positive expectation bias in both contexts, and this effect was more pronounced in the communicative context. Our study provides the first evidence for the impact of oxytocin on dogs' judgement bias and also shows that the social-communicative nature of the task situation modulates the effect of oxytocin.

The order of ostensive and referential signals affects dogs' responsiveness when interacting with a human.

Ostensive signals preceding referential cues are crucial in communication-based human knowledge acquisition processes. Since dogs are sensitive to both human ostensive and referential signals, here we investigate whether they also take into account the order of these signals and, in an object-choice task, respond to human pointing more readily when it is preceded by an ostensive cue indicating communicative intent. Adult pet dogs (n = 75) of different breeds were presented with different sequences of a three-step human action. In the relevant sequence (RS) condition, subjects were presented with an ostensive attention getter (verbal addressing and eye contact), followed by referential pointing at one of two identical targets and then a non-ostensive attention getter (clapping of hands). In the irrelevant sequence (IS) condition, the order of attention getters was swapped. We found that dogs chose the target indicated by pointing more frequently in the RS as compared to the IS condition. While dogs selected randomly between the target locations in the IS condition, they performed significantly better than chance in the RS condition. Based on a further control experiment (n = 22), it seems that this effect is not driven by the aversive or irrelevant nature of the non-ostensive cue. This suggests that dogs are sensitive to the order of signal sequences, and the exploitation of human referential pointing depends on the behaviour pattern in which the informing cue is embedded.

Dogs' social susceptibility is differentially affected by various dog-Human interactions. A study on family dogs, former shelter dogs and therapy dogs.

When pre-treated with social stimuli prior to testing, dogs are more susceptible to human influence in a food preference task. This means, after a positive social interaction they are more willing to choose the smaller amount of food indicated by the human, as opposed to their baseline preference for the bigger amount. In the current study we investigate if and how various forms of social interaction modulate choices in the same social susceptibility task, testing dogs with varying early life history (pet dogs, therapy dogs, former shelter dogs). In line with previous studies, dogs in general were found to be susceptible to human influence as reflected in the reduced number of "bigger" choices in the human influence, compared to baseline, trials. This was true not only for pet dogs with a normal life history, but also for dogs adopted from a shelter. Therapy dogs, however, did not uniformly change their preference for the bigger quantity of food in the human influence trials; they only did so if prior to testing they had been pre-treated with social stimuli by their owner (but not by a stranger). Pet dogs were also more influenced after pre-treatment with social stimuli by their owner compared to ignoring and separation; however after pre-treatment by a stranger their behaviour did not differ from ignoring and separation. Former shelter dogs on the other hand were equally influenced regardless of pre-treatment by owner versus stranger. In summary these results show that dogs' social susceptibility is modulated by both interactions immediately preceding the test as well as by long term social experiences.

Comment on "Human-directed attachment behaviour in wolves suggests standing ancestral variation for human-dog attachment bonds".

In their recent paper, Hansen Wheat et al. (Ecology and Evolution, 2022, 12, e9299) claimed that hand raised 23-week-old wolves showed the same attachment behaviour towards their handler in the Strange Situation Test (SST) (Determinants of infant behavior, 1969, 4, 111) as dogs. At first glance, their results seem to contradict previous findings that domestication caused a unique change in social-affiliative behaviours in dogs (Animal Behaviour, 2005, 70, 1367). We argue that no persuading evidence was presented to claim that "wolves can show attachment behaviours towards humans comparable to those of dogs". When dealing with a behaviour system (Child Development, 1977, 48, 1184), the subjects' behaviour must meet consistent criteria (Behavioural and Brain Science, 1978, 3, 417), and a few behavioural preferences should not be used to claim the presence of an attachment system, especially, if the experiment violates basic assumptions of the original test. We believe the intriguing scientific question is whether the dog-owner relationship is qualitatively different from what could be observed in the wolf-hand raiser relation. Assessing all available data, our answer is still yes; dogs are unique in this respect.

Methodological comparison of cancellation versus two-way choice spatial attention tests in humans and dogs.

Introduction: Behavioural problems in family dogs are amongst the leading reasons for relinquishment to shelters which adversely affects animal welfare. Recent research suggests that certain problematic behavioural patterns might be analogous to human psychiatric disorders. Veterinary diagnosis of such conditions, however, is scarce, probably due to the lack of appropriate measurement tools. The current study focuses on dog behaviour resembling the human hemispatial neglect condition, which manifests itself as a deficit in attention to and awareness of one side of the space. Methods: Healthy human subjects (N = 21) and adult family dogs (N = 23) were tested with tools aimed to measure spatial attention. Tests administered to humans included validated paper and pencil neuropsychological tools to assess hemispatial neglect (cancellation tasks), as well as the canine version of that task (visuo-spatial search task). Dogs were tested with the same visuo-spatial search task as well as a two-way choice task. Results: Results show that both in case of dogs and humans the visuo-spatial search task detects individual variation in subjects' side preferences. However, subjects' performance in the different tasks were not related.

Six facial prosodic expressions caregivers similarly display to infants and dogs.

Parents tend to use a specific communication style, including specific facial expressions, when speaking to their preverbal infants which has important implications for children's healthy development. In the present study, we investigated these facial prosodic features of caregivers with a novel method that compares infant-, dog- and adult-directed communication. We identified three novel facial displays in addition to the already described three facial expressions (i.e. the 'prosodic faces') that mothers and fathers are typically displaying when interacting with their 1-18 month-old infants and family dogs, but not when interacting with another adult. The so-called Special Happy expression proved to be the most frequent face type during infant- and dog-directed communication which always includes a Duchenne marker to convey an honest and intense happy emotion of the speaker. These results suggest that the 'prosodic faces' play an important role in both adult-infant and human-dog interactions and fulfil specific functions: to call and maintain the partner's attention, to foster emotionally positive interactions, and to strengthen social bonds. Our study highlights the relevance of future comparative studies on facial prosody and its potential contribution to healthy emotional and cognitive development of infants.

The influence of voice familiarity and linguistic content on dogs' ability to follow human voice direction.

Domestic dogs are well-known for their abilities to utilize human referential cues for problem solving, including following the direction of human voice. This study investigated whether dogs can locate hidden food relying only on the direction of human voice and whether familiarity with the speaker (owner/stranger) and the relevance of auditory signal features (ostensive addressing indicating the intent for communication to the receiver; linguistic content) affect performance. N = 35 dogs and their owners participated in four conditions in a two-way object choice task. Dogs were presented with referential auditory cues representing different combinations of three contextual parameters: the (I) 'familiarity with the human informant' (owner vs. stranger), the (II) communicative function of attention getter (ostensive addressing vs. non-ostensive cueing) and the (III) 'tone and content of the auditory cue' (high-pitched/potentially relevant vs. low-pitched/potentially irrelevant). Dogs also participated in a 'standard' pointing condition where a visual cue was provided. Significant differences were observed between conditions regarding correct choices and response latencies, suggesting that dogs' response to auditory signals are influenced by the combination of content and intonation of the message and the identity of the speaker. Dogs made correct choices the most frequently when context-relevant auditory information was provided by their owners and showed less success when auditory signals were coming from the experimenter. Correct choices in the 'Pointing' condition were similar to the experimenter auditory conditions, but less frequent compared to the owner condition with potentially relevant auditory information. This was paralleled by shorter response latencies in the owner condition compared to the experimenter conditions, although the two measures were not related. Subjects' performance in response to the owner- and experimenter-given auditory cues were interrelated, but unrelated to responses to pointing gestures, suggesting that dogs' ability to understand the referential nature of auditory cues and visual gestures partly arise from different socio-cognitive skills.

Dog brains are sensitive to infant- and dog-directed prosody.

When addressing preverbal infants and family dogs, people tend to use specific speech styles. While recent studies suggest acoustic parallels between infant- and dog-directed speech, it is unclear whether dogs, like infants, show enhanced neural sensitivity to prosodic aspects of speech directed to them. Using functional magnetic resonance imaging on awake unrestrained dogs we identify two non-primary auditory regions, one that involve the ventralmost part of the left caudal Sylvian gyrus and the temporal pole and the other at the transition of the left caudal and rostral Sylvian gyrus, which respond more to naturalistic dog- and/or infant-directed speech than to adult-directed speech, especially when speak by female speakers. This activity increase is driven by sensitivity to fundamental frequency mean and variance resulting in positive modulatory effects of these acoustic parameters in both aforementioned non-primary auditory regions. These findings show that the dog auditory cortex, similarly to that of human infants, is sensitive to the acoustic properties of speech directed to non-speaking partners. This increased neuronal responsiveness to exaggerated prosody may be one reason why dogs outperform other animals when processing speech.

Comprehension and utilisation of pointing gestures and gazing in dog-human communication in relatively complex situations.

The aim of the present investigation was to study the visual communication between humans and dogs in relatively complex situations. In the present research, we have modelled more lifelike situations in contrast to previous studies which often relied on using only two potential hiding locations and direct association between the communicative signal and the signalled object. In Study 1, we have provided the dogs with four potential hiding locations, two on each side of the experimenter to see whether dogs are able to choose the correct location based on the pointing gesture. In Study 2, dogs had to rely on a sequence of pointing gestures displayed by two different experimenters. We have investigated whether dogs are able to recognise an 'indirect signal', that is, a pointing toward a pointer. In Study 3, we have examined whether dogs can understand indirect information about a hidden object and direct the owner to the particular location. Study 1 has revealed that dogs are unlikely to rely on extrapolating precise linear vectors along the pointing arm when relying on human pointing gestures. Instead, they rely on a simple rule of following the side of the human gesturing. If there were more targets on the same side of the human, they showed a preference for the targets closer to the human. Study 2 has shown that dogs are able to rely on indirect pointing gestures but the individual performances suggest that this skill may be restricted to a certain level of complexity. In Study 3, we have found that dogs are able to localise the hidden object by utilising indirect human signals, and they are able to convey this information to their owner.

Does the A-not-B error in adult pet dogs indicate sensitivity to human communication?

Recent dog-infant comparisons have indicated that the experimenter's communicative signals in object hide-and-search tasks increase the probability of perseverative (A-not-B) errors in both species (Topál et al. 2009). These behaviourally similar results, however, might reflect different mechanisms in dogs and in children. Similar errors may occur if the motor response of retrieving the object during the A trials cannot be inhibited in the B trials or if the experimenter's movements and signals toward the A hiding place in the B trials ('sham-baiting') distract the dogs' attention. In order to test these hypotheses, we tested dogs similarly to Topál et al. (2009) but eliminated the motor search in the A trials and 'sham-baiting' in the B trials. We found that neither an inability to inhibit previously rewarded motor response nor insufficiencies in their working memory and/or attention skills can explain dogs' erroneous choices. Further, we replicated the finding that dogs have a strong tendency to commit the A-not-B error after ostensive-communicative hiding and demonstrated the crucial effect of socio-communicative cues as the A-not-B error diminishes when location B is ostensively enhanced. These findings further support the hypothesis that the dogs' A-not-B error may reflect a special sensitivity to human communicative cues. Such object-hiding and search tasks provide a typical case for how susceptibility to human social signals could (mis)lead domestic dogs.

Social Stimulation by the Owner Increases Dogs' (Canis familiaris) Social Susceptibility in a Food Choice Task-The Possible Effect of Endogenous Oxytocin Release.

Recent evidence suggests a human-like susceptibility to social influence in dogs. For example, dogs tend to ignore their 'natural' preference for the larger amount of food after having seen a human's explicit preference for a smaller quantity. However, it is still unclear whether this tendency to conform to the partner's behaviour can be influenced by social stimuli and/or the neurohormone oxytocin as primers to prosocial predispositions. In Experiment I, eighty two dogs were tested using Prato-Previde et al.'s food quantity preference task. In Experiment I, we investigated in a 2 × 2 design how (i) a 10-minute-long social stimulation by the owner versus a socially ignoring pre-treatment as well as (ii) on-line ostensive communications versus no communication during task demonstration affect dogs' (N = 82) choices in the abovementioned food choice task. Results indicate that the owners' pre-treatment with social stimuli (eye contact, petting) increased dogs' susceptibility to the experimenter's food preference, but the salient ostensive addressing signals accompanying human demonstration masked this social priming effect. In Experiment II, N = 32 dogs from the subjects of Experiment I were retested after oxytocin (OT) or placebo (PL) pre-treatments. This experiment aimed to study whether intranasal administration of oxytocin as compared to placebo treatment would similarly increase dogs' tendency to re-enact the human demonstrator's counterproductive choice in the same task. Results showed an increased susceptibility to the human preference in the OT group, suggesting that both socially stimulating pre-treatment and the intranasal administration of oxytocin have similar priming effects on dogs' social susceptibility.

Intranasal Oxytocin Improves Social Behavior in Laboratory Beagle Dogs (Canis familiaris) Using a Custom-Made Social Test Battery.

For a long time, oxytocin has been thought to have a generally positive effect on social cognition and prosocial behavior; however, recent results suggested that oxytocin has beneficial effects only under certain conditions. The aim of the present study was to explore potential associations between social competence and the effect of intranasal oxytocin on the social behavior of laboratory beagle dogs. We expected oxytocin treatment to have a more pronounced positive effect on dogs with lower baseline performance in a social test battery. Thirty-six adult dogs of both sexes received 32 IU intranasal oxytocin and physiological saline (placebo) treatment in a double-blind, cross-over design, with 17-20 days between the two sessions. Forty minutes after the treatment, dogs participated in a social test battery consisting of eight situations. The situations were carried out within one session and took 20-30 min to complete. Principal component analysis on the coded behaviors identified four components (Willingness to interact, Preference for social contact, Non-aversive response to nonsocial threat, and Non-aversive response to social threat). The subjects' behavior during the placebo condition was used to assess their baseline performance. We found that oxytocin treatment had a differential effect on the behavior depending on the baseline performance of the individuals in all components, but only two treatment × baseline performance interactions remained significant in a less sensitive analysis. In accordance with our hypothesis, oxytocin administration increased dogs' contact seeking and affiliative behaviors toward humans but only for those with low baseline performance. Dogs with low baseline performance also showed significantly more positive (friendly) reactions to social threat after oxytocin administration than after placebo, while for dogs with high baseline performance, oxytocin administration led to a more negative (fearful) reaction. These results indicate that similar to those on humans, the effects of oxytocin on dogs' social behavior are not universally positive but are constrained by individual characteristics and the context. Nevertheless, oxytocin administration has the potential to improve the social behavior of laboratory beagle dogs that are socially less proficient when interacting with humans, which could have both applied and animal welfare implications.

Why do dogs (Canis familiaris) select the empty container in an observational learning task?

Many argue that dogs show unique susceptibility to human communicative signals that make them suitable for being engaged in complex co-operation with humans. It has also been revealed that socially provided information is particularly effective in influencing the behaviour of dogs even when the human's action demonstration conveys inefficient or mistaken solution of task. It is unclear, however, how the communicative nature of the demonstration context and the presence of the human demonstrator affect the dogs' object-choice behaviour in observational learning situations. In order to unfold the effects of these factors, 76 adult pet dogs could observe a communicative or a non-communicative demonstration in which the human retrieved a tennis ball from under an opaque container while manipulating another distant and obviously empty (transparent) one. Subjects were then allowed to choose either in the presence of the demonstrator or after she left the room. Results showed a significant main effect of the demonstration context (presence or absence of the human's communicative signals), and we also found some evidence for the response-modifying effect of the presence of the human demonstrator during the dogs' choice. That is, dogs predominantly chose the baited container, but if the demonstration context was communicative and the human was present during the dogs' choice, subjects' tendency to select the baited container has been reduced. In agreement with the studies showing sensitivity to human's communicative signals in dogs, these findings point to a special form of social influence in observational learning situations when it comes to learning about causally opaque and less efficient (compared to what comes natural to the dog) action demonstrations.