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Attachment to humans: A comparative study on hand-reared wolves and differently socialized dog puppies

Using the Strange Situation Test originally developed for testing the mother-infant relationship in humans, we compared the attachment behaviour of extensively socialized (hand-reared) dog, Canis familiaris, and wolf, Canis lupus, puppies towards their human caregiver with that of pet dog puppies of the same age. The experiment was designed to study whether (1) dog puppies as young as 16 weeks show attachment to a human caregiver, (2) extensive socialization by human caregivers affects attachment behaviour of dog puppies and (3) evolutionary changes (in the form of species-specific differences between wolf and dog pups) affect the emergence of dog-human attachment. We found a characteristic selective responsiveness to the owner in young dogs, similar to that observed in adults. This finding supports the view that puppies show patterns of attachment towards their owners. Extensive socialization had only a minor effect on the attachment behaviour in dog puppies, as the behaviour of pet dogs and hand-reared dogs was basically similar. However, we found a significant species-specific difference between wolves and dogs: both extensively socialized and pet dog puppies were more responsive to the owner than to an unfamiliar human participant, whereas extensively socialized wolves were not. Behavioural differences could be best explained by assuming that selective processes took place in the course of domestication (genetic changes) that are related to the attachment system of the dog.

Dog and owner demographic characteristics and dog personality trait associations

The aim of this study was to analyze the relationships between four personality traits (calmness, trainability, dog sociability and boldness) of dogs (Canis familiaris) and dog and owner demographics on a large sample size with 14,004 individuals. German speaking dog owners could characterize their dog by filling out a form on the Internet. There were five demographic variables for dogs and nine for owners. Two statistical methods were used for investigating the associations between personality and demographic traits: the more traditional general linear methods and regression trees that are ideal for analyzing non-linear relationships in the structure of the data. The results showed that calmness is influenced primarily by the dogs age, the neutered status, the number of different types of professional training courses (e.g. obedience, agility) the dog had experienced and the age of acquisition. The least calm dogs were less than 2.5 years old, neutered and acquired after the first 12 weeks of age, while the calmest dogs were older than 6.9 years. Trainability was affected primarily by the training experiences, the dogs age, and the purpose of keeping the dog. The least trainable dogs had not received professional training at all and were older than 3 years. The most trainable dogs were those who participated in three or more types of professional training. Sociability toward conspecifics was mainly determined by the age, sex, training experience and time spent together. The least sociable dogs were older than 4.8 years and the owners spent less than 3h with the dog daily. The most sociable dogs were less than 1.5 years old. Males were less sociable toward their conspecifics than females. Boldness was affected by the sex and age of the dog and the age of acquisition. The least bold were females acquired after the age of 1 year or bred by the owner. The boldest dogs were males, acquired before the age of 12 weeks, and were younger than 2 years old. Other variables, including the owners gender, age, education, previous experience with dogs, the number of people and dogs in the household, and purpose of keeping the dogs had minor, but detectable effects. The results suggest that on-line questionnaires are a very effective means for collecting data about dog behavior, especially if owners are motivated by instant feedback. However, note that the characteristics of dogs in the present study were reported by the owners, and the associations with the traits do not necessarily represent a causal relationship.

Dogs (Canis familiaris) learn from their owners via observation in a manipulation task

Eighty-seven pet dogs (Canis familiaris) were involved in an experiment in which they had to solve a task to obtain a ball. After witnessing a full demonstration by their owner (10 times pushing the handle of the box, which released a ball), most dogs preferred to touch the handle sooner and more frequently in comparison with other parts of the box, and they used the handle to get the ball. In contrast, dogs in 3 control groups developed their own respective methods. The lack of emergence of the ball and playing after the demonstration did not affect the learning performance strongly. This suggests that in dogs the outcome of a demonstration plays only a restricted role in the manifestation of social learning.

Chapter 3 The Dog as a Model for Understanding Human Social Behavior

This chapter was originally published in the book Advances in The Study of Behavior, Vol. 39, published by Elsevier, and the attached copy is provided by Elsevier for the authors benefit and for the benefit of the authors institution, for non-commercial research and educational use including without limitation use in instruction at your institution, sending it to specific colleagues who know you, and providing a copy to your institution’s administrator.

Social behaviour of dogs encountering AIBO, an animal-like robot in a neutral and in a feeding situation

The use of animal-like autonomous robots might offer new possibilities in the study of animal interactions, if the subject recognises it as a social partner. In this paper we investigate whether AIBO, a dog-like robot of the Sony Corp. can be used for this purpose. Twenty-four adult and sixteen 4-5 months old pet dogs were tested in two situations where subjects encountered one of four different test-partners: (1) a remote controlled car; (2) an AIBO robot; (3) AIBO with a puppy-scented furry cover; and (4) a 2-month-old puppy. In the neutral situation the dog could interact freely with one of the partners for 1 min in a closed arena in the presence of its owner. In the feeding situation the encounters were started while the dog was eating food. Our results show that age and context influence the social behaviour of dogs. Further, we have found that although both age groups differentiated the living and non-living test-partners for some extent, the furry AIBO evoked significantly increased responses in comparison to the car. These experiments show the first steps towards the application of robots in behavioural studies, notwithstanding that at present AIBOs limited ability to move constrains its effectiveness as social partner for dogs.

Molecular and behavioral analysis of the intron 2 repeat polymorphism in the canine dopamine D4 receptor gene

Genetic polymorphisms in the human dopamine D4 receptor (DRD4) gene, especially the exon 3 variable number of tandem repeats (VNTR), have been related to several psychiatric disorders and personality traits. A homologous exon 3 VNTR has been described in dogs, and we previously showed an association between the DRD4 exon 3 polymorphism and activity/impulsivity trait in German shepherds. In this study, we present a detailed analysis of the intron 2 VNTR of the DRD4 gene. A short and a long form of the intronic variation were identified in 678 unrelated dogs from five breeds and in 22 wolves. For molecular analysis, the intron 2 region was cloned into a promoterless luciferase reporter vector that led to an elevation in transcriptional activity. Moreover, an allelic difference in promoter activity was detected, and a repressive effect of the long allele was observed. Behavioral analysis of 96 unrelated German shepherds showed a significant association between the social impulsivity endophenotype of the Greeting Test and both the exonic (P = 0.002) and the intronic (P = 0.003) VNTRs of the DRD4 gene. Moreover, an additive effect of the two polymorphisms was also shown (Spearman’s rho = 0.356, P = 0.0004). In conclusion, these results give further support to our previous findings that the DRD4 gene is associated with dog behavior. We also present molecular evidence for the functional role of the intron 2 VNTR in the canine DRD4 gene.

Polymorphism in the tyrosine hydroxylase (TH) gene is associated with activity-impulsivity in German Shepherd Dogs

We investigated the association between repeat polymorphism in intron 4 of the tyrosine hydroxylase (TH) gene and two personality traits, activity-impulsivity and inattention, in German Shepherd Dogs. The behaviour of 104 dogs was characterized by two instruments: (1) the previously validated Dog-Attention Deficit Hyperactivity Disorder Rating Scale (Dog-ADHD RS) filled in by the dog owners and (2) the newly developed Activity-impulsivity Behavioural Scale (AIBS) containing four subtests, scored by the experimenters. Internal consistency, inter-observer reliability, test-retest reliability and convergent validity were demonstrated for AIBS. Dogs possessing at least one short allele were proved to be more active-impulsive by both instruments, compared to dogs carrying two copies of the long allele (activity-impulsivity scale of Dog-ADHD RS: p = 0.007; AIBS: p = 0.023). The results have some potential to support human studies; however, further research should reveal the molecular function of the TH gene variants, and look for the effect in more breeds.

DRD4 and TH gene polymorphisms are associated with activity, impulsivity and inattention in Siberian Husky dogs

Both dopamine receptor D4 (DRD4) exon 3 and tyrosine hydroxylase (TH) intron 4 repeat polymorphisms have been linked to activity and impulsivity in German Shepherd dogs (GSDs). However, the results in GSDs may not be generalisable to other breeds, as allelic frequencies vary markedly among breeds. We selected the Siberian Husky for further study, because it is highly divergent from most dog breeds, including the GSD. The study sample consisted of 145 racing Siberian Huskies from Europe and North America. We found that this breed possesses seven DRD4 length variants, two to five more variants than found in other breeds. Among them was the longest known allele, previously described only in wolves. Short alleles of the DRD4 and TH repeat polymorphisms were associated with higher levels of activity, impulsivity and inattention. Siberian Huskies possessing at least one short allele of the DRD4 polymorphism displayed greater activity in a behavioural test battery than did those with two long alleles. However, the behavioural test was brief and may not have registered variation in behaviour across time and situations. Owners also completed the Dog-Attention Deficit Hyperactivity Disorder Rating Scale (Dog-ADHD RS), a more general measure of activity and attention. Siberian Huskies from Europe with two short alleles of the TH polymorphism received higher ratings of inattention on the Dog-ADHD RS than did those with the long allele. Investigation of the joint effect of DRD4 and TH showed that dogs possessing long alleles at both sites were scored as less active-impulsive than were others. Our results are aligned with previous studies showing that DRD4 and TH polymorphisms are associated with activity-impulsivity related traits in dogs. However, the prevalence of variants of these genes differs across breeds, and the functional role of specific variants is unclear.

Fetching what the owner prefers? Dogs recognize disgust and happiness in human behaviour

Research using the two-object choice paradigm showed that dogs prefer the object associated with the happy human emotion. However, they provided rather ambiguous results regarding the negative emotions. We assumed that differences between the dogs’ and owners’ interest towards the ‘negative’ object might be responsible for this. In our experiment, dogs observed their owner expressing different emotions towards two uniform plastic bottles. Five dog groups were tested based on the condition they received: (1) happy versus neutral, (2) happy versus disgust, (3) neutral versus disgust and (4–5) neutral vs neutral, as control groups. Contrary to previous studies using free choice paradigm, we used a task-driven approach. After the demonstration, the dogs had to retrieve one object to the owner. The dogs’ performance in the two neutral–neutral groups did not differ from the chance level. In contrast, subjects were able to distinguish between the happy and neutral expression of the owner: they both approached and fetched the ‘happy’ object. In the happy–disgusted and neutral–disgusted groups, the dogs approached the bottles randomly, suggesting that they found the ‘disgusting’ and ‘neutral’ objects equally attractive. Nevertheless, the dogs preferentially retrieved the object marked with the relatively more positive emotion (happy or neutral) to the owner in both conditions. Our results demonstrate that dogs are able to recognize which is the more positive among two emotions, and in a fetching task situation, they override their own interest in the ‘disgusting’ object and retrieve what the owner prefers.

Lessons from the canine Oxtr gene: Populations, variants and functional aspects

Oxytocin receptor (OXTR) acts as a key behavioral modulator of the central nervous system, affecting social behavior, stress, affiliation and cognitive functions. Variants of the Oxtr gene are known to influence behavior both in animals and humans; however, canine Oxtr polymorphisms are less characterized in terms of possible relevance to function, selection criteria in breeding and domestication. In this report, we provide a detailed characterization of common variants of the canine Oxtr gene. In particular (1) novel polymorphisms were identified by direct sequencing of wolf and dog samples, (2) allelic distributions and pairwise linkage disequilibrium patterns of several canine populations were compared, (3) neighbor joining (NJ) tree based on common single nucleotide polymorphisms (SNPs) was constructed, (4) mRNA expression features were assessed, (5) a novel splice variant was detected and (6) in vitro functional assays were performed. Results indicate marked differences regarding Oxtr variations between purebred dogs of different breeds, free‐ranging dog populations, wolf subspecies and golden jackals. This, together with existence of explicitly dog‐specific alleles and data obtained from the NJ tree implies that Oxtr could indeed have been a target gene during domestication and selection for human preferred aspects of temperament and social behavior. This assumption is further supported by the present observations on gene expression patterns within the brain and luciferase reporter experiments, providing a molecular level link between certain canine Oxtr polymorphisms and differences in nervous system function and behavior.