Intraspecific attachment in adult domestic dogs (Canis familiaris): Preliminary results

The Welfare of Dogs as an Aspect of the Human-Dog Bond: A Scoping Review

The close bond that can exist between humans and their dogs is an important aspect of the evolutionary, economic, and social connections between the two species. There is a need for a better understanding of the place of the dog within the human-dog bond and on ways the human-dog bond affects dog welfare. We conducted a scoping review to investigate to what extent and in what ways dog welfare is addressed in the research literature on the human-dog bond. We identified 706 publications on the human-dog bond from across the globe that were published from 2012 to 2023. We found that 246 of these 706 publications had a focus on dog welfare. Our review showed that the interplay of characteristics and backgrounds of owners/handlers and their dogs was linked to dog welfare in multiple, both positive and negative, ways. Our review is limited by the fact that most of the research that we reviewed involved pet dogs and in majority came from Western, Educated, Industrialized, Rich, Democratic (WEIRD) societies. There is a need for a better understanding of how the human-dog bond affects the welfare of working, assistance, and service dogs.

Canine Socialisation: A Narrative Systematic Review

There are over 10 million pet dogs in the UK alone, and they have become a member of modern human families. If not properly socialised as puppies, dogs have a higher risk of problematic behaviours during adulthood, yet socialisation studies are lacking. Much of the experimental research was carried out at least 50 years ago, and the importance of socialisation was demonstrated so clearly that further studies with unsocialised controls would be deemed unethical. In this review, the aim was to evaluate all literature relevant to canine socialisation. This review used PRISMA-P guidelines to identify 29 studies: 14 were questionnaire-based studies (two of which also had a testing element), 15 included some form of experimental manipulation relating to socialisation, and one was a purely observational study. Based on this literature review, we recommend future research into minimum necessary socialisation levels, as well as breed differences in the timing of effective socialisation. Such studies will help owners and breeders produce well-adjusted adult dogs.

Physiological Indicators of Acute and Chronic Stress in Securely and Insecurely Attached Dogs Undergoing a Strange Situation Procedure (SSP): Preliminary Results

Simple Summary

The attachment bond that dogs form towards their owners shares similar features with the bond children form towards their caregivers. Insecurely attached children struggle to find support from their caregivers and therefore to regulate their own emotional response in times of distress. We aimed to investigate whether the quality of dog attachment to the owner may affect their physiological response to stress. We selected ten insecure and ten secure dogs from a sample of individuals who underwent a Strange Situation Procedure (SSP) to assess their attachment pattern towards the owner. The SSP is specifically designed to progressively generate stress. We collected saliva samples before and after the test to measure cortisol concentrations, as an indicator of acute stress, as well as a hair sample to assess chronic stress. We also measured blood pressure, heart rate, respiratory rate and rectal temperature after the completion of the test. The results showed that salivary cortisol concentrations were higher in insecure dogs, particularly after the test. Heart rate also tended to be higher in insecure dogs. No difference in hair cortisol levels were found between secure and insecure dogs. Dogs’ physiological response to acute stress may be affected by the quality of the attachment to the owners.

Abstract

The quality of the attachment bond towards the caregiver may affect the dog’s physiological responses to stressful stimuli. This study aimed to measure chronic and acute physiological parameters of stress in ten securely and ten insecurely attached dogs. The twenty experimental subjects were selected from a sample of dogs that participated with their owners in the Strange Situation Procedure. Saliva samples were collected before (T0) and after (T1) the test. Blood pressure, heart rate, respiratory rate, and rectal temperature were measured after the test, only. At this time, a hair sample was also collected. RM ANOVA was used to analyse cortisol concentrations between secure and insecure dogs at T0 and T1. Mann–Whitney U test or T test were used for other physiological parameters. Insecure dogs had significant higher salivary cortisol concentrations than secure dogs at T1 (p = 0.024), but only a non-significant trend towards higher cortisol concentrations at T0 (p = 0.099). Post-test heart rate also tended to be higher in insecure compared to secure dogs (p = 0.077). No significant differences in hair cortisol concentration were found. The quality of attachment may affect the dog’s physiological response to acute stress, at least when related to separation from the caregiver. The effect of attachment on chronic stress requires further investigation.

Development of the Dog Attachment Insecurity Screening Inventory (D-AISI): A Pilot Study on a Sample of Female Owners

Simple Summary

The Strange Situation Procedure is a laboratory test originally designed to assess the quality of a child’s attachment bond to their mother and is widely used in dogs to assess their attachment bond towards the owner. However, the SSP is time consuming and limits the amount and variety of obtainable data. In order to overcome these limitations, we adapted a three-dimensional parent-report scale, named the Attachment Insecurity Screening Inventory (AISI) 6–12, originally developed to assess 6- to 12-year-old children’s attachment insecurity, to dog–owner dyads, and we assessed scale consistency and validity. A first statistical analysis performed on the responses provided by 524 female owners to the online questionnaire revealed five scale dimensions named “physical contact”, “control”, separation anxiety”, “owner as emotional support”, and “owner as a source of positive emotion”. However, a further forced extraction of three components resulted in subscales that mirrored the ones reported for the original AISI in terms of item composition (i.e., ambivalent, avoidant, and disorganized). The three subscales also had satisfactory to good measures of internal reliability. The final scale was named the Dog Attachment Insecurity Screening Inventory (D-AISI). Although promising, it needs to be refined and tested for more validity measures.

Abstract

To date, the Strange Situation Procedure is the only tool available to investigate the quality of the dog’s attachment bond towards the owner. This study aimed to adapt a parent-report scale, named the Attachment Insecurity Screening Inventory (AISI) 6–12, originally designed to assess 6- to 12-year-old children’s attachment insecurity, to dog–owner dyads and assess measures of consistency and validity. The online questionnaire was completed by 524 female dog owners. Principal component analysis (PCA) revealed five components named, respectively, “physical contact”, “control”, “separation anxiety”, “owner as emotional support”, and “owner as a source of positive emotion”. Because of the three-factor structure of the original AISI, a PCA with a pre-fixed set of three factors was also performed. The resulting subscales mirrored the ones found for the original scale (i.e., ambivalent, avoidant, and disorganized), although four items did not fit the model. Internal reliability appeared to be satisfying for the ambivalent and the disorganized subscales, and good for the avoidant subscale. The theoretical background and the results of this study suggest that the three-dimensional model represents a better solution for the interpretation of the Dog Attachment Insecurity Screening Inventory (D-AISI). Although promising, this scale requires refinement and assessment of additional validity measures.

Intraspecific and Interspecific Attachment between Cohabitant Dogs and Human Caregivers

In recent years there has been growing interest in uncovering evolutionary and lifetime factors that may contribute to the domestic dog's (Canis lupus familiaris) success in anthropogenic environments. The readiness with which dogs form social attachments, their hyper-social focus, and social flexibility have all been areas of investigation. Prior research has demonstrated that many pet dogs form infant-caregiver type attachments toward human caretakers, even into adulthood. However, it is unknown if adult dogs form similar attachment bonds to other species, including cohabitant dogs, or if the dog-human relationship is unique in this respect. In the current study we used the Secure Base Test to evaluate behavioral indicators of stress reduction, proximity seeking and exploration, classifying dog-human and dog-dog dyads into attachment style categories. As in prior studies, we found that the majority of our dog-human dyads met the traditional criteria for infant-caregiver type attachment. However, the majority of dogs did not display this form of attachment toward cohabitant dog partners. Instead, behaviors observed in dog-dog relationships better matched attachment classifications described in human sibling attachment research. Overall, companion dogs were significantly less likely than human caretakers to elicit behaviors associated with attachment security in a focal dog. Dog-human attachment may play a distinct and important role in the success and resilience of adult dogs living in at least some anthropogenic environments. Bonds formed with other adult dogs, while important, likely serve a different function.

The Indispensable Dog

Dogs' remarkable success in living in a human-dominated world rests on a set of adaptations to cohabitation with humans. In this paper, I review the nature of these adaptations. They include changes in reproductive and foraging behavior from their ancestor species, wolves, which can be understood as adaptations to the change from hunting live prey to feeding on human food residues. Dogs also show several changes in social behavior which are more controversial and even somewhat paradoxical. Contrary to theories of canine domestication which view dogs as less aggressive and more cooperative than wolves, several studies show that dogs' social interactions with conspecifics are more hierarchical and competitive than are wolves'. As scavengers rather than hunters, dogs do not need to cooperate with conspecifics the way that wolves do. But how then can we understand dogs' willingness to cooperate with humans? I propose an integrated account of dogs' social behavior that does not assume that dogs need to recognize the species-identity of the individuals with whom they interact. Because of the overlap in formal signals of dominance and submission between dog and human and people's complete control over the resources dogs need, I propose that people occupy a status of "super-dominance" over dogs. This conception suggests several new lines of research which could shed light on the human-dog relationship to the benefit of both partners.

Quantitative Behavioral Analysis and Qualitative Classification of Attachment Styles in Domestic Dogs: Are Dogs with a Secure and an Insecure-Avoidant Attachment Different?

Simple Summary

Previous limited literature suggest that dogs present the same attachment styles as those observed in children towards their caregivers, namely secure, insecure-avoidant, insecure-ambivalent, and disorganized. However, such classification for dogs has never been corroborated by the simultaneous analysis of quantitative measures of behavior recorded during the Strange Situation Procedure (SSP). Since several modified SSPs have been used to investigate dog-to-owner attachment, in this study, two different groups of dog-owner dyads underwent two different versions of the SSP. Dogs were classified based on their attachment pattern toward the owner. For this purpose, we developed a new adaptation of the classification used for human infants. In addition, dogs’ behavior was recorded throughout the test. Behavioral differences between dogs classified as secure and avoidant were investigated. Results suggest that the classification used was effective at identifying secure and avoidant attachment styles in dogs. Like in children, behavioral differences between secure and avoidant dogs were particularly evident as the test progressed. While secure dogs showed an increase in proximity/contact seeking behaviors toward their owners, avoidant dogs did not. Larger samples may be needed in future studies to support these findings and to be able to include also ambivalent and disorganized dogs.

Abstract

Since several modified Strange Situation Procedures (SSP) have been used to investigate dog-to-owner attachment, in this study two different samples of dog-owner dyads underwent two modified versions of the SSP. Dogs’ attachment style to the owner was assessed based on a novel adaptation of the attachment pattern classification used for infant-caregivers. Dogs’ behavioral data were collected using continuous sampling and, in the second protocol, also with a scoring system for greeting and social play. In both studies, secure and avoidant dogs’ behavior was compared using the Mann Whitney test, while differences within each group across episodes were analyzed using the Wilcoxon paired sample test. The classification seemed to be effective at identifying both avoidant and secure attachment patterns in dogs. As expected, differences in key attachment behaviors, such as proximity/contact seeking toward the caregiver, between secure and avoidant dogs were more evident in the final episodes of the test. Differently from secure dogs, avoidant dogs did not show an increase in proximity/contact seeking behavior with the caregiver in any of the procedures. Further studies with larger samples are needed to support the effectiveness of this classification and investigate on the remaining attachment styles.

Effects of Stroking on Salivary Oxytocin and Cortisol in Guide Dogs: Preliminary Results

This pilot study aimed at investigating how salivary oxytocin levels are affected by human interaction and isolation in eight guide dogs (six Labrador retrievers and two golden retrievers; four males and four females, 21.87 ± 1.36 months old) just before assignment to the blind person. Each dog engaged, at one-week intervals, in a positive (5 min of affiliative interaction with their trainer) and a negative (5 min of isolation) condition. Saliva samples used for Enzyme Immunoassay (EIA) quantification of salivary oxytocin were collected before and immediately after both experimental conditions. In order to assess potential hypothalamic pituitary adrenal (HPA) axis activation that could have affected oxytocin levels, saliva samples were collected 15 min after both experimental conditions for EIA quantification of salivary cortisol and a behavioral assessment was performed during the negative condition. The results were compared using the Wilcoxon test (p < 0.05). Oxytocin concentrations showed a statistically significant increase after the positive interaction (p = 0.036) and no difference after the negative one (p = 0.779). Moreover, no difference (p = 0.263) was found between the cortisol concentrations after each experimental condition and no signs of distress were observed during the isolation phase. These preliminary findings support the hypothesis that stroking dogs has positive effects on their emotional state independently of hypothalamic pituitary adrenal axis activation.

Pet dogs' relationships vary rather individually than according to partner's species

Most dogs worldwide are free-ranging animals that form relationships mainly with conspecifics, yet research has focused mainly on the dog-human bond, leading to the hypothesis that dogs evolved specific abilities to form a unique relationship with humans. Although widespread, this hypothesis has not, as yet, been tested. Here we compared the relationships pet dogs form with their owner and with other dogs living in the same household. Using a bottom-up approach, we analyzed dogs’ behavior in a test battery with both dog and human partners. Results revealed that pet dogs’ relationships are characterized by three components (i.e. reference, affiliation and stress). A comparison between dogs’ intra- and inter-specific relationships found that overall dogs refer more to their owner, but also that some dogs form stronger affiliative bonds with conspecifics than with their owner. Moreover, we tested how different partners could help dogs cope with a stressful situation. We found that the type of relationship, rather than the partner species, predicts how dogs react to a social threat. Our results suggest that dogs can form relationships of comparable qualities with both humans and other dogs, and that these relationships vary along multiple components across different partners.

Dog-Owner Attachment Is Associated With Oxytocin Receptor Gene Polymorphisms in Both Parties. A Comparative Study on Austrian and Hungarian Border Collies

Variations in human infants' attachment behavior are associated with single nucleotide polymorphisms (SNPs) in the oxytocin receptor (OXTR) gene, suggesting a genetic component to infant-mother attachment. However, due to the genetic relatedness of infants and their mothers, it is difficult to separate the genetic effects of infants' OXTR genotype from the environmental effects of mothers' genotype possibly affecting their parental behavior. The apparent functional analogy between child-parent and dog-owner relationship, however, offers a way to disentangle the effects of these factors because pet dogs are not genetically related to their caregivers. In the present study we investigated whether single nucleotide polymorphisms of pet dogs' OXTR gene (-213AG,-94TC,-74CG) and their owners' OXTR gene (rs53576, rs1042778, rs2254298) are associated with components of dog-owner attachment. In order to investigate whether social-environmental effects modulate the potential genetic influence on attachment, dogs and their owners from two different countries (Austria and Hungary, N = 135 in total) were tested in a modified version of the Ainsworth Strange Situation Test (SST) and questionnaires were also used to collect information about owner personality and attachment style. We coded variables related to three components of attachment behavior in dogs: their sensitivity to the separation from and interaction with the owner (Attachment), stress caused by the unfamiliar environment (Anxiety), and their responsiveness to the stranger (Acceptance). We found that (1) dogs' behavior was significantly associated with polymorphisms in both dogs' and owners' OXTR gene, (2) SNPs in dogs' and owners' OXTR gene interactively influenced dog-human relationship, (3) dogs' attachment behavior was affected by the country of origin, and (4) it was related to their owners' personality as well as attachment style. Thus, the present study provides evidence, for the first time, that both genetic variation in the OXTR gene and various aspects of pet dogs' environmental background are associated with their attachment to their human caregivers.

The importance of early life experiences for the development of behavioural disorders in domestic dogs

Behavioural disorders are a major reason for euthanasia and sheltering of pet dogs. The prevention and treatment of behavioural disorders requires a better understanding of the underlying causes. Early life experiences, such as maternal care, attachment and socialisation, have long lasting and serious consequences for the behavioural and physiological development of an individual. The complex interplay between these factors is likely to have consequences for the future dog-owner bond and the vulnerability to develop behavioural disorders. Here, we summarise the current literature on the interactions between maternal care, attachment formation, and the sensitive socialisation period and their potential consequences on adult dog behaviour. Based on the findings we highlight gaps in knowledge and provide suggestions for future research which are necessary to formulate recommendations for pet dog breeding and socialisation.

Influence of Maternal Care on Behavioural Development of Domestic Dogs (Canis Familiaris) Living in a Home Environment

Simple Summary

Maternal care in dogs and its impact on the behavioural development of puppies has become the subject of growing research interest. In order to determine the effects of maternal care on the behaviour of family dog puppies, maternal care during the first three weeks after birth was observed in 12 litters of puppies reared in a home environment (72 puppies). The behavioural responses of the puppies were assessed at two months of age, in an arena and an isolation test. In both tests, the amount of maternal care was found to be positively associated with some stress behaviours and, in the arena test, also with the puppies’ interest in an unfamiliar person who was present during the test. These behaviours are similar to those observed during the separation of other young mammals from an attachment figure with which they have a high quality of bond. Amount of maternal care was also found to be negatively associated with exploration and play. The difference in results between the present study and our previous study involving laboratory dogs reared in relative social isolation suggests that the developmental trajectory of puppies is influenced by a combination of maternal behaviour and social and physical environmental enrichment.

Abstract

Maternal care has been shown to affect the development of the brain, behaviour, social skills and emotional systems of the young of many mammalian species including dogs. The aim of the present study was to determine the effects of maternal care on the behavioural responses of family dog puppies towards environmental and social stimuli. In order to do this, maternal care (licking puppy’s ano-genital area, licking the puppy, nursing and mother-puppy contact) during the first three weeks after birth was assessed in 12 litters of domestic dog puppies reared in home environments (total = 72 puppies). The behavioural responses of puppies were assessed in an arena and an isolation test, which were performed when the puppies were two-month old. Data were analysed using principal components analysis and projection to latent structures regression. A systematic relationship was found between maternal care and behaviour in both tests. In the arena test, maternal care was found to be positively associated with approach to the stranger, attention oriented to the stranger, time spent near the enclosure, yawning, whining and yelping (R²Y = 0.613, p = 8.2 × 10⁻⁹). Amount of maternal care was negatively associated with the number of squares crossed and the time spent individually playing with the rope. In the isolation test, the amount of maternal care was positively associated with standing posture, paw lifting, and howling, and it was negatively associated with yawning, lying down and nose licking (R²Y = 0.507, p = 0.000626). These results suggest that the amount of maternal care received during early life influences the pattern of behavioural responses and coping strategies of puppies at two-months of age. On the basis of these findings it could be speculated that early maternal care contributes to adaption to the environment in which family puppies are developing, with particular regard to social relationships with people.

Exploring the existence and potential underpinnings of dog-human and horse-human attachment bonds

This article reviews evidence for the existence of attachment bonds directed toward humans in dog-human and horse-human dyads. It explores each species' alignment with the four features of a typical attachment bond: separation-related distress, safe haven, secure base and proximity seeking. While dog-human dyads show evidence of each of these, there is limited alignment for horse-human dyads. These differences are discussed in the light of the different selection paths of domestic dogs and horses as well as the different contexts in which the two species interact with humans. The role of emotional intelligence in humans as a potential mediator for human-animal relationships, attachment or otherwise, is also examined. Finally, future studies, which may clarify the interplay between attachment, human-animal relationships and emotional intelligence, are proposed. Such avenues of research may help us explore the concepts of trust and bonding that are often said to occur at the dog-human and horse-human interface.