Psychosocial and Psychophysiological Effects of Human-Animal Interactions
US National Library of Medicine National Institutes of Health PMCID: PMC3408111
During the last decade it has become more widely accepted that pet ownership and animal assistance in therapy and education may have a multitude of positive effects on humans. Here, we review the evidence from 69 original studies on human-animal interactions (HAI) which met our inclusion criteria with regard to sample size, peer-review, and standard scientific research design. Among the well-documented effects of HAI in humans of different ages, with and without special medical, or mental health conditions are benefits for: social attention, social behavior, interpersonal interactions, and mood; stress-related parameters such as cortisol, heart rate, and blood pressure; self-reported fear and anxiety; and mental and physical health, especially cardiovascular diseases. Limited evidence exists for positive effects of HAI on: reduction of stress-related parameters such as epinephrine and norepinephrine; improvement of immune system functioning and pain management; increased trustworthiness of and trust toward other persons; reduced aggression; enhanced empathy and improved learning. We propose that the activation of the oxytocin system plays a key role in the majority of these reported psychological and psychophysiological effects of HAI. Oxytocin and HAI effects largely overlap, as documented by research in both, humans and animals, and first studies found that HAI affects the oxytocin system. As a common underlying mechanism, the activation of the oxytocin system does not only provide an explanation, but also allows an integrative view of the different effects of HAI. During the last decades, animal assistance in therapy, education, and care has greatly increased. Today, the value of animal-assisted interventions [AAI, including animal-assisted therapy (AAT) and activities] is widely acknowledged. In the light of the rapid development of the practice of AAI, research evaluating the effects of AAIs as well as studies investigating the basic effects of human-animal interaction (HAI) and the underlying mechanisms seem to lag behind. Still, there is already quite a body of scientific literature on this topic. However, this is spread out over a number of journals and fields, constraining an integrative view. In the following, we will provide an overview of studies assessing effects of AAI as well as pet ownership which meet certain scientific criteria. In addition, we propose a common underlying mechanism for the majority of the positive effects of HAI: i.e., the activation of the oxytocinergic system and its role in social stress modulation. This system can be linked directly to many of the observed physiological effects of HAI and may also be indirectly associated with the other, mainly psychological, effects. Thereby, we provide a coherent body of theory for integrating the diverse endocrinological, psychophysiological, and psychosocial effects of HAI found in different studies. Furthermore, we give a well-founded overview of scientifically documented effects of HAIs which today are a quite popular topic in the general literature, as are first speculations on underlying mechanisms including the oxytocin system (e.g., Olmert, 2009).
We will start our rationale with a review of the literature on effects of HAI and thereafter we will present a short overview of the oxytocinergic system and its psychophysiological effects. We propose that oxytocin (OT) release may contribute to explain many of the effects of HAI documented by the studies included in our review.
Criteria for Inclusion of Studies in This Review
In this review we focus on the effects of HAI on psychosocial variables such as empathy and social interactions and on human physical and mental health, including effects on hormones and the autonomic nervous system assessed via variables such as heart rate or blood pressure. Effects could result from either companion animal ownership or animal contacts, in experimental settings or animal-assisted interventions. Studies not directly related to these topics were excluded, for example, on pet ownership and attitudes toward smoking, or other variables which could indirectly influence health or social contacts (e.g., Milberger et al., 2009; Zimolag and Krupa, 2009). Furthermore, we excluded the following contexts: reports on relations between human personality and animal-related issues; the link between animal abuse and interpersonal violence; attitudes toward pets in general or in connection with animal welfare.
The prime criterion for inclusion was the publication of the original research in a peer-reviewed scientific journal. Mainly Medline and PsychLit were used for the article searches. Search terms were: HAI, AAT, animal-assisted activity, “therapeutic riding” and “equine facilitated therapy.” However, since we focus on psychosocial and psychophysiological effects in this review, studies employing horses in physiotherapy with a mere assessment of effects on movement or balance were excluded (e.g., Cherng et al., 2004; Beinotti et al., 2010). From several hundred publications found via the terms “pet,” “cat,” or “dog” we included relevant original research articles (see Table Table1)1) as well as reviews and meta-analyses. The second criterion was that the study design allowed to attribute any effect found with a high probability to the animal interaction rather than to any other possible confounding variable. Hence, studies with a pre-post-measurement design, but without control group were excluded. The third criterion for inclusion was a sample size of at least 10 subjects (per group).
Effects on social interaction
Interacting with animals influences social interaction between humans and related factors important in this respect, such as trust, empathy, aggression, and a positive mood.
Increased positive social attention from others and stimulation of social behavior
A relatively large body of research investigated the effect of a friendly animal on the perception of the human in its company and on the stimulation of social behavior. This is also called the “social catalyst effect” when it refers to the facilitation of interpersonal interactions.
Hart et al. (1987) and Eddy et al. (1988), for example, showed that the company of a service dog promoted friendly social attention, smiles, and conversation from others for persons in wheelchairs. Wells (2004) studied the behavior of 1800 strangers toward a female experimenter in six different conditions: accompanied by a Labrador retriever pup, by an adult Labrador, by an adult Rottweiler, being in the presence of a teddy bear or a plant, or being alone as control conditions. In the alone condition, the experimenter was ignored more than with the teddy or plant, but got more attention in the company of a dog. The Rottweiler led to more non-responses than the pup or the adult Labrador, which elicited most smiles and verbal responses. Also, in a classroom of first-graders, the presence of a dog was associated with increased attention toward the teacher in comparison to class in the absence of the dog (Kotrschal and Ortbauer, 2003).
Interaction with an animal is per se a form of social behavior. The following research assessed the effect of animal presence on this aspect without further investigating effects in interpersonal behavior. Children with autism interacted most frequently and for the longest periods with a real dog in comparison to objects or a person (Prothmann et al., 2009). Also children with pervasive developmental disorders (including autism) were more playful in interaction with a live dog compared to toys, and also more aware of their social environment in the presence of the dog (Martin and Farnum, 2002).
Effects on social interaction
Interacting with animals influences social interaction between humans and related factors important in this respect, such as trust, empathy, aggression, and a positive mood.
Increased positive social attention from others and stimulation of social behavior
A relatively large body of research investigated the effect of a friendly animal on the perception of the human in its company and on the stimulation of social behavior. This is also called the “social catalyst effect” when it refers to the facilitation of interpersonal interactions.
Hart et al. (1987) and Eddy et al. (1988), for example, showed that the company of a service dog promoted friendly social attention, smiles, and conversation from others for persons in wheelchairs. Wells (2004) studied the behavior of 1800 strangers toward a female experimenter in six different conditions: accompanied by a Labrador retriever pup, by an adult Labrador, by an adult Rottweiler, being in the presence of a teddy bear or a plant, or being alone as control conditions. In the alone condition, the experimenter was ignored more than with the teddy or plant, but got more attention in the company of a dog. The Rottweiler led to more non-responses than the pup or the adult Labrador, which elicited most smiles and verbal responses. Also, in a classroom of first-graders, the presence of a dog was associated with increased attention toward the teacher in comparison to class in the absence of the dog (Kotrschal and Ortbauer, 2003).
Interaction with an animal is per se a form of social behavior. The following research assessed the effect of animal presence on this aspect without further investigating effects in interpersonal behavior. Children with autism interacted most frequently and for the longest periods with a real dog in comparison to objects or a person (Prothmann et al., 2009). Also children with pervasive developmental disorders (including autism) were more playful in interaction with a live dog compared to toys, and also more aware of their social environment in the presence of the dog (Martin and Farnum, 2002).
Several studies assessed changes in social interaction not via direct observation, but rather indirectly. Paul and Serpell (1996) found that normal families who obtained a dog, 1 month later engaged in more leisure activities together and their children were more often visited by friends. In a classroom of first-graders, the presence of a dog led to a better social integration among students as documented via indirect psychometric indicators (Hergovich et al., 2002) as well as via direct behavior observation (Kotrschal and Ortbauer, 2003). Also adults profit from animal contact with regard to social relationships, such as patients with substance abuse in an AAT group program, who rated the therapeutic alliance with the therapist as more positive after 26 sessions than the control group without an animal present (Wesley et al., 2009). Fournier et al. (2007) reported that prison inmates significantly improved in social skills via AAT and in normal adult couples, owning pets stabilized the marriage after the children had left home (Na and Richang, 2003).
Based on the presented evidence we conclude that contact with companion animals holds the potential to promote social interaction and functioning in children and adults with or without mental health problems.
About the authors and credits:
http://www.ncbi.nlm.nih.gov/pmc/
Andrea Beetz,1,* Kerstin Uvnäs-Moberg,2,3 Henri Julius,1 and Kurt Kotrschal4,5
1Department of Special Education, Institut für Sonderpädagogische Entwicklungsförderung und Rehabilitation, University of Rostock, Rostock, Germany
2School of Life Science, University of Skövde, Skövde, Sweden
3Department of Animal Environment and Health, Swedish University of Agriculture, Skara, Sweden
4Konrad Lorenz Forschungsstelle Gruenau, Gruenau im Almtal, Austria
5Department of Behavioural Biology, University of Vienna, Vienna, Austria
Edited by: Lara Bellardita, Fondazione IRCCS Istituto Nazionale dei Tumori, Italy
Reviewed by: Takefumi Kikusui, Azabu University, Japan; Lynette Arnason Hart, University of California Davis, USA; Erhard Olbrich, University of Erlangen-Nürnberg, Germany
*Correspondence: Andrea Beetz, Department of Special Education, Institut für Sonderpädagogische Entwicklungsförderung und Rehabilitation, University of Rostock, August-Bebel-Straße 28, 18055 Rostock, Germany. e-mail: moc.liamg@zteeb.m.aerdna
This article was submitted to Frontiers in Psychology for Clinical Settings, a specialty of Frontiers in Psychology.
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Copyright © 2012 Beetz, Uvnäs-Moberg, Julius and Kotrschal.
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