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Pet Therapy: The Science Behind Petting Animals

Written by Catherine Zhang and Edited by Gouri Ajith

Image by Lenka Novotná from Pixabay

With booming popularity at both public and private schools across the nation, animal therapeutic sessions are often marketed as a way to help students relax by providing a temporary escape from the mundane routine of typical academic life. Although the benefits of these therapeutic events are typically limited to the happiness and stress-relief experienced by those interacting with the animals, research on hormones and specialized cells of the nervous system (called nerve cells) has shown that not only humans benefit from petting the animals, but also the animals being petted.

Oxytocin, the “love hormone,”  is released when an owner and his or her dog interact with one another through stimulation from gentle touch [1]. Since the hormone is also released when stimulating milk ejection during breastfeeding, promoting uterine contractions during labor in females, and facilitating bonding between mom and child, the relationship between pet and owner can be compared to that between a mother and her infant [1]. In addition to its social-bonding qualities, oxytocin is also closely associated with anti-stress properties, such as decreased blood pressure and lower levels of the stress hormone—cortisol [2]. This suggests that the love and comfort a child experiences from its mother is also applicable to that experienced by an animal and its loving owner — as the oxytocin has calming effects for both mother and child when nurturing and for both owner and pet when petting animals. 

To study the relationship between animals and their owner, a 2017 study analyzed blood samples collected from both owners and their dogs at 1, 3, 5, 15, 30, and 60-minute intervals by using catheters, which are thin tubes that can be inserted into a vein to draw blood [3]. The study analyzed the hormone levels present in the blood samples and concluded that both humans and dogs had increased oxytocin levels when the owners pet their dogs. Although this study focused primarily on the correlation between hormone levels of both the dog and its owner, this data may be extrapolated to the context of strangers calmly petting animals too — as the hormone is released by gentle touch in any encounter regardless of who is petting the dog. This study suggests that both animals and humans benefit from positive interactions with one another, as the gentle touch inflicted on animals increases oxytocin levels for both species, thus invoking the anti-stressing effects.

In addition, a 2013 experiment concluded that the mice studied actually preferred to be “pet.” A specific type of nerve cell called MRGPRB4 was discovered in hairy skin that conveys pleasure when stimulated by “massage-like strokes” of the skin, but not by mechanical stimulation, such as pinching or poking. Furthermore, these MRGPRB4 nerve cells lit up only when the mouse was softly stroked [4]. To test if the mice actively preferred the effects of MRGPRB4 nerve cell activation, the researchers genetically modified a group of mice with MRGPRB4 nerve cells that activated when injected with a specific drug. To detect if the mice experienced pleasant stimulation from the activation of the specific nerve cell, the researchers created a chambered box with three rooms of differing color schemes and layouts so that the mice would be able to differentiate among each room. In one specific room, the researchers injected the mice with the drug that activated MRGPRB4 nerve cells. When given the option to roam around, the mice preferred staying in the same room where they were given the drug treatment — implying that the drug treatment had a calming effect and functioned as positive reinforcement for the animals. The results of this study suggest that when given a choice, the mice preferred having their MRGPRB4 nerve cells activated, thus opting to receive the same stimulation as being pet. Despite being collected only from mice trials, the data in this experiment may be projected to other hairy animals, such as dogs and cats. Additionally, since a similar nerve cell has been identified in humans, further research may locate its counterpart in other animal species as well [5].

As both the animals and humans benefit from the mutualistic relationship established when petting the animal, animal therapy sessions are effective in helping both animal and human de-stress. Through further testing, researchers hope to invent a calming lotion or drug that may invoke the same pleasant stimulation that gentle strokes convey [6]. Although animal therapy sessions are immensely popular as they are opportunities for students to pet cute animals, the biological benefits of these sessions to both animals and humans are often underplayed due to a lack of awareness among the general public.

References: 

  1. Burbach, J. P., Young, L. J., Russell, A., J. (2006). Oxytocin: synthesis, secretion, and reproductive functions. Knobil and Neill’s Physiology of Reproduction, 2:3055-3112.
  2. Uvnas-Moberg, K. (1998). Antistress pattern induced by oxytocin. News Physiology, 13:22-25.
  3. Petersson, M., Uvnäs-Moberg, K., Nilsson, A., Gustafson, L. L., Hydbring-Sandberg, E., & Handlin, L. (2017). Oxytocin and cortisol levels in dog owners and their dogs are associated with behavioral patterns: an exploratory study. Frontiers in Psychology, 8:1796.
  4. Vrontou, S., Wong, A. M., Rau, K. K., Koerber, R. H., Anderson, D. J. (2013). Genetic identification of C fibres that detect massage-like stroking of hairy skin in vivo. Nature, 493:669-673.
  5. Liu, Q., Tang, Z., Surdenikova, L., Kim, S., Patel, K. N., Kim, A., Ru, F., Guan, Y., Weng, H., Geng, Y., Undem, B., Kollarik, M., Chen, Z., Anderson, D., Dong, X. (2009). Sensory neuron-specific GPCR Mrgprs are itch receptors mediating chloroquine-induced pruritus. Cell, 139:1353-1365.
  6. Pennisi, E. (2013). Why Petting Feels Good. [online] Science | AAAS. Available at: https://www.sciencemag.org/news/2013/01/why-petting-feels-good [Accessed 17 May 2019].​
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