Oxytocin's Role in Social Bonding: Insights from Human-Rat Interactions

In a groundbreaking study published in the journal Current Biology on June 23, 2025, researchers at Okayama University, Japan, have revealed that pleasant tactile stimulation, such as tickling, significantly enhances social bonding between humans and rats. This research sheds light on the neurobiological mechanisms that facilitate the formation of interspecies relationships, highlighting the pivotal role of oxytocin, a hormone known for its role in social bonding and emotional regulation.

The study, led by Dr. Himeka Hayashi, a Project Assistant Professor at Okayama University, involved a series of experiments where juvenile rats were subjected to 10 days of tickling by human hands. The researchers measured the rats' vocalizations, specifically their ultrasonic calls in the 50 kHz frequency range, which are associated with pleasurable emotions. Surprisingly, the rats began emitting these vocalizations consistently after the fifth day of tickling, indicating a development of affinity-like behavior towards their human handlers.

According to Dr. Hayashi, "We revealed part of the neural circuitry underlying why naturally wary animals become attached to humans. We discovered that during the process of rats becoming tame to human hands, the action of oxytocin in a specific brain region mediates the effects of pleasant tactile stimulation and controls the formation of social bonds across species."

The researchers observed that the expression of oxytocin receptors increased in the ventrolateral part of the ventromedial hypothalamus (VMHvl) of the rats' brains, suggesting that oxytocin plays a crucial role in their response to tactile stimulation. Furthermore, inhibiting oxytocin signaling in this region reduced the rats' affinity-like behavior towards human touch.

Dr. Hirotaka Sakamoto, a professor at Okayama University and a key contributor to the study, emphasized the significance of these findings, stating, "This study opens new avenues for understanding the neural mechanisms behind social bonding not only in animals but also in humans. The knowledge gained here may inform therapeutic approaches for individuals who face challenges in social interactions."

The implications of this research extend beyond the realm of animal behavior. The study suggests that similar mechanisms may underlie the interactions between humans and companion animals, such as dogs and cats. By understanding how tactile stimulation influences social bonds, new therapeutic strategies can be developed to aid individuals with social interaction difficulties, including those on the autism spectrum or with social anxiety.

The findings underscore the importance of physical contact in fostering emotional connections and social cohesion. In a world where digital interactions often overshadow personal connections, this research highlights the fundamental need for tactile stimulation in building trust and affection.

In summary, the research from Okayama University not only enhances our understanding of the bond between humans and rats but also emphasizes the broader implications for human-animal interactions. As Dr. Hayashi concluded, "Uncovering the neural basis of cross-species affinity can pave the way for innovative therapeutic strategies that leverage physical interaction to enhance social connection and emotional well-being."

This study represents a significant step forward in behavioral neuroendocrinology and opens new pathways for future research aimed at understanding the complex dynamics of social bonding across species.

### About Okayama University Okayama University is one of Japan's leading academic institutions, dedicated to advancing research and education across a wide range of fields. The university's commitment to sustainable development and innovative research continues to contribute to global scientific knowledge.

### Future Directions As researchers delve deeper into the intricate relationship between tactile stimulation and social bonding, future studies may explore the applications of these findings in therapeutic settings, potentially transforming how we approach social interaction challenges in both humans and animals.