Summary: A new study from Okayama University shows that pleasant touch strengthens social bonds between humans and rats by activating oxytocin signaling in the brain. Repeated tickling increased rats’ 50 kHz vocalizations, led them to prefer human interaction, and raised oxytocin receptor expression in the ventrolateral ventromedial hypothalamus (VMHvl).
When researchers blocked oxytocin signaling in that brain region, the rats’ affinity-like behaviors toward human hands decreased, confirming oxytocin’s central role in this form of cross-species bonding. These results offer insights into how tactile stimulation supports social connection and suggest potential applications for therapies that use animal-assisted contact to support people with social interaction difficulties.
Key facts:
- Oxytocin link: Pleasant touch enhances oxytocin signaling and strengthens social bonds.
- Tickling effect: Juvenile rats developed a clear preference for human interaction after repeated tickling that mimics play.
- Therapeutic potential: Findings may guide interventions that leverage touch and animal contact to improve social well-being.
Source: Okayama University
Pleasant tactile stimulation drives social bonding
Physical contact, especially gentle and playful touch, is a fundamental driver of social bonding across mammalian species. In many animals, tactile interactions underpin parent–infant attachment and peer play, producing behaviors and vocal signals associated with positive emotional states. In juvenile and adolescent rats, for example, rough-and-tumble play elicits 50 kHz ultrasonic vocalizations that are widely interpreted as markers of pleasure.
Researchers have shown that human-administered tickling, when it resembles natural play, triggers the same type of 50 kHz calls. Over repeated sessions, rats come to prefer interaction with the human hand used in tickling, demonstrating a learned affinity for that source of pleasant tactile stimulation.
In the study published in Current Biology (Volume 35, Issue 12, June 23, 2025), the research team investigated how repeated human touch alters brain chemistry and behavior in juvenile-adolescent rats. Over a 10-day training period, rats were tickled by human hands in a way that mimicked peer play. The animals began producing 50 kHz vocalizations consistently from about day five, and these vocalizations increased through day ten—evidence that repeated tickling produced pleasurable responses.
Following the training, rats completed a conditioned place preference test and spent more time in the location associated with tickling, indicating a measurable affinity for the tickling experience. At the neural level, repeated tickling led to increased expression of oxytocin receptors (OTR) in the VMHvl, a specific subregion of the ventromedial hypothalamus. When oxytocin signaling in the VMHvl was inhibited, the rats showed reduced affinity-like behaviors toward human hands, demonstrating a causal role for oxytocin pathways in this form of bonding.
To trace the origin of oxytocin fibers projecting to VMHvl, the team performed retrograde and anterograde tracing studies. Results indicated that a fraction of oxytocin-positive fibers in the VMHvl arise from the supraoptic nucleus (SON), suggesting that magnocellular oxytocin neurons contribute to the modulation of affinity-like behavior elicited by human touch.
“We revealed part of the neural circuitry underlying why naturally wary animals become attached to humans,” says Dr. Himeka Hayashi, lead author. “During the process of rats becoming tame to human hands, oxytocin acting in the VMHvl mediates the effects of pleasant tactile stimulation and helps form social bonds across species.” Professor Hirotaka Sakamoto and other collaborators also contributed significantly to the work.
These findings clarify how specific oxytocin-sensitive neurons in the VMHvl respond to repeated play-like touch and drive behavioral changes that reflect social preference. Understanding this mechanism deepens our knowledge of how tactile experiences shape social behavior and may inform therapeutic strategies.
By uncovering the neural basis of cross-species affinity, the study suggests that structured, pleasant physical interaction with animals could be harnessed to improve social engagement and emotional well-being. Such approaches may be relevant for developing support and interventions for people who face challenges with social interaction.
About this tactile stimulation and bonding research news
Author: Yuichi Iida
Source: Okayama University
Contact: Yuichi Iida – Okayama University
Image: Image credit: Neuroscience News
Original research: Open access. “Oxytocin facilitates human touch-induced play behavior in rats” by Hirotaka Sakamoto et al., Current Biology.
Abstract
Oxytocin facilitates human touch-induced play behavior in rats
Pleasant touch sensations are fundamental to social bonding, but the neural mechanisms behind affinity-like behaviors remain incompletely understood. This work shows that juvenile-adolescent rats, which naturally produce 50 kHz ultrasonic vocalizations during peer play, develop a strong preference for human hands through repeated tickling that mimics rough-and-tumble interactions. Repeated tickling increased oxytocin receptor expression in the VMHvl, and inhibiting oxytocin signaling in this region reduced the rats’ affinity-like behaviors toward human hands. Tracing studies identified the supraoptic nucleus as a source of some oxytocin fibers to the VMHvl, indicating that magnocellular oxytocin neurons may regulate this cross-species bonding. These results advance our understanding of how oxytocin shapes social behavior and may guide development of therapeutic approaches that use touch and animal contact to foster positive social interactions.