Summary: Researchers developed a fully automated cooperation task showing that rats engage in true reciprocity, not just mutual benefit. Social interaction enhanced success, while dampened interaction reduced cooperative performance. The experience of reciprocity also increased empathy, as rats displayed stronger emotional responses to partners’ distress.
Crucially, oxytocin release in the orbitofrontal cortex underpinned both fair cooperation and empathy, pointing to an internal biological mechanism that prevents free-riding and stabilizes cooperation.
Key Facts
Reciprocity Training: Rats learned to reciprocate in a structured “pay-first, reward-later” task.Oxytocin’s Role: Oxytocin in the orbitofrontal cortex drove cooperation and empathy, reducing free-riding.Empathy Boost: Rats with reciprocity experience showed stronger emotional contagion toward their partners.
Source: Science China Press
Cooperation in nature can yield immediate mutual benefits or depend on delayed reciprocity. The latter is vulnerable to “free-riding,” where a beneficiary fails to return help, and classical theories emphasize external enforcement (e.g., second- and third-party punishment).
Yet such mechanisms are limited in real-world animal settings.
In Science Bulletin, researchers led by Zuoren Wang (CEBSIT, Chinese Academy of Sciences) and Yulong Li (Peking University) present a fully automated reciprocal cooperation task in rats.
Two rats, placed in adjacent chambers, must poke their respective ports within a 1-second window to complete a cooperative trial; only one receives water, and the beneficiary alternates randomly across trials—creating a “pay-first, reward-later” structure.
With training, rats showed robust direct reciprocity rather than mere mutualism, and richer social interaction predicted faster, more successful cooperation; adding a transparent barrier that dampened interaction reduced reciprocal performance.
The team then asked whether reciprocity experience shapes empathy, assessed via an observational fear paradigm. Compared with individually trained controls, reciprocity-trained rats displayed higher emotional contagion toward their partners whether co-housed or separately housed—while demonstrators’ shock responses, observers’ social attention, and 22-kHz calls did not differ between groups, arguing for a specific effect of reciprocity experience.
To probe mechanism, the authors combined GRAB-OXT1.0 with fiber photometry recording and found markedly higher oxytocin release in the orbitofrontal cortex (OFC) during reciprocity than during mutualism or individual tasks.
More importantly, oxytocin-deficient (OXT-KO) rats free-ride more often, were less likely to reciprocate after betrayal, and failed to show the empathy increase seen in wild-type animals—implicating oxytocin-mediated empathy as a key internal brake on free-riding that stabilizes cooperation.
Together, the findings position OFC oxytocin signaling and empathy as an intrinsic motivational pathway complementing external enforcement models of cooperation.
Funding: Science and Technology Innovation 2030 Major Project (2022ZD0205100); Strategic Priority Research Program of the Chinese Academy of Sciences (XDB32010300); Shanghai Municipal Science and Technology Major Project (2018SHZDZX05)
About this oxytocin and social neuroscience research news
Author: Bei Yan
Source: Science China Press
Contact: Bei Yan – Science China Press
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Oxytocin-mediated empathy internally facilitates cooperative behaviors in rats” by Zuoren Wang et al. Science Bulletin
Abstract
Oxytocin-mediated empathy internally facilitates cooperative behaviors in rats
Reciprocity is considered one of the vital mechanisms that sustain the evolution of cooperative behavior.
However, free-riding, where assistance is received but not reciprocated, poses a serious threat to reciprocity behavior, which relies on future payback. Previous theories proposed that third-party punishment plays a vital role in preventing free-riding behavior.
However, this external mechanism has inherent limitations, particularly in situations where third parties are absent.
Empathy, the ability to perceive and share the emotional states of others, has long been considered a driving force behind prosocial behavior, yet its role in cooperative behavior remains underexplored.
In this study, we have designed a new reciprocity paradigm, and demonstrate that rats’ reciprocity behavior can stably establish even in the absence of the external mechanisms.
Additionally, reciprocity experiences can enhance the empathy of wild type rats, but not oxytocin-deficient rats, towards their partners. Furthermore, oxytocin-deficient rats exhibit more free-riding behaviors.
Through fiber photometry recording of oxytocin probe, we found that oxytocin is remarkably released in the orbitofrontal cortex during the reciprocity task, significantly exceeding levels observed in both mutualism and individual tasks.
Based on our results, we suggest that oxytocin-mediated empathy enhancement reduces rats’ free-riding behavior towards their partners, thereby making reciprocity behavior more stable.
This empathy-mediated internal driving force complements the previously proposed external mechanisms, providing new theories and perspectives for understanding the evolution of cooperative behavior.