After just one week living in a natural environment, the rats that had been kept in captivity underwent a surprising transformation.
Laboratory mice "escape" anxiety after a week back in the wild.
An outdoor laboratory where mice are released back into the wild (Photo: Cornell University).
A groundbreaking study from Cornell University (USA) has just revealed the ability to "reset" the psychological state of laboratory mice after only one week of being returned to a semi-natural environment.
This discovery not only surprised the scientific community but also opened up new avenues for understanding the mechanisms of anxiety formation and maintenance in animals, and possibly in humans as well.
Accordingly, scientists released dozens of mice, which were accustomed to living in laboratory cages, into a large outdoor space where they could freely dig burrows, climb, and be exposed to diverse natural stimuli.
Remarkably, after only about seven days, the anxiety levels of these mice returned to normal , similar to those of individuals living in the wild, completely eliminating the fear responses characteristic of the laboratory environment.
Matthew Zipple, the lead researcher, emphasized: "We released them into the wild for a week, and they returned to their original anxiety levels."
He argued that "returning mice to their natural environment" would not only prevent the formation of laboratory-induced fear responses, but also potentially "reset" responses that had already formed.
This discovery is significant, offering new insights into the emergence and maintenance of anxiety in animals, which could potentially help humans better understand their own psychological state.
In behavioral research, mice are often used as models to investigate anxiety through the Advanced Maze Model (EPM) – a device consisting of closed and open branches. Mice tend to explore but quickly return to enclosed spaces, which is considered a manifestation of agoraphobia (fear of open environments).
Notably, this reaction is often very persistent, even resistant to common anti-anxiety medications such as SSRIs.
This opens the door to further research in humans.
In the experiment, 44 mice were released from their familiar cages to live in a large outdoor area where they could dig burrows, climb, and were exposed to natural light, wind, smells, and a much wider variety of stimuli than in an artificial environment.
When returned to the EPM maze, these mice no longer avoided the open branches but explored both open and closed spaces in a balanced way, as if they were encountering the experiment for the first time.
Releasing mice into the wild may help prevent the development of fear responses induced by laboratory experiments (Photo: Getty).
It is noteworthy that this "reboot" effect appeared in all individuals, regardless of whether they had been raised in a laboratory since birth or were only confined to cages later on.
This suggests that a poor living environment and limited experiential learning are key factors driving anxiety responses, rather than inherent biological traits of the species.
According to neuroscientist Michael Sheehan, this finding may reflect a general principle: diverse experiences help organisms more accurately assess what constitutes a real threat. "If you experience many different things each day, you'll be better able to distinguish between what's scary and what's not," he said.
Conversely, a life with too few experiences can cause any new stimulus to be interpreted by the brain as a threat, thereby generating anxiety.
This also suggests that in humans, an overly protected life, lacking diverse experiences and challenges, can inadvertently contribute to the development of anxiety.
Although anxiety is a complex phenomenon with many interwoven biological, psychological, and social factors, this study highlights the crucial role of the living environment. Sometimes, simply expanding our experiential space is enough to change how we react to the world around us.