Researchers at Cornell University have discovered that simply allowing laboratory mice access to a natural environment can significantly reduce or even eliminate anxiety behaviors developed in controlled settings. The findings call into question the validity of current anxiety testing methods and hint at a deeper connection between environmental exposure and the formation of fear responses – a principle that may extend to humans.
The Problem with Lab Anxiety Tests
Traditional anxiety research relies heavily on tests like the elevated plus maze (EPM). In the EPM, mice exhibit a predictable pattern: initial exploration of open, exposed areas followed by a retreat to enclosed, safer spaces. This is interpreted as fear, and it’s a response so ingrained that even anti-anxiety drugs struggle to suppress it. The issue, as this new research suggests, may not be inherent fear, but a lack of environmental context.
The Rewilding Experiment
The team freed 44 lab mice to roam a large outdoor enclosure for one week. The mice were allowed to burrow, climb, and experience natural stimuli. Upon their return to the EPM, the results were striking: mice now explored both open and closed maze arms equally, as if encountering the maze for the first time. This occurred regardless of whether the mice had been raised in a lab environment from birth or were introduced to the outdoors later in life.
Why This Matters: Sensory Calibration
Neurobiologist Michael Sheehan explains that anxiety may stem from a limited “library of experiences.” A narrow, controlled environment like a lab can create heightened fear responses when encountering anything unfamiliar. In contrast, exposure to a diverse and unpredictable natural environment appears to “calibrate” fear responses, making novel experiences less threatening.
“If you experience lots of different things that happen to you every day, you have a better way to calibrate whether or not something is scary or threatening… But if you’ve only had five experiences, you come across your sixth experience, and it’s quite different from everything you’ve done before, that’s going to invoke anxiety.”
Rethinking Lab Testing and Human Anxiety
These findings suggest that what we perceive as anxiety in lab mice may be an artifact of their restricted environment, not a fundamental biological trait. The research raises the possibility that current anxiety studies might be measuring environmental deprivation rather than inherent fear. Similar principles may apply to human anxiety, suggesting that varied and even slightly risky experiences could play a role in reducing overreactions to novel stimuli.
The team is now exploring how these findings influence our understanding of anxiety development in both animals and humans, challenging the assumption that anxiety is solely hardwired into biology. The results underscore the importance of environmental enrichment, not just for animal welfare, but for more accurate scientific inquiry.
