Mice released into wild show unexpected anxiety relief

In an unexpected experiment that deviated from the usual methods of altering animal behaviour through chemical interventions or physical manipulation, scientists at Cornell University recently conducted a study where they simply opened the cages of lab mice. The results? A dramatic shift in their anxiety levels, achieved through exposure to the natural world.

The experiment involved releasing lab mice that had spent their lives in tightly controlled indoor environments into a large outdoor enclosure. Once outside, the mice were free to dig, climb, burrow, and explore real dirt while being exposed to natural weather conditions and new, unfamiliar smells. After just one week, the mice showed a significant reversal of the anxiety behaviours that researchers typically see as persistent, Vice writes. 

“We put them in the field for a week, and they returned to their original levels of anxiety behaviour,” said biologist Matthew Zipple in an interview with Cornell News. "No medication. No prolonged intervention. Just exposure to a broader world."

The experiment

To understand why these findings are so significant, it’s important to know how anxiety is typically measured in lab mice. Researchers usually use an apparatus called the elevated plus maze, a raised platform shaped like a plus sign, which has two enclosed arms and two exposed ones. Mice are more likely to explore the open arms, but quickly retreat to the enclosed arms. This retreat is considered a sign of anxiety, and it is often difficult to reverse, even with anti-anxiety medications.

However, in this new experiment, the outdoor mice showed significantly less fear. Their anxiety responses softened as they navigated the unfamiliar terrain and sensory input in the wild. Zipple explained that being in a more naturalistic environment “both blocks the formation of the initial fear response, and it can reset a fear response that’s already been developed.”

Neurobiologist Michael Sheehan framed this idea in a way that may resonate with many.

“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,” Sheehan said. “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.”

The study suggests that in many cases, situational responses may be misinterpreted as permanent traits, especially when animals are raised in sterile, controlled environments. For these lab mice, the solution to their anxiety came not from medication or direct intervention but from simply giving them more space to explore and learn.

By Sabina Mammadli