When you hear a doorbell and a car horn, your brain immediately knows these sounds are different. Now scientists have discovered something surprising: a mouse's brain organizes those sounds in almost the same way.
Researchers at Johannes Gutenberg University Mainz in Germany have found that humans and mice build similar mental maps of sounds. Even more fascinating, these maps stay remarkably stable as both species learn new sounds and make decisions about them.
"It is difficult to imagine how someone other than yourself perceives the world," said Johannes P.H. Seiler, one of the study's lead researchers. "Even more difficult is it to imagine how the world sounds for other species, such as mice."
To test how brains represent sounds, Seiler, senior author Simon Rumpel, and their team designed an experiment using the same set of pulsed sounds for both humans and mice. These weren't just any sounds — they varied in the number of clicks, the rhythm, and the pitch, all tuned so both species could actually hear them. (Mice can detect much higher frequencies than humans, which makes sound comparisons tricky.)
Participants heard pairs of sounds and rated how similar they felt on a scale from "not similar at all" to "fully similar." Meanwhile, mice in the study learned to press a button when they heard certain sounds that shared a rhythmic pattern — earning a small food reward for getting it right. Humans earned a few dollars for completing the task.
The researchers then built what they call "representational maps" — basically a picture of how the brain organizes these different sounds. When they compared the human maps to the mouse maps, they looked strikingly alike.
"Based on the responses to the individual stimuli, we obtained information on how similar or different sounds are perceived," the researchers explained. "This allowed us to construct a so-called representational map for humans and mice reflecting the corresponding perceptual 'landscape,' and to compare these representational maps between species."
Perhaps the most surprising finding: these mental sound maps didn't change much even after both species had learned to tell the sounds apart. The maps were just as stable before, during, and after the learning process. This suggests that when we learn new sounds, our brains don't completely rebuild our understanding — instead, they expand what we already know.
The study, published in the journal Communications Psychology, adds to growing evidence that humans and other mammals share some fundamental ways of processing the world around them. And it raises an intriguing possibility: maybe we're not so different from our mouse cousins after all, at least when it comes to how we hear.