The squeak of a mouse tells most people to buy a mousetrap, but it tells some researchers a lot more. According to an April 1 study in PLoS ONE, mouse noises indicate certain states of mind, and monitoring their sounds can help scientists learn more about emotion, reward seeking and communication.

In addition to audible squeaks, mice produce ultrasonic noises—squeaks so high that humans cannot hear them. Males sing a complex song during sex and squeak when they are tickled, females chirp when around other females, and mouse pups squeak when their mothers abandon them. These vocalizations transform as the situation changes, too—male mice squeak more frequently as they get closer to ejaculation, and female mice make a ruckus when their female playmates have chocolate on their breath. Scientists at the University of Toronto, Northwestern University and the National Institutes of Health speculated that these noises and their intensities were linked to the activation of dopamine, a brain chemical involved in pleasure and reward seeking. They bred mice to lack certain aspects of dopamine function and monitored the resulting din. Sure enough, the dopamine-deprived mice were quieter on all counts, suggesting that mouse squeaks relate both to the experience of pleasure and to the desire for it.

The specially bred mice can teach scientists much about both mouse behavior and the human brain. “Because mouse genes are so similar to many human genes, it gives you a way of studying the genes for complex behaviors,” says John Yeomans, a psychologist at the University of Toronto and the lead researcher of the study. Labs are already starting to use mouse noises to study language development, social bonding and diseases that have symptoms related to communication, including schizophrenia and autism.

Editor's Note: This story was originally printed with the title "Song of the Mouse"