Rats Make a Special Sound When They Eat Chocolate
Friday, October 16, 2026175 words3 minutes172 reads
Rats use ultrasonic calls, sounds too high for humans to hear. Researchers in Japan recorded pairs of male rats while they ate chocolate. With a computer method, they identified a 40-kilohertz call whose line rose and fell like an upside-down U.
The call was closely timed to eating. In one experiment, 97.2% of the inverted-U calls came within one second of a bite or chewing. The rats made far more of these calls while eating chocolate than while eating regular food. The amount of food they ate was similar in the comparison.
The team also gave rats naloxone, a drug that blocks opioid receptors. The calls became less frequent. Opioid systems help regulate reward-related processes, so this result suggests that the calls may be linked to positive feelings during tasty eating.
However, the study did not prove what a call means. Because two rats lived in each cage, the recordings could not show which individual rat was calling at a particular moment. The sounds may be useful clues, not a direct translation of rat thoughts.
