Rats make an ultrasonic sound when they eat chocolate

There’s nothing better than sinking your teeth into a sweet, creamy chocolate bar. Rats think so, too—and they may announce their chocolate-infused joy to the world at ultrasonic frequencies. Researchers have previously linked ultrasonic rat vocalizations with different emotional and motivational states in the animals, such as in reaction to rewarding stimuli. For example, the rodents vocalize in this way when eating something sweet. Now, a team of researchers in Japan have