Sept. 29, 2005 — Scientists have taught dolphins to combine both rhythm and vocalizations to produce music, which has resulted in an extremely high-pitched, short version of the "Batman" theme song.

The findings, outlined in two studies, represent the first time that nonhuman mammals have demonstrated that they can recognize rhythms and reproduce them vocally.

"Humans are sensitive to rhythms embedded in sequences of sounds, but we typically consider this skill to be part of processing for language and music, cognitive domains that we consider to be uniquely human," said Heidi Harley, lead author of both studies. "Clearly, aspects of those domains are available to other species."

The studies will be presented at the joint meeting of the Acoustical Society of America and NOISE-CON 2005, which runs from Oct. 17-21 in Minneapolis.

Harley, who is associate professor of social sciences at the New College of Florida in Sarasota, told Discovery News that both studies tested dolphins at The Living Seas exhibit at the Disney World Resort's Epcot Center in Lake Buena Vista, Fla.

The researchers first had an adult male bottlenose dolphin position itself in front of an underwater sound projector, called a hydrophone, that produced six different 14-kHz, four-second rhythms. The dolphin was rewarded for performing a certain behavior to each rhythm.

For example, when Rhythm 1 played, it waved its pectoral fin and when Rhythm 2 played, it tossed a ball.

The various rhythms were played at different frequencies and tempos to ensure the dolphin was recognizing rhythms instead of just frequencies or sound durations.

Another adult male next was trained to produce similar rhythms using a pneumatic switch, which essentially is a small, air-filled ball that is connected to a computer that then generated sounds whenever the dolphin depressed the switch.

"The dolphin was reinforced for producing a specific rhythm to a specific object," said Harley. "For example, when we presented him with a 'Batman' doll, he received a fish for producing a specific rhythm — in this case, a short sound and then a long one."

She added, "If you recall the original 'Batman' TV series musical intro you'll probably remember the way they sang 'Bat-maaaaaaaan.'"

The dolphin spontaneously vocalized to the rhythms, so the researchers started to reward the male with fish whenever it matched its "singing" to the rhythms. By the end of the studies, the scientists could show an object, such as the Batman doll, which represented a certain rhythm/vocalization combo to the dolphin, and it would create the correct sounds both vocally and using the switch.

Gordon Bauer, associate professor of psychology at the New College of Florida who did not work on the studies, told Discovery News, "This is the first report, to my knowledge, of a nonhuman mammal's ability to discriminate rhythmic patterns."

Bauer, however, doubts that dolphins realize they are producing what people consider to be "music."

"I think music is a human construct," he said. "I doubt that it has pertinence to animals, although the elements of music, such as pitch, time, timbre, rhythm, etc., may be incorporated into animal communication."

Harley agrees, and hopes the everyday vocalizations of dolphins will be analyzed in terms of their rhythmic content. In the near future, she and her team are planning to test the dolphins on their ability to recognize recordings of their own rhythms by having them associate their own sound creations with identifying objects similar to the "Batman" doll.