A DIVER carrying a computer that tries to recognise dolphin sounds and generate responses in real time will soon attempt to communicate with wild dolphins off the coast of Florida. If the bid is successful, it will be a big step towards two-way communication between humans and dolphins.
Since the 1960s, captive dolphins have been communicating via pictures and sounds. In the 1990s, Louis Herman of the Kewalo Basin Marine Mammal Laboratory in Honolulu, Hawaii, found that bottlenose dolphins can keep track of over 100 different words. They can also respond appropriately to commands in which the same words appear in a different order, understanding the difference between "bring the surfboard to the man" and "bring the man to the surfboard", for example.
But communication in most of these early experiments was one-way, saysDenise Herzing, founder of the Wild Dolphin Project in Jupiter, Florida. "They create a system and expect the dolphins to learn it, and they do, but the dolphins are not empowered to use the system to request things from the humans," she says.
Since 1998, Herzing and colleagues have been attempting two-way communication with dolphins, first using rudimentary artificial sounds, then by getting them to associate the sounds with four large icons on an underwater "keyboard".
By pointing their bodies at the different symbols, the dolphins could make requests - to play with a piece of seaweed or ride the bow wave of the divers' boat, for example. The system managed to get the dolphins' attention, Herzing says, but wasn't "dolphin-friendly" enough to be successful.
Herzing is now collaborating with Thad Starner, an artificial intelligence researcher at the Georgia Institute of Technology in Atlanta, on a project named Cetacean Hearing and Telemetry (CHAT). They want to work with dolphins to "co-create" a language that uses features of sounds that wild dolphins communicate with naturally.
Knowing what to listen for is a huge challenge. Dolphins can produce sound at frequencies up to 200 kilohertz - around 10 times as high as the highest pitch we can hear - and can also shift a signal's pitch or stretch it out over a long period of time.
The animals can also project sound in different directions without turning their heads, making it difficult to use visual cues alone to identify which dolphin in a pod "said" what and to guess what a sound might mean.
To record, interpret and respond to dolphin sounds, Starner and his students are building a prototype device featuring a smartphone-sized computer and two hydrophones capable of detecting the full range of dolphin sounds.
A diver will carry the computer in a waterproof case worn across the chest, and LEDs embedded around the diver's mask will light up to show where a sound picked up by the hydrophones originates from. The diver will also have a Twiddler - a handheld device that acts as a combination of mouse and keyboard - for selecting what kind of sound to make in response.
Herzing and Starner will start testing the system on wild Atlantic spotted dolphins (Stenella frontalis) in the middle of this year. At first, divers will play back one of eight "words" coined by the team to mean "seaweed" or "bow wave ride", for example. The software will listen to see if the dolphins mimic them. Once the system can recognise these mimicked words, the idea is to use it to crack a much harder problem: listening to natural dolphin sounds and pulling out salient features that may be the "fundamental units" of dolphin communication.
The researchers don't know what these units might be. But the algorithms they are using are designed to sift through any unfamiliar data set and pick out interesting features (see "Pattern detector"). The software does this by assuming an average state for the data and labelling features that deviate from it. It then groups similar types of deviations - distinct sets of clicks or whistles, say - and continues to do so until it has extracted all potentially interesting patterns.
Once these units are identified, Herzing hopes to combine them to make dolphin-like signals that the animals find more interesting than human-coined "words". By associating behaviours and objects with these sounds, she may be the first to decode the rudiments of dolphins' natural language.
Justin Gregg of the Dolphin Communication Project, a non-profit organisation in Old Mystic, Connecticut, thinks that getting wild dolphins to adopt and use artificial "words" could work, but is sceptical that the team will find "fundamental units" of natural dolphin communication.
Even if they do, deciphering their meanings and using them in the correct context poses a daunting challenge. "Imagine if an alien species landed on Earth wearing elaborate spacesuits and walked through Manhattan speaking random lines from The Godfather to passers-by," he says.
"We don't even know if dolphins have words," Herzing admits. But she adds, "We could use their signals, if we knew them. We just don't."