Among the words we use most often, short ones like "I," "a" and "the" top the list. It turns out we're not the only ones who strive for this type of efficiency in the way we communicate. Dolphins, found a new study, do it, too.
It's the first evidence that another species follows one of the basic rules that defines all human languages: the law of brevity.
The work, which is just one step in a larger attempt to understand the evolution of communication, also suggests that humans might not be as special as we like to think we are.
"Indirectly, this is telling us something about us," said David Lusseau, a behavioral ecologist at the University of Aberdeen, in Scotland. "More broadly, it is helping us understand how you get to this level of complexity. Is there only a limited way to reach it or can you reach it in many different manners?"
In their long-term quest to understand how complex communication systems developed, Lusseau and colleague Ramon Ferrer-i-Cancho chose to study dolphins because the animals are far removed from humans on the evolutionary tree. They diverged from us 65 million years ago, and their brains are built differently from ours. At the same time, dolphins are known to communicate with a repertoire of about 30 non-vocal behaviors.
When one dolphin performs a side flip or a series of side flips, for example, the rest of the group stops what it's doing and moves on to something else. Scientists aren't sure if the side-flipper is expressing a desire or an order. Still, the message gets across.
The researchers broke down each of these 30 behaviors into individual units. A side flip, for example, requires a dolphin to jump and land on its side — for a total of two behavioral units. Head butting takes four units, as two individuals jump, hit and use their heads. A simple turn involves just one unit, so does a forced blow of air out of a partially closed blowhole.
After hundreds of hours of observation and analyses, the scientists concluded that dolphins perform simple, one-move behaviors more often than complicated, multi-faceted actions.
Scientists call this phenomenon the "law of brevity," and it exists in all human languages.
"The more you're going to have to say something, the shorter you want it to be so you can diminish the amount of time it takes you to communicate," said Lusseau, who is also looking for other types of similarities between human and dolphin communication systems.
"The listener is trying to make the least effort possible to understand what is said to him or her," he said. "The speaker is trying to make the least effort possible to communicate."
Until now, scientists had never documented the law of brevity in another species, but research behaviorist Brenda McCowan suspects that that dolphins and humans aren't the only ones who use it. Systems of communication, she said, might simply need to be structured in certain ways in order to work.
"This work contributes to the growing body of data that humans are not as unique as once thought and that we have profound similarities in our behavior and communication with other animals," said McCowan, of the University of California, Davis.
"Among other compelling data that support how profoundly similar we are to other animals," she added. The new study "should provoke us to think about our relationship with other animals and their place in society."