LinguaLive20200609
All animals communicate.
Crabs wave their claws at each other to signal that they’re healthy and ready to mate（交尾する）. Cuttlefish（イカ）use pigmented（色付いた）skin cells called chromatophores（色素体） to create patterns on their skin that act as camouflage or warnings（警報）to rivals. Honeybees perform complex dances to let other bees know the location and quality of a food source.
All of these animals have impressive communication systems, but do they have language? To answer that question, we can look at four specific qualities that are often associated with language: discreteness（離散性）, grammar（文法性）, productivity（生産性）, and displacement（転移性）.
Discreteness means that there is a set of individual units, such as sounds or words, that can be combined to communicate new ideas, like a set of refrigerator poetry magnets you can rearrange to create different phrases. Grammar provides a system of rules that tells you how to combine those individual units. Productivity is the ability to use language to create an infinite（無限の） number of messages. And displacement is the ability to talk about things that aren’t right in front of you, such as past, future, or fictional events.
So, does animal communication exhibit any of these qualities? For crabs and cuttlefish, the answer is no. They don’t combine their signals in creative ways. Those signals also don’t have to be in a grammatical order, and they only communicate current conditions, like, "I am healthy," or "I am poisonous." But some animals actually do display some of these properties（特性）. Bees use the moves, angle, duration（継続性）, and intensity（強度）of their waggle（揺れ動く）dance to describe the location and richness of a food source. That source is outside the hive（ミツバチの巣箱）, so they exhibit the property of displacement. They share that language trait with prairie（牧草）dogs, which live in towns of thousands, and are hunted by coyotes（コヨーテ）, hawks（タカ）, badgers（アナグマ）, snakes, and humans. Their alarms calls indicate the predator’s size, shape, speed, and, even for human predators, what the person is wearing and if he’s carrying a gun.
Great apes（類人猿）, like chimps and gorillas, are great communicators, too. Some have even learned a modified（修正されれた） sign language. A chimpanzee named Washoe demonstrated discreteness by combining multiple signs into original phrases, like, "Please open. Hurry." KoKo, a female gorilla who understands more than 1000 signs, and around 2000 words of spoken English referred to a beloved（最愛の）kitten that had died. In doing so, she displayed displacement, though it’s worth noting that the apes in both of these examples were using a human communication system, not one that appeared naturally in the wild. There are many other examples of sophisticated animal communication, such as in dolphins, which use whistles to identify age, location, names, and gender. They can also understand some grammar in a gestural language researchers use to communicate with them. However, grammar is not seen in the dolphin’s natural communication.
While these communication systems may have some of the qualities of language we’ve identified, none display all four. Even Washoe and KoKo’s impressive abilities are still outpaced（超えられる）by the language skills of most three-year-old humans. And animals' topics of conversation are usually limited. Bees talk about food, prairie dogs talk about predators, and crabs talk about themselves.
Human language stands alone due to the powerful combination of grammar and productivity, on top of discreteness and displacement. The human brain can take a finite number of elements and create an infinite number of messages. We can craft and understand complex sentences, as well as words that have never been spoken before. We can use language to communicate about an endless range of subjects, talk about imaginary things, and even lie. Research continues to reveal more and more about animal communication. It may turn out that human language and animal communication aren’t entirely different but exist on a continuum（連続体）. After all, we are all animals.
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