The Law all Languages Obey
ONSCREEN: Can math reveal if animals have language?
TALITHIA WILLIAMS: Consider ours for a moment.
In 1945, linguist George Zipf asked his students to plot out the frequency of each of the 264,430 words used in James Joyce's Ulysses.
LAURANCE DOYLE: He drew a straight line through it, and it had a 45-degree, minus-1 slope.
TALITHIA WILLIAMS: Oddly, the most frequent word occurred exactly twice as often as the second most frequent word, three times as often as the third most frequent word, and so on down the line.
In the logarithmic scale that mathematicians use, it looks like this.
LAURANCE DOYLE: So, he thought, "That's interesting, what if I take another book?"
TALITHIA WILLIAMS: Darwin's Origin of Species.
LAURANCE DOYLE: Same thing. "What if I take a Chinese book?" Same thing.
TALITHIA WILLIAMS: Turns out, every human language on the planet follows this rule, from Swahili to Arabic to Eskimo. It's called Zipf's law.
BRENDA MCCOWAN: It suggests it that the structure of language is fundamentally the same, across different languages.
TALITHIA WILLIAMS: So, what about animals? Brenda McCowan at U.C. Davis and Laurance Doyle at SETI-yes, the search for extraterrestial intelligence-wanted to find out. So, they decided to analyze one of the most intelligent animals we know: dolphins. They communicate with an elaborate repertoire of whistles.
BRENDA MCCOWAN: By categorizing whistles into what we would call words, if you will. And I don't mean that literally, but the idea is to categorize signals into types.
LAURANCE DOYLE: Brenda McCowan had collected a bunch of signals and gotten their frequency of occurrence. And one morning, I got up and decided, "Well, I wonder if this obeys Zipf's law."
TALITHIA WILLIAMS: And wouldn't you know.
LAURANCE DOYLE: It obeyed Zipf's law. So, I went and had a cup of tea, and then I went back and did it again. And it obeyed Zipf's law.
BRENDA MCCOWAN: I was pretty excited. Because, I mean, it could have been anything. I mean, what's the probability that you're going to find something that is a negative-one slope in another species? It's, it's, you know, not only exciting, but seems highly improbable.
LAURANCE DOYLE: It's one of those moments in science, where you're going, "Wait a second, dolphins have a communication system with potential complexity as complex as humans." It doesn't measure meaning, but it does measure what they could be saying.
NOVA Wonders What’s the Universe Made Of?
Produced and Directed by: Kirk Wolfinger and Owen Palmquist
Additional Producing by Vincent Liota
Digital Producer: Michael Rivera
© WGBH Educational Foundation 2018