Machine learning has been used to automatically translate long-lost languages
In 1886, the British archaeologist Arthur Evans came across an ancient stone bearing a curious set of inscriptions in an unknown language. The stone came from the Mediterranean island of Crete, and Evans immediately traveled there to hunt for more evidence. He quickly found numerous stones and tablets bearing similar scripts and dated them from around 1400 BCE.
That made the inscription one of the earliest forms of writing ever discovered. Evans argued that its linear form was clearly derived from rudely scratched line pictures belonging to the infancy of art, thereby establishing its importance in the history of linguistics.
He and others later determined that the stones and tablets were written in two different scripts. The oldest, called Linear A, dates from between 1800 and 1400 BCE, when the island was dominated by the Bronze Age Minoan civilization.
The other script, Linear B, is more recent, appearing only after 1400 BCE, when the island was conquered by Mycenaeans from the Greek mainland.
Evans and others tried for many years to decipher the ancient scripts, but the lost languages resisted all attempts. The problem remained unsolved until 1953, when an amateur linguist named Michael Ventris cracked the code for Linear B.
His solution was built on two decisive breakthroughs. First, Ventris conjectured that many of the repeated words in the Linear B vocabulary were names of places on the island of Crete. That turned out to be correct.
His second breakthrough was to assume that the writing recorded an early form of ancient Greek. That insight immediately allowed him to decipher the rest of the language. In the process, Ventris showed that ancient Greek first appeared in written form many centuries earlier than previously thought.
Ventris’s work was a huge achievement. But the more ancient script, Linear A, has remained one of the great outstanding problems in linguistics to this day.
It’s not hard to imagine that recent advances in machine translation might help. In just a few years, the study of linguistics has been revolutionized by the availability of huge annotated databases, and techniques for getting machines to learn from them. Consequently, machine translation from one language to another has become routine. And although it isn’t perfect, these methods have provided an entirely new way to think about language.
Enter Jiaming Luo and Regina Barzilay from MIT and Yuan Cao from Google’s AI lab in Mountain View, California. This team has developed a machine-learning system capable of deciphering lost languages, and they’ve demonstrated it by having it decipher Linear B—the first time this has been done automatically. The approach they used was very different from the standard machine translation techniques.
First some background. The big idea behind machine translation is the understanding that words are related to each other in similar ways, regardless of the language involved.
So the process begins by mapping out these relations for a specific language. This requires huge databases of text. A machine then searches this text to see how often each word appears next to every other word. This pattern of appearances is a unique signature that defines the word in a multidimensional parameter space. Indeed, the word can be thought of as a vector within this space. And this vector acts as a powerful constraint on how the word can appear in any translation the machine comes up with.
These vectors obey some simple mathematical rules. For example: king – man + woman = queen. And a sentence can be thought of as a set of vectors that follow one after the other to form a kind of trajectory through this space.
The key insight enabling machine translation is that words in different languages occupy the same points in their respective parameter spaces. That makes it possible to map an entire language onto another language with a one-to-one correspondence.
In this way, the process of translating sentences becomes the process of finding similar trajectories through these spaces. The machine never even needs to “know” what the sentences mean.
This process relies crucially on the large data sets. But a couple of years ago, a German team of researchers showed how a similar approach with much smaller databases could help translate much rarer languages that lack the big databases of text. The trick is to find a different way to constrain the machine approach that doesn’t rely on the database.
Now Luo and co have gone further to show how machine translation can decipher languages that have been lost entirely. The constraint they use has to do with the way languages are known to evolve over time.
The idea is that any language can change in only certain ways—for example, the symbols in related languages appear with similar distributions, related words have the same order of characters, and so on. With these rules constraining the machine, it becomes much easier to decipher a language, provided the progenitor language is known.
Luo and co put the technique to the test with two lost languages, Linear B and Ugaritic. Linguists know that Linear B encodes an early version of ancient Greek and that Ugaritic, which was discovered in 1929, is an early form of Hebrew.
Given that information and the constraints imposed by linguistic evolution, Luo and co’s machine is able to translate both languages with remarkable accuracy. “We were able to correctly translate 67.3% of Linear B cognates into their Greek equivalents in the decipherment scenario,” they say. “To the best of our knowledge, our experiment is the first attempt of deciphering Linear B automatically.”
That’s impressive work that takes machine translation to a new level. But it also raises the interesting question of other lost languages—particularly those that have never been deciphered, such as Linear A.
In this paper, Linear A is conspicuous by its absence. Luo and co do not even mention it, but it must loom large in their thinking, as it does for all linguists. Yet significant breakthroughs are still needed before this script becomes amenable to machine translation.
For example, nobody knows what language Linear A encodes. Attempts to decipher it into ancient Greek have all failed. And without the progenitor language, the new technique does not work.
But the big advantage of machine-based approaches is that they can test one language after another quickly without becoming fatigued. So it’s quite possible that Luo and co might tackle Linear A with a brute-force approach—simply attempt to decipher it into every language for which machine translation already operates.
If that works, it’ll be an impressive achievement, one that even Michael Ventris would be amazed by.
Ref: arxiv.org/abs/1906.06718 : Neural Decipherment via Minimum-Cost Flow: from Ugaritic to Linear B
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