In 1899, Inazo Nitobe published a book in English called Bushido: The Soul of Japan. Nitobe was born into a samurai family and later became a Christian. He wrote the book after a Belgian legal scholar asked him how Japan taught morality without religious instruction in its schools. Nitobe came to realize the answer was the samurai ethics he had grown up with. He described them through seven virtues: rectitude, courage, benevolence, politeness, veracity, honor and loyalty.
Bushido became an international bestseller, with U.S. President Theodore Roosevelt counting it among his favorite books. More than a century later, two psychologists at Nagoya University in Japan, Ryota Takano and Minoru Karasawa, have used computational language analysis to study the book. They examined how its moral values are structured and expressed, and how the book compares with hundreds of other English-language moral and cultural texts. Psychology has relied heavily on Western populations, and this study asks how values from elsewhere are understood.
A common psychology framework groups moral values into six basic concerns, including care, fairness and respect for authority. The researchers found that, among Bushido's seven virtues, honor is tied to more of these concerns than any other.
They also compared Bushido with 30 other English-language books about Japanese culture. The closer a book's mix of moral concerns matched Bushido's, the more widely it tended to be published, translated and cited in the West. The study, published in PNAS Nexus , shows how a psychology-based method can measure the values expressed in writing. It suggests that Japanese values may have reached Western readers partly because of how Nitobe expressed them, not only because of what they were.
How to measure moral values in a book
Psychologists often measure a person's moral values with a questionnaire. One widely used example is the Moral Foundations Questionnaire. People rate how much they agree with statements such as "Caring for people who have suffered is an important virtue" and "I feel that most traditions serve a valuable function in keeping society orderly." The answers are grouped into six moral concerns: care, equality, proportionality (rewards that match a person's contribution), loyalty to one's group, respect for authority and purity.
To apply the latest version of this questionnaire to text, the researchers used a method called contextualized construct representation, or CCR. A language model turned each sentence in every book and each of the 36 questionnaire statements into numbers that represent their meaning. The team then measured how closely each sentence matched each statement in meaning. A higher score meant the text expressed that moral concern more clearly. To check that the results did not depend on one particular model, the researchers scored the sentences again with three other language models, and the scores closely matched.
"The method is very simple. It calculates the similarity between sentences," said Takano, a lecturer at Nagoya University's Graduate School of Informatics and the study's first author. "On one side is a sentence from Bushido, and on the other is a statement from an established questionnaire. For comparison, we applied the same method to hundreds of other English-language texts from the free online library Project Gutenberg. These included works on Christianity, the Bible and Japanese culture."
Compared with the other texts, Bushido showed a distinctive pattern across the six moral concerns. It expressed all six slightly more clearly than the rest did on average. The clearest differences were observed in respect for authority. Takano noted that this pattern is consistent with samurai culture, which placed great importance on social hierarchy.
The researchers then measured how widely each book about Japanese culture had spread in the West. They counted English editions, translations into French, German, Spanish, Italian and Dutch, and citations on Google Scholar. Bushido ranked second among these books, just behind The Book of Tea. Among the books about Japanese culture, those whose mix of moral concerns more closely matched Bushido's tended to rank higher.
Honor based on patience
The researchers also analyzed the seven chapters of Bushido that each describe one virtue. Across the seven virtues, some moral concerns tended to score high or low together. They used this pattern to sort the six concerns into two broad groups. One included respect for authority, equality, proportionality and purity. The other included care and loyalty to one's group. Honor was the only virtue strongly tied to both groups.
"Meiyo is not the same as honor in the Western sense, which is more related to self-enhancement and prestige," Takano said. "Meiyo is based on patience. Samurai had to control their emotions and suppress negative feelings. Our study describes how an English-language book presented Japanese ideals to Western readers. It does not reconstruct the ethics of historical samurai."
Coauthor Karasawa, a designated professor at the Graduate School of Informatics, added: "Bushido presented Japanese values in terms Western readers could relate to, while keeping its own distinct character. Now, with advances in natural language processing, we can measure the values in hundreds of texts at once. That lets us compare moral traditions across cultures in ways that traditional reading cannot easily do."
The researchers aim to apply the method to classics, religious texts and literature from other cultures to learn how cultural values are shared and accepted across countries and regions.
