Vector Poetics: Parallel Couplet Detection in Classical C hinese Poetry (2024)

Abstract: This paper explores computational approaches for detecting parallelism in classical Chinese poetry, a rhetorical device where two verses mirror each other in syntax, meaning, tone, and rhythm. We experiment with five classification methods: (1) verb position matching, (2) integrated semantic, syntactic, and word-segmentation analysis, (3) difference-based character embeddings, (4) structured examples (inner/outer couplets), and (5) GPT-guided classification. We use a manually annotated dataset, containing 6,125 pentasyllabic couplets, to evaluate performance. The results indicate that parallelism detection poses a significant challenge even for powerful LLMs such as GPT-4o, with the highest F1 score below 0.72. Nevertheless, each method contributes valuable insights into the art of parallelism in Chinese poetry, suggesting a new understanding of parallelism as a verbal expression of principal components in a culturally defined vector space.

## introduction parallelism is a rhetorical and structural device where two poetic verses correspond with each other in terms of syntax, meaning, tone, and rhythm. the most widely recognized form of parallelism in chinese culture are the red couplets, known as fai chun or chun lian, traditionally placed on either side of the doors during lunar new year, but the most exquisite ones can be found in classical poetry. parallelism requires careful selection of words to maintain symmetry while expressing complementary or contrasting ideas, making it a hallmark of linguistic artistry in chinese poetic craft. consider the following, classic example of a pentasyllabic parallel couplet: each character (syllable) in the first line corresponds syntactically and semantically with a character at the same position in the second line: 山 ("mountain") and 潭 ("pond") both describe natural elements, while 光 ("light") and 影 ("reflection") refer to visual phenomena. similarly, 悦 ("pleases") and 空 ("empties") are verbs that describe the effects of these phenomena on 鸟 性 ("bird's nature") and 人心 ("human heart"), respectively. this correspondence creates a balanced and harmonious structure, parallel in both form and meaning. while not all chinese poetry contains parallel structures, one of the most rewarding aspects of reading regulated verses like the one shown above lies in uncovering the intricate correspondences between characters, words, and entire lines. these may be readily apparent, as in our example, or more subtly concealed, drawing upon obscure references and tropes from classical literature that only the most knowledgeable readers will fully appreciate. in this paper, we report on our attempts to develop a computational method for detecting parallelisms in poetic verses. this complex task involves numerous linguistic dimensions, such as word segmentation, semantic comparison, and partof-speech alignment, stretching to the limit the abilities of language models and their emergent properties. yet beyond the technical challenges, computational studies of parallelism can also shed new light on the broader questions of how meaning is generated through language and how humans perceive, structure, and understand the world through patterns and relationships. ## previous work modern scholars and traditional literati alike have long debated what constitutes a parallel couplet, identifying various categories of parallelisms. in the chapter "parallel phrasing" from his literary mind and the carving of dragons, liu xie (460-522) distinguishes four kinds of couplets: verbal (言对), material (事对), antithetical (反对), and direct (正对) @xcite . a japanese scholar monk, , proficient in chinese classical literary criticism, identifies as many as 29 different types of couplets @xcite . wang li, a prominent modern chinese linguist, argues that the classification of words-pairing nouns with nouns, verbs with verbs, etc.-is foundational to understanding parallelism @xcite . andrew plaks views parallelism not merely as a stylistic tool but as a fundamental mode of textual organization and argumentation @xcite . zhang longxi offers a comparative east-west view on parallelism as a way of reasoning common to all humans as embodied beings @xcite . cai zong-qi traces the development of parallel patterning in chinese literature beginning with pre-qin writings and becoming prominent during the six dynasties @xcite . from the natural language processing (nlp) perspective, research on parallelism in chinese poetry has drawn relatively little attention. lee et al. have applied pos-tagging to detect syntactic parallelism in tang poetry, confirming traditional views that the middle couplets (2nd and 3rd) in a 4-couplet poem are more often syntactically parallel than the outer couplets (1st and 4th) @xcite . few other studies focus on the automatic generation of parallel couplets @xcite @xcite . projects like the chinese classical poetry matching dataset (ccpm) provide structured data that facilitates the study of semantic relationships in poetry, enabling models to better understand the nuances of parallelism by matching ancient chinese lines with their modern translations @xcite . another prominent approach is the use of transformer-based models, such as the transcouplet model, which leverages a fusion of embeddings, including glyph, pinyin, and part-of-speech embeddings, to capture the syntactic and phonetic nuances of chinese couplets. the model employs both a transformer encoder and decoder to generate the second line of a couplet given the first, ensuring that the generated line adheres to the linguistic rules of parallelism @xcite . yet another innovative method is the coupgan, which utilizes a generative adversarial network (gan) for couplet generation. this model focuses on learning the intricate balance between semantic meaning and structural symmetry that characterizes high-quality couplets @xcite . all of these studies contribute to the ongoing efforts to apply advanced machine learning techniques to the generation and analysis of chinese parallel couplets, pushing the boundaries of how well machines can replicate this sophisticated form of poetic expression. ## dataset our manually-annotated test dataset, used to compare different classification methods, contains 6,125 pentasyllabic couplets divided into two classes: parallel (2,139 samples) and non-parallel (3,986 samples). all couplets come from the socalled "six dynasties" (222-589), a transformative period in the history of chinese literature which witnessed the development of parallel poetry, ultimately leading to the elegant regulated verses of the tang (618-907) and the following eras. the manual annotation ensures a good amount of reliable data to conduct evaluation. since each method has been using a different training dataset, we provide detailed descriptions of the training process in the relevant subsections.