Coherence, the quality of a text that makes it meaningful and unified, operates on both local and global levels. While local coherence concerns the relationships between adjacent sentences, global coherence refers to the overall unity and organization of a text. Global coherence models attempt to explain how readers or listeners construct a mental representation of the text's main topic and how different parts of the text contribute to this overall understanding. These models, however, are not uniformly applied across all genres, as different genres have distinct conventions and expectations that shape how coherence is achieved and perceived.
One prominent model is Kintsch's Construction-Integration model, which posits that readers build a network of interconnected propositions as they process a text. Global coherence is achieved when these propositions form a stable and interconnected network, centered around a macroproposition representing the main topic. This model emphasizes the role of background knowledge and inference in establishing coherence. While applicable to various texts, its emphasis on propositional relationships might be more suited to expository genres like academic articles, where logical connections and clear argumentation are paramount.
Another influential perspective comes from Rhetorical Structure Theory (RST), which focuses on the hierarchical organization of text. RST proposes that text segments are related to each other through rhetorical relations, such as cause-effect, elaboration, and contrast. Global coherence, in this view, arises from the well-structured arrangement of these relations, with certain segments (nuclei) being more central to the text's purpose than others (satellites). RST can be applied to a wide range of genres, but it is particularly useful in analyzing persuasive texts, where the hierarchical arrangement of arguments and supporting evidence is crucial.
Narrative genres, such as short stories and novels, rely heavily on causal networks, as proposed by Trabasso and van den Broek's causal network model. This model emphasizes the importance of understanding the causal relationships between events in a story. Global coherence in narratives is achieved when readers can construct a coherent chain of events that leads to a satisfying resolution. This model highlights the role of plot structure and character motivations in creating coherence in narrative texts.
Genre conventions significantly influence how global coherence is established and perceived. In scientific writing, for instance, global coherence is often achieved through a clear thesis statement, logical argumentation, and the use of headings and subheadings to guide the reader. The focus is on clarity, precision, and objectivity. In contrast, in literary genres, such as poetry, global coherence might be more implicit, relying on thematic connections, symbolism, and imagery. The reader is often invited to actively participate in constructing meaning and making connections.
Consider the difference between a news article and a poem. A news article typically adheres to a strict structure (e.g., inverted pyramid) with a clear focus on factual information. Global coherence is maintained through a concise summary of the key events and a logical progression of details. A poem, on the other hand, might employ fragmented syntax, metaphorical language, and non-linear progression. Global coherence might emerge from recurring motifs, emotional tone, or a central theme that is gradually revealed through the interplay of images and sounds.
While global coherence models provide valuable frameworks for understanding how texts achieve unity, their application varies across genres. Different genres employ different strategies to guide readers or listeners in constructing a coherent representation of the text, reflecting the diverse purposes and conventions of human communication.
