Work Smarter...Not Harder: Efficient Minimization of Dependency Length in SOV Languages (2404.18684v2)

Abstract: Dependency length minimization is a universally observed quantitative property of natural languages. However, the extent of dependency length minimization, and the cognitive mechanisms through which the language processor achieves this minimization remain unclear. This research offers mechanistic insights by postulating that moving a short preverbal constituent next to the main verb explains preverbal constituent ordering decisions better than global minimization of dependency length in SOV languages. This approach constitutes a least-effort strategy because it's just one operation but simultaneously reduces the length of all preverbal dependencies linked to the main verb. We corroborate this strategy using large-scale corpus evidence across all seven SOV languages that are prominently represented in the Universal Dependency Treebank. These findings align with the concept of bounded rationality, where decision-making is influenced by 'quick-yet-economical' heuristics rather than exhaustive searches for optimal solutions. Overall, this work sheds light on the role of bounded rationality in linguistic decision-making and language evolution.

• The paper demonstrates that a least-effort strategy determines preverbal word order by positioning the shortest constituent adjacent to the verb, effectively minimizing dependency lengths.
• The study employs corpus analysis and simulated sentence variants from the Universal Dependency Treebank to compare natural and counterfactual structures.
• Findings show that natural SOV sentences yield significantly shorter dependency lengths than random orderings, supporting theories of cognitive economization.

Exploring Preverbal Constituent Ordering in SOV Languages

Introduction to SOV Language Structures

In some languages like Hindi and Japanese, the typical sentence structure follows a Subject-Object-Verb (SOV) order. This ordering inherently affects how sentences are processed in human brains, which manage limited cognitive resources like memory. Languages tend to arrange words in a way that makes them easier to process, a phenomenon supported by Dependency Locality Theory (DLT). DLT posits that minimizing the distance between syntactically related elements (dependencies) reduces cognitive load.

The Least-Effort Strategy in Preverbal Ordering

Recent findings suggest a specific strategy called the "least-effort" strategy that seems prevalent across seven major SOV languages. This strategy posits that the ordering of words before the verb is not random or exhaustively optimal but follows a heuristic approach where speakers place the shortest preverbal constituent adjacent to the verb. This placement effectively shortens the length of all dependencies associated with the verb in one swoop, making it a cognitively economical choice.

Groundwork and Hypothesis Testing

The paper utilized a large-scale corpus analysis from the Universal Dependency Treebank, which spans languages like Basque, Hindi, Japanese, Korean, Latin, Persian, and Turkish. By simulating different word order permutations and analyzing the natural (corpus) and counterfactual (simulated) sentence structures, the researchers tested the prevalence of the least-effort strategy against a global optimization of dependency lengths.

• Corpus Analysis: This involved comparing the natural sentences from the corpus against generated variants with altered preverbal configurations.
• Simulation of Variants: By permuting the order of preverbal constituents, researchers created alternative sentence forms to compare against the original corpus sentences.
• Measurement Metrics: They quantified the dependency lengths and constituent lengths, assuming that shorter lengths closer to the verb indicate ease of processing.

Findings from the Study

The analysis revealed compelling evidence supporting the least-effort strategy:

1. Preference for Shortest Constituent Adjacent to the Verb: Across the examined languages, there was a consistent preference for placing the shortest constituent next to the verb, significantly more frequently than by chance.
2. Impact of Number of Constituents: The tendency to employ the least-effort strategy was more pronounced in sentences with a higher number of preverbal constituents, suggesting an adaptive strategy to manage increasing cognitive load.
3. Superiority over Random Ordering: Sentences from the natural corpus generally exhibited shorter dependency lengths than randomly generated sentence variants, affirming that natural language tends to favor configurations that ease cognitive processing.

Theoretical and Practical Implications

These findings underscore a cognitive economization in linguistic structuring aligned with the principles of bounded rationality, where decision-making favors satisfactory and practical outcomes over perfect optimization. This insight enhances our understanding of language processing and evolution, suggesting that language structures might have adapted to cognitive capacities over time.

Furthermore, the recognition of patterns in sentence structuring can have applications in NLP technologies, improving the design of algorithms for language translation, parsing, and generation systems that better mimic or understand human linguistic preferences.

Future Directions

Further exploration into real-time language processing, the interaction between cognitive constraints and grammatical structures, and extending analyses to other language typologies could provide deeper insights into the universality and limitations of the least-effort strategy.

Overall, this paper not only enriches our comprehension of SOV languages but also opens avenues for integrating cognitive heuristics into linguistic theory and computational models, making them more aligned with human language usage and processing.