What Determines the Order of Verbal Dependents in H indi? Effects of Efficiency in Comprehension and Production (2020)

Abstract: Word order flexibility is one of the distinctive features of SOV languages. In this work, we investigate whether the order and relative distance of preverbal dependents in Hindi, an SOV language, is affected by factors motivated by efficiency considerations during comprehension/production. We investigate the influence of Head–Dependent Mutual Information (HDMI), similarity-based interference, accessibility and case-marking. Results show that preverbal dependents remain close to the verbal head when the HDMI between the verb and its dependent is high. This demonstrates the influence of locality constraints on dependency distance and word order in an SOV language. Additionally, dependency distance were found to be longer when the dependent was animate, when it was case-marked and when it was semantically similar to other preverbal dependents. Together the results highlight the crosslinguistic generalizability of these factors and provide evidence for a functionally motivated account of word order in SOV languages such as Hindi.

## introduction natural languages are known to be influenced by a pressure for efficiency, that is, languages should enable speakers to communicate as well as possible, subject to constraints on the complexity of production and comprehension @xcite @xcite . one area where efficiency pressures appear to have a large effect is in word order: for example, across languages, the distribution of word orders can be well predicted using the principle of dependency length minimization, the idea that words in syntactic dependencies are under a pressure to be close to each other @xcite ). dependency length minimization is motivated by efficiency because it results in lower working memory requirements for language production and comprehension. here, we take up the question of whether word orders can be predicted using efficiency in an area that goes beyond dependency length minimization. in particular, we examine how efficiency pressures may influence the order of pre-verbal dependencies in a verb-final language, hindi. we formalize a number of measures of the complexity of comprehension and production, drawing from the psycholinguistic literature, and we test what effect these measures have on word order as observed in a large dependency treebank. the paper is arranged as follows: in section 2, we describe the various psycholinguistic factors used to investigate preverbal ordering and review related work. section 3 describes the data and methods used to undertake the various analyses. in section 4 we present the results. section 5 discusses the implications of our results and concludes. ## psycholinguistic factors influencing word order we consider four psycholinguistically-motivated factors as predictors of the order of verbal dependents in hindi. ## results in this section we discuss the length and ordering of preverbal nominal dependencies. we first discuss how the length is affected by the factors discussed above. we then discuss how they affect the wordorder. ## discussion the results show that comprehension/production efficiency based factors affect dependency distance and ordering of preverbal dependents in hindi. previous work investigating dependency distance has demonstrated that sov languages allow for longer dependency distance between the verb and its prior dependents @xcite @xcite . the current work makes an important contribution by highlighting that compared to preverbal adjuncts, the core arguments (subject, indirect object and direct object) tend to be closer to the verb in an sov language like hindi. additionally, when the hdmi between the preverbal dependent and the verb is high, they tend to be close to each other. the hdmi difference between a pair of dependencies also correctly predicts their order. this provides compelling evidence that, all else being equal, the preverbal dependents in an sov language such as hindi are under information-theoretic locality constraints. indeed, recent behavioral studies (e.g., @xcite suggest that clause final verb prediction in hindi suffers with increased distance between prior arguments and the upcoming verb. the current findings also highlight certain conditions under which locality constraints can be overridden, leading to increased distance between preverbal arguments and the verb. these factors relate to well established processing constraints such as animacy-driven accessibility and similarity-based interference. language-specific characteristics also influence syntactic configurations. in the current study, the presence of nominal case-markers tends to increase the dependency distance between the verb and its prior dependents. this could highlight the predictive strength of case-markers vis-à-vis a verb type @xcite . under such a setting, the locality constraint can be violated, leading to longer dependency distance. the results also raise some inconsistencies. one such inconsistency was that the dependency distance prediction for factors such as hdmi and case-marking in the case of direct object is not borne out. it is possible that compared to other arguments, the relationship between a direct object and verb is distinct @xcite . if this is true, then we should be able to replicate the do pattern found in the current study for other sov languages. the other inconsistency in the result was that the prediction for word order with respect to similarity-based interference turned out to be incorrect in the order-based analyses. the current work does not probe the effect of discourse/information structure on word order. @xcite have proposed a discourse-centric mapping of word position vis-à-vis the verb and discourse function -topic maps to the sentence initial position, focus maps to the immediate preverbal position, background information maps to the postverbal position and completive information maps to the non-immediate preverbal position. such information structure roles can be difficult to ascertain automatically, but future work can attempt to investigate the role of these factors in the context of the current work. ## conclusion our work provides evidence in support of the information locality hypothesis which states that headdependent are under pressure to be close to each other when they are strongly associated with each other. it also supports other efficiency-driven factors such as similarity-based interference, accessibility, and the presence of case-markers, which act as countervailing forces to keep the distance between the dependent and its verbal head long. together these factors influence the dependency distance and word order patterns in an sov language like hindi.