Dependency Resolution Difficulty Increases with Distance in Persian Separable Complex Predicates: Evidence for Expectation and Memory-Based Accounts.

Molood S Safavi,Samar Husain,Shravan Vasishth

doi:10.3389/fpsyg.2016.00403

Abstract

Delaying the appearance of a verb in a noun-verb dependency tends to increase processing difficulty at the verb; one explanation for this locality effect is decay and/or interference of the noun in working memory. Surprisal, an expectation-based account, predicts that delaying the appearance of a verb either renders it no more predictable or more predictable, leading respectively to a prediction of no effect of distance or a facilitation. Recently, Husain et al. (2014) suggested that when the exact identity of the upcoming verb is predictable (strong predictability), increasing argument-verb distance leads to facilitation effects, which is consistent with surprisal; but when the exact identity of the upcoming verb is not predictable (weak predictability), locality effects are seen. We investigated Husain et al.'s proposal using Persian complex predicates (CPs), which consist of a non-verbal element—a noun in the current study—and a verb. In CPs, once the noun has been read, the exact identity of the verb is highly predictable (strong predictability); this was confirmed using a sentence completion study. In two self-paced reading (SPR) and two eye-tracking (ET) experiments, we delayed the appearance of the verb by interposing a relative clause (Experiments 1 and 3) or a long PP (Experiments 2 and 4). We also included a simple Noun-Verb predicate configuration with the same distance manipulation; here, the exact identity of the verb was not predictable (weak predictability). Thus, the design crossed Predictability Strength and Distance. We found that, consistent with surprisal, the verb in the strong predictability conditions was read faster than in the weak predictability conditions. Furthermore, greater verb-argument distance led to slower reading times; strong predictability did not neutralize or attenuate the locality effects. As regards the effect of distance on dependency resolution difficulty, these four experiments present evidence in favor of working memory accounts of argument-verb dependency resolution, and against the surprisal-based expectation account of Levy (2008). However, another expectation-based measure, entropy, which was computed using the offline sentence completion data, predicts reading times in Experiment 1 but not in the other experiments. Because participants tend to produce more ungrammatical continuations in the long-distance condition in Experiment 1, we suggest that forgetting due to memory overload leads to greater entropy at the verb.

Highlights

A long-standing claim in sentence processing is that increasing distance in a linguistic dependency, such as a noun-verb dependency, leads to greater processing difficulty (Chomsky, 1965; Just and Carpenter, 1992; Gibson, 2000; Lewis and Vasishth, 2005); it is common to refer to this increase in processing difficulty as the locality effect
A weak interaction was seen: stronger locality effects were seen in the control conditions than in the complex predicate conditions
If entropy or some other entropy-based measure turns out be an explanation for locality effects, can we argue for a simpler account that only appeals to information-theoretic metrics? A major empirical problem for such a reductionist account would be the large range and variety of intervention effects. for a review and computational modeling) that can only be explained through memory-based accounts

Summary

Introduction

A long-standing claim in sentence processing is that increasing distance in a linguistic dependency, such as a noun-verb dependency, leads to greater processing difficulty (Chomsky, 1965; Just and Carpenter, 1992; Gibson, 2000; Lewis and Vasishth, 2005); it is common to refer to this increase in processing difficulty as the locality effect. There is evidence consistent with the memory-based explanation in English, German, Chinese, Russian, and Hindi, (Hsiao and Gibson, 2003; Grodner and Gibson, 2005; Bartek et al, 2011; Vasishth and Drenhaus, 2011; Levy et al, 2013; Husain et al, 2014, 2015), research on some of these languages has uncovered evidence that increasing noun-verb distance facilitates processing at the verb (Konieczny, 2000; Vasishth, 2003; Vasishth and Lewis, 2006; Jaeger et al, 2008; Vasishth and Drenhaus, 2011; Levy and Keller, 2013; Husain et al, 2014; Jäger et al, 2015) One explanation for these anti-locality effects is in terms of surprisal (Hale, 2001; Levy, 2008). We will refer to surprisal as the expectation-based account, following the terminology of Levy (2008)

Methods

Results

Discussion

Conclusion