The online processing of the ambiguous null object in Mandarin among patients with Broca’s aphasia

ABSTRACT

Background: Research on how patients with Broca’s aphasia and concomitant agrammatism process dependency structures online offers a window into the understanding of how language is organized in the mind. Previous studies have shown that patients evince differential performances on dependency structures generated at different levels of linguistic representation. The present study extends this line of research to investigate patients’ online processing of referential dependencies involving ambiguous pronominal interpretations.

Aims: Mandarin, unlike English, allows the object to be missing (null) in some contexts, rendering these null pronominal forms as ambiguous between two interpretations (strict vs. sloppy), which are generated in different levels of linguistic representation. This study examined Mandarin-speaking healthy and agrammatic aphasic participants’ processing of the two interpretations of the null pronominal form such as Zhangsan qile ta de ma, Lisi ye qile e “literally: Zhangsan rode his horse and Lisi rode, too”, where Lisi rode either Zhangsan’s horse (strict) or Lisi’s horse (sloppy).

Methods & Procedures: Two experiments, employing a Cross-Modal Picture Priming paradigm, manipulated three probe picture conditions (strict, sloppy, control) and two probe positions (at the verb phrase offset and 400 ms afterwards). Experiment 1 tested neurologically unimpaired controls in order to establish the time course of processing as a standard of comparison. Experiment 2 tested patients with agrammatic aphasia.

Outcomes and Results: Immediately at the verb phrase offset where the null object is structurally licensed, unimpaired individuals primed both the strict and the sloppy interpretations, with no significant difference in reaction times between the two conditions. At the position 400 ms after the verb phrase offset; however, unimpaired participants did not show priming of either of the two interpretations. Patients showed the opposite pattern: at verb phrase offset, they did not show threshold-level priming of either of the two interpretations; 400 ms afterwards, they showed priming of both the strict and sloppy interpretations, with the strict interpretation eliciting significantly longer reaction times than the sloppy interpretation.

Conclusions: Patients’ delay in priming both the strict and the sloppy interpretations shows that patients evince a temporal delay when processing dependency structures, which may arise from patients’ deficit with lexical integration. Additionally, patients spent significantly longer reaction times on the strict interpretation relative to the sloppy interpretation, which confirms the prediction that that the former, which is generated in the level of discourse, is computationally more costly than the latter, which is generated in the level of semantics.

KEYWORDS:

• Generative syntax
• processing
• aphasia
• ambiguity
• cross-modal picture priming

Acknowledgements

We thank Matthew Walenski and Michael Walsh Dickey for their suggestions with the earlier versions of this paper. Additionally, we thank our research assistants, our participants and their families for their time.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1. It is noted that pronominal interpretations can be derived in different levels of representation, which arises from those counterexamples against Binding Principle B. The Binding Principle B originally proposed by Chomsky (1981) operates in the syntax level and accounts for the obligatory non-coreference between pronouns and their antecedents in certain structures (such as *John_i likes him_i). However, some counterexamples against Principle B were noted, such as Zelda_i/j adores her_i/j teachers (Reinhart, 1983) and John and Mary have a lot in common. He loves her and she_i loves her_i (Evans, 1980). Some studies (Bach & Partee, 1980; Grodzinsky & Reinhart, 1993; Heim, 1982; Reinhart, 1983), therefore, propose that the interpretation of pronouns needs to be accounted for via a dual route, i.e., in terms of both principle B, which operates in the syntax level, and other rules (such as Rule i in (2)), which operates in the discourse (or pragmatics) level.

2. In addition to the sloppy interpretation and the strict interpretation noted above, this sentence has a third interpretation that Bill touched a third person’s dog and John touched this person’s dog, where the reference of his in the first conjunct is derived from non-linguistic contexts. As only the strict and sloppy interpretations are relevant to the present study, the third interpretation is left aside.

3. The level of representation where the sloppy interpretation is generated is named differently depending on the specific theoretical approaches in the generative syntax theory. For example, some earlier studies (Grodzinsky & Reinhart, 1993; Sag, 1976; Williams, 1977) take this level to be syntax, and Frazier and Clifton (2000) take it to be Logical Form, whereas Reuland (2001) takes it to be semantics. The differences among these terms are not crucial to the present study. Our study adopts the Primitives of Binding framework proposed in Reuland (2001), according to which the sloppy interpretation is generated in the semantics level.

4. One concern about CMP is that the task of responding to a probe might involve some integration of the target into the ongoing sentence (Nicol et al., 2006). In order to circumvent this problem, we used picture probes since probe pictures instead of lexical probes are argued to be able to avoid integration effects better (Love et al., 2009) and we presented sentences at a normal speech rate, instead of at a slowed speech rate.

5. To preview the relevant results in Experiment 2, we found that patients evinced no significant priming of either the strict or the sloppy interpretation at PP1, which excluded the possibility that the priming of both the strict and the sloppy interpretations at PP2 is due to residual activation at PP1.

6. When we constructed the stories, we made sure that the pictures depicting the three characters in the strict condition, the sloppy condition and the control condition, respectively, depicted the same gender so that gender confounding was avoided.

7. An example of the thirty filler stories used in both experiments:

a. Xiao  tu      he    xiao   mao   zaishulinli  chifan.

Little rabbit  and  little   cat  in the forest   eat

‘Little Rabbit and Little Cat are eating in the forest.’

b. Xiao tu         chi   huluobo.

Little  rabbit  is  eating a carrot

‘Little Rabbit is eating a carrot.’

c. Xiao mao    chi        yu.

Little cat  is eating   fish

‘Little Cat is eating fish.’

d. Tamen  dou  hen  gaoxing.

   they  both  very  happy

‘They were both very happy.’

8. An example of the comprehension question is as follows:

Gushi  li   yigong     you  jige   dongwu

story  in  altogether  how  many  animal

‘How many people are there in the story?’

9. The results of this experiment seem to contradict the predictions of the Primitives of Binding framework, which predicts that the sloppy interpretation, which is generated in the semantics level, should be easier to access than the strict interpretation, which is generated in the discourse level. We speculate that this contradiction arises because the stimuli used in this experiment were carefully controlled such that the strict and the sloppy interpretations were equally accessible as reported by the participants in the pretest. Future research will investigate in detail how the Primitives of Binding framework works as far the strict/sloppy interpretations of the null object are processed among unimpaired people.

10. The reading comprehension of patients were assessed using the comprehension subtest of the Mandarin version of the Western Aphasia Battery. The scores of the patients ranged from 5.1 to 7.1 (M = 6.1, SD = 0.7).

11. This finding is also compatible with the claim that patients with Broca’s area damaged are vulnerable in resolving competing sources of information (Dickey & Thompson, 2009; Novick et al., 2010), as the strict interpretation and the sloppy interpretation are derived from different levels of representation. The exact relation between Broca’s area and the ambiguity resolution, however, is beyond the scope of the present study.

12. Although the null object construction in Mandarin exhibits strict/sloppy ambiguity, which is a special property of Mandarin, it is relatively hard to find many sentences that can allow both the strict interpretation and the sloppy interpretation at the same time. Future research will try to improve the design to increase the number of stimulus stories for testing both healthy normal controls and patients.

Additional information

Funding

The work reported in this paper was supported by the National Social Sciences Foundation of China [19BYY025].