How left inferior frontal cortex participates in syntactic processing: Evidence from aphasia

We report on three experiments that provide a real-time processing perspective on the poor comprehension of Broca’s aphasic patients for non-canonically structured sentences. In the first experiment we presented sentences (via a Cross Modal Lexical Priming (CMLP) paradigm) to Broca’s patients at a normal rate of speech. Unlike the pattern found with unimpaired control participants, we observed a general slowing of lexical activation and a concomitant delay in the formation of syntactic dependencies involving “moved” constituents and empty elements. Our second experiment presented these same sentences at a slower rate of speech. In this circumstance, Broca’s patients formed syntactic dependencies as soon as they were structurally licensed (again, a different pattern from that demonstrated by the unimpaired control group). The third experiment used a sentence-picture matching paradigm to chart Broca’s comprehension for non-canonically structured sentences (presented at both normal and slow rates). Here we observed significantly better scores in the slow rate condition. We discuss these findings in terms of the functional commitment of the left anterior cortical region implicated in Broca’s aphasia and conclude that this region is crucially involved in the formation of syntactically-governed dependency relations, not because it supports knowledge of syntactic dependencies, but rather because it supports the real-time implementation of these specific representations by sustaining, at the least, a lexical activation rise-time parameter.     

The processing of extraposed structures in English

In most languages, most of the syntactic dependency relations found in any given sentence are projective: the word-word dependencies in the sentence do not cross each other. Some syntactic dependency relations, however, are non-projective: some of their word-word dependencies cross each other. Non-projective dependencies are both rarer and more computationally complex than projective dependencies; hence, it is of natural interest to investigate whether there are any processing costs specific to non-projective dependencies, and whether factors known to influence processing of projective dependencies also affect non-projective dependency processing. We report three self-paced reading studies, together with corpus and sentence completion studies, investigating the comprehension difficulty associated with the non-projective dependencies created by the extraposition of relative clauses in English. We find that extraposition over either verbs or prepositional phrases creates comprehension difficulty, and that this difficulty is consistent with probabilistic syntactic expectations estimated from corpora. Furthermore, we find that manipulating the expectation that a given noun will have a postmodifying relative clause can modulate and even neutralize the difficulty associated with extraposition. Our experiments rule out accounts based purely on derivational complexity and/or dependency locality in terms of linear positioning. Our results demonstrate that comprehenders maintain probabilistic syntactic expectations that persist beyond projective-dependency structures, and suggest that it may be possible to explain observed patterns of comprehension difficulty associated with extraposition entirely through probabilistic expectations.     

Ambiguity in the brain: what brain imaging reveals about the processing of syntactically ambiguous sentences

Two fMRI studies investigated the time course and amplitude of brain activity in language-related areas during the processing of syntactically ambiguous sentences. In Experiment 1, higher levels of activation were found during the reading of unpreferred syntactic structures as well as more complex structures. In Experiments 2A and 2B higher levels of brain activation were found for ambiguous sentences compared with unambiguous sentences matched for syntactic complexity, even when the ambiguities were resolved in favor of the preferred syntactic construction (despite the absence of this difference in previous reading time results). Although results can be reconciled with either serial or parallel models of sentence parsing, they arguably fit better into the parallel framework. Serial models can admittedly be made consistent but only by including a parallel component. The fMRI data indicate the involvement of a parallel component in syntactic parsing that might be either a selection mechanism or a construction of multiple parses.     

The Effect of Prosody on Distributional Learning in 12‐ to 13‐Month‐Old Infants

Distributional information is a potential cue for learning syntactic categories. Recent studies demonstrate a developmental trajectory in the level of abstraction of distributional learning in young infants. Here we investigate the effect of prosody on infants' learning of adjacent relations between words. Twelve‐ to thirteen‐month‐old infants were exposed to an artificial language comprised of 3‐word‐sentences of the form aXb and cYd, where X and Y words differed in the number of syllables. Training sentences contained a prosodic boundary between either the first and the second word or the second and the third word. Subsequently, infants were tested on novel test sentences that contained new X and Y words and also contained a flat prosody with no grouping cues. Infants successfully discriminated between novel grammatical and ungrammatical sentences, suggesting that the learned adjacent relations can be abstracted across words and prosodic conditions. Under the conditions tested, prosody may be only a weak constraint on syntactic categorization. Copyright © 2011 John Wiley & Sons, Ltd.     

Syntactic awareness in young monolingual and bilingual (Urdu–English) children

In two experiments, bilingual (Urdu and English) 5- and 6-year-old children outperformed their monolingual (English) peers when asked to detect grammatically incorrect sentences on a syntactic awareness test. This result occurred when children were tested in English (Experiment 1) and when they were tested in English or in Urdu (Experiment 2). Bilingual children aged 3 and 4 were better at detecting grammatically incorrect sentences than their monolingual peers, but only when tested in Urdu. However, no significant differences appeared in monolingual and bilingual children's ability to detect grammatically correct sentences, suggesting that both grammatically correct and incorrect sentences should be used to obtain an accurate measure of syntactic awareness. The issue of whether it is bilingualism or the properties of a language that affect syntactic awareness is considered.     

What children say when asked “What?”: A study of the use of syntactic knowledge

The present study explores two questions: What is the nature of older children's syntactic knowledge; how is that knowledge used in an everyday speech situation? Six-, eight-, and ten-year-olds repeated grammatical sentences as read by the first experimenter. Half the sentences were syntactically clear, half slightly distorted. Clear versions displayed basic grammatical relations and constituent structure perspicuously. The second experimenter, who sat at the other end of the room, asked “What?” after each sentence. The syntactic changes children might make to accommodate the listener were examined. Although the children made a variety of changes, at all ages they tended to change distorted versions to clear ones, and to repeat clear versions. The results suggest that children's syntactic knowledge is deeper and more accessible than had been supposed.     

The effect of syntactic structure upon speech initiation times of stuttering and nonstuttering speakers

Past research has shown that adults who stutter tend to be slower than adults who do not stutter at initiating various speech-like movements, nonsense syllables, words, short phrases, and simple sentences. The present study sought to extend this research by examining the effect that syntactic structure has upon stutterers' and nonstutterers' ability to initiate sentences. Eleven persons who stutter (mean age=22.2 years) and 11 nonstuttering controls (mean age=23.3 years) read, rehearsed, and then reproduced a series of 96 sentences within a simple reaction time paradigm. The sentences were presented in four blocks of 24 sentences, and each block contained one version of each of the 24 base sentences. Versions of the base sentences varied, from simple to complex, along four levels of syntactic complexity. Results indicated that speech initiation times (SITs) were significantly longer for participants who stutter than they were for nonstuttering controls for three of the four sentence types. There was no significant difference in SITs across the four sentence types for either group. Among the stuttering participants, there was no significant correlation between stuttering severity and overall initiation time for the sentences. Consistent with other studies, the present findings suggest that persons who stutter are slower than persons who do not stutter at planning and/or initiating motor movements associated with speech production. EDUCATIONAL OBJECTIVES: The reader will be able to (1). describe how persons who stutter typically perform during various reaction time tasks, (2). explain the rationale for examining the effect of syntactic complexity upon speech initiation time, (3). discuss how the speech initiation times of persons who stutter compare to those of persons who do not stutter during the production of various types of sentences, (4). identify future research needs in this area.     

Deep and surface structure in children's sentence learning

Fifth-graders were asked to learn 32 syntactically varied, semantically unrelated sentences containing combinations of agentive, objective and instrumental case relations. Five learning trials, each followed by a noun-prompted recall test, were provided. Recall patterns indicated that variations in surface structure complexity (i.e., verb voice and sentential position of noun prompts) exerted less influence on Ss' memory for sentences than deep structures. Several trials were required for Ss to reproduce syntactic details accurately and many transformational errors were observed. Even then, children were unable to learn one syntactic form. Although patterns of recall were more consistent with deep structure predictions, results were not completely supportive of Fillmore's analysis of deep structure in terms of case relations, and the possibility that other non-linguistic means were used to store sentences loomed as an alternative to the deep structure view.     

Feature Centrality and Conceptual Coherence

Conceptual features differ in how mentally tranformable they are. A robin that does not eat is harder to imagine than a robin that does not chirp. We argue that features are immutable to the extent that they are central in a network of dependency relations. The immutability of a feature reflects how much the internal structure of a concept depends on that feature; i.e., how much the feature contributes to the concept's coherence. Complementarily, mutability reflects the aspects in which a concept is flexible. We show that features can be reliably ordered according to their mutability using tasks that require people to conceive of objects missing a feature, and that mutability (conceptual centrality) can be distinguished from category centrality and from diagnosticity and salience. We test a model of mutability based on asymmetric, unlabeled, pairwise dependency relations. With no free parameters, the model provides reasonable fits to data. Qualitative tests of the model show that mutability judgments are unaffected by the type of dependency relation and that dependency structure influences judgments of variability.     

Eye movements of young and older adults during reading

The eye movements of young and older adults were tracked as they read sentences varying in syntactic complexity. In Experiment 1, cleft object and object relative clause sentences were more difficult to process than cleft subject and subject relative clause sentences; however, older adults made many more regressions, resulting in increased regression path fixation times and total fixation times, than young adults while processing cleft object and object relative clause sentences. In Experiment 2, older adults experienced more difficulty than young adults while reading cleft and relative clause sentences with temporary syntactic ambiguities created by deleting the that complementizers. Regression analyses indicated that readers with smaller working memories need more regressions and longer fixation times to process cleft object and object relative clause sentences. These results suggest that age-associated declines in working memory do affect syntactic processing.     

Predicted errors in children's early sentence comprehension

Children use syntax to interpret sentences and learn verbs; this is syntactic bootstrapping. The structure-mapping account of early syntactic bootstrapping proposes that a partial representation of sentence structure, the set of nouns occurring with the verb, guides initial interpretation and provides an abstract format for new learning. This account predicts early successes, but also telltale errors: Toddlers should be unable to tell transitive sentences from other sentences containing two nouns. In testing this prediction, we capitalized on evidence that 21-month-olds use what they have learned about noun order in English sentences to understand new transitive verbs. In two experiments, 21-month-olds applied this noun-order knowledge to two-noun intransitive sentences, mistakenly assigning different interpretations to "The boy and the girl are gorping!" and "The girl and the boy are gorping!". This suggests that toddlers exploit partial representations of sentence structure to guide sentence interpretation; these sparse representations are useful, but error-prone.     

Children's command of quantification

In this article we present data from two sets of experiments designed to investigate how children and adult speakers of English and Kannada (Dravidian) interpret scopally ambiguous sentences containing numerally quantified noun phrases and negation (e.g. Donald didn't find two guys). We use this kind of sentence as a way to find evidence in children's linguistic representations for the hierarchical structure and the abstract relations defined over these structures (in particular, the relation of c-command) that linguists take to be at the core of grammatical knowledge. Specifically, we uncover the existence of systematic differences in the way that children and adult speakers resolve these ambiguities, independent of the language they speak. That is, while adults can easily access either scope interpretation, 4-year-old children display a strong preference for the scopal interpretation of the quantified elements which corresponds to their surface syntactic position. Crucially, however, we show that children's interpretations are constrained by the surface hierarchical relations (i.e. the c-command relations) between these elements and not by their linear order. Children's non-adult interpretations are therefore informative about the nature of the syntactic representations they entertain and the rules they use to determine the meaning of a sentence from its structure.     

The relative accessibility of semantic and deep-structure syntactic concepts

Three experiments were conducted to determine the relative accessibility of semantic and deep-structure syntactic concepts. In Experiment 1, which employed a concept-formation task, subjects learned the concept “deep-structure subject” more slowly than the case concept “experiencer.” In Experiments 2 and 3, which employed a new recognition memory procedure, subjects performed more poorly when the sentences to be remembered were differentiated on the basis of deep-structure syntactic relations than when they were differentiated on the basis of semantic relations. These results favor Fillmore’s case grammar, or another semantically based theory, rather than the “standard theory” of Chomsky in a model of linguistic behavior.     

Information structure expectations in sentence comprehension

In English, new information typically appears late in the sentence, as does primary accent. Because of this tendency, perceivers might expect the final constituent or constituents of a sentence to contain informational focus. This expectation should in turn affect how they comprehend focus-sensitive constructions such as ellipsis sentences. Results from four experiments on sluicing sentences (e.g., The mobster implicated the thug, but we can't find out who else) suggest that perceivers do prefer to place focus late in the sentence, though that preference can be mitigated by prosodic information (pitch accents, Experiment 2) or syntactic information (clefted sentences, Experiment 3) indicating that focus is located elsewhere. Furthermore, it is not necessarily the direct object, but the informationally focused constituent that is the preferred antecedent (Experiment 4). Expectations regarding the information structure of a sentence, which are only partly cancellable by means of overt focus markers, may explain persistent biases in ellipsis resolution.     

Examining the role of lexical frequency in the acquisition and processing of sentential complements

We present empirical data showing that the relative frequency with which a verb normally appears in a syntactic construction predicts young children's ability to remember and repeat sentences instantiating that construction. Children aged 2;10–5;8 years were asked to repeat grammatical and ungrammatical sentential complement sentences (e.g., ‘I think + S’). The sentences contained complement-taking verbs (CTVs) used with differing frequencies in children's natural speech. All children repeated sentences containing high frequency CTVs (e.g., think) more accurately than those containing low frequency CTVs (e.g., hear), and made more sophisticated corrections to ungrammatical sentences containing high frequency CTVs. The data suggest that, like adults, children are sensitive to lexico-constructional collocations. The implications for language acquisition are discussed.     

Conflict and surrender during sentence processing: an ERP study of syntax-semantics interaction

Recent ERP studies report that implausible verb-argument combinations can elicit a centro-parietal P600 effect (e.g., "The hearty meal was devouring …"; Kim & Osterhout, 2005). Such eliciting conditions do not involve outright syntactic anomaly, deviating from previous reports of P600. Kim and Osterhout (2005) attributed such P600 effects to structural reprocessing that occurs when syntactic cues fail to support a semantically attractive interpretation ('meal' as the Agent of 'devouring') and the syntactic cues are overwhelmed; the sentence is therefore perceived as syntactically ill-formed. The current study replicated such findings and also found that altering the syntactic cues in such situations of syntax-semantics conflict (e.g., "The hearty meal would devour …") affects the conflict's outcome. P600s were eliminated when sentences contained syntactic cues that required multiple morphosyntactic steps to "repair". These sentences elicited a broad, left-anterior negativity at 300-600ms (LAN). We interpret the reduction in P600 amplitude in terms of "resistance" of syntactic cues to reprocessing. We speculate that the LAN may be generated by difficulty retrieving an analysis that satisfies both syntactic and semantic cues, which results when syntactic cues are strong enough to resist opposing semantic cues. This pattern of effects is consistent with partially independent but highly interactive syntactic and semantic processing streams, which often operate collaboratively but can compete for influence over interpretation.     

Understanding Disorders in Agrammatic Patients: Capacity or Structural Deficits?

Several hypotheses have been advanced in recent years to understand difficulties in agrammatic patients. Some of them are of a structural kind, as the deficiency is said to lie in some of the linguistic system components. Others are of a functional type, as it is stated that the problem of these patients lies in the loss of processing capacity.Using the existence of a syntactic type of structure in Spanish, that active sentences do not follow the canonical S-V-O order, we will try to prove in this article whether agrammatic patients' problems are due to memory span loss or to one of the syntactic process mechanisms. To this end, the performances of three groups of patients are contrasted. Agrammatic, anomic, and normal Spanish speakers are given several tasks of sentence–picture matching and tests of memory span.Results show that agrammatic patients have specific difficulties processing certain syntactical structures; however, their memory deficiencies are not more pronounced than in other patients. It can be concluded, therefore, that the deficiencies of agrammatic patients are of a structural character rather than due to memory span loss.     

晚期汉-英二语者英语被动句句法加工的ERP研究*

选取二语中等熟练者和高熟练者两类中国大学生被试,共40人(27女,13男),年龄为20~29岁,平均年龄23.88岁。采用ERP技术,以直译型英语被动句和意译型英语被动句作为实验材料,通过比较无违例、―句法违例句1‖(动词过去分词形式错误)、―句法违例句2‖(动词过去分词错误用为动词原形而造成的句法违例)以及―句法违例句3‖(动词过去分词误用为动词现在分词形式)条件下的行为数据和ERP多维数据变化的基础上,探讨了二语熟练度和语言间句法结构相似性对汉-英双语者英语被动句句法加工过程的影响。结果表明：高熟练者的反应时和正确率整体上优于中等熟练者;难易度不同的句法错误信息会直接影响被动句的加工,对明显有错误的句法信息的反应速度最快,―正确的局部句法信息‖反应时最长。对明显有错误的句法信息的正确反应率最高,最根本的句法结构的错误信息最低。最根本的句法结构的错误信息引发的P600最大,无违例条件引发的P600最小;高熟练者对最根本的句法结构的错误信息引发最大的P600效应,中等熟练者的P600效应未受不同句法错误信息的影响。行为指标支持句法加工相似性效应——直译句反应快、正确率高;意译句反应慢、正确率低。并且此效应在中等熟练者身上表现更加明显。但是脑神经活动模式未表现出句法结构相似性效应,说明二语熟练度在英语被动句加工中具有更为显著的作用。