Filling gaps: Decision principles and structure in sentence comprehension

The correct grammatical characterization of sentences containing filler-gap dependencies is a topic of considerable theoretical interest in linguistics. In some grammatical frameworks, these dependencies are representef in terms of conditions on the permissible indexing of structures (or alternative structure evaluation conditions) which a representation must adhere to in order to be well-formed. In other frameworks, constraints on permissible filler-gap dependencies are simply inherent in the set of phrase structure rules contained in the grammar of a language.The processing of sentences with multiple (potential) filler-gap dependencies was investigated in two experiments. The first experiment provided evidence for three claims. First, the human sentence processor abides by a strategy of assigning the most recent potential filler to a gap. Hence, ‘recent filler’ sentences where this assignment proves to be correct takes less time to comprehend than ‘distant filler’ sentences where this decision turns out to be incorrect. Second, the recent filler strategy is itself just a special case of a more general strategy of assigning the most salient potential filler to a gap. Third, unambiguous sentences in which a filler-gap assignment is disambiguated by ‘control’ information specified by individual verbs gives rise to the same recent filler errors as ambiguous sentences. This suggests that tentative filler-gap assignments are made by the processor before all of the relevant constraints on permissible filler-gap dependencies are consulted by the processor.The second experiment tested an alternative hypothesis that the more complex ‘distant filler’ sentences took longer to comprehend in the first experiment only because these sentences often contained verbs which license two adjacent gaps. The experiment showed that there was a significant recent filler effect in sentences that did not contain adjacent gaps and that this effect did not interact with verb class.The finding that the processor delays use of verb-control information is extremely surprising. It may be explained by the fact that this information is only relevant to one type of gap (‘equi-gaps’) and what type of gap the processor is dealing with often can not be determined unambiguously at the time when it initially encounters a gap in its left-to-right processing of a sentence.If our interpretation of these findings is correct, they argue for a considerable amount of structure in the sentence comprehension system. Further, they favor a view of sentence processing in which processing operations involving constraints on the permissible indexing (or evaluation) of structures lag behind the processor's structure building operations. Hence, the results favor those grammatical theories which preserve this distinction over grammatical theories which provide a uniform characterization of all syntactic well-formedness conditions.     

Phonology competes with syntax: experimental evidence for the interaction of word order and accent placement in the realization of Information Structure

In this paper, we investigate the interaction of phonological and syntactic constraints on the realization of Information Structure in Greek, a free word order language. We use magnitude estimation as our experimental paradigm, which allows us to quantify the influence of a given linguistic constraint on the acceptability of a sentence. We present results from two experiments. In the first experiment, we focus on the interaction of word order and context. In the second experiment, we investigate the additional effect of accent placement and clitic doubling. The results show that word order, in contrast to standard assumptions in the theoretical literature, plays only a secondary role in marking the Information Structure of a sentence. Order preferences are relatively weak and can be overridden by constraints on accent placement and clitic doubling. Our experiments also demonstrate that a null context shows the same preference pattern as an all focus context, indicating that 'default' word order and accent placement (in the absence of context) can be explained in terms of Information Structure. In the theoretical part of this paper, we formalize the interaction of syntactic and phonological constraints on Information Structure. We argue that this interaction is best captured using a notion of grammatical competition, such as the one developed by Optimality Theory (Prince & Smolensky, 1993, Optimality theory: constraint interaction in generative grammar (Technical Report No. 2). Center for Cognitive Science, Rutgers University, Piscataway, NJ; Science 275 (1997) 1604). In particular, we exploit the optimality theoretic concept of constraint ranking to account for the fact that some constraint violations are more serious than others. We extend standard Optimality Theory to obtain a grammar model that predicts not only the optimal (i.e. grammatical) realization of a given input, but also makes predictions about the relative grammaticality of suboptimal structures. This allows us to derive a constraint hierarchy that accounts for the interaction of phonological and syntactic constraints on Information Structure and models the acceptability patterns found in the experimental data.     

What infants know about syntax but couldn't have learned: experimental evidence for syntactic structure at 18 months

Generative linguistic theory stands on the hypothesis that grammar cannot be acquired solely on the basis of an analysis of the input, but depends, in addition, on innate structure within the learner to guide the process of acquisition. This hypothesis derives from a logical argument, however, and its consequences have never been examined experimentally with infant learners. Challenges to this hypothesis, claiming that an analysis of the input is indeed sufficient to explain grammatical acquisition, have recently gained attention. We demonstrate with novel experimentation the insufficiency of this countervailing view. Focusing on the syntactic structures required to determine the antecedent for the pronoun one, we demonstrate that the input to children does not contain sufficient information to support unaided learning. Nonetheless, we show that 18-month-old infants do have command of the syntax of one. Because this syntactic knowledge could not have been gleaned exclusively from the input, infants' mastery of this aspect of syntax constitutes evidence for the contribution of innate structure within the learner in acquiring a grammar.     

On the preferred form of the double object construction

Two groups of 15 adults participated in two preference rating tasks for written sentence forms. Pairs of sentences were presented to the subjects which differed only in the grammatical form used to express the double object construction (one which has both a direct and an indirect object). Several hypotheses were formulated regarding the nature of subjects' preferences for various combinations of grammatical form and pronominalization. Results indicated that adults show clear preferences for one grammatical form in most instances and that rules can be formulated for these preferences. The relevance of these results for the examination of current language assessment tests and the development of language training programs is discussed.     

Is there a direct relation between the development of vocabulary and grammar?

Previous studies of individual differences have revealed strong correlations between children's vocabulary and grammatical abilities, and these data have been used to support theoretical accounts positing direct developmental relations between these two areas of language. However, between‐person differences do not necessarily reflect intra‐individual dynamics. Thus, in the present study, we analysed longitudinal data from three annual assessments of vocabulary and grammar in 217 children (M_age = 4 years and 3 months at first assessment) using a modelling strategy with some utility in distinguishing relations at the between‐ and within‐person levels. The results revealed strong correlations between grammar and vocabulary at the between‐person level, but the evidence of direct dependencies between the variables at the within‐person level was rather limited. Specifically, we found a small direct contribution from grammar to vocabulary for children between the ages of 4 and 5, but there was no evidence of any direct contributions from vocabulary to grammar. Further analyses suggested that the home literacy environment may represent a common source of individual differences in children's vocabulary and grammatical skills. In light of these results, we argue that the evidence of direct relations between vocabulary and grammatical development in preschool‐aged children may not be as strong as previously assumed.     

Agrammatic production of subject-verb agreement: the effect of conceptual number.

Three experiments tested the hypothesis that the deficit underlying agrammatic sentence production difficulties can be characterized as a limitation of computational resources and that these resources are not restricted to syntactic processing. This hypothesis was tested by eliciting subject-verb agreement errors in a sentence fragment completion paradigm. Sentence fragments were complex noun phrases, containing a subject (head) noun and a modifying prepositional phrase, containing a "local" noun. We varied the number of "tokens" a singular head noun referred to. Therefore, in one condition, grammatical and conceptual number of the head noun mismatched, whereas these numbers were the same in another condition. In Experiments 1 and 2, we observed an effect of this variable (i.e., more agreement errors when conceptual number was plural and grammatical number singular) in normal controls. Broca's aphasics, on the other hand, showed no effect. Experiment 3 consisted of a sentence/picture matching test. This test showed that the lack of effect with Broca's aphasics cannot be attributed to a comprehension deficit. We argue that these results are incompatible with the notion of a limitation in resources specific for syntactic processing. Instead, we interpret this as the result of a trade-off: Broca's aphasics lack computational resources to take into account both grammatical and conceptual information in morphosyntactic processing and rely on grammatical information only.     

Grammaticality,Acceptability, and Probability: A Probabilistic View of Linguistic Knowledge

The question of whether humans represent grammatical knowledge as a binary condition on membership in a set of well‐formed sentences, or as a probabilistic property has been the subject of debate among linguists, psychologists, and cognitive scientists for many decades. Acceptability judgments present a serious problem for both classical binary and probabilistic theories of grammaticality. These judgements are gradient in nature, and so cannot be directly accommodated in a binary formal grammar. However, it is also not possible to simply reduce acceptability to probability. The acceptability of a sentence is not the same as the likelihood of its occurrence, which is, in part, determined by factors like sentence length and lexical frequency. In this paper, we present the results of a set of large‐scale experiments using crowd‐sourced acceptability judgments that demonstrate gradience to be a pervasive feature in acceptability judgments. We then show how one can predict acceptability judgments on the basis of probability by augmenting probabilistic language models with an acceptability measure. This is a function that normalizes probability values to eliminate the confounding factors of length and lexical frequency. We describe a sequence of modeling experiments with unsupervised language models drawn from state‐of‐the‐art machine learning methods in natural language processing. Several of these models achieve very encouraging levels of accuracy in the acceptability prediction task, as measured by the correlation between the acceptability measure scores and mean human acceptability values. We consider the relevance of these results to the debate on the nature of grammatical competence, and we argue that they support the view that linguistic knowledge can be intrinsically probabilistic.     

Specific language impairment: a deficit in grammar or processing?

Specific Language Impairment (SLI) is observed in children who fail to acquire age-appropriate language skills but otherwise appear to be developing normally. There are two main hypotheses about the nature of these impairments. One assumes that they reflect impairments in the child's innate knowledge of grammar. The other is that they derive from information-processing deficits that interfere with several aspects of language learning. There is considerable evidence that SLI is associated with impaired speech processing; however, the link between this deficit and the kinds of grammatical impairments observed in these children has been unclear. We suggest that the link is provided by phonology, a speech-based code that plays important roles in learning linguistic generalizations and in working memory.     

Syntactic Creativity Errors in Children's Wh-Questions

Previous work has reported that children creatively make syntactic errors that are ungrammatical in their target language, but are grammatical in another language. One of the most well-known examples is medial wh-question errors in English-speaking children's wh-questions (e.g., What do you think who the cat chased? from Thornton, 1990). The evidence for this non-target-like structure in both production and comprehension has been taken to support the existence of innate, syntactic parameters that define all possible grammatical variation, which serve as a top-down constraint guiding children's language acquisition process. The present study reports new story-based production and comprehension experiments that challenge this interpretation. While we replicated previous observations of medial wh-question errors in children's sentence production (Experiment 1), we saw a reduction in evidence indicating that English-speaking children assign interpretations that conform to the medial wh-question pattern (Experiment 2). Crucially, we found no correlation between production and comprehension errors (Experiment 3). We suggest that these errors are the result of children's immature sentence production mechanisms rather than immature grammatical knowledge.     

Word Order Processing in a Second Language: From VO to OV

Event-related potential studies on second language processing reveal that L1/L2 differences are due either to proficiency, age of acquisition or grammatical differences between L1 and L2 (Kotz in Brain Lang 109(2–3):68–74, 2009). However, the relative impact of these and other factors in second language processing is still not well understood. Here we present evidence from behavioral and ERP experiments on Basque sentence word order processing by L1Spanish–L2Basque early bilinguals (Age of Aquisition  \(=\)  3 years) with very high proficiency in their L2. Results reveal that these L2 speakers have a preference towards canonical Subject–Object–Verb word order, which they processed faster and with greater ease than non-canonical Object–Subject–Verb. This result converges with the processing preferences shown by natives and reported in Erdocia et al. (Brain Lang 109(1):1–17, 2009). However, electrophysiological measures associated to canonical (SOV) and non-canonical (OSV) sentences revealed a different pattern in the non-natives, as compared to that reported previously for natives. The non-native group elicited a P600 component that native group did not show when comparing S and O at sentence’s second position. This pattern of results suggests that, despite high proficiency, non-native language processing recruits neural resources that are different from those employed in native languages.     

Sentence interpretation in normal and aphasic Hindi speakers.

In interpreting a sentence, listeners rely on a variety of linguistic cues to assign grammatical roles such as agent and patient. The present study considered the relative ranking of three cues to agenthood (word order, noun animacy, and subject-verb agreement) in normal and aphasic speakers of Hindi. Because animacy plays a grammatical role in Hindi (determining the nature and acceptability of sentences without accusative marking), this language is relevant to the claim that Broca's aphasia involves a dissociation between grammar and semantics. Results of Study 1 with normal Hindi-dominant speakers showed that animacy is the strongest cue in this language, while agreement is the weakest cue. In Study 2, Hindi-English bilinguals were tested in both their languages. Most showed the normal animacy-dominant monolingual pattern in Hindi, with a mixture of strategies from both languages in their interpretation of English. A substantial minority showed mixed strategies in both languages. Only 5 of 48 subjects displayed a complete separation between languages, with animacy dominance in Hindi and word order dominance in English. In Study 3, two Hindi-English bilinguals with Broca's aphasia were tested in both languages. Results indicate (a) greater use of animacy in Hindi than in English and (b) greater use of word order in English than in Hindi. The strategies displayed by these patients fall well within the range observed among bilingual normals. We conclude that the use of animacy in sentence interpretation by these aphasic patients reflects preservation of normal, language-specific processing strategies; it cannot be interpreted as a nonlinguistic strategy developed to compensate for receptive agrammatism. Results are discussed in light of other cross-linguistic evidence on sentence comprehension in monolingual and bilingual aphasics.     

Studying the grammatical aspects of word recognition: lexical priming,parsing, and syntactic ambiguity resolution

Two experiments are reported examining the relationship between lexical and syntactic processing during language comprehension, combining techniques common to the on-line study of syntactic ambiguity resolution with priming techniques common to the study of lexical processing. By manipulating grammatical properties of lexical primes, we explore how lexically based knowledge is activated and guides combinatory sentence processing. Particularly, we find that nouns (like verbs, see Trueswell & Kim, 1998) can activate detailed lexically specific syntactic information and that these representations guide the resolution of relevant syntactic ambiguities pertaining to verb argument structure. These findings suggest that certain principles of knowledge representation common to theories of lexical knowledge—such as overlapping and distributed representations—also characterize grammatical knowledge. Additionally, observations from an auditory comprehension study suggest similar conclusions about the lexical nature of parsing in spoken language comprehension. They also suggest that thematic role and syntactic preferences are activated during word recognition and that both influence combinatory processing.     

Artificial grammar learning in children: abstraction of rules or sensitivity to perceptual features?

We examined sensitivity to grammatical sequences of colors in an artificial grammar learning task in a sample of 120 children aged between 5 and 8 years. The aim of the experiment was to test whether the children would preferentially learn the specific salient features of the items they were exposed to or the rules that generated these items. The children were divided into two experimental groups (identical grammar but training items differing in their surface features) and a control group (random items). The results showed that regardless of age, participants learned the most frequent salient features of the items, as well as some kind of abstract relational information. However, the 8-year-olds presented a more complex result profile, with one of the experimental groups apparently developing sensitivity to grammatical rules. These results are discussed with reference to the main current models of implicit learning. Overall, the results provided more support for stimulus-specific processing models than for rule-based models.     

Processing Coordinate Structures

Coordination often involves syntactically like categories. Based on the results of four reading time studies, it is argued here that the syntactic like-category restriction is not grammatical. Coordination of unlike categories can be just as acceptable as coordination of like categories. However, syntactically like category coordination is processed faster than coordination of unlike categories even when the two sentence types are judged to be fully acceptable. Further, parallelism of conjuncts facilitates processing regardless of whether it is parallelism in the category of the conjuncts (a property which the grammar might regulate) or parallelism in the internal structure of the conjuncts (a property which the grammar does not regulate, on anyone's view). Parallelism did not facilitate processing when the structure of a subject and object were manipulated, implying that parallelism effects are largely limited to the conjuncts of a coordinate structure and not due simply to the repetition of a phrase with a particular shape.     

Case and Reanalysis

In this paper we discuss an asymmetry in the Case system of German and its implications for human sentence processing: the asymmetry between nominative/accusative and dative case. Starting from the assumption that dative case has a distinct grammatical representation--dative DPs are embedded into an extra structural layer KP--the results of two experiments will be presented, which show that dative assignment during reanalysis is accompanied by additional processing operations that are not needed when accusative or nominative are assigned. In particular, we show that dative assignment during reanalysis triggers reaccess to the mental lexicon, giving rise to greater processing difficulty. We conclude with a discussion of empirical and theoretical consequences of our findings.     

Assessing resource demands during sentence processing in Parkinson's disease

Patients with Parkinson's disease (PD) have sentence comprehension difficulty, but it is unclear whether this is due to a deficit in grammatical processing or to an executive resource limitation. To assess grammatical processing in PD while minimizing task-related demands, PD patients and healthy control subjects performed a word detection procedure that assesses sensitivity to grammatical agreements in sentences in an "on-line" fashion. With this technique, we found that control subjects and PD patients are equally sensitive to grammatical agreement violations in sentences. A traditional, resource-demanding measure of sentence comprehension was also administered to the same PD patients. In comparison to healthy controls, PD patients were significantly impaired in their relative comprehension of sentences containing object-gap subordinate clauses compared to subject-gap subordinate clauses. Performance on several executive resource measures was also impaired in PD, and this correlated with their comprehension performance. Sensitivity to grammatical agreements with the word detection procedure, in the context of sentence comprehension difficulty on a traditional measure, suggests that PD patients' executive resource limitations contribute to their sentence comprehension difficulty.     

Seven principles of surface structure parsing in natural language

In generative grammar there is a traditional distinction between sentence acceptability, having to do with performance, and sentence grammaticality, having to do with competence. The attempt of this paper is to provide a characterization of the notion ‘acceptable sentence’ in English, with some suggestions as to how this characterization might be made universal. The procedure is to outline a set of procedures which are conjectured to be operative in the assignment of a surface structure tree to an input sentence. To some extent, these principles of parsing are modeled on certain parsing techniques formulated by computer scientists for computer languages. These principles account for the high acceptability of right branching structures, outline the role of grammatical function words in sentence perception, describe what seems to be a fixed limit on short-term memory in linguistic processing, and hypothesize the structure of the internal syntactic processing devices. The operation of various classes of transformations with regard to preparing deep structures for input to parsing procedures such as those outlined in the paper is discussed.     

The influence of semantic fit on on-line sentence processing

The interactive influence of verb complement preferences and noun phrase semantic fit on resolution of temporary syntactic ambiguity was investigated in an eye movement experiment. The present semantic fit manipulation included noun phrases that fit well as direct objects of the verbs that they followed and noun phrases that were possible but less likely direct objects of the verbs in question. This contrasted with existing research on the use of verb complement preferences and semantic fit during sentence processing, in which processing of noun phrases that are possible direct objects has been compared with processing of noun phrases that are not possible direct objects of the verbs that they follow. Verb complement preference information and noun phrase semantic fit interacted at early stages of on-line sentence processing. Implications of these results for interactive and structural models of sentence processing are discussed.     

The Concomitant Effects of Phrase Length and Informational Content in Sentence Comprehension

Recent evidence suggests that phrase length plays a crucial role in modification ambiguities. Using a self-paced reading task, we extended these results by examining the additional pragmatic effects that length manipulations may exert. The results demonstrate that length not only modulates modification preferences directly, but that it also necessarily changes the informational content of a sentence, which itself affects modification preferences. Our findings suggest that the same length manipulation affects multiple sources of constraints, both structural and pragmatic, which can each exert differing effects on processing.     

The temporal structure of spoken sentence comprehension in Chinese

Three experiments with 60 native Chinese speakers were conducted to examine the temporal structure of spoken sentence comprehension in Chinese. In the two sentence-gating experiments, listeners heard sentence fragments of various sizes, either successively or individually, and decided on the agent role of the sentence. In the agent-naming experiment, listeners repeated aloud the sentence agent upon hearing the sentence. Converging evidence was derived from these experiments indicating the usefulness of sentence gating in tapping into the temporal structure of comprehension and in evaluating listeners’ comprehension on the basis of partial information. Results from these experiments show that partial sentence information plays a very important role in Chinese sentence comprehension, and that Chinese listeners integrate incomplete and ungrammatical sentence fragments by reference to complete and grammatical models in the language. It is argued that these processing characteristics reflect properties of the Chinese language in which few morphological, grammatical, and syntactic constraints are placed on the relationships between sentence constituents.