Effects of age, speed of processing, and working memory on comprehension of sentences with relative clauses

Two hundred participants, 50 in each of four age ranges (19-29, 30-49, 50-69, 70-90) were tested for working memory, speed of processing, and the processing of sentences with relative clauses. In Experiment 1, participants read four sentence types (cleft subject, cleft object, subject-subject, subject-object) in a word-by-word, non-cumulative, self-paced reading task and made speeded plausibility judgments about them. In Experiment 2, participants read two types of sentences, one of which contained a doubly center embedded relative clause. Older participants' comprehension was less accurate and there was age-related slowing of online processing times in all but the simplest sentences, which increased in syntactically complex sentences in Experiment 1. This pattern suggests an age-related decrease in the efficiency of parsing and interpretation. Slower speed of processing and lower working memory were associated with longer online processing times only in Experiment 2, suggesting that task-related operations are related to general speed of processing and working memory. Lower working memory was not associated with longer reading times in more complex sentences, consistent with the view that general working memory is not critically involved in online syntactic processing. Longer online processing at the most demanding point in the most demanding sentence was associated with better comprehension, indicating that it reflects effective processing under some certain circumstances. However, the poorer comprehension performance of older individuals indicates that their slower online processing reflects inefficient processing even at these points.     

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.     

Sentence Complexity and Working Memory Effects in Ambiguity Resolution

Two self-paced reading experiments using a paraphrase decision task paradigm were performed to investigate how sentence complexity contributed to the relative clause (RC) attachment preferences of speakers of different working memory capacities (WMCs). Experiment 1 (English) showed working memory effects on relative clause processing in both offline RC attachment preferences and in online reading time measures, but no effects of syntactic complexity. In Experiment 2 (Korean), syntactic complexity due to greater distance between integrating heads, as measured by the dependency locality theory (Gibson in Cognition 68:1–76, 1998), significantly increased the proportion of attachment to NP1. However, no effects of working memory were found. The difference in results between English and Korean is proposed to be due to head-directionality effects. The results of our study support the conclusion that working memory-based accounts provide a better explanation than previous language-dependent accounts for differences in RC attachment preferences. We propose that previous language dependent-accounts of cross-linguistic differences in RC processing have overlooked the interaction between individual WMC and a language’s general structure, which is a central factor in RC attachment.     

The subordination effect: Evidence from self-paced reading and recall

Engelkamp and Rummer (2002) demonstrated that auditorily presented subordinate causal sentences are better retained than coordinate sentences. This subordination effect was explained by suggesting that subordinate sentences are merged more easily in memory than coordinate sentences. The present paper enlarges Engelkamp and Rummer's findings with respect to three aspects. First, it demonstrates that the subordination effect can only be found if a verbatim but not a content related recall score is used. Second, using self-paced reading, it demonstrates a processing advantage for subordinate sentences. This reading time advantage was only observed if the subordinate clause preceded the matrix clause. Third, it excludes an alternative explanation of the subordination effect which attributes memory differences to the fact that the critical causal conjunction word was presented earlier in subordinate than in coordinate sentences. In sum, our findings suggest a direct contribution of syntactic information to sentence regeneration.     

Chinese subject-relative clauses are more difficult to process than the object-relative clauses

This paper presents an experiment that compared high and low working memory span readers' abilities to process Chinese subject-relative and object-relative clause structures in a self-paced reading paradigm. Comprehension performance results indicated that the object-relative structure was easier to understand than the subject-relative structure. Reading time results showed that participants with low working memory span read the subject-relative structures more slowly than the object-relative structures, but there was no reading time difference for the high working memory span participants. The experiment provides further evidence that the Chinese subject-relative clause structure is more difficult to process than the Chinese object-relative clause structure, especially for low working memory span individuals. Furthermore, these results support a syntactic storage account of the observed complexity difference.     

Constituent Length Affects Prosody and Processing for a Dative NP Ambiguity in Korean

Two sentence processing experiments on a dative NP ambiguity in Korean demonstrate effects of phrase length on overt and implicit prosody. Both experiments controlled non-prosodic length factors by using long versus short proper names that occurred before the syntactically critical material. Experiment 1 found that long phrases induce different prosodic phrasing than short phrases in a read-aloud task and change the preferred interpretation of globally ambiguous sentences. It also showed that speakers who have been told of the ambiguity can provide significantly different prosody for the two interpretations, for both lengths. Experiment 2 verified that prosodic patterns found in first-pass pronunciations predict self-paced reading patterns for silent reading. The results extend the coverage of the Implicit Prosody Hypothesis [Fodor, J Psycholinguist Res 27:285–319, 1998; Prosodic disambiguation in silent reading. In M. Hirotani (Ed.), NELS 32 (pp. 113–132). Amherst, MA: GLSA Publications, 2002] to another construction and to Korean. They further indicate that strong syntactic biases can have rapid effects on the formulation of implicit prosody.     

Comparisons of Online Reading Paradigms: Eye Tracking, Moving-Window, and Maze

This study compares four methodologies used to examine online sentence processing during reading. Specifically, self-paced, non-cumulative, moving-window reading (Just et al. in J Exp Psychol Gen 111:228–238, 1982), eye tracking (see e.g., Rayner in Q J Exp Psychol 62:1457–1506, 2009), and two versions of the maze task (Forster et al. in Behav Res Methods 41:163–171, 2009)—the lexicality maze and the grammaticality maze—were used to investigate the processing of sentences containing temporary structural ambiguities. Of particular interest were (i) whether each task was capable of revealing processing differences on these sentences and (ii) whether these effects were indicated precisely at the predicted word/region. Although there was considerable overlap in the general pattern of results from the four tasks, there were also clear differences among them in terms of the strength and timing of the observed effects. In particular, excepting sentences that tap into clause-closure commitments, both maze task versions provided robust, “localized” indications of incremental sentence processing difficulty relative to self-paced reading and eye tracking.     

Re-examining the contribution of visuospatial working memory to inhibition of return

Castel and colleagues (Percept Psychophys 65(6):970–981, 2003) proposed that visuospatial working memory is needed to retain and update the irrelevant but attended location in an inhibition of return (IOR) procedure. In a series of three experiments, we re-examined this hypothesis by loading visuospatial working memory and manipulating the timing of encoding. When the visuospatial memory items were presented right after the cue, as in Castel et al. (Percept Psychophys 65(6):970–981, 2003), we replicated the lack of IOR in the dual-task condition (Experiment 1). However, when we presented the visuospatial memory items before the spatial cue, to control for retroactive interference in encoding, we found robust IOR effects (Experiment 2); the effect remained strong even when participants were prevented from using verbal labels to rehearse the memory material (Experiment 3). We conclude that IOR does not seem to depend on retaining the position of the irrelevant cue in visuospatial working memory.     

Aging and individual differences in binding during sentence understanding: Evidence from temporary and global syntactic attachment ambiguities

We report an investigation of aging and individual differences in binding information during sentence understanding. An age-continuous sample of adults (N = 91), ranging from 18 to 81 years of age, read sentences in which a relative clause could be attached high to a head noun NP1, attached low to its modifying prepositional phrase NP2 (e.g., The son of the princess who scratched himself/herself in public was humiliated), or in which the attachment site of the relative clause was ultimately indeterminate (e.g., The maid of the princess who scratched herself in public was humiliated). Word-by-word reading times and comprehension (e.g., who scratched?) were measured. A series of mixed-effects models were fit to the data, revealing: (1) that, on average, NP1-attached sentences were harder to process and comprehend than NP2-attached sentences; (2) that these average effects were independently moderated by verbal working memory capacity and reading experience, with effects that were most pronounced in the oldest participants and; (3) that readers on average did not allocate extra time to resolve global ambiguities, though older adults with higher working memory span did. Findings are discussed in relation to current models of lifespan cognitive development, working memory, language experience, and the role of prosodic segmentation strategies in reading. Collectively, these data suggest that aging brings differences in sentence understanding, and these differences may depend on independent influences of verbal working memory capacity and reading experience.     

Plausibility and Verb Subcategorization in Temporarily Ambiguous Sentences: Evidence from Self-Paced Reading

A self-paced reading experiment investigated processing of sentences containing a noun-phrase that could temporarily be mistaken as the direct-object argument of a verb in a subordinate clause but actually constituted the syntactic subject of the main clause (often referred to as an early vs. late closure ambiguity). Subcategorization preference of the subordinate verb and plausibility of the syntactic misanalysis were manipulated. Elevated reading times occurred during processing of the temporarily ambiguous noun-phrase for those sentences where the noun-phrase was an implausible direct-object of the preceding verb, regardless of the verbs subcategorization preferences. Elevated reading times were observed for all sentence types following syntactic disambiguation. Subsequent correlational analyses showed that the verbs individual subcategorization preferences affected processing time on the critical noun-phrase and the syntactically disambiguating main verb.     

The on-line resolution of the sentence complement/relative clause ambiguity: evidence from Spanish

Two self-paced reading experiments investigated syntactic ambiguity resolution in Spanish. The experiments examined the way in which Spanish subjects initially interpret sentences that are temporarily ambiguous between a sentence complement and a relative clause interpretation. Experiment 1 examined whether the sentence complement preference found in English is observed in Spanish speaking subjects. In Experiment 2, verbal mood was manipulated in order to study the influence of verb-specific information on sentence processing. Since subcategorization for a subjunctive complement clause is generally assumed to be a lexical property of some verbs, the manipulation of the mood of the embedded verb affords us an interesting and novel way to examine the influence of lexical information on syntactic ambiguity resolution. Experiment 1 showed that Spanish speakers initially interpret the ambiguous that-clause as a sentence complement. Experiment 2 showed that verb-specific information, in particular, the information that specificies that a verb subcategorizes for a subjunctive complement, is accessed and used rapidly and affects the ambiguity resolution process. The results are discussed in relation to current models of sentence processing.     

The effect of noun phrase type on working memory saturation during sentence comprehension

Double centre-embedded structures such as “the rat the cat the boy chased ate was brown” seem ungrammatical to many human subjects. Using an offline complexity judgement task, Gibson and Thomas (1999) demonstrated that people found such sentences no more difficult to understand when the second verb phrase (VP) was omitted, relative to a condition where all the required VPs were present. According to the Syntactic Prediction Locality Theory (SPLT; Gibson, 1998), this syntactic illusion is determined by the high working memory cost associated with the integration of the second VP. This cost could be reduced by replacing the third noun phrase (the boy) by a pronoun, making the reader more sensitive to the omission of the second VP. This hypothesis was tested in two experiments using French sentences. Both experiments confirmed the syntactic illusion when the second VP was not a pronoun. The second experiment measured the reading times of the VPs and showed that the pronoun induced a longer reading time of the final VP when the second VP was omitted. The overall results indicate a condition under which human subjects could process the most complex part of a sentence with more than one embedded relative clause. The overall results are consistent with most of the hypotheses derived from the SPLT although offline complexity judgements could not be the most sensitive measure to test some of these hypotheses.     

Effects of Irrelevant Sounds on Phonological Coding in Reading Comprehension and Short term Memory

The effects of irrelevant sounds on reading comprehension and short-term memory were studied in two experiments. In Experiment 1, adults judged the acceptability of written sentences during irrelevent speech, accompanied and unaccompanied singing, instrumental music, and in silence. Sentences varied in syntactic complexity: Simple sentences contained a right-branching relative clause ( The applause pleased the woman that gave the speech ) and syntactically complex sentences included a centre-embedded relative clause ( The hay that the farmer stored fed the hungry animals ). Unacceptable sentences either sounded acceptable ( The dog chased the cat that eight up all his food ) or did not ( The man praised the child that sight up his spinach ). Decision accuracy was impaired by syntactic complexity but not by irrelevant sounds. Phonological coding was indicated by increased errors on unacceptable sentences that sounded correct. These error rates were unaffected by irrelevant sounds. Experiment 2 examined effects of irrelevant sounds on ordered recall of phonologically similar and dissimilar word lists. Phonological similarity impaired recall. Irrelevant speech reduced recall but did not interact with phonological similarity. The results of these experiments question assumptions about the relationship between speech input and phonological coding in reading and the short-term store.     

Utilization of Prosodic Information in Syntactic Ambiguity Resolution

Two self paced listening experiments examined the role of prosodic phrasing in syntactic ambiguity resolution. In Experiment 1, the stimuli consisted of early closure sentences (e.g., “While the parents watched, the child sang a song.”) containing transitive-biased subordinate verbs paired with plausible direct objects or intransitive-biased subordinate verbs paired with implausible direct objects. Experiment 2 also contained early closure sentences with transitively and intransitive-biased subordinate verbs, but the subordinate verbs were always followed by plausible direct objects. In both experiments, there were two prosodic conditions. In the subject-biased prosodic condition, an intonational phrase boundary marked the clausal boundary following the subordinate verb. In the object-biased prosodic condition, the clause boundary was unmarked. The results indicate that lexical and prosodic cues interact at the subordinate verb and plausibility further affects processing at the ambiguous noun. Results are discussed with respect to models of the role of prosody in sentence comprehension.     

Executive control is shared between sentence processing and digit maintenance: Evidence from a strictly timed dual-task paradigm

We investigated whether the comprehension of syntactically difficult sentences taxes the executive control component of working memory more than the comprehension of their easier counterparts. To that end, we tested the effect of sharing executive control between sentence comprehension and the maintenance of a digit load in two dual-task experiments with strictly controlled timing (Barrouillet, Bernardin, & Camos, 2004). Recall was worse after participants had processed one (Experiment 2) or two (Experiment 1) difficult sentences than after they had processed one or two easy sentences, respectively. This finding suggests that sentence processing and the maintenance of a digit load share executive control. Processing syntactically difficult sentences seems to occupy executive control for a longer time than processing their easy counterparts, thereby blocking refreshments of the memory traces of the digits so that these traces decay more and recall is worse. There was no effect of the size of the digit load on sentence-processing performance (Experiment 2), suggesting that sentence processing completely occupied executive control until processing was complete.     

Active memory processes in visual sentence comprehension: Clause effects and pronominal reference

Two experiments were conducted to investigate active memory processes during reading. Subjects read two-clause sentences one word at a time at a self-paced rate. Following each sentence a probe word was presented; subjects were to decide if this word occurred in the sentence they had just read. The first experiment examined clausal effects during reading. Reaction times to items from the final clause were shorter than those to items from a previous clause even when the same number of words intervened. The second experiment used the clause effect to address the issue of proniminal reference. Results indicated that a pronoun in the final clause activated the meaning of its antecedent, thus demonstrating that the method is sensitive to both surface and meaning codes in active memory.     

Effects of Age and Location in Chinese Relative Clauses Processing

Three experiments investigated Chinese relative clause processing with children, youths and elders using sentence-picture matching and self-paced reading methods. In Experiment 1, we found that object-extracted clause were easier to comprehend than subject-extracted clause , and object-modified relative clause (i.e., object-modified subject-extracted clause\(\backslash \)object-modified object-extracted clause) were difficult to comprehend than subject modified relative clause (subject-modified subject-extracted clause\(\backslash \)subject-modified object-extracted clause). Importantly, this paper also found 5–6.5 ages may be critical for children to comprehend RCs in Chinese. Experiment 2 also showed that S-ORCs were easier to comprehend than S-SRCs for youths and elders. Further, elders have more difficulty comprehending RCs than youths. Experiment 3 indicated that there were no significant differences in difficulty between O-SRCs and O-ORCs, and no differences were found between youths and elders. In general, our findings gave support to predictions of working memory-based theory, and also indicated that RCs processing has an intricate course. Many factors such as syntactic, language specificity, experience, personality, must all be considered in sentence processing.     

Syntactic structure and the garden path

The experiment investigated locally ambiguous English sentences containing “complement” verbs such as believe, which can be followed either by a direct object or by a complement clause. These two sentence types were compared with unambiguous sentences in which the complement clause was introduced by the word that. Subjects processed numerous examples of these sentences in a word-by-word self-paced reading task. At the disambiguation point after the ambiguous noun phrase, longer reading times were obtained for reduced complement constructions compared with direct object sentences. Such an effect has been attributed to the operation of the parsing principle Minimal Attachment (Frazier and Rayner, 1982). This principle predicts that subjects assume falsely that the noun phrase after the complement verb in the reduced complement constructions is the direct object, resulting in the need for subsequent structural reanalysis. However, longer times in the disambiguating zone were also found for the unambiguous that complements. Thus, the complexity difference seems not to represent “garden-pathing” as a result of the operation of Minimal Attachment, but may instead reflect the extra complexity caused by having to handle two sets of clausal relations instead of just one.     

The Effect of Phonemic Repetition on Syntactic Ambiguity Resolution: Implications for Models of Working Memory

Two reading experiments investigated the extent to which the presence of phonemic repetition in sentences influenced processing difficulty during syntactic ambiguity resolution. In both experiments, participants read sentences silently as reading time was measured. Reading time on sentences containing a temporary syntactic ambiguity was compared to reading time on unambiguous control sentences. Sentences either did or did not contain repeated phonemes. The results showed that reading time was longer for sentences containing a syntactic ambiguity than for unambiguous control sentences. Reading time was also longer on sentences containing repeated phonemes than on sentences that did not contain repeated phonemes. Phonemic repetition did not increase the time taken for syntactic ambiguity resolution; rather, the effects of syntactic ambiguity and phonemic repetition were temporally distinct, with the effect of phonemic repetition following the effect of syntactic ambiguity. Implications for theories of working memory are discussed.