Memory-load interference in syntactic processing

Participants remembered a short set of words while reading syntactically complex sentences (object–extracted clefts) and syntactically simpler sentences (subject–extracted clefts) in a memory–load study. The study also manipulated whether the words in the set and the words in the sentence were of matched or unmatched types (common nouns vs. proper names). Performance in sentence comprehension was worse for complex sentences than for simpler sentences, and this effect was greater when the type of words in the memory load matched the type of words in the sentence. These results indicate that syntactic processing is not modular, instead suggesting that it relies on working memory resources that are used for other nonsyntactic processes. Further, the results indicate that similarity–based interference is an important constraint on information processing that can be overcome to some degree during language comprehension by using the coherence of language to construct integrated representations of meaning.     

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.     

The relationship between age, processing speed, working memory capacity, and language comprehension

A total of 50 elderly individuals and 48 college students were tested on several measures of processing speed and of working memory capacity. Language processing was tested with an on-line measure of sentence processing efficiency, an end-of-sentence acceptability judgement task, and a paragraph comprehension test. Elderly individuals performed more poorly than college students on the speed of processing and working memory measures and had longer listening times overall on the sentence processing measures. Elderly individuals did not, however, have overall longer listening times at the most capacity-demanding regions of the harder sentence types. Correlational analyses failed to establish a relationship between the increase in syntactic processing load at the capacity-demanding region of the harder sentence type and the measures of working memory capacity, but did establish a relationship between paragraph comprehension and working memory capacity. The data are argued to provide evidence that the WM system used to structure sentences syntactically is separate from that used in other aspects of language comprehension.     

The relationship between age,processing speed,working memory capacity,and language comprehension

A total of 50 elderly individuals and 48 college students were tested on several measures of processing speed and of working memory capacity. Language processing was tested with an on‐line measure of sentence processing efficiency, an end‐of‐sentence acceptability judgement task, and a paragraph comprehension test. Elderly individuals performed more poorly than college students on the speed of processing and working memory measures and had longer listening times overall on the sentence processing measures. Elderly individuals did not, however, have overall longer listening times at the most capacity‐demanding regions of the harder sentence types. Correlational analyses failed to establish a relationship between the increase in syntactic processing load at the capacity‐demanding region of the harder sentence type and the measures of working memory capacity, but did establish a relationship between paragraph comprehension and working memory capacity. The data are argued to provide evidence that the WM system used to structure sentences syntactically is separate from that used in other aspects of language comprehension.     

On-line syntactic processing under concurrent memory load

Thirty-six university students were tested in a plausibility judgment task using a self-paced listening paradigm under no-interference and two-digit load conditions. Listening times were longer at syntactically more complex portions of syntactically more complex sentences, and greater loads led to increased listening times. However, listening times at syntactically more complex positions in syntactically more complex sentences did not increase more than listening times at comparable positions in syntactically simple sentences under digit load conditions. The results indicate that a concurrent memory load does not reduce the availability of working memory resources used for on-line syntactic processing and, thus, provide evidence that the working memory system used for assigning syntactic structure is separate from that measured by standard working memory tasks.     

The consequences of reduced memory span for the comprehension of semantic versus syntactic information

Aphasic patients with restricted memory spans were assessed on their comprehension of syntactically simple sentences varying in numbers of content words and on their comprehension of sentences matched in content words but varying in syntactic complexity. Three different presentation modes were used: unlimited visual presentation, limited visual presentation, and auditory presentation. The difference between performance in the unlimited and limited modes was used as a measure of the extent to which memory decrements caused comprehension failure. These difference scores were related to memory span in order to assess whether the memory involved in sentence processing overlaps that assessed by a memory span task. For the sentences varying in number of content words, performance was worse for the limited presentation modes than the unlimited mode, and the difference between unlimited and limited presentation modes was highly related to memory span. For the sentences varying in syntactic complexity, there was no clear reduction in performance for limited presentation modes, and the difference scores did not relate to memory span. The results support the view that the processing of sentences with many content words draws on the short-term memory capacity assessed by memory span, while the processing of syntactic complexity does not.     

Relational processing and working memory capacity in comprehension of relative clause sentences

Previous research has indicated that the cognitive load imposed by tasks in various content domains increases with the complexity of the relational information processed. Sentence comprehension entails processing noun-verb relations to determine who did what to whom. The difficulty of object-extracted relative clause sentences might stem from the complex noun-verb relations they entail. Across three studies, participants read 16 types of object- and subject-extracted relative clause sentences at their own pace and then responded to a comprehension question for each sentence. Relational processing was assessed using a premise integration task or a Latin square task. These tasks predicted comprehension of object-relatives before and after controlling for subject-relatives. Working memory (WM) capacity was assessed using reading span or forward and backward digit span tests. WM tasks predicted comprehension of object-relatives before but not after controlling for subject-relatives. Comprehension of object-relatives relied more heavily on a domain-general capacity to process complex relations than on WM capacity.     

Localization of Syntactic Comprehension by Positron Emission Tomography

Positron Emission Tomography (PET) was used to determine regional cerebral blood flow (rCBF) when eight normal right-handed males read and made acceptability judgments about sentences. rCBF was greater in Broca's area (particularly in the pars opercularis) when subjects judged the semantic plausibility of syntactically more complex sentences as compared to syntactically less complex sentences. rCBF was greater in left perisylvian language areas when subjects had to decide whether sentences were semantically plausible than when subjects had to decide whether syntactically identical sentences contained a nonsense word. The results of this experiment suggest that overall sentence processing occurs in regions of the left perisylvian association cortex. The results also provide evidence that one particular aspect of sentence processing (the process that corresponds to the greater difficulty of comprehending center-embedded than right-branching relative clause sentences) is centered in the pars opercularis of Broca's area. This process is likely to be related to the greater memory load associated with processing center-embedded sentences.     

Phonological short-term memory contributions to sentence processing in young children

Two experiments investigated the contribution of phonological short-term memory to the processing of spoken sentences by 4- and 5-year-old children. In Experiment 1, sentences contained either short or longer words, and varied in syntactic structure. Overall, repetition but not comprehension of the sentences was significantly influenced by word length. In Experiment 2. children selected on the basis of their high phonological short-term memory ability were founded to be superior at repeating sentences to children of lower phonological short-term memory ability, although the two groups did not differ in their comprehension accuracy for the same sentences. In both experiments, comprehension and repetition performance were differently influenced by particular sentence structures. It is proposed that sentence repetition in children is constrained by phonological memory capacity, and is therefore directly influenced by memory-related factors that include the length and number of words in sentences, and individual differences in memory skills.     

Click monitoring revisited: An on-line study of sentence comprehension

Spoken sentence comprehension is based upon rapid and complex psychological processes, yielding a constantly fluctuating cognitive load. The aim of this study was to evaluate on-line click monitoring, a classical but poorly exploited experimental method, which should allow for an easy measurement of processing load at any chosen point of experimental sentences. In Experiments 1 and 2, we obtained longer latencies to clicks located at the boundary of reversible object relative clauses than to clicks identically located in subject relatives and to clicks located earlier within object relatives. Experiment 3 further revealed that this effect of syntactic type was specific to transposed object relatives and did not occur with normal object relatives. In Experiment 4, we observed longer latencies with semantically reversible than with irreversible sentences, but no difference between actives and passives. These results were obtained under strict control of potential lexical and phonological biases, and suggest that on-line click monitoring may be one useful tool in the study of sentence comprehension.     

Effect of Repeated Evaluation and Repeated Exposure on Acceptability Ratings of Sentences

This study investigated the effect of repeated evaluation and repeated exposure on grammatical acceptability ratings for both acceptable and unacceptable sentence types. In Experiment 1, subjects in the Experimental group rated multiple examples of two ungrammatical sentence types (ungrammatical binding and double object with dative-only verb), and two difficult to process sentence types [center-embedded (2) and garden path ambiguous relative], along with matched grammatical/non-difficult sentences, before rating a final set of experimental sentences. Subjects in the control group rated unrelated sentences during the exposure period before rating the experimental sentences. Subjects in the Experimental group rated both grammatical and ungrammatical sentences as more acceptable after repeated evaluation than subjects in the Control group. In Experiment 2, subjects answered a comprehension question after reading each sentence during the exposure period. Subjects in the experimental group rated garden path and center-embedded (1) sentences as higher in acceptability after comprehension exposure than subjects in the control group. The results are consistent with increased fluency of comprehension being misattributed as a change in acceptability.     

Similarity-based interference during language comprehension: Evidence from eye tracking during reading

The nature of working memory operation during complex sentence comprehension was studied by means of eye-tracking methodology. Readers had difficulty when the syntax of a sentence required them to hold 2 similar noun phrases (NPs) in working memory before syntactically and semantically integrating either of the NPs with a verb. In sentence structures that placed these NPs at the same linear distances from one another but allowed integration with a verb for 1 of the NPs, the comprehension difficulty was not seen. These results are interpreted as indicating that similarity-based interference occurs online during the comprehension of complex sentences and that the degree of memory accessibility conventionally associated with different types of NPs does not have a strong effect on sentence processing.     

The influence of contextual constraints on recall for words within sentences

Two experiments examined predictions of the relational-distinctive processing view to account for the influence of sentence constraints on memory of target words. In Experiment 1, congruous expected words were recalled better than incongruous words. Words appearing in high-constraint sentences were recalled better than words appearing in low-constraint sentences. In Experiment 2, word expectancy and sentence constraint interacted so that unexpected congruous words appearing in high-constraint sentences were recalled better than their expected counterparts, but this difference was not present for low-constraint sentences. A hybrid model including aspects of the featural restriction model of sentence constraint and the relational-distinctive processing view is proposed.     

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.     

The Effects of Syntactic Complexity on Processing Sentences in Noise

This paper discusses the influence of stationary (non-fluctuating) noise on processing and understanding of sentences, which vary in their syntactic complexity (with the factors canonicity, embedding, ambiguity). It presents data from two RT-studies with 44 participants testing processing of German sentences in silence and in noise. Results show a stronger impact of noise on the processing of structurally difficult than on syntactically simpler parts of the sentence. This may be explained by a combination of decreased acoustical information and an increased strain on cognitive resources, such as working memory or attention, which is caused by noise. The noise effect for embedded sentences is less than for non-embedded sentences, which may be explained by a benefit from prosodic information.     

工作记忆与汉语歧义句加工的眼动研究

以符合“VP+N1+的+N2”格式的述宾型歧义短语组成的句子为材料,采用2×2的混合设计,即2(工作记忆广度：高、低)×2(续接方式：偏正、述宾),采用眼动记录法,考察被试对歧义短语的语义加工过程。结果发现：（1）在无前语境的暂时句法歧义句中,不同的续接方式在句子的最初加工过程中的作用不显著,而在最终的理解过程中作用显著。（2）工作记忆高有利于句子的理解,但对歧义短语的两种意思的提取和保持的作用不显著。     

Role of Working Memory in Typically Developing Children’s Complex Sentence Comprehension

The influence of three mechanisms of working memory (phonological short-term memory (PSTM capacity), attentional resource control/allocation, and processing speed) on children's complex (and simple) sentence comprehension was investigated. Fifty two children (6-12 years) completed a nonword repetition task (indexing PSTM), concurrent verbal processing-storage task (indexing resource control/allocation), auditory-visual reaction time (RT) task (indexing processing speed), and a sentence comprehension task that included complex and simple sentences. Correlation and regression analyses were run to determine the association between the memory variables and sentence comprehension accuracy. Results revealed: (1) none of the memory variables correlated with simple sentence comprehension, (2) resource control/allocation and processing speed correlated significantly with complex sentence comprehension, even after covarying for age, and (3) attentional functioning and processing speed predicted complex sentence comprehension (after accounting for age). Results were interpreted to suggest that working memory is significantly involved in school age children's comprehension of familiar complex sentence structures.     

Perceptual components of situation models

These experiments examined the hypothesis that situation model construction involves perceptual processing--specifically, processing that involves visuospatial information. In this research, a dual-task paradigm was used to demonstrate that tasks that engage visuospatial processes interfere more with the generation of a situation model than tasks that are less likely to involve these processes or tasks that are verbal in nature. Using Albrecht and O'Brien's (1993) contradiction effect as evidence of situation model construction, Experiment 1 demonstrated that participants reading short texts while simultaneously holding high-imagery sentences in memory failed to show a significant contradiction effect in comparison with readers holding low-imagery sentences in memory. In Experiment 2, participants reading texts while retaining a difficult visuospatial memory load showed disrupted comprehension in comparison with readers retaining a verbal memory load.     

Attentional resource and processing speed limitations during sentence processing in Parkinson's disease

Several studies have suggested that patients with Parkinson's disease (PD) have sentence comprehension difficulty in part because of their limited executive resources. However, these assessments confound the executive resources contributing to sentence comprehension with the resources needed for task performance. In the present study, we used a word detection technique that minimizes task demands in order to evaluate attentional and processing speed resources during the comprehension of simple sentences without subordinate clauses and sentences containing subject-relative and object-relative center-embedded subordinate clauses. We found that PD patients have poor sensitivity to phonetic errors embedded in unbound grammatical morphemes, regardless of the clausal structure of the sentence, suggesting difficulty attending to grammatical morphemes. We also found that PD patients are significantly slowed in their sensitivity to phonetic errors in content words embedded in object-relative center-embedded sentences. Slowed sensitivity to content words in object-relative sentences was correlated with timed executive measures of planning. On a traditional measure of comprehension, these PD patients were impaired for sentences containing object-relative center-embedded clauses compared to sentences with subject-relative center-embedded clauses, and comprehension of object-relative sentences was correlated with executive measures. Our findings are consistent with the claim that limited executive resources for strategic attention and processing speed contribute to the sentence comprehension difficulties of PD patients.