Comprehension of long distance number agreement in probable Alzheimer's disease

Abstract

Two cross-modal naming experiments examined the role of working memory in processing sentences and discourses of various lengths. In Experiment 1, 10 memory impaired patients with probable Alzheimer's disease (AD) and 10 healthy elderly control participants showed similar sensitivity to violations of subject-verb number agreement in a short sentence condition and similar degradation to this sensitivity in a long sentence condition. Performance in neither length condition correlated with performance on working memory tasks, suggesting that the processes involved in interpreting a grammatical dependency between adjacent and nonadjacent elements are different from those required in the working memory tasks. In Experiment 2, the same 10 AD patients were less sensitive than the 10 control participants to pronounantecedent number agreement violations in a short discourse condition, but neither group was affected by additional length. In this experiment, performance in both the short and long conditions correlated with working memory performance. These results show that grammatical and discourse dependencies pose different memory and processing demands, and that these differences are not simply due to differences in the amount of intervening material between dependent words. The results also suggest that while the working memory de cits characteristic of AD do not interfere with on-line grammatical processing within sentences, they do compromise on-line discourse processing across sentences.

Differences in the cognitive demands of word order, plural, and subject-verb agreement constructions

“…Thus, these results add to those of prior studies using production and comprehension methodologies that have also found either load and/or span to be significantly related to subject-verb agreement. The few prior studies that have failed to find this relationship (Almor et al, 2001;Bock & Cutting, 1992;McDonald, 2006) show numerical tendencies in the same direction; perhaps the lack of significance in those results is due to power, or to the difficulty of the materials or tasks used.…”

“…Arguing against a tie between working memory and the processing of agreement are studies in which no detrimental effect of load has been found (McDonald, 2006), or that have failed to find a correlation between working memory span and performance on agreement tasks (Almor, MacDonald, Kempler, Andersen, & Tyler, 2001;Bock & Cutting, 1992, Experiments 1 and 3). These differences in results cannot be explained by the type of load used or by determining whether span was measured using 1,500 msec.…”

Normal and pathological development of subject–verb agreement in speech production: a study on French children

“…The spoken realization of agreement production appears as a good candidate for automaticity given that it meets with the usual characteristics of automatized processes like high speed, low error rate, lack of effort required, and absence of general capacity use. The hypothesis of an automatic computation of agreement in such local Spec-head configurations accounts for the reports that working memory abilities of unimpaired adults do not correlate with their agreement performance in such structures (Bock & Cutting, 1992), and that Alzheimer patients, in spite of their working memory impairment, have no trouble dealing with local agreement checking (Almor et al, 2001).…”

“…However, according to the authors, this decrease would not be related to working memory since they reported no correlation between attraction errors and the performance of their participants in a working memory test. Along these lines, Almor and colleagues (Almor, MacDonald, Kempler, Andersen, & Tyler, 2001) reported that Alzheimer patients, who suffer from a severe working memory impairment, are able to process subject-verb dependencies just as well as their control group. In contrast, the processing of long-distance discourse dependencies like pronounantecedent relationships was found to be significantly affected in Alzheimer patients.…”

“…If the subject's number feature is lost, the system can either use the available number feature on the local noun (as attested by the attraction effect, still present), or select the number feature by chance (as attested by the high proportion of errors in the match conditions). The report by Almor et al (2001) that Alzheimer patients are in difficulty when dealing with non-local dependencies like antecedent -pronoun agreement, in spite of their good performance in local relationships, further indicates that the involvement of working memory resources in agreement depends on configurational properties of the sentence.…”