INT'L. J. AGING AND HUMAN DEVELOPMENT, Vol. 31 (2) 111-134,1990

ANAPHOR COMPREHENSION IN YOUNGER AND OLDER ADULTS*

ELIZABETH M. ZELlNSKl SHARl A. MIURA Leonard Davis School of Gerontology University of Southern California

ABSTRACT

This research was aimed at evaluating adult age differences in language comprehension, which has been hypothesized to decline in normal older adults. Three experiments were conducted to investigate the comprehension rate of pairs of related sentences. In Experiment 1, the related material consisted of either terms repeated from the first sentence or terms associatively related to the antecedent. In Experiment 2, the generality of the antecedent term in the sentence pairs varied, as did its typicality. In both experiments, young-old (age 55-69) and old-old (age 70-87) adults read the target sentences in the pairs more slowly than did young adults (age 20-36); age, however, did not interact with the condition. Experiment 3 repeated the conditions of Experiment 2, but, since only one sentence at a time was visible during a trial, the participants had to remember the first sentence while reading the target sentence. Young participants (aged 20-35) showed the same treatment effects as in Experiment 2, but the old (aged 55-86) showed deficits in online comprehension. The results of the three experiments suggest that the speed of comprehension processes required to match related terms in sentence pairs are not impaired with age as long as they do not have to be remembered.

It was originally assumed that once language was acquired in childhood, linguistic functions remained stable throughout life in normal individuals [l]. Language comprehension, however, also has been assumed to be heavily dependent on working memory capacity [2], and because there is evidence that older people * This research was supported ZelinSki.

grand AG4114 from the National Institute on Aging to E. M.

111

0 1990, Baywood Publishing Co., Inc.

doi: 10.2190/A2DN-D7FF-GQ7X-NAUF http://baywood.com

112 / ZELlNSKl AND MlURA

have a deficit in working-memory capacity (i.e., the capacity to store previously processed material while simultaneously processing incoming information [3,4], processing resource models of cognitive deficits with age predict that older adults should have difficulty in understanding the more complex aspects of language [5,61. Research dealing with comprehension of complex sentences has shown declines in performance with age [7-91. Studies have also indicated that older people have more difficulty than younger ones in drawing inferences from information implicit in discourses [lo-141, in detecting semantic anomalies in passages, as well as in the accuracy of attributing actions to the appropriate characters in stories involving multiple protagonists [5]. These results reinforced the suggestion that language comprehension is impaired in elderly adults. When participants are not required to recall information to complete the comprehension task, however, older people typically do not differ from younger ones. For example, reasoning from discourses is unimpaired when the premises are available for participants to review, but it is when sentences have to be remembered [15]. Assignment of pronouns to the appropriate characters in two-character stories also does not change with age as long as the information about the referent is correctly remembered [16]. These studies suggest that the comprehension difficulties of older adults are confounded with general age-related memory deficits, rather than to a working-memory capacity deficit [3]. The work reported here involves studying the speed of comprehension in younger and older people to determine whether there are age differences in online processes. In the three experiments, reading time served as an index of the processes involved in comprehension, since longer reading times have been associated both with increasing linguistic complexity [17-191 and with greater involvement with working memory [20-221. Our experiments examined one particular aspect of language comprehension-comprehension of anaphora (terms referring to material presented earlier in a discourse). Anaphora serve the linguistic function of providing cohesion across propositions in discourse, so that people can recognize that sequences of sentences form a discourse and create mental models representing the discourse, a crucial step in comprehending it. Age-related deficits in anaphor comprehension therefore have important implications for older adults’ understanding of written texts and discourse in general. In the first two experiments, the materials read were visible throughout each trial. We utilized this approach as an approximation to natural reading processes, so that understanding, rather than remembering, was emphasized and the effects of manipulations thought to affect the demands of comprehension could be evaluated. In the third experiment, each sentence was visible only as it was read so that we could determine how memory affects online comprehension in younger and older adults. The model of anaphor comprehension is based on a synthesis of models developed by others, notably Garrod and Sanford [23] and Tyler and Marslen-

ANAPHOR COMPREHENSION I 113

Wilson [24]. According to this model, comprehension of coreferents involves: processing antecedent material for meaning and using it to predict what will follow in the discourse; reading the new material and searching for terms that potentially match those in the given material and matching the new terms with those already in working memory; and if the antecedent and anaphor terms match sufficiently, integrating antecedent and anaphor statements into a new unit in the mental representation of the discourse. Comprehension of anaphoric reference is achieved when integration occurs. We assumed that the process of comprehending individual sentences in this paradigm is automatic, or at least, invariant with age [13]. Integrating individual coreferential sentences into a new unit, however, is not automatic [15] nor is it automatic for younger people [25]. The experiments reported on here involve measures of reading time, patterns of errors to fact and inference questions, and ratings of comprehensibility of sentence pairs in order to evaluate age differences in integration of coreferential sentence pairs. Experiment 1 investigated the simplest kind of anaphor matching: comparison of terms that are identical across sentences, and terms that are semantically related. Experiment 2 involved more complex matching requirements for integration: varying the generality of the antecedent and the strength of associations across antecedent-anaphor pairs. Experiment 3 repeated the conditions of Experiment 2 but examined reading times when only one sentence is visible at a time. The processing resources deficit model predicts that age interacts with the ease of matching antecedents and anaphora, with older adults having greater difficulty as the matching requirements for comprehension become more complex even when the antecedent sentence is visible. A general memory deficit model predicts that in Experiments 1 and 2, older people would be able to complete the matching processes at rates parallel to younger adults, and they would show integration deficits only when they have to remember the antecedents, as in Experiment 3.

EXPERIMENT 1 Matching involves comparing networks of semantic associations between terms, and when sufficient commonalities are found, integration of coreferential terms takes place. The extensiveness of the comparisons made in the matching process can be documented by the time it takes to read and comprehend anaphoric-sentence pairs. For example, college-aged readers take less time to comprehend pairs of sentences as coreferential if the antecedent and anaphor terms are identical, (a) Ed was given an alligator for his birthday. (b) The alligator was his favorite present. than if the antecedent is a category and the anaphor is a member of that category,

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(c) Ed was given lots of things for his birthday. (d) The alligator was his favorite present [18j. Matching identical terms in coreferential sentence pairs is faster than matching category names with exemplars, presumably because semantic activation is identical for the identical terms. Matching is slower for nonidentical but related terms because semantic activation differs across them, and this requires searching through activated nodes before the terms are matched in working memory and comprehended as coreferents [23]. In Experiment 1, the effects of matching identical or related antecedent and coreferent terms, which were category-exemplar pairs, were studied in younger and older adults.

Method Participants - In all three experiments, participants were recruited from the faculty, staff, students, and support groups of the University of Southern California. In the first two experiments, participants were in one of three age ranges: young, aged twenty-one to thirty-six; young-old, aged fifty-five to sixty-nine, or old-old, aged seventy to eighty-seven. (In the third experiment, the two groups of older adults were combined.) Participants all indicated that they were in good health and had no difficulty in reading from the computer screens used in the experiments. They were either native English speakers or fluent in English. All participants were paid $10.00 for their participation. In Experiment 1, there were twenty-four young (M age = 26.04), twenty-six young-old (M age = 64.26), and twenty-six old-old (M age = 73.13) participants. Data for two young-old and two old-old participants were eliminated, however, because more than 10 percent of their responses to comprehension questions were erroneous. This reduced n to twenty-four in each age group. The gender of the participants was almost equally distributed within age groups, with at least eight males per group. All participants had at least one year of college education, with mean years of schooling of 16.58 for the young, 13.61 for the young-old, and 16.00 for the old-old. The difference in educational attainment was reliable (F (2,67) = 3.63, p < .05); the young and old-old had more formal schooling than the young-old. Participants were also high in verbal ability, as measured by the vocabulary subtest of the Shipley-Hartford Institute of Living Scale [26]. Young participants had a mean score of 32.13, young-old, 30.74, and old-old, 36.54 out of a total of 40 points. There were no age differences in vocabulary scores. Materials - Sixty-four sets of two-alternative sentence pairs were constructed. One pair in a set used identical antecedent-anaphorterms; the other used category and exemplar terms, with the category name in the antecedent sentence. Related terms were chosen from the norms collected by Howard [27] and by Battig and Montague [28]. The category name and exemplar used in each sentence pair were matched for frequency in English, and sentences within each pair were

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matched on the number of words they contained. Sentence lengths ranged from seven to nine words, with eight words as the modal length. Half of the sentence pairs were presented with category-exemplar terms, half with identical terms, and were counterbalanced across participants. Sentence pairs were also randomized with the restriction that no more than two pairs in the same condition directly followed each other. Comprehension questions were presented after each sentence pair in order to ensure that participants were actually reading them. For all pairs in the identical-terms condition and half the pairs in the related-terms condition, there was a fact question based on information from one of the two sentences. For the remaining pairs in the related-terms condition, there was an inference question requiring integration of the matching terms across both sentences. Half the questions were correctly answered with a “yes,” half with a “no.” “No” questions were constructed by replacing the matching term with a word from the same class (i.e., a category name or exemplar) that could plausibly fit the sentence tested. Examples of the sentence pairs and test items are: (e) Barbara had always wanted to have a horse. (f) The horse she got was a black mare. (identical) (g) Was the horse she got a black mare? (fact) (h) We donated an appliance to our church. (i) The refrigerator will be much appreciated there. (related) (j) Did we donate a refrigerator to our church? (inferencelyes) (k) Did we donate a washer to our church? (inferenceho) Procedure - Participants were given written instructions explaining the task and the question-answering procedure. They received ten practice trials with sample sentence pairs followed by fact or inference questions to familiarize them with the kinds of materials used. Participants were seated in front of an Apple IIe computer. They were instructed to press the space bar to summon the antecedent sentence, to read it at their own pace for comprehension, to press the space bar again for the target sentence, read that sentence, and to press the space bar a third time for the comprehension question. To answer the question, they pressed either the open apple key to the left of the space bar or the solid apple key to the right. The keys were counterbalanced across participants as to whether they indicated a yes or no response. Both sentences and the question were visible throughout the trial. The computer screen was cleared between trials. Participants completed twenty practice trials, and then began the sixty-four trials of the experiment. All participants were tested individually. Following the experiment, they rated the comprehensibility of the sentence pairs on 5-point scales, with 1 indicating that the sentence pair was very hard to understand and 5 that it was very easy.

Measures - The reading time for each sentence, the response time to the comprehension questions, and the correctness of responses to the comprehension questions were collected. Trials on which questions were answered incorrectly

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were eliminated, as were those on which a reading or response time was more than four standard deviations from the participant’s mean reading time across sentences in all trials. In all three experiments, fewer than 3 percent of all trials had to be discarded for this reason, and there were no age differences in the number of trials eliminated. Multivariate analyses of variance for repeated factors (MANOVA’S) were conducted on reading times, comprehension-questionresponse times, and error rates in Age (young vs. young-old vs. old-old) x Condition (identical vs. related) designs. Where appropriate, Newman-Keuls contrasts were used to identify group differences leading to significant F ratios. The critical value for contrasts and simple-effects test used to determine significance is reported where relevant. The level of significance for all tests was set at p c .05.

RESULTS Control analyses - There were no main effects or interactions of counterbalancing conditions, so these effects were not evaluated any further. As is generally found, “no” responses were faster than “yes” responses, but results for the response times and accuracy rates were not differentially affected. Response times for comprehension questions were therefore combined across answers. To check on the possibility of spillover effects-where the rate of reading previous sentences in texts can influence the speed of reading subsequent material [29]-reading times for the antecedent sentences in the treatment conditions were evaluated. As seen in Table 1, there were no reliable main effects or interactions, indicating that no spillover effects were observed. Anaphor-sentence results - The MANOVA revealed no reliable age differences in reading times of target sentences. The condition effect seen in Table 1, however, was reliable across participants, F (1,69) = 31.34, p c ,001, and across materials, F (1,63) = 20.01, p c .001; the anaphora of identical-term sentences Table 1. Mean Antecedent- and Anaphor-Sentence Reading Times (msec) in Experiment 1

Young Antecedent Identical Term Related Term

Young-Old

Old-Old

2,546 (1,017) 2,481 (981)

2,824 (1,033) 2,898 (1,106)

2,959 (1,121) 3,007 (1,154)

2,762 (900) 2,893 (1,242)

3,018 3,255

(836) (966)

3,184 (1,189) 3,621 (1,426)

Anaphor Identical Term Related Term

Note: Standard deviations are in parentheses.

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Table 2.Mean Comprehension-Question Response Times (msec) and Mean Proportion of Errors (in Parentheses) in Experiment 1 Young

Facts Inferences

2,885 (.04) 3,197 (.07)

Young-Old

4,609 (.03) 5,135 (.lo)

Old-Old

4,569 (.04) 5,746 (.07)

~~

Table 3.Mean Comprehensibility Ratings of Sentence Pairs in Experiment 1 Young

Young-Old

Old-Old

4.66 4.43

4.86 4.70

4.97 4.86

~

Identical Term Related Term

Note: Ratings are made on a scale of 1 to 5 where 1 means very difficult and 5 means very easy to understand.

were read more quickly (M= 2,958 msec) than those of related terms (M = 3,256 msec). The Age x Condition interaction was not significant, F (1,69) = 1 . 7 0 , < ~ .19. Comprehension-question results - Analyses of the mean proportion of errors by item type (fact vs. inference) showed no age differences, but participants were more likely to make errors on inferences (M = .08) than on facts (.04), F (1,69) = 24.61,~ < .001. Table 2 does not indicate that this is because of a speed-accuracy tradeoff, since participants responded more quickly to fact (M = 4,021 msec) than to inference items (M = 4,693 msec), F (1,69) = 38.99, p < .001.One explanation for this finding is that there were fewer inference than fact items, as inferences could only be tested on related pairs, and participants may have been confused about how to answer these items correctly. Since there was no interaction of age with item type in Experiment 1 on errors (F c l),this result was not considered problematic. Finally, there was an overall age difference in response times to the comprehension questions (F (2,69) = 6.38, p < .003); the young participants (M = 3,041 msec) were faster than the young-old (M = 4,870 msec) or old-old (M = 5,158 msec) participants who did not differ from each other according to NewmanKeuls contrasts. (The critical difference for comparisons of adjacent means was 1,370 msec.) The age difference is not surprising, as differences between younger and older adults in response times where decisions are required are typical [30]. Comprehensibility ratings results - Analyses of the comprehensibility ratings of the sentence pairs in this experiment indicated that participants found the pairs easy to understand (Mrating = 4.79, but there were age differences in ratings, as shown in Table 3, F (2,69) = 3.87, p < .05, with the old-old and young-old giving higher ratings (M = 4.78 and 4.92, respectively) than the young (M = 4.54). There was also a condition effect-sentence pairs containing identical

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terms were given higher ratings (M = 4.83) than those with related terms (M = 4.67)-F(1,69) = 20.80,p < .001. This corroborates the reading-time findings.

Discussion In Experiment 1, the older adults read the anaphor sentences more slowly than did the younger adults but not reliably so. The significant condition effect, coupled with the absence of an Age x Condition interaction, indicated that participants of all ages needed more time to comprehend the sentences with related terms, which suggested that the matching process involved more comparisons in that condition than in the identical-terms condition. The fact that age did not interact with condition indicated that both groups of older people were not burdened excessively relative to the younger people by the additional demands of matching the related terms in order to integrate the sentence pairs. The young-old and old-old also did not differ in reading times or in response times to comprehension questions; they did not make more errors to the questions than did the young; and age did not interact with condition or item type on error rate. In rating the comprehensibility of the sentence pairs, older people actually gave higher ratings than did younger people. Comprehensibility ratings followed the pattern of anaphor reading times; identica1 pairs were rated as easier to understand than related pairs, and no interactions of condition with age were found. Thus, contrary to the predictions of a processing resource deficit model of comprehension, the older participants appeared to have no more difficulty than the younger participants in understanding the materials presented. The results of Experiment 1may suggest that the highly educated, highly verbal older adults who participated in the research were able to maintain their comprehension skills as well as relatively fast rates of reading even into old age. The variance in reading times seen in Table 1, however, probably contributes to the nonsignificant F ratios. More important is the evidence that comprehension appears to be unimpaired in both the young-old and old-old participants, but Experiment 1 only evaluates relative differences in comprehension speed when the antecedent and anaphoric terms are either identical or closely related. Whether an Age x Condition interaction would be found when the relationship between terms is less clear had to be determined. In Experiment 2, we included two different manipulations aimed at investigating more complex aspects of the matching of antecedents and anaphor sentences.

EXPERIMENT 2 In this experiment, we examined age differences in comprehension of sentence pairs under two conditions. First, we varied the generality of the antecedents. Younger adults take longer to comprehend coreferential sentences if the

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antecedent term is general, such as a category name, and its coreferent term is specific, such as a category exemplar,

0)

A bird would sometimes wander into the house. (m) The robin was attracted by the larder.

than if the terms are presented in the reverse order, (n) A robin would sometimes wander into the house. (0) The bird was attracted by the larder [23]. Matching a specific coreferent term to a general antecedent takes more time because the anaphor is harder to predict under this condition. In addition, the antecedent has many more associations activated in working memory than the coreferent, and a more thorough search for overlapping information must be conducted than for mapping a general coreferent term onto a specific antecedent. Our second manipulation varied the level of association between antecedent and anaphor terms. The matching model suggests that the matching of strongly related coreferents should be faster than the matching of weakly related ones because they are more readily predicted and the associative networks of strongly related referents are more similar-the decision that terms are coreferents is clearer in the case of strongly related terms. Garrod and Sanford found that typical exemplar referents such as robin in sentence pairs like (1) and (m) or (n) and (0)were comprehended faster than when atypical referents such as goose were substituted for robin [23].

Method Participants - Data had to be discarded for one young, two young-old, and two old-old participants because more than 10 percent of their responses to comprehension questions were erroneous. Of the remaining participants, there were twenty-four young (M age 24.33), twenty-four young-old (M age 64.79, and twenty-four old-old (M age 72.87) people. There were ten males in the oldest and youngest groups and five in the young-old group. Participants had a college-education and were high in verbal ability; their means for years of schooling and vocabulary scores were 17.63 and 35.00 for the young, 15.40 and 33.90 for the young-old, and 16.04 and 36.43 for the old-old. The three age groups did not differ in vocabulary scores, but the young had more years of schooling than did the two older groups, who did not differ from each other, F (2,69) = 5 . 8 6 , c~ .01. Materials and procedure - Sixty-four sets of two sentence pairs were constructed using category-exemplar terms from the norms of Howard [27] and Battig and Montague [%].'Typical exemplars were either the first or second listed for their category, and atypical ones were those in the last 10 percent of items listed within a category. Exemplars within a category were matched for frequency in

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English. Sentences in each pair were matched for the number of words and their lengths ranged from seven to nine words, with eight words as the mode. They were written to be comprehensible for both a typical and an atypical exemplar, with typicality counterbalanced across participants. Generality of antecedents was manipulated so that half of the antecedent sentences within each condition contained the category name, half the exemplar. This was also counterbalanced. Sentence pairs were randomized with the restriction that pairs for the same Generality x Typicality condition did not directly follow each other. For half the sentence pairs, there was a fact question, and for half, an inference question with half the questions correctly answered with a “yes.” The procedure and measures described for Experiment 1 were also used here. Data were analyzed in Age x Generality (general vs. specific) x Typicality (typical vs. atypical) designs.

Results Control analyses - As in Experiment 1, counterbalancing had no effect on performance, and patterns of response times to the comprehension questions were identical regardless of whether the answers were “yes” or “no,” so results were collapsed across these factors. Also as in the first experiment, reading times for the antecedent sentences in the treatment conditions were not affected by age, the two conditions, or their interactions, indicating that no spillover effects were observed (see Table 4). Anaphor-sentenceresults - In this analysis, there were reliable age differences in reading times, F (2,69) = 7.38, p c .01. As seen in Table 4, the young read the anaphor sentence more quickly (M = 2,581 msec) than did the young-old (M = 3,336 msec) and the old-old (M = 3,689), who did not differ from each other. (The critical value for a comparison of adjacent means was 585 msec.) The effect of generality was also reliable, F (1,69) = 1 1 . 6 4 , c~ .01, with materials as random (F (1,63) = 5.68, p < .04) and with participants as random, targets of general sentences were read more slowly (M = 3,291 msec) than were those of specific ones (M = 3,114 msec). The Age x Generality interaction was not significant, F (1,69) = 1 . 0 5 , c~ .35. The typicality effect was marginally reliable in the materials analysis, F (1,69) = 3.13, p c .08;typical exemplars were read more quickly (M= 3,157 msec) than were atypical ones (M = 3,247 msec). The Age x Typicality interaction was not reliable, however, F c 1. The only interaction obtained was of Generality x Typicality, which was marginal for the analysis over materials, F (1,69) = 3.04, p c .09. Simpre-effects tests showed that when the antecedent was general, anaphors containing a typical exemplar were read more quickly (3,212 msec) than were those containing atypical ones (3,368 msec). When the antecedent was specific, there was no anaphor reading-time difference, regardless of whether the

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Table 4.Mean Antecedent- and Anaphor-Sentence Reading Times (msec) in Experiments 2 and 3. Experiment 2 Antecedent Specific Term Typical Atypical General Term Typical Atypical Anaphor Specific Term Tyical Atypical General Term Typical Atypical

Young

Young-Old

2,287 (823) 2,412 (945)

Experiment 3

Old-Old

Young

Old

2,618 (856) 2,610 (784)

2,207 (698) 2,352 (754)

2,733 (814) 2,872 (916)

2,379 (874) 2,328 (740)

2,560 (788) 2,539 (727)

2,288 (769) 2,298 (752)

2,854 (943) 2,937 (785)

2,552 (785) 2,521 (720)

3,242 (788) 3,233 (929)

1,877 (553) 1,937 (572)

2,633 (868) 2,775 (929)

2,578 (730) 2,675 (810)

3,388 (970) 3,478 (1,093)

1,918

2,605 (899) 2,678 (951)-

(5011

(1,548)

2,033 (636)

Note: Standard deviations are in parentheses.

antecedent was typical (3,102 msec) or atypical (3,126 msec); the critical value for a difference between adjacent means was 97 msec.

Comprehension-question results - Reading times for the fact and inference questions were evaluated in an Age x Question Type (fact vs. inference) x Generality x typicality MANOVA. Table 5 depicts response times and the mean proportion of errors for the comprehension questions. The only reliable effect was that of age on response times F(2,67) = 7.78, p < .Ol). Young participants responded to questions more quickly (M = 2,746 msec) than did either the young-old (M = 5,000 msec) or the old-old (M = 4,920 msec), who did not differ from one another. Table 5 also shows that error rates in Experiment 2 were lower than in Experiment 1. This is difficult to interpret, since participants in both experiments came from the same base population and were about the same age within age groups, highly verbal, and well educated. The distribution of fact and. inference comprehension questions varied across experiments, and with an equal distribution of

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Table 5. Mean Comprehension-Question Response Times (msec) and Mean Proportion of Errors (in Parentheses) in Experiment 2 Young

Specific Term Typical Fact Items Inference Items Atypical Fact Items Inference Items General Term Typical Fact Items Inference items Atypical Fact items Inference items

Young-Old

Old-Old

2,492 2,548

4,580 4,780

4,888 (.02) 4,499 (.02)

2,757 2,534

4,445 4,352

4,896 (.03) 4,829 (.05)

2,699 2,626

4,641 4,776

4,513 (.03) 4,657 (.03)

2,682 2,561

4,909 4,563

4,752 (.05) 5,133 (.08)

these items in Experiment 2, it is probable that participants simply had less difficulty in responding to questions consistently than in Experiment 1, where there were three fact questions far every inference. Analysis of the proportion of errors indicated that there were fewer errors made on fact than on inference items (.03 versus .04) (F(1,69) = 6.07, p < .02), for general (M = .04) than for specific (M = .03) antecedent-sentencepairs (F (1,69) = 14.38,p < .OOl), and for typical compared to atypical items (.03 and .05, respectively) (F (1,69) = 16.25,p < .OOl). The latter treatment effects were mediated c .01. Simpleby a reliable Generality x Typicality interaction,D (1,69) = 6 . 3 0 , ~ effects tests (critical value for a difference between adjacent means = .02) indicated that there was a significant difference between means for the specific antecedent-sentence pairs as a function of typicality (M for typical = .03, and M for atypical = .06) but no difference for general antecedent pairs (M for typical = .04,atypical = .03). Despite the pattern of statistically significant findings reported here, we maintain that they have little functional importance for the results because the interactions of any of these effects with age produced Fs < 1. Also, response times for the comprehension questions see in Table 5 suggest a general tendency for speed-accuracy tradeoffs here.

Comprehensibility-rating results - Analyses of the comprehensibility ratings of the sentence pairs in this experiment as seen in Table 6 indicated that all participants found the pairs comprehensibIe(M rating = 4.72). There were no age, generality, or typicality effects or any interactions in ratings. These results may suggest that the conditions in which sentence pairs appeared were not perceived as differentfrom one another as were pairs in Experiment 1,in which the discrepancies

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Table 6. Mean Comprehensibility Ratings of Sentence Pairs in Experiments 2 and 3 Experiment 2

Specific Item Typical Atypical General Term Typical AtvDical

Experiment 3

Young

Young-Old

Old-Old

Young

Old

4.59 4.54

4.79 4.79

4.79 4.78

4.84 4.82

4.86

4.60 4.56

4.74 4.77

4.77 4.84

4.03

4.79 4.70

4.78

4.03

Note: Ratings are made on a scale of 1 to 5 where 1 means very difficult to understand and 5 means very easy to understand.

in anaphor reading times and comprehensibility ratings between conditions were larger.

Discussion In Experiment 5 older adults read the anaphor sentences more slowly than did younger adults. They did not differ from the younger adults in their rate of reading the antecedent sentences. Even for antecedents, however, older participants were consistently slower than were the younger participants. There was a reliable generality effect; category-first or general antecedents produced slower reading times for anaphor sentences compared to exemplar-first or specific ones. This replicated the work of Garrod and Sanford [23] who suggested that matching the coreferents requires more operations when the antecedent is general. The typicality effect was only marginally reliable, contradicting the predictions of Garrod and Sanford. Recent work by Roth and Shoben [31], however, shows that typicality effects are mediated by sentence context rather than by the associations between individual words established in norms [31]. The words chosen as typical and atypical exemplars were obtained from lists of words from category norms, and it is probable that the sentences used in this experiment partially neutralized the effects of typicality. The marginal Generality x Typicality interaction suggests that the effects of typicality were mediated to some extent by the generality of the antecedent, in which atypicality of an exemplar slowed reading time of an anaphor sentence only if the antecedent contained a category term. This supports the notion that accurate prediction of the anaphor is less likely and matching involves more comparisons between terms when the antecedent is general, but because the interaction missed significance?it must be interpreted cautiously. The most critical finding is that age did not interact with either of the treatments, indicating that older adults did not differ from younger adults in how they dealt

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with associative matching of information. All three age groups showed a reliable generality effect, with slower reading of the target sentence when its antecedent was a general category name than when it was a more specific category member. All three age groups also showed a trend towards the expected typicality effect. There were no age differences or interactions in comprehensibility ratings or in error rates in responses to comprehension questions. Taken together, these results suggest that the older participants had little difficulty in comprehending the materials used in Experiment 2, even though they read anaphoric sentences more slowly than did younger participants. The matching processes required in this experimental task appeared to be unimpaired with age. The findings of Experiments 1and 2 suggest that, under the conditions studied, older adults had no difficulty in comprehending target sentences. The data in Tables 1and 4 indicate, however, that older adults showed more slowing under the conditions that produced slower reading times. Because the reading times were long and there was more variance in the data of the older adults, we conducted three additional sets of analyses in order to provide assurance that age did not interact with treatments in these experiments. First, following the suggestions of Winer [32], we transformed the reading times in both experiments using their base-10 logarithms. The results remained the same. Second, we calculated difference scores across conditions to control for aging effects on reading times and analyzed for age differences. Again, the results were not significant. Finally, we combined the probabilities of the Fs obtained for the interactions of age with treatments for both experiments, according to the method given by Winer; the probabilities did not approach significance. There was no evidence from the data of the first two experiments that age interacted with the treatments tested, providing no support for a processing resources account of written-language comprehension deficits in elderly adults. In the initial arguments, it was suggested that older adults might not show anaphor-comprehensiondeficits when memory load was low. Indeed, that is what we found in Experiments 1 and 2. Such results offer partial confirmation that memory problems might be the source of apparent comprehension deficits in older adults, as suggested by Light and Capps [16]. The critical test of this hypothesis, however, cannot be made without directly evaluating the effects of memory on comprehension in older adults. To do this, we conducted Experiment 3.

EXPERIMENT 3 Experiment 3 had two purposes: to evaluate the effects of having to remember the antecedent sentence on anaphor reading time in young and old adults and to obtain purer measures of comprehension time than were obtained in the previous experiments. Because participants could review the antecedents once the anaphor

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sentences were presented, it was possible that part of the time recorded for reading the anaphor sentences was actually used for review. In Experiment 3, sentences were presented individually and cleared from the computer screen as soon as participants pressed the key to summon the next sentences in the trial sequences. It was assumed that older adults would have more difficulty in comprehending anaphor sentences when the antecedents had to be held in memory.

Method Participants - In this experiment, participants came from the same populations as in Experiments 1and 2. Because no differences between young-old and old-old participants’ reading times or error rates in the earlier studies were found, the distinction was dropped, individuals aged fifty-five to eighty-five were dropped, with individuals included in the old group. There were twenty old participants tested, but data from two of them had to be excluded because of equipment failures. Of the remaining eighteen older participants, four were male and fourteen female. Their mean age was 68.78. They had a mean of 16.72 years of schooling and scored a mean of 36.39 on the Shipley-Hartford vocabulary test. The young group consisted of twenty participants, seven of which were male, with a mean age of 24.80 (range 20-35). They had a mean of 15.70 years of school, and scored 32.10 on the vocabulary test. There was no significant age difference in education, but the older participants scored reliably higher on the vocabulary test, F (1’36) = 1 7 . 2 3 , ~c .001. Materials and procedure - The sentence pairs used in Experiment 2 were used here. Because pilot work with twenty young participants indicated that error rates to the yes/no comprehension questions were over 20 percent when the sentences were not available for review, we rewrote the questions with a multiplechoice format. As in the previous experiments, inference items were constructed by substituting the matching term from the sentence in the pair that was not queried. A multiple-choice inference item for sentences (n) and (0)would be: @) What was attracted by the larder? 1. a robin 2. a thrush

Fact items involved using the same matching term as in the original sentence within a pair as in (9): (q) What would sometimes wander into the house? 1. a robin 2. a thrush

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The response alternatives for comprehension questions were always of the same class, so they were both either category names or exemplars. Comprehension questions were counterbalanced for which sentence in the pair was queried, which alternative was correct, whether the response involved a fact or an inference and the treatment condition of the sentence pair. The procedure was identical to that used in the previous experiments except that sentences were cleared from the computer screen each time the space bar or response keys were pressed. Data were analyzed using the same measures and designs as in Experiment 2 except for the age variable which had two rather than three levels.

Results Control anaZyses - Counterbalancing had no effects on reading, response times, or error rates. There was an age effect on reading time for the antecedents, however, F (1,36) = 4 . 8 5 , ~ c .03-the old group read more slowly than the young (2,849 msec vs. 2,286), as seen in Table 4. There was also a highly reliable typicality effect on reading time, F (1,36) = 12.06, p c .001; sentences in the typical condition (M = 2,506) were red more quickly than were those in the read atypical condition (M = 2,600). No other effects or interactions approached significance. Because of the possibility of spillover effects, which would be observed in a significant typicality effect, the analysis of target-sentence reading times was conducted with the antecedent reading times as covariates. The results of a repeated-measuresmultivariate analysis of covariance(MANCOVA) were identical to those of the MANOVA on target-sentence times without the covariates. In fact, the only reliable effect of the covariates was on the age main effect, which remained significant, and not for typicality, so we will report the MANOVA rather than the MANCOVA results with participantsand materials as random. Anaphor-sentence reading times - Table 4 reports the mean target reading times for the two age groups as a function of condition. As in Experiment 2, the effect of age was significant, F (1,36) = 9.28, p c .01. Younger participants read the anaphor sentence at a mean rate of 1,941 msec and the older participants at a mean of 2,673 msec. Contrary to the findings of Experiment 2, the effect for Generality was not reliable for either the participants or materials analysis: it was apparently obscured because of the Age x Generality interaction, F (1,36) = 1 0 . 2 7 , ~c .01. The source of the interaction, as determined by simple-effects tests, was that younger participants showed the predicted generality effect, with a 69 msec advantage for anaphora with specific antecedents over those with general ones. (The critical value for a significant difference between adjacent means was 59 msec). Older participants also differed in their reading times across generality conditions, showing a trend in the opposite direction with a 63 msec advantage for anaphora of general- over specific-antecedentsentences.

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Table 7. Mean Comprehension-Question Response Times (msec) and Mean Proportion of Errors (in Parentheses) in Experiment 3

Young Specific Term Typical Fact Items Inference Items Atypical Fact Items Inference Items General Term Typical Fact Items Inference Items Atypical Fact Items Inference Items

Old

1,990 1,925

2,876 2.716

1,977 1,920

2,940 2,972

1,825 2,006

2,736 2.829

1,921 2,019

2,775 2,924

In this experiment, there were significant effects of typicality for both the participants, F (1,36) = 11.94, p c .001, and for the materials analysis, F (1,63) = 3.57, p c .06. Targets of sentence pairs in the typical condition were read faster (2,239 msec) than were those in the atypical condition (2,336 msec). No other interaction involving age approached significance. Comprehension-questionresults - Table 7 shows the response times and the mean proportion of errors for the comprehension questions. As in the previous experiments, there was a significant effect of age on response times, F (1,36) = 16.87,p c .001; the old responded more slowly (old M = 2,846 msec); young M = 1,948 msec). There was also an effect of typicality, F (1,36) = 6.00, p c .05; responses to items on sentence pairs containing atypical items (2,406 msec) were slower than those on pairs with typical ones (2,340 msec). As indicated below, however, there was no effect of typicality on error rates, so the functional significance of this response-time finding is unclear. The only other significant finding in the analysis of response times was an interaction of item type with generality, F (1,36) = 1 4 . 1 6 , c~ .001. Simple-effects tests (with a critical value of 72 msec for a difference between adjacent means) revealed that, for sentence pairs with specific antecedents, participants responded significantly faster on items requiring inference compared to fact memory (2,359 and 2,421 msec, respectively). For pairs with general antecedents, participants were slower on inferences than on facts (2,422 and 2,291 msec, respectively). In the analysis of the proportion of errors, there was an Item Type x Generality interaction, F (1,36) = 14.15, p c .001. Simple-effects tests (critical value for a

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significant difference = .015) showed that error rates were lower for inferences (.01) than for facts (.03) when the sentence pair had a specific antecedent. Errors did not differ for inferences (.01) and facts (.025) for general-antecedent pairs.

There is no evidence for a speed-accuracy tradeoff in responses to the comprehension questions, as error rates were higher in the interaction when response times were slower. The importance of the Item Type x Generality interactions for errors and response times is not clear. More critical is the fact that age did not interact with treatments on either measure. Comprehe~ibility-ratingresults - As in the two previous experiments, participants generally rated the sentence pairs as very comprehensible (see Table 6). Unlike Experiment 2, however, treatments affected the ratings of the comprehensibility of the sentence pairs, with a significant effect of generality, F (1,36) = 6.64, p < .01, and a marginally reliable Age x Generality interaction, F (1,36) = 2 . 8 7 ,< ~ .lo. Participants rated sentence pairs in the general-antecedent condition as more difficult (M = 4.78) than those in the specific-antecedent condition (M = 4.83). With a critical value of .07 for the simple-effects test of the Age x Generality interaction, younger participants showed no differences in mean ratings (4.83 for specific; 4.81 for general). Older participants gave lower comprehensibility ratings for general-antecedent pairs (4.75) than for specific-antecedent pairs (4.84). Despite the marginal significance of the age and generality interaction, the absolute differences in ratings are small.

Discussion As in Experiment 2, younger participants showed the generality effect, with faster reading times for anaphora of specific antecedents than for general ones. Older participants, however, who read more slowly than did the younger participants, showed the opposite effect. These findings are contrary to those predicting an exacerbated generality effect in the older group, as suggested by a workingmemory-capacity account. Experiment 3 involved remembering the antecedent sentences, and it is probable that in the online reading task, older people had some difficulty doing so, thereby short-circuiting the process of matching and sentence integration. The problem appeared to be confined to the online task, as older people showed sensitivity to the relative difficulty of the general-antecedent sentence pairs in making their ratings. There were also no age differences in error rates. Because errors were intentionally minimized in the reading time paradigm, however, floor effects preclude the availability of direct evidence that older people could not remember the antecedents. There is implicit evidence of the difficulty in online comprehension for older people from an informal comparison of results in Experiments 2 and 3. Experiment 3 clearly showed faster reading of anaphor sentences relative to Experiment

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2. We combined the data from young-old and old-old participants in Experiment 2 for comparison with the data from old participants in Experiment 3. For the older participants, there was a difference of 698 msec for specific antecedents and 933 msec for general ones. For the younger participants, the difference between experiments was 629 msec for the specific and 651 for the anaphora of general antecedents. This suggests that both younger and older participants spent over 600 msec reviewing the antecedents in Experiment 2 before summoning the comprehension question. (The discrepancy in differences across experiments for older participants 'in the general-antecedent condition was at variance with this interpretation, but it was probably an artifact of the interaction in Experiment 3.) Because age did not interact with generality in Experiment 2, it is also probable that both age groups used approximately a similar and constant amount of time across conditions for reviewing the antecedent. This implies that the interaction of Experiment 3 occurred because older participants could not remember the antecedent and were unable to review it. Although age interacted with generality, it did not interact with typicality of the exemplars. Because the typicality effect may be the result of spillover from reading times of the antecedent sentences, we cannot determine whether this effect reflects integration processes or the effects of having read antecedents in the typical condition more quickly. The spillover explanation makes some sense in light of the fact that typicality was only marginally significant in Experiment 2. Also, the absence of a Generality x Typicality interaction in Experiment 3 indicates that the marginal interaction of the second experiment was not replicable. The typicality effect of Experiment 3 might therefore be less robust than it appears to be, and this may account for the nonsignificant interaction with age. Another possibility is that no interaction occurred because the typicality effect reflects automatic activation of semantic associations at different levels of relatedness, which is invariant with age [33]. This is unfortunately a circular argument about the task requirements, and without independent evidence, we prefer not to invoke it. More critical to this argument is that if the typicality effect reflects automatic processes, it would have been found in Experiment 2.

GENERAL DISCUSSION The work reported on here adds to a growing body of findings showing that when memory requirements are minimized, older adults have little difficulty in comprehending and drawing inferences from brief texts [15,16]. The experiments examined the speed of anaphor comprehension. Anaphora signal that sentences in texts are interrelated and recognition of anaphora is a basic process critical to discourse comprehension. Experiment 1examined age differences when matching either required identifying antecedent-anaphor terms as identical or as related. As in previous research [MI, people took longer to read the anaphor sentence when related terms rather than identical ones were presented. Experiment 2 examined

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the effects of varying the predictability of the anaphoric term in the generality condition and the associative relationship of terms in the typicality condition. As Garrod and Sanford found, people read the anaphor sentence more slowly when the antecedent was general than when it was specific [23]. A similar effect was predicted and observed for typicality, but it was marginally reliable. Age did not interact with any of the conditions tested, so it appears that the matching processes studied here showed no impairment with age. In both experiments, patterns of errors to comprehension questions and ratings of the comprehensibility of sentence pairs showed either no age differences or higher ratings on the part of older participants in Experiment 1. These results underscore the findings that the increasing difficulty of matching under the conditions varied in these experiments did not have an adverse effect on older participants’ performance, even when the old-old, who were up to eighty-seven years of age, were tested. In Experiment 3 the memory demands of the task were increased by removing antecedents from view while participants read the anaphor sentences. Under those conditions, older participants showed qualitative differences in online comprehension. They read anaphora in the general-antecedent condition more quickly than those in the specific one, whereas younger participants showed the expected generality effect. These results suggest that older adults may not have been integrating the antecedents with their anaphora under the conditions of Experiment 3 as younger adults did. When asked to rate the sentence pairs after completing the reading-time portion of the experiment, older participants showed sensitivity to the pairs with general antecedents, however, rating them as more difficult than those with specific ones. Here both sentences were in view, so it is not surprising that older participants showed the normal generality effect. The processing resources deficit model predicted that older adults should have had more difficulty than younger ones under conditions where comprehension required more matches between antecedent and anaphor terms, since it has been claimed that older adults’ “encodings will contain less associative and inferential information” [6, p. 2081. We found no evidence to support this claim in Experiments 1and 2, however. Only in Experiment 3 when participants were not able to refer to antecedents when reading anaphor sentences was online comprehension disrupted in the older adults. The results of Experiment 3 imply that older adults’ memory problems might be responsible for online comprehension deficits because reading times were well over 600 msec faster than in Experiment 2, suggesting that in Experiment 2 part of the anaphor reading time was spent reviewing the antecedent. A second reason to suspect that the problem only occurs because of the memory requirements is that older participants rated sentence pairs under the condition assumed to require more extensive matching as more difficult to understand after completing the reading task.

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An alternative view supported by our findings has been developed by Zacks and Hasher [13]. They hypothesized that working-memory capacity involves allocation of pools of resources between storage and processing functions. Older adults are not deficit in the capacities allocated to processing functions, but they do have reduced storage, which interferes with integration of multiple propositions into a single unit. This account corroborates with the results of Experiment 3, although the experiment does not directly test this hypothesis. Although our results suggest that language comprehension is not a problem in older adults when the load on memory required for comprehension is minimal, what constitutes a minimal load probably involves more than simply having both coreferential sentences available for review during trials. For example, Light and Capps [16] reported that older people were impaired in assignment of an anaphoric pronoun when a sentence changing the topic of the initial sentence intervened between the antecedent and the anaphor, and that the problem was a result of the fact that they could not recall the antecedent information to make the correct assignment. The sentences in Light and Capp’s experiments were not visible to participants, but it is unclear whether the older participants would have had less difficulty in pronoun assignment if the sentences had been, because of the topic change. There is evidence that topic changes slow comprehension when younger adults are reading [34].This occurs because topical information is maintained in working memory during discourse processing but is deleted when it is no longer relevant to the propositions currently being comprehended. When a topic is reinstated in a passage, the mental representation of textual material relevant to it must be retrieved from long-term memory and reinstated into working memory [27]. Because older people are likely to have retrieval problems, their ability to reinstate previously deleted material from long-term memory into working memory might be impaired. Whether older people have more difficulty comprehending material involving topic changes and reinstatements during reading is a question for further research. In sum, the results of the present experiments in antecedent-anaphor matching suggest that when they do not have to remember antecedent material, older people comprehend what they read as easily as younger ones do. This suggests that the reading skills of the older adults tested here are excellent and that their ability to process language is slowed by a constant amount with age. Whether this is true only for the highly educated, highly verbal adults tested here needs to be established. These results are encouraging in that they support the findings of other work examining skilled behavior in elderly adults [35, 361, where skills are maintained at high levels, despite decrements in the component processes underlying those skills such as response time and memory. In determining whether older adults do indeed have difficulties in understanding written language, the nature of the memory requirement involved in

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discourse comprehension tasks, the compensatory mechanisms that may be used to maintain skill levels in reading, and individual differences in reading skills all need to be evaluated. ACKNOWLEDGMENT

The authors gratefully acknowledge the comments on earlier versions of this article by Michael Gilewski. The authors also thank Cheri Anthony and Jeff Hyde for assistance in programming and testing participants in Experiment 3. REFERENCES 1. H. H. Clark and E. V. Clark, Psychology andLanguage, Harcourt Brace Jovanovich, New York, 1977. 2. T. A. van Dijk and W. Kintsch, Strategies of Discourse Comprehension, Academic Press, New York, 1983. 3. L. L. Light and P. A. Anderson, Working-memory Capacity, Age, and Memory for Discourse, Journal of Gerontology, 40, pp. 737-747,1985. 4. R. E. Wright, Aging, Divided Attention, and Processing Capacity, Journal of Gerontology, 36, pp. 605-614,1981. 5. G. Cohen, Language Comprehension in Old Age, Cognitive Psychology, 11, pp. 412-428, 1979. 6 . F. I. M. Craik and M. Byrd, Aging and Cognitive Deficits: The Role of Attentional Processes, in Aging and Cognitive Processes, F. I. M. Craik and S. Trehub (eds.), Plenum, New York, 1982. 7. M. Bergman, Aging and the Perception of Speech, University Park Press, Baltimore, Maryland, 1980. 8. 0. B. Emery, Language and Aging, ExperimentalAging Research, 11, pp. 1-60,1985. 9. S. Kemper, Imitation of Complex Syntactic Constructions by Elderly Adults, Applied Psycholingustics, 7, pp. 277-288,1986. 10. G. Cohen, Inferential Reasoning in Old Age, Cognition, 9, pp. 59-72,1981. 11. R. E. Till, Verbatim and Inferential Memory in Young and Elderly Adults, Journal of Gerontology, 40, pp. 316-323,1985. 12. R. E. Till and D. A. Walsh, Encoding and Retrieval Factors in Adult Memory for Implicational Sentences, Journal of Verbal Learning and Verbal Behavior, 19, pp. 1-16, 1980. 13. R. T. Zacks and L. Hasher, Capacity Theory and the Processing of Inferences, in Language and Memory in Old Age, L. L. Light and D. M. Burke (eds.), Cambridge University Press, Cambridge, England, 1988. 14. R. ‘r.Zacks, L. Hasher, B. Doren, V. Hamm, and M. S. Attig, Encoding and Memory of Explicit and Implicit Information, Journal of Gerontology, 42, pp. 418-422,1987. 15. L. L. Light, E. M. Zelinski, and M. Moore, Adult Age Differences in Reasoning from New Information, Journal of Experimental Psychology: Learning, Memory, and Cognition, 8, pp. 435-447, 1982.

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Direct reprint requests to: Elizabeth M. Zelinski Leonard Davis School of Gerontology University of Southern California Los Angeles, CA 90089-0191