integrating different types of information into hydrological model parameter estimation: application...

JOURNAL OF VERBAL LEARNING AND VERBAL BEHAVIOR 19, 263--275 (1980)

Integrating Different Types of Information in Text

CAROL H. W A L K E R

Military Personnel Center

A N D

BONNIE J. F. MEYER

Arizona State University

This investigation was designed to answer two major questions: (a) does height of information in the content s t ructure of text affect the probability of integrating the information, and (b) is it possible to differentiate be tween integration that occurs during acquisit ion and integration that takes place at retrieval. Resul ts of an inference verification task suggested that information high in the s t ructure is more likely to be integrated than information low in the s tructure. These effects were observed in two instruct ion groups (learn and read) and in two presenta t ion modes (separate and consecut ive) . In addition, premises occurring together in the text (consecut ive presentat ion) were found to promote faster correct decisions than premises occurring separately. These verification time resul ts were interpreted as evidence that s tructural integration (i.e., integration at acquisition) is more likely when premises occur together in an information source than when they occur separately.

Within a passage of text, some of the relationships among ideas and sets of ideas are stated explicitly. Other relationships are only implied and thus must be derived or inferred by the reader. This inferential process is continuous and often automatic during reading, as the reader attempts to integrate the separate but related facts presented in the text into a meaningful con- ceptual whole. While certain inferential relationships are detected during reading, it is not necessary to integrate all possible pairs of related facts in order to understand a text. A primary purpose of the present study was to test for an effect of height in the content structure on the probability of integrating two related facts. Additionally, an attempt is made to distinguish between

This research was suppor ted in part by an Arizona State Univers i ty Facul ty Grant . This paper is based on a doctoral dissertat ion submit ted by the first au thor to Arizona State Univers i ty . The au thors wish to thank Rick Yekovich for critical commen t s on an earlier version o f the manuscr ipt . We also ex tend special thanks to Barbara Hayes -Roth who created the original passages. Send reprint reques ts to: Carol H. Walker, 4000 Westga te Drive, Alexandria, Va. 22309.

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situations where integration occurred at acquisition (also known as structural integration) and situations where integration occurred at retrieval.

The topic of structural integration in memory has been the focus of a number of recent papers (Bransford & Franks, 1971; Carpenter & Just, 1977; Hayes-Roth & Thorndyke, 1979; Hayes-Roth & Walker, 1979; Kintsch, 1974, Chap. 8; Walker & Meyer, in press; Yekovich & Walker, 1978). Bransford and Franks (1971) demonstrated that subjects spontaneously integrated the information contained in a series of semantically related ideas and stored this information as a structurally integrated memory representation. Kintsch (1974, Chap. 8) reported similar findings. He studied the processing of implicit propositions, and found that subjects could accurately recognize test sentences as true even when the information in the sentences had not been stated explicitly in the text. He concluded that whether or not critical sentences were explicitly given in a paragraph, the reader inferred the corresponding proposition and stored it in memory as part of

0022-5371/80/030263-13502.00/0 Copyright © 1980 by Academic Press, Inc. All rights nf reproduction in any form reserved.

264 W A L K E R A N D MEYER

the text base that was his memory for the meaning of the paragraph.

Hayes-Roth and Thorndyke (1979) in- vestigated the conditions under which integration was likely to occur. Using pairs of facts where each fact expressed part of the information in a complex idea, Hayes-Roth and Thorndyke identified two factors that differentially affected the likelihood of forming an integrated memory representation: (a) the degree of correspondence in the wording of common information in the related facts, and (b) whether or not the related facts occurred consecutively in a passage of text. Based on their findings that identical wording and consecutive presentation of related facts facilitated integration, they concluded that lexical units (rather than propositions) form the basis for repre- senting facts in memory.

The probability of processing implicit propositions does not depend solely on the learner's ability to integrate. As Hayes- Roth and Thorndyke (1979) noted, errors on an inferential reasoning test can be produced either by failure to integrate related facts or by memory failure for the individual facts themselves. Consequently, test performance in their study was consid- erably lower than 100%. Hayes-Roth and Walker (1979) designed a subsequent experiment to study configural effects in memory. In the Hayes-Roth and Walker study, subjects were encouraged to read the passages slowly, carefully, and as many times as they needed to, in order to learn the information. In addition, subjects were urged to pay close attention to details and were given a test over the factual information in the texts. As might be expected, these special instructions improved sub- jec ts ' memory for individual facts. Of greater interest was the finding that these subjects spontaneously integrated a high percentage of the related propositions contained in the texts, even though the facts within each pair were only tangentially related to one another. This tendency to integrate enabled the subjects to correctly verify almost twice as many inferences as

compared to a condition in which they didn't learn the texts beforehand but had access to them during the verification task (Hayes-Roth & Walker, 1979).

This finding that an appropriate configu- ration of relevant facts in memory facili- tates integration suggests a relationship between the content structure of text and the probability of integrating textual information. Meyer (1975) has defined the content structure of a passage as the hierarchi- cally arranged semantic grammar of the propositions or ideas contained in the passage and the relationships among these ideas. She demonstrated that ideas high in the structure are better remembered after reading or listening to a passage than ideas low in the structure (see also Kintsch, Kozminsky, Streby, McKoon, & Keenan, 1975; Meyer & McConkie, 1973). If prominent ideas in the content structure of an information source are better remembered, it would follow that the related information common to these prominent ideas should have a correspondingly higher probability of successful integration (see Goetz, 1979). That is, since ideas or facts that are high in the content structure are more accessible, they should also be more susceptible to si- multaneous activation (and integration) than ideas low in the structure. One purpose of the present experiment was to test this hypothesis.

At this point, an important distinction should be made. While structural integration (i.e., the integration process that occurs during acquisition, resulting in an integrated memory representation) is of primary importance in this paper, it does not preclude the possibility that separately stored facts may be integrated at time of retrieval. While at least one previolas study dealing with integration has acknowledged this possibility (Hayes-Roth & Thorndyke, 1979), most theories have assumed integration to be strictly a structural phenomenon. In the current context, however, integration at retrieval is a reasonable possibility. As Kintsch (1974, Chap. 8) has argued, a reader is motivated to process an implicit

INTEGRATING INFORMATION IN TEXT 265

proposition (i.e., integrate) if the processing of subsequent propositions depends on the implicit proposition. In Kintsch's study the propositions were successively presented components of complex ideas. There are cases, however, when two integratable facts are separated such that there is little motivation for spontaneous integration. For instance, two propositions that occur low in the content structures of separate information sources should be less susceptible to structural integration because comprehension of the latter proposition is probably not predicated on integrating it with the former proposition. In other words, recognizing that a relationship exists between two details in separate episodes would be less critical to comprehension than integrating consecutively presented main ideas.

In the following experiment subjects read passages and were tested on their ability to integrate related facts. It was predicted that the probability of integrating facts that occurred high in the content structure of the passages would be greater than the probability of integrating facts that occurred low in the structure. To distinguish between situations where integration occurred at acquisition and situations where integration occurred at retrieval, two additional factors were manipulated. Inferential premises were either separated or occurred consecutively in the texts. Subjects were instructed either to read the passage once or to learn the information in the passage as com- pletely as possible. In addition to accuracy on the inference verification test, verification times were also recorded. It was assumed that verification of inferences based on premises integrated at acquisition would be faster than verification of inferences based on premises that were retrieved separately and integrated at the time of the test.

METHOD

Materials and Design

Two sets of stories were used in the present experiment. The stories described vari- ous aspects of life in the mythical country of Morinthia, and were adapted from mate-

rials previously used by Hayes-Roth and Thorndyke (1979) and Hayes-Roth and Walker (1979). The topics of the two sets of stories were: (1) Revolution in Morinthia and (2) Religious customs and beliefs in Morinthia. A distinctive feature of these stories is that embedded within each set are four pairs of integratable facts; these pairs of facts may be used as premises to justify conclusions that are inferable from the text but are never stated explicitly. Two versions of each story set were constructed for the present experiment in order to conform to the experimental manipulations described in the following paragraph.

The experimental manipulations in the current study included: two levels of IN- STRUCTION (read versus learn), two levels of mode of PRESENTATION (separate versus consecutive), and two levels of HEIGHT of integratable information in the content structure (high versus low). The design was thus a 2 x 2 x 2 fac- torial design with repeated measures on the last two factors.

Of the three factors in the experiment, only mode of presentation involved manip- ulation of materials. The common information in the integratable premises was either separate (integratable premises were presented on separate pages) or consecutive (premises occurred together in the text). The original sets of stories used b y Hayes-Roth and Walker (1979) were constructed as pairs of passages (separate presentation); therefore, integrated versions where the premises occurred consecutively were constructed for the present investigation. In the following example from the Revolution set, integratable premises are separated by intervening text. Note that the related information is italicized and corresponding premises are identified by number and superscript.

(1) The Spring Episode was the first revolution in Morinthia. It occurred shortly before dawn on April 17, 1843. The revolution was undoubtedly caused by the tyranny imposed upon the Morin- thian people by (2) King Egbert, the dictator. For months, Egbert had extracted half of all the

266 WALKER AND MEYER

earnings of the people. However, the immediate cause of the outbreak appeared to be a minor crime committed several days earlier. A peasant had poached several chickens from the royal henhouse to serve at his daughter's wedding. It seemed a minor offense to the people, but (3) in Morinthia, everyone who disobeyed the law was punished severely. The peasant was seized by the royal guards and thrown into prison. (4) The Morinthian prison was populated exclusively by the king's enemies. The townspeople were thrown into a frenzy at the severity of the sentence. Even those who swore loyalty to Egbert joined the crowds demanding freedom for the peasant. The crowds stormed the palace. An effigy of the king was burned. Egbert commanded them to respect his authority and disperse at once.

The Curfew Episode was the second attempted revolution in Morinthia. (1') All Morinthian revolutions were failures. The outbreak occurred on March 27, 1844, because (3') some youths disobeyed the curfew law. The law had been a source of friction between the townspeople and the government for some time. The people welcomed the opportunity to flood the streets, throwing stones and damaging property. Albert Profiro, a young Morinthian tradesman, took it upon himself t o try and calm the people. Al- though (2') Albert hated all dictators and their governments, he hated anarchy in the streets even more. So he positioned himself on a platform in the center of the town square and called upon the people to return to their homes. Un- fortunately, when the royal soldiers arrived, they only saw a young man shouting to the crowd, and assumed he was responsible for the riot. Albert was arrested and thrown into prison. Although Albert spent 3 bitter years in prison, his experi- ence brought some good with it as well. (4 ' ) / t was in prison that Albert met Anastacia De Ville, whom he subsequently married.

Note that premises (1) and (1') can be combined to justify the conclusion "The Spring Episode was a failure"; (2) and (2') can be combined to justify "Albert Profiro hated King Egbert"; (3) and (3') allow one to infer correctly that "The youths who disobeyed the curfew law were punished severely"; and, the combination of (4) and (4') vali- dates the conclusion that "Anastacia De- Ville was an enemy of the king." The consecutive version of the Revolution set is presented in the appendix.

To determine the height of the inferential premises in the content s t ructure , the

stories were segmented into linguistic sub- units and analyzed according to the method of prose analysis developed by Meyer (1975). Pairs of integratable premises were classified as either high, located in the top half of a passage's content structure, or low, located in the bottom half of this hier- archical structure (see Table 1). The passages were constructed to insure that an equal number of the pairs of premises occurred high and low in the content structure of each version of each story. Finally, the number of words in each story was deter- mined and adjustments were made to ap- proximately equate the passages in length (mean length = 392 words, SD = 25.8).

Both instruction conditions (read and learn) received identical sets of materials. Each subject saw one version of each story set. Order of presentation was counter- balanced using one Latin square. Height of integratable premises in the content structure was controlled across both versions of both stories.

Dependent measures were (a) accuracy on a verification task; (b) decision time on the verification task; and (c) free recall. Precise definitions and details of these dependent variables are presented in the procedure section.

Subjects

Thirty-two Arizona State University students participated as subjects in the 2-hour exper iment . Students were ei ther paid ($2.00 per hour) or offered course credit in return for their participation.

Procedure

Subjects were tested individually. Each subject was given general instructions, practice materials, instructions on the verification task, instructions specific to either the " read" or " learn" instruction condition, experimental texts, verification items, blank pages for free recall, and a final test of the inferences in syllogism form.

General instructions. Subjects were advised that this was an experiment on story memory. They were informed that ques-

I N T E G R A T I N G I N F O R M A T I O N IN TEXT

T A B L E 1 ATTRIBUTES OF PASSAGES USED IN THE EXPERIMENT

267

Attr ibute

Passage

Revolut ion Religion

N u m b e r o f idea units in each passage ' s content s t ructure

Total levels in the content s t ructure of the passages

Levels classified as high in the content s tructure

Levels classified as low in the content s t ructure

N u m b e r o f high-level idea units N u m b e r o f low-level idea units

130 160

6 9

1 - 3 1 - 5

4 - 6 6 - 9

44 71 86 89

tions in the form of statements would be presented following each story (or pair of stories in the segregated presentation condition). They were to decide if the statements were true or false, based on the information in the stories. Sometimes the information needed to make these t r ue - f a l s e dec i s i ons was exp l i c i t l y s t a t ed in the stories; other times the truth or falsity of the statements could be deduced from the stories. Subjects were encouraged to ask ques t i ons w h e n e v e r t hey we re u n s u r e about any aspect of the task or the procedure. They were advised that additional instructions would be provided when necessary throughout the duration of the experiment. When the exper imenter was satisfied that a subject unders tood the basic purpose and procedure of the study, a practice set of materials was presented.

Practice stories. The primary purpose of the practice exercise was to familiarize the sub jec t wi th the task , p r o c e d u r e , and equipment. Subjects were advised to read the stories through once, slowly and carefully. Fol lowing the p resen ta t ion of the practice stories, detailed instructions on the verification task were presented.

Instructions for the verification task. In- structions for the verif icat ion task were detailed and specific. Subjects were told that their primary task was to decide if test sentences were true or false. They were reminded that a sentence could be true be-

cause it was explicitly stated in the text or because it could be proved true by combining pieces of related information avail- able in the text.

Subjects were advised to tell the experimenter when they arr ived at a decision by saying " t r u e " or " f a l s e " as soon as they decided. They were to indicate how they arrived at their decisions by "thinking out loud" in order to produce justification for their decisions.

Read versus learn instructions. Follow- ing the p rac t ice sess ion, subjects were given instructions pertaining to the two sets of experimental texts. Read versus learn was a between subject factor with 16 sub- jec ts randomly assigned to each group. Subjects in the read condition were told to read the material through once at their normal reading speed. Subjects in the learn condi t ion were ins t ruc ted to read each story carefully, as many times as needed, in order to learn the information. They were urged to pay close attention to detail and to try and remember as much as possible. In addition, the exper imenter suggested to the learn subjects that they underline important points in the text, to help them remember.

Verification task. Af te r r e a d i n g (or learning) the first experimental text, subjects were given a verification test. Four types of statements were used on the verification tests: (a) true statements that were explicitly stated in the text; (b) false state-


ments that could be refuted by information explicitly stated in the text; (c) true statements that were not explicitly stated but could be proved true by combining pieces of related information from the text (as il- lustrated in the examples in the materials section); and (d) false statements that were not necessarily true given the information in the texts. Since better performance was expected when inferential premises occurred high in the content structure, explicit statements were included on the verification task to determine whether high- low differences were due to memory failure or failure to integrate. There were two true statements explicit from the text, two false explicit statements, four true inferences, and four false inferences, ordered randomly, on the test following each presentation of topically related material.

All subjects were urged to produce a cont inuous verbal descr ip t ion of their thoughts while performing the verification task. These descript ions were tape recorded and subsequently transcribed. The verification time for each t rue-fa lse judg- ment was measured by a Hunter Kloc- kounter and recorded in each instance by the experimenter. The measured interval began as soon as the subject started to read the inference out loud. A voice relay at- tached to the timer picked up the sound of the subject's voice, activating the timing device. The timed interval stopped when the subject made a decision. The time that elapsed while the subject read the to-be- verified inference out loud was included in the timed interval because presumably processing was going on during this time. In- ferences based on premises high and low in the structure were matched for number of words so that reading times would be comparable in the two conditions. True explicit statements high and low in the structure and false explicit statements high and low in the structure were also equated for length. Since there were no premises to support false inferences, the classification of these inferences based on height in the content

structure was not possible. This r e a d - verify (or l e a r n - v e r i f y ) procedure was repeated with the second experimental text for each subject.

Free recall. After subjects were tested on both topics, they were asked to recall the two stories in the order of original presentation. These free recall tests were in written form and were self-paced.

Syllogism test. Finally, each subject was given a written test of 16 inferences in syllogism form. On this test, each inference was immediately preceded by a pair of premises. True inferences were preceded by the two facts from the text necessary to justify the inference. False inferences were preceded by facts that were related to the inference but did not necessarily prove it to be true. Subjects recorded their t rue-fa lse judgments on IBM answer sheets. Analyses of verification items were conditional on correct syllogism responses. The order of presentation was randomized.

RESULTS

The data were first analyzed using a three-factor multivariate analysis of variance. The three factors were height of the integratable premises in the content structure (high vs. low), presentation mode of the integratable premises (separate vs. consecutive), and type of instructions (read vs. learn). Both height in the content structure and mode of presentation were repeated measures. The three dependent measures were accuracy in verifying true inferences, verification time to verify true inferences, and proportion of idea units recalled on the free recall task. Of the four types of items on the verification test (true explicit statements, false explicit statements, true inferences, and false inferences), true inferences were selected as the critical item because correct verification of a true inference is evidence of both retrieval success and integration. Verifying or refuting an explicit statement tests only recognition, not integration. False inferences are not supported by premises from the text; therefore, they

I N T E G R A T I N G I N F O R M A T I O N IN T E X T 269

cannot be classified according to height in the s t ructure . Mean accu racy scores on true inferences, verification t imes of correct true inferences and proport ions of idea units recal led are p re sen ted in Table 2. Overall mult ivariate F ratios were significant for all three main effects. The learn group outper formed the read group, mul- t ivariate F(3,28) = 12.83, p < .0001. Con- secutive presentat ions were preferable to separa te presenta t ions , mul t ivar ia te F(3, 28) = 4.11 p < .01. Informat ion high in the structure was more facilitative than information low in the s t ructure, mult ivariate F(3, 28) = 27.98, p < .0001. Additionally, the interaction be tween type of instructions and presentat ion mode was reliable, mul- t ivariate F(3, 28) = 3.22, p < .03. Based on the significant results of these mult ivariate tests, individual univariate tests will also be reported. Tests of verification accuracy and verification t ime are presented in the next section. Results of the free recall task are presented separate ly in a subsequent section.

Verification Results Verification accuracy. The ef fec ts o f

type of instructions and height of information in the content s tructure on verification accuracy of true inferences were reliable, F(1, 30) = 8.95, p < .005 and F(1, 30) = 8.36, p < .007. True inferences were verified more accurate ly by the learn group than the read group; true inferences based on premises high in the content structure were verified more accurate ly than true in- f e r ences b a s e d on p r e m i s e s low in the structure.

The co r rec t ly ver i f ied t rue inferences were classified to determine the basis for the t rue dec is ion . T h r e e c lass i f i ca t ions were defined: (a) cor rec t ly just i f ied true inferences, (b) assert ions, and (c) other justifications. To correct ly just ify a true inference, it was necessary for a subject to produce the two premises f rom the text that irrefutably p roved the inference to be true. For example , product ion of

"Wel l , it said King Egbert was a dictator and Albert Profiro hated all dictators and their gov- e rnments , so tha t ' s t rue . "

was scored as a correct justif ication for the true inference "Albe r t Profiro hated King Egber t . " I f the subject claimed that a true inference had been explicitly stated in the text, for example ,

" Y e s , t ha t ' s true, it said tha t Albert hated King Egber t . "

then the correct verification was scored as an assertion. The third classification, other justifications, included responses based on contextual cues, world knowledge, or per- sonal bias. For example , the response

"Wel l , I guess Albert hated the king. I mean the king th rew him in jail w h e n he w a s n ' t even guilty. And if someone threw me in jail for a cr ime I d idn ' t commit , I 'd hate him. So tha t ' s probably t rue . "

was scored as an " o t h e r just i f icat ion." Of the 256 true inferences, 223 were correct ly verified. Of these 223 correct verifications, 145 were appropr ia te ly justified, 51 were assert ions, and 27 received some other type of support .

A three-factor analysis of the justified trues again revealed a superiori ty for learn (.~ = 1.406) over read (Y~ = .859), F(1, 30) = 16.96, p < .001, and an effect for height in the content structure (high = 1.437, low = .828), F(1, 30) = 40.23, p < .001. Mode of presentat ion was not significant. Thus, not only were inferences based on high premises more likely to be correct ly verified, they also were more likely to be appropriately justified. And regardless of the height o f integratable p remises , subjects in the learn group justified more true inferences than subjects in the read group.

Only 51 responses were classified as assertions. There were five subjects who produced no responses in this category. When the degrees of f reedom were adjusted ac- cordingly, a three-factor analysis of variance on assert ions yielded a significant effect only on the presentat ion mode factor, F(1, 25) = 7.157, p < .025. Subjects were

270 W A L K E R A N D M E Y E R

more than twice as likely to claim that inferences based on consecu t ive premises had been explicitly stated than inferences based on separate premises (means = .546 and .250, respectively). Type of instructions and height in the structure were not s ignif icant in this analys is . The 27 responses classified as "o the r just if ications" were not analyzed due to their low fre- quency of occurrence.

Correct responses to other types of items on the verification test were also scored. The explicitly stated items were correct ly verified in 244 out of 256 cases (95.3% correct recognition). Of the 12 errors committed, 5 were in response to true items and 7 in response to false explicit items. Because of this ceiling effect on immediate recognition of explicitly presented information, no further analyses were performed on these data.

In summary, while both the learn and read groups were equally adept at recognizing explicit statements from the text, the learn group displayed a marked superiority in (a) verifying inferences, (b) verifying true inferences, and (c) producing the appropriate justifications to support their correct decisions. True inferences based on premises high in the structure were more likely to be correct ly verified as true and more likely to be appropriately justified by both ins t ruct ion groups. Asser t ions based on consecutive premises were more than twice as frequent as assertions based on separate premises.

Verification times. In contrast to the pre- vious section on verification accuracy, a three-factor analysis of variance on verification times for true inferences produced different results. While the main effects for type of instructions and height of information in the content structure failed to reach significance, the main effect for presenta- t ion mode and the in te rac t ion be tween mode of presentation and type of instructions were both highly reliable, F(1, 30) = 11.09, p < .002, and F(1, 30) = 7.30, p < .01. That is, learn and read groups did not

differ significantly in the amount of time required to verify a true inference. Neither was there a ver i f icat ion t ime dif ference between inferences based on premises high and low in the structure. However , inferences based on premises that occurred together in the text were verified faster than inferences based on premises that occurred separately, and this difference w a s reliably larger in the learn group than in the read group (see Table 2).

Verification times were also analyzed for the justified trues. For eight of the 128 observations (6.25%), subjects failed to justify any true inferences. Cell means were sub- stituted in these cases. Of the three factors in the analysis, only presentation mode affected verification time of justified trues, F(1, 30) = 25.94, p < .001. As was the case with correct (but not necessarily justified) true inferences, verification times were faster for justified true inferences based on premises that occurred together in the text. Jus- tified trues based on premises that occurred separately were verif ied accurate ly , but verification times were slower.

In summary, degree of proximity of inferential premises within the tex t was the most significant factor in the verification time data. While height of premises in the s t ruc ture and type of ins t ruc t ions were powerful determiners of verification accuracy, only presentat ion mode and the in- t e rac t ion be tween ins t ruc t ion type and mode proved reliable as predictors of verification time.

Results of Free Recall Analyses Free recall was the third variable in the

r e s p o n s e v e c t o r a n a l y z e d in the multivariate analysis. Since the total number of idea units differed between the two passages (see Table 1), proportion of idea units recal led was the dependen t measure of in te res t . In the t h r e e - f a c t o r un iva r i a t e analysis, both the type of instructions and height main effects were highly reliable, F(1, 30) = 34.54, p < .001 and F(1, 30) = 45.96, p < .001 (see Table 2). The learn

INTEGRATING INFORMATION IN TEXT

TABLE 2 CELL MEANS FOR CORRECT VERIFICATIONS OF TRUE INFERENCES, VERIFICATION TIMES FOR

TRUE INFERENCES, AND PROPORTION OF IDEA UNITS RECALLED

271

Integrated Segregated

High Low High Low

Learn

Read

Correct verifications a 2.000 1.812 1.812 1.750 (1.843) Verification time b 4.977 6.128 8.300 10.944 (7.596) Proportion of idea .798 .642 .864 .734 (.759)

traits recalled Correct verifications ~ 1.750 1.500 1.812 1.500 (1.640) Verification time b 6.762 6.793 7.171 7.233 (6.999) Proportion of idea .630 .480 .563 .525 (.550)

units recalled (1.875) (1.656) (1.812) (1.625) (5.870) (6.460) (7.736) (9.106) (.714) (.561) (.713) (.629)

Note. Row means and column means are presented in parentheses. These data represent only those test inferences to which subjects responded correctly on the final syllogism

test. Accuracy on the syllogisms was over 99% and did not differ among conditions. Verification times are expressed in seconds.

group recalled 75.9% of the information contained in the text, indicating that they had formed relatively complete memory representations of the presented material. The read group recalled 55.0% of the information. Both groups recalled more high idea units than low idea units (means = 71.4 and 59.5%, respectively).

Two further observations are relevant in the present context. First, there were very few position intrusions in the recall protocols. Even when a pair of premises had been integrated to justify a true inference, the premises were most often recalled in the positions they occupied in the presented texts. Of the 338 inferential premises produced on the free recall protocols, only 10 switched mode of presentation (2.9%). Of these 10, 8 had been segregated at presentation and were integrated by the subject in the recall protocol. The remaining two had occurred together in the text but were separated by the subject during recall.

Second, a count was made of the number of times a subject failed to justify a true inference but subsequently succeeded at producing both premises at free recall. Since both premises were accessible in memory at retrieval, this measure was as-

sumed to be relatively pure measure of integration failure. The probability of not jus- tifying a true inference given recall of both premises was. 19. In 24 of the 125 instances where both premises were produced at free recall, subjects failed to correctly justify the corresponding true inference on the verification test. Due to the relatively small number of observations in this category, further analyses were not attempted. How- ever, it is worth noting that 17/24 observations were low in the content structure and 14/24 occurred in the segregated presentation condition.

Thus the major free recall results were consistent with the results of the verification task. Both text structure and instructions to learn affected performance. High information was recalled more often than low information, and increased processing produced superior overall recall.

DISCUSSION

The data from this investigation were analyzed to answer two main questions: (a) does the height of information in the content structure of text affect the probability of integrating the information, and (b) is it possible to differentiate between integra-


tion that occurs during acquisition and integration that takes place at retrieval. Results bearing on each of these questions will be discussed separately.

Effects of Height of Information in the Content Structure The results obtained in this study suggest

that height of information in the content structure of text is an important factor in integration. True inferences based on premises high in the structure were more likely to be correctly judged as true and more likely to be appropriately justified than true inferences based on premises low in the structure. These effects were observed in both instruction groups (learn and read) and in both presentation modes (separate and consecutive). High-level inferences were appropriately justified 71.8% of the time, while low-level inferences were correctly justified in only 41.4% of the responses. An additional 16.4% of the high- level inferences were falsely recognized as statements explicit from the text. Since responses of this type (assertions) indicated recognition of the truth value of an inference (e.g., that "Anastacia DeVille was an enemy of the king"), these assertions were also evidence of integration (Bransford & Franks, 1971). Among the low-level inferences, 23.4% were asserted to be statements explicit from the text. Thus overall 88.2% of the high-level premises were integrated as opposed to 64.8% of the low-level premises.

In addition to these quantitative differences in integrated memory representations based on premises high and low in the content structure, the justified true responses also provided evidence of qualitative differences between the two groups of responses. Correctly verified high-level inferences were more likely to be appropriately justified, indicating recognition of the truth value of the statement and ability to recall the specific supporting evidence from the text. Correctly verified low-level inferences, on the other hand, were more likely

to be falsely recognized as statements explicit from the text. Thus, while the gist of the low-level information was often re- tained, the specific wording was likely to be forgotten.

Subjects' inability to remember the specific wording of the low-level premises was a probable cause of their failure to verify low-level inferences. Hayes-Roth and Thorndyke (1979) showed that identical wording of common information facilitated integration of two related facts. If subjects in the present experiment were unable to remember the specific wording of low-level premises, it follows that they were less likely to detect a relationship between these premises, either at acquisition or retrieval. Recognition rates for the high and low explicit statements support this claim of integration failure. If integration had been equally likely with high and low premises, then the ability to recognize the truth value of high and low inferences would have been comparable to the subjects' ability to accurately recognize high and low true explicit statements. This was not the case. In the present investigation, no differences were observed between recognition rates for high and low explicit statements. True explicit statements were verified and false explicit statements were refuted accurately and quickly, regardless of their level in the hier- archy. Similar results have been reported by other authors (e.g., McKoon, 1977; Miller , Per ry , & Cunn ingham, 1977; Thorndyke & Yekovich, in press). In the Miller et al. paper, the difference between mean proportions for superordinate (.5773) and subordinate (.6296) items correctly recognized on an immediate test failed to reach significance, dependent t (21) = -1.52. McKoon (1977) reported that sentences containing topic information were recognized faster and more accurately than sentences containing details, but only after a 25-minute delay. When testing was immediate, the differences were not significant. In contrast, significant differences were observed in the present experiment between

I N T E G R A T I N G I N F O R M A T I O N IN T E X T 273

subjects' abilities to verify high and low implicit statements. Since their ability to recognize the truth value of low-level information was not impaired, subjects' inferior performance on the verification of low-level inferences was probably due to memory failure for specific wording of low-level information and consequent failure to integrate.

Integration at Acquisition versus Integration at Retrieval

The verification accuracy data provided evidence that learners can successfully integrate related facts to acquire information which is only implicit in a text. In addition, both the data from the justified true responses and the free recall protocols indicated that subjects often could distinguish this implicit information from propositions explicitly stated in the passage. Up to this point, however, no distinction has been made between structural integration (integration that occurs at acquisition resulting in a structurally integrated memory representation) and integration that occurs at retrieval as a result of a retrieval cue. In this section, an attempt will be made to differentiate between structural integration and integration at retrieval.

Presumably, if two premises are integrated at acquisition, the implicit proposition that results from this integrative process is stored together with the premises. That is, if a reader encounters

(1) The outbreak occurred because some youths disobeyed the curfew law.

(2) In Morinthia, everyone who disobeyed the law was punished severely.

in a text and spontaneously integrates these two facts, then the resulting implicit proposition

(3) The youths who disobeyed the curfew law were punished severely.

would be stored together with (1) and (2). If this is true, then the presentation of(3) on a verification test would require only that the reader recognize an already stored propo-

sition. This recognition task would be sim- pler than the process of simultaneously activating two separately stored propositions in order to verify an inference at retrieval. This simplified retrieval process (i.e., recognition) should result in correspondingly faster verification times for structurally integrated premises. Premises stored separately may be accessible at retrieval, resulting in an accurate verification, but the time to accomplish verification in this case would be slower.

Data from the present experiment indicate that premises presented together in the text (consecutive presentation) are more likely to be structurally integrated than premises presented separately, and that this tendency is magnified in the learn condition. While mode of presentation produced no significant differences in verification accuracy, inferences based on premises that occurred together in the text were verified significantly faster than inferences based on premises that were presented separately. In fact, the time to verify true inferences based on consecutively presented premises (,~ = 6.1635 seconds) was almost identical to the time required to recognize true explicit statements (X = 6.1916 seconds), while the verification time for inferences based on separate premises was reliably slower (X = 8.4213 seconds).

Additional support for the contention that premises appearing together in the text are more likely to be structurally integrated than premises separated by intervening material comes from the assertion data. As- sertions (claims that inferences based on the text were explicitly stated) were more than twice as likely in the consecutive presentation condition, indicating that premises appearing together were most likely to result in structurally integrated memory representations.

In summary, learners appear to be relatively adept at recognizing explicitly presented textual information immediately after presentation. However, if learners are required to make judgments or decisions


based on information from several sources, then information high in the structure and r e l a t i v e l y c o m p l e t e m e m o r y representations appear to be facilitative. Fur- thermore, while accurate decisions can be made regardless of whether premises occur together or separately in the text, consecutively presented facts promote faster decisions.

APPENDIX

(1') All Morinthian revolutions were failures. (1) The Spring Episode was the first revolution in Morinthia. It occurred shortly before dawn on April 17, 1843. The revolu- t ion was u n d o u b t e d l y caused by the tyranny imposed upon the Morinthian people by King Egbert. However, the immediate cause of the outbreak appeared to be a minor crime committed several days earlier. A peasant had poached several chickens from the royal henhouse to serve at his daughter's wedding. The peasant was seized by the royal guards and thrown into prison. The townspeople were thrown into a frenzy at the severity of the sentence. Even those who swore loyalty to Egbert joined the crowds demanding freedom for the peasant . The crowds stormed the palace. An effigy of the king was burned. Egbert commanded them to respect his authority and disperse at once.

The Curfew Episode was the second attempted revolution in Morinthia. This outbreak occurred on March 27, 1844, because (3') some youths disobeyed the curfew law. It seemed a minor offense to the people, (3) but in Morinthia, everyone who disobeyed the law was punished severely. The law had been a source of friction between the townspeople and the government for some time. The people welcomed the opportunity to flood the streets, throwing stones and damaging property. For months, (2) Egbert, the dictator, had extracted half of all the earnings of the people. (2') Albert Profiro, a young Morinthian tradesman, hated all dictators and their governments. But he

hated anarchy in the streets even more. So he took it upon himself to try and calm the people. He positioned himself on a platform in the center of the town square and called upon the people to return to their homes. Unfortunately, when the royal soldiers arrived, they only saw a young man shouting to the crowd, and assumed he was responsible for the riot. Albert was arrested and thrown into prison. (4) The Morinthian prison was populated exclusively by the king's enemies. (4') It was in prison that Albert met Anastacia DeVille, whom he subsequently married. Thus, although Al- bert spent 3 bitter years in prison, his expe- rience brought some good with it as well.

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(Received November 12, 1979)

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