the context in which an unknown word is embedded involves more than the ... Baldwin, 1986), while the effects of context clues have generally been found to be ...
European Journal of Psychology ofEducation 1998. Vol. XIII. n";. 131-154 © 1998. I.S.P.A.
The role of reading comprehension in word meaning acquisition during reading Irene-Anna N. Diakidoy University ofCyprus, Cyprus
The purpose of this study was to explore the influence of reading comprehension on the acquisition of word meanings from context and to compare it to the effects of local context characteristics, such as proximity and directness of context clues. The study also examined the effects of prior topic and enabling concept knowledge. Sixth-grade students were pretested on their knowledge of target vocabulary from two expository passages appropriate for their grade and reading level. The students were then familiarized with selected main concepts from one passage and, subsequently, read both experimental passages. Half of the target words appeared in an informative context, while the rest appeared in an less-informative context. A comprehension test and a vocabulary posttest followed the reading ofeach passage. Hierarchical Regression analyses indicated that reading comprehension level and prior main concept knowledge facilitated vocabulary learning from context. In comparison, the effect ofpresence or absence of informative context clues was not significant. These findings .underline the need for a reconceptualization of context to take into account the mental representation that readers construct in addition to the printed text that surrounds an unfamiliar word.
Introduction The purpose of this study was to explore the extent to which comprehension of text facilitates the acquisition of word meanings from context. The position that is advanced is that the context in which an unknown word is embedded involves more than the explicit text information Khat surrounds the word. Understanding and learning from text involves the construction of a mental representation that includes explicit text infonnation as well as inferences that result from the activation of relevant background knowledge. This mental representation will serve as the context on the basis of which specific inferences about an unknown word's meaning will be drawn. If that is the case, it can be expected that level of comprehension and factors that affect it will influence the extent to which word meaning acquisition from context takes place. This research was completed at the Center for the Study of Reading, University of Illinois at Urbana-Champaign, U.S.A. I thank Richard C. Anderson, Bill Nagy, David Pearson, and David Zola for their insightful comments and reviews, I also thank the children and the teachers of Jefferson Middle School, Champaign, Illinois, for their enthusiastic participation in the study.
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Vocabulary acquisition from context The importance of vocabulary acquisition from an educational standpoint is revealed by the well-documented relationship that exists between vocabulary knowledge and reading comprehension (Anderson & Freebody, 1981; Sternberg & Powell, 1983). Nagy (1988) and Simonsen and Singer (1992) have argued that vocabulary knowledge is fundamental to reading comprehension, since one cannot understand text without knowing what most of the words mean. An even stronger point is made by Sternberg (1987) who claims that the state of one's vocabulary knowledge is highly predictive of one's level of reading comprehension. Reading comprehension is not only a major goal of schooling from early on, but is also a necessary prerequisite later, when the goal shifts from learning to read to learning new information as a result of reading. Another line of research has pointed out that the sheer volume of new vocabulary that the average elementary school student is expected to encounter and to acquire in the course of one year is substantial (Miller & Gildea, 1987; Nagy & Anderson, 1984; Nagy & Herman, 1987). Although different estimates vary due to the definition of word that is used by different researchers, the dictionary used to estimate the total word stock of the language, andlor the criterion employed to measure word knowledge (Nagy, Herman, & Anderson, 1985; Zechmeister, Chronis, Cull, D'Anna, & Healy, 1995), the fact remains that there is a large amount of word learning that does and must occur in a relatively short period of time. Because direct and explicit instruction of individual words cannot fully account for this remarkable growth in vocabulary knowledge (Herman & Weaver, 1988; Nagy, Anderson, & Herman, 1987), it has been proposed that children must be learning words through some other means, the most plausible candidate of which being through context during the course of normal reading (Jenkins, Stein, & Wysocki, 1984; Sternberg, 1987). Therefore, an ability to acquire word meanings from context is a major asset, contributing further to text comprehension and providing an indication of the ability to learn from text. The goal then from an educational perspective is to find an effective and efficient way to induce children to take advantage of the context and to promote independent word learning. A number of studies have examined vocabulary acquisition from context and the factors that might affect it (Carnine, Kameenui, & Coyle, 1984; Jenkins et al., 1984; Konopak, 1988; Nagy et al., 1987; Nist & Olejnik, 1995; Schatz & Baldwin, 1986; Shu, Anderson, & Zhang, 1995). Although in most of these studies there was some learning from context, the absolute gains in word knowledge were small. One problem with the research on vocabulary acquisition from context has to do with the way context has been conceptualized and defined. Context has been taken more or less to represent the written text that happens to surround a given word. This conceptualization appears to underlie studies in which the immediate context of the word was extracted from a larger autonomous, or self-contained text (Schatz & Baldwin, 1986), and studies that have focused on the effects of the presence, type, and proximity of context clues (Carnine et aI., 1984; Diakidoy & Anderson, 1991; Konopak, 1988). When context represented an excerpt from a larger passage, no learning from context was found to take place (Schatz & Baldwin, 1986), while the effects of context clues have generally been found to be weak (Diakidoy & Anderson, 1991; Konopak, 1988). It appears that a context clue unless it is very close to the unfamiliar word and very explicit such as a well-known synonym or a direct definition is not likely to be picked up and utilized by the learner (Sternberg, 1987). Although this research has focused on and explored a substantial number of diverse text, word, and learner factors, it has failed to adequately take into account that such learning necessarily takes place within the situational context of normal reading. A major goal of reading, and especially school reading, is to comprehend the text and to acquire new information from it. For this to be accomplished, the reader must continually engage in the development of a coherent mental representation of the situation described in the
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text (Brewer, 1987; Kintsch, 1986). Since normally readers do not read simply to learn new words, we must necessarily assume that it is in the process of adding to and modifying the knowledge base that the meanings of difficult or unknown words are also acquired. As with the comprehension and learning from text, it is hypothesized that the quality and richness of the mental representation - in terms of the amount and strength of the links established among pieces of text information - that the reader has been able to construct will also facilitate word meaning acquisition from context. This constructed representation of text meaning will ultimately serve as the context for a particular word. This conceptualization of context shares similarities with the distinction that Stanovich (1986) makes between the nominal context, which represents the printed information, and the effective context, which represents the information that is actually used by the reader. According to the perspective adopted here, the degree to which a reader has been able to construct a coherent mental representation in order to comprehend the text and learn from it should be directly and positively related to the amount of word learning that we witness. In summary, a reconceptualization of word meaning acquisition from context is proposed to reflect that the processes that are responsible for such learning are similar to the processes that are responsible for learning new information from text in general. The present study was designed to specifically explore the viability of this proposal. The effects of factors such as level of comprehension and relevant prior knowledge of main concepts were explored and compared to the effects of the directness and explicitness of the immediately surrounding context. Reading comprehension and vocabulary knowledge
Even though a positive correlation between vocabulary knowledge and reading comprehension has been a consistent finding, a direct causal link, as it would be indicated by strong positive effects of vocabulary instruction on comprehension, has not been well established (Graves, 1986; Mezynski, 1983). According to Anderson and Nagy (1989), understanding text normally depends on knowledge that goes beyond specific word knowledge, and readers can comprehend the text without necessarily figuring out the meaning of a few unfamiliar words (Anderson & Freebody, 1981; Jenkins & Dixon, 1983). Therefore, a more adequate account would be to assume that the relationship between vocabulary knowledge and reading comprehension is a more complex one allowing for the possibility that not only reading comprehension can influence word knowledge up to a certain level where the influence is reversed, but also that there are factors that the processes of comprehension and vocabulary acquisition share and which can be responsible for both (Curtis, 1987; Stanovich, 1986). If we assume that word learning from context does take place during reading, then it is more or less futile to conceive of such learning without presupposing some level of comprehension. Comprehension can function to make information from context more easily available and the reader more likely to devote resources to processing a word. On the other hand, a high percentage of unfamiliar words in a passage may disrupt comprehension to the point that critical information about a word's meaning is no longer available from context. If the reader has not achieved a satisfactory level of text comprehension, then it is doubtful whether relevant text information can be utilized for the purpose of inferring the meaning of a given word. It can be hypothesized then that any acquisition of word meaning that might take place as a result of reading is actually a by-product of the comprehension process. Any skills and knowledge required in dealing successfully with complex discourse can also be expected to apply in the task oflearning word meanings from context. Words normally do not occur in isolation or in very simple sentence contexts, but within complex sentences embedded in complex discourse. Research on text comprehension has helped establish the importance of integrating text information, of constructing a model on the basis of what is
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given in relation to what is known, of generating inferences to fill parts of the model that are missing, and of being flexible to adjust and modify newly constructed hypotheses as needed in order to arrive at a coherent interpretation of the text (Anderson & Pearson, 1984; Bransford, Barclay, & Franks, 1972; Bransford & McCarrell, 1974; Kintsch, 1986). VanDaalen-Kapteijns and Elshout-Mohr (1981), in a detailed analysis of the processes involved in deriving word meanings from context, have shown that learners must not only be able to form a rough hypothesis of what the meaning of a word might be from initial encounters, but they also have to have the flexibility to take into account subsequent pieces of information, to integrate them, and to modify initial models accordingly. As Just and Carpenter (1987) have pointed out, the kind of processing identified in this research is very similar to the kind of processing that is assumed to underlie the comprehension of text. Whereas in reading comprehension the reader has to construct hypotheses about what the text is about, given text information and relevant stored knowledge, in word meaning acquisition from context the learner has to construct hypotheses about what would constitute a plausible meaning for a particular unfamiliar word, again on the basis of text information and background knowledge. Therefore, part of the relationship that exists between vocabulary knowledge acquired from context and comprehension can be accounted for by the fact that both involve similar learning processes. Words cannot be separated from the concepts they represent, and, therefore, learning a word meaning represents learning something about the concept that underlies the word. Moreover, concepts come in clusters that are systematically interrelated (Anderson & Freebody, 1981). If a passage is to be comprehended, then the connections between the concepts must be noted or inferred. When an unfamiliar word is encountered in a passage, the concept that underlies it is ordinarily an integral part of the conceptual network underlying the whole text. Any information about word meanings is stored as part of this overall network of interrelations among concepts. Chunking and integrating information for comprehension purposes should make the search for distant clues easier and their relationship to the unfamiliar word more clear. Some support for the above hypothesis comes from studies that have examined the effects of teaching students strategies for inferring word meanings from context (Graves & Buikema, 1990; Herman & Weaver, 1988). The findings indicated that students became more aware of unfamiliar words and more prone to reason about their meanings when they had been taught by means of modeling to take into account the flow of events in the story as well as more specific clue information (Herman & Weaver, 1988) and to piece clues together in order to guess word meanings on their own (Graves & Buikema, 1990). It appears that such an instructional approach involves nothing more than tying pieces of information together and drawing inferences, a practice that is useful both in comprehension and in independent word learning. Background knowledge
A major determinant of how well or how deeply a text will be understood is the relevant knowledge that the reader will bring to bear on the task (Anderson & Pearson, 1984; Rumelhart & Ortony, 1977; Scha, Bruce, & Polanyi, 1986; Simonsen & Singer, 1992; Spilich, Vesonder, Chiesi, & Voss, 1979). The role that background knowledge plays and its potential effects are easily inferable when it comes to word learning as well. Freebody and Anderson (1983) have argued that when the topic is familiar, the reader has available a schema that can often serve as the basis for appropriate estimates of meaning when difficult or unknown words are encountered. According to Drum and Konopak (1987) a reader's prior topic knowledge remains an important source for learning meanings even when the text contains appropriate and explicit clues.
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Possessing relevant knowledge in a domain means, among other things, that at least a substantial number of the major concepts in the domain are known. It also means that the ways in which these concepts are or can be related are known to some degree as well. These concepts can be thought of as enabling concepts in the sense that they may facilitate the learning of other unknown concepts (Ausube1, 1960). It can be assumed then that a rich knowledge base, as indicated by enabling concept knowledge and general topic knowledge, can help generate and constrain initial hypotheses about any unfamiliar words by guiding the reader to notice the position and function of the concept underlying the word in the network. The same knowledge can support inferencing when the necessary links or information are missing. The extent of the influence that background knowledge can exert on word learning can be implied in the findings of studies that have focused on vocabulary acquisition from context. Nagy et al. (1987) found that fewer words were learned from conceptually difficult passages, that is, passages that had a higher proportion of conceptually difficult or unfamiliar words. The higher the proportion of conceptually difficult words in a passage the less knowledge the reader possesses about the topic. It is apparent from these findings that the availability of relevant topic knowledge can potentially influence the degree of word learning that will take place. The present study
The major hypothesis underlying this research is that level of comprehension achieved by the reader is a major factor influencing incidental word learning as opposed to more narrowly defined factors such as the directness and explicitness of the local context that happens to surround an unfamiliar word. The present study was designed to specifically address the following questions: a) To what extent does comprehension of text facilitate word meaning acquisition from context? b) To what extent does prior knowledge facilitate word meaning acquisition from context? c) If achieving a high level of comprehension does have a positive effect on word learning, then does this effect persist even in the absence of direct clues in the immediate context of an unfamiliar word? Half of all the unfamiliar words that readers encountered in text were followed by direct and explicit clues, such as synonyms or short definitions, while the rest were embedded in less-informative, more natural local contexts. Comprehension level was assessed by means of a sentence verification task that included both literal and inferential comprehension items. To provide for a more direct manipulation of comprehension level, the reading of the passages was preceded by a familiarization treatment. Half of all readers were familiarized with the topic of one passage, while the rest were familiarized with the topic of the other passage. The familiarization treatment consisted of reading a short introductory passage designed to explain some of the most central, superordinate concepts in the passage. The introductory passages closely resembled advance organizers in the sense that they provided relevant knowledge at a more general level (Ausubel, 1960; 1978). The participants (sixth grade students) were pretested on their knowledge of unfamiliar target words, and were tested again after reading a passage to allow for any increases in word knowledge as a result of reading to become apparent. In addition to the target words, students were tested on their knowledge of enabling concepts on both testing occasions. Enabling concepts in this research were operationalized as words representing superordinate or main idea concepts. By virtue of their centrality in the overall theme and superordinate position,
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enabling concepts may provide an estimate of prior topic knowledge, and, if known, serve as anchor points to which subordinate concepts underlying unfamiliar words can be attached (Ausubel, 1960; Albrecht & O'Brien, 1991; Anderson & Freebody, 1981). Knowledge of enabling concepts was assessed in this research in order to explore its role in comprehension and word meaning acquisition from context. Specifically, it was hypothesized that (a) after controlling for prior word knowledge, sixth graders who score high on the comprehension test after reading will show increased gain in word knowledge when compared to students whose performance on the comprehension test is low; (b) sixth graders who have been familiarized with main topic concepts by reading a short introductory passage before the main selection will have higher scores on the comprehension test and will show more gain in word knowledge than students who have not read the introductory passage; and (c) an informative local context will facilitate word learning but comprehension will have a positive influence on the learning of all words, and this difference in learning will be more pronounced for words that are found in less informative contexts. In addition the effects of enabling concept knowledge in subsequent word meaning acquisition from context were also explored.
Method Participants
The participants were 73 sixth graders from one middle school in a medium-sized midwestern town in the U.S.A. There were 25 students in Class 1, 19 students in Class 2, and 29 students in Class 3. The students were tested in their intact classrooms. Although standardized scores of ability were not made available, vocabulary knowledge information was provided by the general vocabulary and enabling concept sections of the vocabulary pretest. Vocabulary knowledge was used as a stratifying variable to assign subjects to conditions. Experimental passages
Two expository passages, 850-1000 words long, were selected from a children's magazine (Beelitz, 1988; Kendall, 1987). Three independent judges with experience in teaching sixth grade rated the passages to be appropriate in terms of overall level of difficulty, and the topics to be moderately familiar to unfamiliar for the target population. For Passage A, "Desert Traders: The Tuareg", there was 100% agreement for level of difficulty. With respect to topic familiarity, two of the raters indicated that the topic was somewhat unfamiliar but not likely to hinder comprehension. For Passage B, "Silk: The Caterpillar Thread", there was 100% agreement for both level of difficulty and topic familiarity. Each student in the study read both passages in different sessions taking place on two consecutive days. The order of passage presentation was counterbalanced among students. Introductory passages
For each target selection a short introductory passage was prepared in the following manner. For each expository passage a key concept was identified that was judged to represent the superordinate theme of the particular passage. Then a short passage (200-300 words long) including definitions, characteristics, and examples of the key concept was constructed (Pearson & Johnson, 1978; Simonsen & Singer, 1992). For Passage A, "Desert Traders: The
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Tuareg", the corresponding introductory passage presented information concerning the characteristics and climate of desert regions. For Passage B, "Silk: The Caterpillar Thread", the corresponding introductory passage presented information about the different types of fabrics that people use in making clothes. The introductory passages were constructed in such a way as to preclude any familiarization with the target words. The purpose of the introductory passages was to provide and/or activate relevant prerequisite knowledge on the basis of which the students can assimilate the information presented in the main expository texts (Ausubel, 1960; 1978). One of the hypotheses examined in this study is that students who possess relevant prior knowledge about a given topic will draw inferences and acquire the meanings of unfamiliar words to a greater extent than students who do not possess such knowledge. Introductory passages in this study were used in an attempt to provide a more powerful manipulation of prior knowledge than simple testing would allow. Target words The target words in each passage were selected on the basis of frequency counts and expert adult ratings. All of the low-frequency words (SF! less than 45) from each passage were included in a list of words along with some low-frequency compounds and high-frequency polysemous words (Carroll, Davies, & Richman, 1971). The polysemous words were included in the list because it was judged that they were used in the passages in a way that was likely to be unfamiliar for sixth graders. The compounds were included because, even though the individual words had high frequency, the particular combinations they formed resulted in low-frequency words. Each word in the list was then evaluated by an independent rater with experience in teaching sixth grade. All of the words identified as likely to be unfamiliar and/or difficult for sixth-grade students were designated as target words. This process resulted in two sets - one for each passage - consisting of 22 target words each (see Appendix A). The target words in each passage were not underlined since the purpose here was to assess the degree of learning that takes place as a result of reading and comprehending the text and not as a result of explicitly guiding the reader to process the target words. Context condition Each target word was presented in one of two context conditions. In Condition A, the word was preceded or followed as closely as possible by a direct and explicit clue. For this purpose the immediate context of each word was slightly modified to incorporate a synonym, a short definition, or a highly constraining modifying phrase. Words in Condition B were in a natural, less-informative context. In case the natural context of a word contained a direct clue, then the clue was deleted in the passage version in which the word was in Condition B. For example, the text sentence "He returned twenty-four years later and wrote about his adventures in the land of Kublai Khan." represents a less-informative context since it does not give any direct clues as to who/what the unfamiliar proper name refers to. In Condition A, the sentence was changed to "He returned twenty-four years later and wrote about his adventures in the land of the emperor Kublai Khan" to constitute a more informative context. The words in each passage were divided in halfby assigning each successive target word to a contextual condition different from that of the preceding target word. Subsequently, two versions of each experimental passage were created. In one version, a given set of target words were in Condition A, while in the second version the same set of words were in Condition B. Therefore, Context Condition was a within-word variable, and each subject saw each target word in only one of the two conditions. Two graduate students in Educational
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Psychology rated the informativeness of the context for each target word in the passages. Agreement between ratings ranged from 81% to 95% far each passage and passage version. Differences were resolved in discussion. The purpose of the contextual manipulation was to control for local context characteristics and to provide for a more adequate test of the hypothesis that high comprehension level will facilitate the learning of words in less-informative contexts. Enabling concepts
For each expository passage a short list of words representing enabling concepts was compiled. The same judges who rated the passages for difficulty and familiarity were asked to underline one or two central words/concepts in each paragraph that they thought represented the topic of that paragraph. The raters were instructed to provide the concepts on their own if they felt that none of the explicitly stated words in the text of the paragraph represented an enabling concept. Only words that were selected by at least two of the three judges were included in a final list for each passage (see Appendix A). From each list, words that were found to be directly related to the superordinate theme concept were included and defined in the appropriate introductory passage. All of the enabling concepts were included in the vocabulary tests. One of the exploratory questions of interest in this study was whether prior knowledge of enabling concepts influenced the acquisition of unfamiliar word meanings. To answer this question, the enabling concepts selected were included in the vocabulary pretest. The same concepts were retested in the vocabulary posttest to explore for the possibility of additional learning as a result of reading. Testing materials
Four comprehension/learning tests and three vocabulary tests were developed. There was one comprehension test for each of the two introductory passages and one for each of the two experimental passages, one vocabulary pretest and two vocabulary posttests. Comprehension tests. A comprehension test, in the form of a sentence verification task, followed the reading of each experimental passage. The sentence verification (yes/no) task and variations of it have been used extensively in comprehension and inferencing research (Bransford et aI., 1972; Dooling & Christiaansen, 1977; Freebody & Anderson, 1983; McKoon & Ratcliff, 1988; Omanson, Warren, & Trabasso, 1978). In the present study it was judged that the sentence verification task would provide an accurate picture of the extent of sixth graders' comprehension and inferencing, and that it would be easier and less time-consuming for these students to complete than either free-recall or multiple-choice measures. The students, after reading each statement, indicated if it was correct or incorrect on the basis of the passage just read. Half of all the statements were designed to assess literal comprehension, while the other half were designed to assess the extent of inferencing that had taken place either during comprehension or during the testing phase. The comprehension test items were categorized as literal or inferential by loosely following the classification system developed by Pearson and Johnson (1978). In this system, comprehension questions are classified by taking into account the source of information that is needed to answer them. Text-explicit questions are literal questions, and appropriate answers can be found explicitly stated in the text. Text-implicit questions are inferential questions, and although they can be answered on the basis of text information, they require that the reader infer relationships among propositions in the text that are not explicitly stated. Script-implicit questions are also inferential questions, but to answer them the reader needs to refer to background knowledge. For the purposes of this study, text-implicit and script-implicit
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questions were grouped together in one category comprising the inferential comprehension part of the test. The inferential items represented unstated relationships among text propositions and background knowledge information, predictions, evaluations, and generalizations. For each experimental passage, a list of possible literal and inferential statements was constructed. these statements targeted both main ideas as well as details. Sentences from the passage that did not include a target word were selected for the literal part of the test. The inferential statements were constructed so that none of the propositions directly supporting a given inference included a target word. A independent rater evaluated each item in the list as either literal or inferential. Only items for which there was 100% agreement between the rater and the investigator were retained in the list. Literal items that were correct consisted of sentences extracted verbatim from the text. Literal items that were false consisted of direct negations of text sentences. Inferential items that were correct consisted of statements that were plausible on the basis of text information and/or background knowledge, and items that were false consisted of implausible statements. Two graduate students read each experimental passage and indicated whether each statement on the list was correct or incorrect. Items for which there was not 100% agreement were dropped. Finally from the remaining items 16 were selected for each passage, eight literal and eight inferential, so that half of the literal and half of the inferential statements were correct while the rest of the items were incorrect. Each comprehension test item was followed by Yes, No and Don't Know options (see Appendix B). For each comprehension test there were an equal number of Yes and No correct responses. Each correct response was given a score of + I, and each incorrect response was given a score of -1. A Don't Know response was given a score of O. This scoring format was adopted to eliminate the need for correction of guessing. The order of statement presentation was randomized, and two test versions with different orders were created. A pilot study with 49 sixth graders from a different school indicated that the comprehension tests for the experimental passages reflected accurately differences in comprehension.
Introductory passage tests. Two sentence verification tests were constructed to assess comprehension and learning from the introductory passages. The purpose of these tests was to ensure that all students after reading a given introductory passage possessed comparable amounts of prerequisite knowledge and level of comprehension. The introductory passage tests were developed and scored in a similar way as the comprehension tests for the experimental passages. Vocabulary pre- and posttests. The purpose of the vocabulary pretest was to assess students' state: of prior knowledge of the target words and the enabling concepts in each experimental passage, and, therefore, to provide a basis for assessing increments in word knowledge as a result of reading. A second purpose of the pretest was to provide an additional measure of topic familiarity as indicated by students' performance on the enabling concepts, and a measure of general vocabulary knowledge. Overall, the vocabulary pretest included 44 target words, 24 enabling concepts, and 10 general vocabulary items representing words at various frequency levels (Appendix A). The vocabulary pretest was in the form of a Contexts Test as proposed by Stallman, Pearson, Nagy, and Garcia (1990). The students were asked to respond Yes, No, or Don't Know to questions in which the target words were used. It has been shown that the contexts test has good reliability and provides an accurate assessment of levels of word knowledge (Stallman et al., 1990). For each vocabulary item, four questions including the target words were constructed. Half of the questions for each word were classified as easy items and were designed to test whether students knew the word's part of speech and general meaning. The other two questions were classified as hard items and were designed to assess whether more specific aspects of the
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word's meaning were known. These items were developed by considering the meaning differences that exist between a word and one or two synonyms or close associates (see Appendix B). The order of presentation of the individual questions was randomized, and two versions were created to eliminate order effects. There was an equal number of Yes and No correct responses across the test and across each item, and the scoring format was the same as that used for the comprehension tests. The vocabulary pretest was administered to 18 undergraduate students enrolled in an Educational Psychology course. Any test items for which there was less 80% agreement were modified or replaced. The two vocabulary posttests were the same as the pretest except that each posttest included only the target words and enabling concepts from one of the two experimental passages. Procedure
About two weeks before the main study, the vocabulary pretest was administered to all participants. The students wen: told that the investigator was interested in what they know about certain words. They were instructed to read each question carefully and to pay attention to the underlined word. For each question they were asked to decide if the information given was correct or if the word was used in an appropriate way. If they had no idea, then they could circle the Don't Know option. Following the instructions, the students worked with the investigator on three sample items. The scores on the general vocabulary and enabling concept section of the pretest were used to stratify students in each classroom in two groups matched on vocabulary knowledge so that each group would represent a range of vocabulary ability. In Session I students in each group studied an introductory passage randomly assigned to the group. The corresponding introductory passage test was administered immediately after the students had finished studying the introductions. In Session 2, all students regardless of the topic they had been familiarized with, read one of the experimental passages. The order of passage presentation was counterbalanced among students. Only one experimental test was presented per session because of time considerations. After all students had finished reading, the corresponding comprehension test and vocabulary posttest were administered in that order. In Session 3 the same steps were followed as in Session 2 except that each student read a different passage from the one read the day before and completed the appropriate comprehension test and vocabulary posttest. The three sessions took place on three consecutive days. Design and analysis
The data were analyzed with Hierarchical Regression procedures following the logic of mixed Analysis of Covariance. The students' scores on the vocabulary and comprehension tests were converted into proportions. The main dependent variable was Target Word Posttest, and Target Word Pretest, Enabling Concept Pretest, and Comprehension were treated as covariates. Target Word Pretest was entered first into the model to remove any variance associated with prior knowledge of the target words. Also, by entering Target Word Pretest first any remaining variance call be attributed to learning from context. Of major interest in the analysis were the effects of Enabling Concept Pretest and Comprehension, indicating any word learning from context due to prior knowledge of enabling concepts and passage comprehension level respectively. Because students came from three different classrooms, Class, coded in two orthogonal contrasts, was also included in the model as a between-subject variable, to remove any variance attributed to differences between the classrooms. To test the hypothesis that word learning
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from context is facilitated by the presence of an informative local context and by prior familiarization with the topic of the passage, Context Condition (informative vs. less-informative) and Familiarization (familiarized vs. not familiarized with topic) represented the two main within-subject factors and were entered next into the model. Because the reading of the passages took place on two different days, Day (Session I vs. Session 2) was also included in the model as a within-subject factor to account for any extraneous variance simply due to the day a particular experimental passage was read. The day a passage was read was counterbalanced among subjects. Also, Day was orthogonal to Familiarization, with half of the students familiarized with a particular topic and reading the corresponding passage on Session 2, one day after the familiarization treatment, and the rest of the students reading the corresponding passage on Session 3, two days after the familiarization treatment. Passage (Passage A vs, Passage B) was also included in the model as a within-subject variable to account for any word learning that could be attributed to passage differences. To examine whether Comprehension has a particular facilitative effect on the learning of words found in less-informative contexts, the effect of the interaction between Comprehension and Context Condition was also tested. The F ratio for each within-subject factor was calculated by taking into account the increment in R2 attributed to that factor: R2 change/(l-Model R2)
[(N-K-S-I )-1] where Model R2 equals the total variance accounted for by the final model, N equals the number of observations, K equals the total number of variables in the model, and S equals the number of subjects. This procedure yields a more conservative test for the within-subject factors. The dependent variable was regressed on the covariates, the between-subject factors, and finally the within-subject factors. Because of missing cases, only the data from 50 subjects were included in the analysis.
Results The means and standard deviations for Target Word Pretest, Target Word Posttest, Enabling Concept Pretest, and Enabling Concept Posttest are presented in Table I. It can be seen that there was an increase in word knowledge after reading the passages for both target words, 1(49)=-4.37, p
