Incidental Word Learning in Science Classes

Contemporary Educational Psychology 25, 184–211 (2000)doi:10.1006/ceps.1998.1001, available online at http://www.idealibrary.com on

Incidental Word Learning in Science Classes

Joanne F. Carlisle, Jane E. Fleming, and Beth Gudbrandsen

Department of Communication Sciences and Disorders, Northwestern University

The purpose of the project was to investigate students’ incidental word learningin science classes that depended on discussion and hands-on activities. In separatestudies, 4th- and 8th-grade students were given pretests and posttests that assesseddepth of knowledge of topical words used in a single unit. In both studies, studentsmade significant improvement in their knowledge of topical words; knowledge ofnontopical words did not improve. Students who started the unit with partial knowl-edge of topical words were likely to learn meanings appropriate for the unit. Depthof topical word knowledge also contributed significantly to improvement on a testof applied problems. While significant incidental word learning occurred over thescience units, students with little or no understanding of topical words at the outsettended to make limited progress in both word learning and learning the ideas andinformation of the unit. The educational implications are potentially serious andneed to be explored in further studies. 2000 Academic Press

School-age children learn thousands of words each year (Anderson &Freebody, 1981; Anglin, 1993; Baumann & Kameenui, 1991). Because thedepth and breadth of their vocabulary affect school learning, it is importantto understand the factors that influence growth in word knowledge. Althoughsome words are learned through explicit instruction, most are learned througha gradual process of inferring word meanings from uses in oral and writtencontexts. The emphasis in both research and educational practice is currentlyon the importance of reading for the development of vocabulary. For exam-ple, Fielding, Wilson, and Anderson (1984) stated that ‘‘there is reason tobelieve that beginning in about the third grade, reading becomes a moreimportant source of vocabulary growth than oral language for most people’’(p. 152).

The studies reported in this article were undertaken to address gaps in our

Address correspondence and reprint requests to Joanne Carlisle, Department of Communica-tion Sciences and Disorders, Northwestern University, 2299 North Campus Drive, Evanston,IL 60208-3560.

The studies reported in this article were made possible by a grant from the Spencer Founda-tion to the first author. We thank Glen Calin and Mark Fisch, and their students at Lake ForestCountry Day School and Haven Middle School for their assistance with this project. We alsothank Joseph Ruggiero and Addison Stone for their comments on drafts of the paper.

1840361-476X/00 $35.00Copyright 2000 by Academic PressAll rights of reproduction in any form reserved.

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knowledge about students’ learning of words in oral contexts. The intent wasnot to challenge the premise that reading is a major source of new wordsfor students to learn but to determine the extent to which significant growthin word knowledge occurs in school learning environments that do not de-pend on reading. If it is found that students’ word knowledge is fostered byoral and experiential learning contexts, the factors that affect word learningin these contexts need to be understood, as they do in reading.

We have chosen to focus on science classes that use inquiry- or activity-based instruction without significant dependence on reading materials. In-struction in such science classes includes various forms of interactive learn-ing, such as discussion, guided projects, and hands-on experiences; wordsare introduced as the currency to negotiate and exchange ideas about topicsand principles. The general question was whether students make significantgrowth in the depth of knowledge of these words during a specific unit ofstudy. Two studies were designed to address this question. In each, perfor-mance on pretests and posttests of topical words (i.e., words central to agiven unit of study) and nontopical words was compared to determinewhether students would show significant gains in the depth of their wordknowledge 1 month after the unit of study. Additionally, we asked whethersimilar results would be found in two separate studies for which grade level,curriculum, and instructional methods were different.

Incidental Word Learning

Incidental word learning in oral contexts makes up the bulk of preschoolchildren’s vocabulary growth, as has been demonstrated by studies of fastmapping and quick incidental learning (QUIL) (Carey, 1978; Rice, 1992).While written contexts may provide a rich source of new words for childrento learn (once they have acquired basic reading skills), children should beexpected to continue learning words from oral contexts as long as there isvariety in the words and word meanings they encounter. Oral contexts mayprovide more contextual support for word learning than written contexts; forexample, the listener can typically ask questions for clarification or elabora-tion, and there may also be a physical referent for the object or action named.Evidence that word knowledge can develop adequately without much expo-sure to or support from reading comes from a study of students with signifi-cant reading disabilities who nonetheless have average to above-average vo-cabularies (Fawcett & Nicolson, 1991). An additional consideration is thatsome students without specific disabilities appear to learn more from lis-tening than from reading (Carlisle & Felbinger, 1991). While Nagy, Herman,and Anderson (1985) demonstrated that learning words from reading ac-counts for a large portion of all the words children learn in a year, there arereasons to suppose that the same would be true for word learning in theenriched oral language contexts of many content-area courses.

186 CARLISLE, FLEMING, AND GUDBRANDSEN

As Baumann and Kameenui pointed out, ‘‘contexts can be generous orparsimonious, helpful or hostile in the amount of assistance they provide thereader or listener’’ (1991, p. 609). A context that is likely to foster wordlearning (1) must have new content that students have a reason for wantingor needing to understand and learn; and (2) must provide sufficiently ‘‘rich’’contextual support so that children unfamiliar with the meaning can inferthe meaning, at least in part, and children with partial knowledge have abasis for developing a more complete understanding (Herman, Anderson,Pearson, & Nagy, 1987; Jenkins, Stein, & Wysocki, 1984; Nagy et al., 1985).The requirement of rich contextual support might be met in academic coursessuch as science and social studies. In such domains new terminology is re-lated to learning ideas and bodies of knowledge, and words are the contentas well as the vehicle for learning ideas and information. Knowledge struc-tures and conceptual networks form the basis for units of instruction so thattopical words are used in relation to one another.

Teaching methods that involve inquiry-based or activity-based instructionmight be likely to stimulate incidental word learning. Interactive discussionand hands-on activities have been found to promote conceptual knowledgeby engagement with subject matter and application to real-world situations(Guzzetti, Snyder, Glass, & Gamas, 1993; Lewis & Linn, 1994) and so mightalso foster learning of topical words.

Depth of Word Knowledge

Incidental word learning refers not only to children’s acquisition of aninitial understanding of unfamiliar words, but also to their acquisition ofmore complete knowledge of familiar words, thus greater depth of knowl-edge. Incidental word learning involves a process of inferring the mean-ing of words from context; the term does not apply to situations in whichteachers provide explicit instruction about word meanings. The inferentialprocess that yields increasing depth of word knowledge may be particularlyimportant for school achievement. Nelson (1996) pointed out that childrenneed well-developed language capabilities to acquire knowledge in schoolcourses. It is through language that they acquire key concepts and ideas (i.e.,forms of knowledge); these are often not attainable through first-hand experi-ence. Superficial knowledge of words may be sufficient for basic comprehen-sion in familiar contexts, but knowledge of words based on a clear conceptionand grasp of semantic relations may be needed for students to understandor use words in unfamiliar contexts (e.g., study of new ideas and information)(Curtis, 1987; Graves, 1987; Kameenui, Dixon, & Carnine, 1987).

Breadth of word knowledge refers to the number of words children know,whereas depth of word knowledge refers to movement along a continuumextending from no knowledge to extensive, decontextualized knowledge ofa particular word. While children add to both the depth and breadth of their

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word knowledge as a natural part of their language learning, acquiring depthof word knowledge is nonetheless a challenging, incremental process. Deepknowledge may include knowledge of multiple meanings of words, meta-phorical uses, understanding of related concepts and words, and/or con-straints that affect appropriate word usage (e.g., Beck & McKeown, 1991).While the incremental process involves inferring meaning based on exposureto an unfamiliar word in a given context, the child must adjust or reconceptu-alize the word’s meaning, based on its use in other contexts. Nelson (1996)has remarked that ‘‘accrual of meaning outside the context of first use is aslow and uncertain process’’ (p. 140).

In science, children often must add to or replace their personal, experien-tial knowledge of word meanings to accommodate the meanings intended bythe teacher, often focused on the abstract conceptual and relational meaningsappropriate for learning in this domain (West & Pines, 1985). Meyerson,Ford, Jones, and Ward (1991) have argued that the goal of word learning inscience should be semantic knowledge: ‘‘Whether a factual, conceptual, orprocess approach is used for science instruction, children must be able touse the language of science in a meaningful way. This requires a depth ofunderstanding of the vocabulary of the discipline which transcends the recog-nition of a word and the contextual setting in which it is used’’ (p. 419).The problem is not restricted to young children. Gilbert, Watts, and Osborne(1985) demonstrated that older students bring a variety of kinds of knowl-edge to the study of science topics. Through an interview based on pictorialrepresentations of problems, they identified five types of ‘‘understanding’’of words (e.g., ‘‘force’’) that students used in their discussion of the prob-lems. For example, one type was ‘‘everyday language’’ (i.e., a word in sci-ence is given an interpretation from common experience) (see pp. 22–23).Van Keulen, Mulder, Goedhart, and Verdonk (1995) have shown that collegestudents do not always integrate uses and meanings appropriate for sciencecourses with everyday meanings. Lack of integration may affect word learn-ing and serve as a barrier to successful learning of the principles and ideasof the science course.

Concept Foundations and Domain Knowledge

The above discussion has emphasized the importance of depth of wordknowledge for learning in content areas. In turn, conceptual foundations andbackground knowledge in a given domain may affect acquisition of wordknowledge; that is, learning words and acquiring domain knowledge (includ-ing key concepts) appear to influence each other. Learning in science, as inother domains of knowledge, involves gradually constructing an understand-ing of a series of interrelated concepts and ideas that form the organizationof knowledge in a particular area. Children’s first theories about knowledgestructures, causes, and processes often involve creative and unexpected con-


nections between experiences (Nelson, 1996). Bloom (1992) has shown thatyoung children construct explanations of phenomena by piecing togetherwhatever prior knowledge and experience they can think to bring to bear onthe situation. His view is that ‘‘meaning includes not only semantic knowl-edge but also episodic knowledge, the products of various mental processes,interpretive frameworks, and emotions, values and aesthetics’’ (pp. 177–178).

Thus, children’s conceptual foundations of topical words and the waythese words are related to the organization of knowledge within that domainmight influence their learning over the course of a unit of study. Support forthis theory is suggested by Scruggs, Mastropieri, Bakken, and Brigham(1993), who found that students with learning disabilities had significantdifficulties learning science vocabulary, remembering only one or two words(out of eight tested) per week of instruction. The researchers suggested thatgaps in background knowledge may have affected the pace or depth of thestudents’ word learning. The results of other studies have also indicated thatthe more children know about a topic and the words used to discuss it, thegreater the likelihood that they will significantly expand their understandingof the words and concepts through new encounters in enriched contexts(Shefelbine, 1990).

Summary

Our review of the research literature suggested that there are reasons toexpect that students learn words incidentally from their content-area classes,but yielded no studies focused on this issue. Our purpose, therefore, was toinvestigate the extent to which students acquire a deeper understanding oftopical words incidentally through encounters with them in oral contexts andwhether improved understanding of topical words is related to learning ideasand information in a unit of study. We chose to study word learning in sci-ence classes because they fulfill two conditions that particularly foster inci-dental word learning: (1) availability of new words (or new meanings offamiliar words) and (2) an enriched and motivating learning environment.As a first exploration of incidental word learning in science classes, we choseto study intact classes taught by teachers who did not provide explicit vocab-ulary instruction or use reading as a basis for learning. In addition, we choseto observe but not manipulate instruction.

FIRST STUDY

The first study focused on fourth graders’ learning about conservation ofnatural resources. This unit of study was selected because it was unrelatedto other topics in the science curriculum that year or the previous year; thus,prior knowledge students brought to the unit of study was not based on recentschool instruction. The teacher used no science textbook and did not rely on

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reading as a means of learning. Instead, his instructional methods entailedintroduction of topics and issues through lecture, films, and discussion andemphasized group activities and individual projects.

For this study, we asked three questions: (a) Would students make signifi-cant gains in recognition and explanation of topical terms but not nontopicalterms? (b) Would breadth of word knowledge (i.e., a measure of generalreceptive vocabulary) account significantly for improvement in topical wordknowledge? and (c) Would students with some initial knowledge of topicalwords acquire significantly deeper word knowledge over the unit, whereasthe students with little or no initial understanding would not?

Method

Subjects

Subjects were 42 4th-graders, 15 males and 27 females, attending a private school in apredominantly white, middle- to upper middle-class suburb of Chicago. They were membersof two classes who constituted the entire 4th-grade of the school, with the exception of onestudent, who was absent for the pretests. Students ranged in age from 9.1 years to 10.6 yearsat the time of the pretest.

Information about the students’ achievement status was obtained from the Peabody PictureVocabulary Test—Revised (PPVT) (Dunn & Dunn, 1981), administered in 3rd grade, andthe Gates-MacGinitie Reading Test, Level 3 (MacGinitie & MacGinitie, 1989), Vocabularyand Comprehension subtests, administered in the 4th grade. The mean standard score on thePPVT was 113.2 (13.28 SD); the Gates–MacGinitie normal curve equivalents were 53.8 (16.0SD) for Vocabulary and 62.2 (15.5 SD) for Comprehension.

Materials

Two tests were developed and administered to each student: a multiple-choice recognitionvocabulary test and an open-ended word interview. The 4th-grade science teacher providedus with a description of his goals, materials, and activities as well as copies of assignments andworksheets he gave the students. Topical words were chosen from handouts and worksheets theteacher used to prepare the students to carry out their class projects and from his descriptionof the content of the unit. These words were used for both of the experimental measuresdiscussed below.

Recognition vocabulary. The recognition vocabulary test consisted of 35 items, including18 topical words (e.g., ‘‘recycle,’’ ‘‘natural resources’’) and 17 nontopical words, drawn fromunits on plant and animal life in 4th-grade science textbooks (e.g., ‘‘carnivore,’’ ‘‘hibernate’’).For each word, the student was asked to choose the one picture from a set of four picturesthat best showed the meaning of the word. Pictures were obtained from grade-school sciencetexts as well as from computer clip art and were evaluated by graduate students not participat-ing in the project to determine how well they portrayed the target words. Items were arrangedin random order.

Word interview. The word interview consisted of 10 words; 7 were topical words (e.g.,‘‘recycle,’’ ‘‘thermostat,’’ ‘‘insulation’’) and 3 were nontopical words (viz., ‘‘predator,’’ ‘‘di-gestion,’’ ‘‘reflection’’). Five of the words were among the 18 on the recognition vocabularytest. The student was asked to explain the meaning of each word (i.e., ‘‘What does the word

mean?’’). Prescribed prompts were used as needed to encourage the student to give afull explanation (e.g., ‘‘Tell me more about ’’ or ‘‘How does that happen?’’). Examin-


ers asked students to define scientific terms they used in their explanations (e.g., ‘‘When youuse the word evaporate, what does that mean?’’).

Procedures

Administration of tests. Pretesting took place several weeks before the start of the unit ofinstruction; posttesting took place 1 month after the unit was completed so that the durabilityof the students’ word learning could be evaluated. The pretest and posttest group administra-tions of the recognition vocabulary test took place on a single day in the students’ classrooms.Students were provided with individual test packets and answer sheets. Instructions for thetest were read to the students, and all subjects completed sample items. Test words were readaloud. Words were repeated as necessary.

The pretest and posttest word interview were each administered over a 5-day period. Stu-dents were interviewed individually in a quiet area of the school library. Responses were tape-recorded, and extensive notes were taken by the examiner.

Scoring procedures. The score on the recognition vocabulary test was the number of itemsanswered correctly, adjusted for guessing by subtracting one-fourth of the correct responsesfrom the total score. For the word interview, a system was developed to rank students’ explana-tion on a depth-of-understanding scale. The scale was designed to capture substantive changesin understanding of word meanings. Each response was given a score of 0 to 4 that reflectedthe accuracy, clarity, and completeness of understanding (see the Appendix). Because wordstend to have specific characteristics associated with their meanings, likely responses for eachword at each scoring level were formulated and used as a guide in the scoring process; toillustrate, responses for ‘‘conservation’’ are given in the Appendix. Two of the researchersindependently scored the entire set of word interviews; the correlation of the scores was .98for the pretest and .97 for the posttest, both p , .001. Disagreements were resolved throughdiscussion.

Science Classes

Classroom observations were conducted in order to document the types of activities in whichstudents were engaged. The science class met twice a week, and the unit lasted for 5 weeks.Five of the classes (50%) were observed by one of the researchers. Classroom sessions weretape-recorded, and extensive field notes were taken. Copies of handouts and other lesson mate-rials were also collected.

The teacher, who has taught middle school and junior high science classes for over 15 years,based his instructional approaches on the belief that students’ learning was facilitated throughengagement in activities. Thus, he gave the 4th-graders various projects to work on. For exam-ple, they completed a project on energy use, which involved collecting information such asthe number of light bulbs or appliances in their houses and the average cost of their families’monthly electric bills. Other projects included home water use, home heating and insulation,a home floor plan, and a water-cycle poster which compared the natural and human-madecycles. Students were provided with worksheets which included guidelines for a particularproject. Projects were worked on individually with the exception of the water-cycle posters,which pairs of students completed in class.

Instructional activities were varied. The teacher gave directions for activities and explainedbackground information. He also reviewed work on the current class project; on one occasionthis led to an informal student discussion of the project. A number of lab activities werecarried out in the classroom. For example, during one lab, students learned about variationin temperature by circulating around the room in small groups to record the temperatures ofthermometers located in various places, such as on the window or near the radiator. Duringthese labs, the teacher set up his own ‘‘station’’ at the front of the room for questions or

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TABLE 1Fourth Graders’ Pretest and Posttest Performances

on Topical and Nontopical Words on the Rec-ognition Vocabulary Test and the World Interview

Measure Pretest Posttest

RV Topical Words 10.8 (1.2) 11.6 (.98)RV Nontopical Words 11.5 (.14) 11.7 (.79)WI Topical Words 12.1 (5.1) 14.4 (5.2)WI Nontopical Words 4.8 (1.0) 5.2 (1.3)

Note. The recognition vocabulary (RV) scoreshave been corrected for guessing. Maximum possi-ble score for word interview (WI) Topical Words is28 and for WI Nontopical is 12. Standard deviationsare given in parentheses.

roamed around the room assisting students in collecting the appropriate information whennecessary. Videotapes or filmstrips were shown, with the teacher pausing from time to timeto ask questions or to clarify important points. Videos included Disney’s ‘‘Power and Energy,’’3-2-1 Contact’s ‘‘The Rotten Truth’’ about pollution, and a PBS special on recycling in Chi-cago. The class also saw a film on the human-made water cycle, including sewage treatmentand the water-filtration process.

We observed no formal vocabulary instruction. The teacher sometimes explained or statedmeanings for words he used in a lesson or activity, but most often simply used topical wordsin context, as is illustrated in the following excerpt, in which he used the word ‘‘insulation’’in his discussion of the home survey assignment:

Teacher: Go up into the attic and measure the thickness of the insulation. Now,before you all have fits . . . Put your hands down. You—if your parents say youcan do it, usually they’ll go with you. Um, you take a ruler, and you go upstairsinto the crawlspace, into the attic. There’s a trap door someplace in a closet or ina room. You get up there . . . there’s insulation, the pink stuff in there. It may notbe pink. What you do is take a ruler and you stick it down in here [referring to adiagram on the blackboard], and you measure how thick the insulation is. When Iwas younger, they put in six inches. What they want now is at least twelve inches.What’s the best insulation?Student: Air.Teacher: Air is the best insulation. Fiber is still good because it has a lot of airspaces in it, and by the way the pink stuff in there is spun glass. If you look undera microscope, it is razor sharp crystals.

Results

Improvement in Word Knowledge

The students’ mean scores on the recognition vocabulary test for topicaland nontopical words, corrected for guessing, and the mean raw scores fortopical and nontopical words on the word interview (pretest and posttest)are shown in Table 1. Our first question was whether the students madesignificant improvement in their ability to explain and to recognize the mean-


ings of topical words after the unit of study, in contrast to performance onnontopical words where no significant improvement was expected. For theword interview, the results of a two-way analysis of variance (ANOVA)showed a significant effect for word type (topical vs nontopical words), F(1,41) 5 14.94, p , .001, and for time of testing (pretest and posttest), F(1,41) 5 46.82, p , .001. The interaction was not significant, F(1, 41) 5 1.74,p 5 .19. For the recognition vocabulary task, the results of a two-wayANOVA showed a significant effect for word type, F(1, 40) 5 13.49, p ,.001, and for time of testing (pretest and posttest), F(1, 40) 5 5.30, p ,.001. The interaction was significant, F(1, 40) 5 10.44, p , .01. Plannedcontrasts showed that students improved over time on the topical words, F(1,40) 5 11.25, p , .01, but not on the nontopical words, F(1, 40) 5 .13,p 5 .72.

Contribution of Breadth of Vocabulary to Growth in Word Learning

The second question concerned the extent to which improvement in topicalword learning was affected by students’ breadth of vocabulary, assessed ona measure of receptive vocabulary (PPVT). Performance on the PPVT wassignificantly correlated to the pretest word interview (.52, p , .001) and theposttest word interview (.49, p , .01). A stepwise regression was carriedout with the posttest word interview (topical words) as the dependent vari-able. The pretest word interview (topical words) was entered first; this ac-counted for a very significant 69% of the variance, F(1, 38) 5 86.29, p ,.001. Then the PPVT was entered; together the variables accounted for 70%of the variance, F(2, 37) 5 42.77, p , .001. (One student did not take thePPVT.) The PPVT contributed a nonsignificant .4% to posttest word inter-view performance, after the effects of the pretest interview were accountedfor. Thus, while receptive vocabulary was related to amount of topical wordknowledge on the interviews, it did not explain the improvement the studentsmade from pretest to posttest.


The third question concerned the expectation that students with some ini-tial knowledge of the topical words would make significant gains in depthof word knowledge, whereas those who did not know the meanings of topicalwords would not. To answer this question, we divided the 4th-graders intothree groups (i.e., 14 students in the top third, middle third, and bottom third),based on performance on the pretest topical words (i.e., the sum of scoreson topical words from the recognition vocabulary test and interview).ANOVA and post hoc tests (Scheffe) showed that the groups differed signi-ficantly from one another, F(2, 39) 5 84.33, p , .001. Cross-tabulation ofthe responses by levels on the depth of knowledge scale (pretest and posttest),

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TABLE 24th-Grade Group Performances by Level on the Posttest Interview Based on Pretest Level

If Pretest Level 0 Level 1 Level 2 Level 3 Level 4

Top-third group5 0 1 (20.0%) 1 (20.0%) 0 (0.0%) 1 (20.0%) 2 (40.0%)5 1 1 (8.3%) 5 (41.7%) 3 (25.0%) 2 (16.7%) 1 (8.3%)5 2 1 (4.3%) 1 (4.3%) 11 (47.8%) 8 (34.9%) 2 (8.7%)5 3 0 (0.0%) 2 (5.0%) 11 (27.5%) 17 (42.5%) 10 (25.0%)5 4 0 (0.0%) 0 (0.0%) 2 (11.1%) 6 (33.3%) 10 (55.6%)

Middle-third group5 0 7 (43.7%) 5 (31.3%) 1 (6.3%) 2 (12.5%) 1 (6.3%)5 1 3 (12.5%) 3 (12.5%) 6 (25%) 9 (37.5%) 3 (12.5%)5 2 1 (2.7%) 4 (10.8%) 14 (37.8%) 16 (43.2%) 2 (5.4%)5 3 0 (0.0%) 0 (0.0%) 9 (45.0%) 10 (50.0%) 1 (5.0%)5 4 0 (0.0%) 0 (0.0%) 0 (0.0%) 1 (100%) 0 (0.0%)

Bottom-third group5 0 30 (69.8%) 4 (9.3%) 7 (16.3%) 2 (4.7%) 0 (0.0%)5 1 3 (13.0%) 9 (39.1%) 10 (43.5%) 1 (4.3%) 0 (0.0%)5 2 0 (0.0%) 2 (8.7%) 15 (65.2%) 6 (26.1%) 0 (0.0%)5 3 0 (0.0%) 1 (11.1%) 4 (44.4%) 4 (44.4%) 0 (0.0%)5 4 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0%) 0 (0.0%)

shown in Table 2, provided a basis for determining whether each group madesignificant changes from pretest (expected) to posttest (observed) perfor-mance. The results of chi-square analyses showed that for the top group,pretest and posttest responses on the levels of the scale did not differ signifi-cantly, with df 4, χ2 5 5.87, p 5 .21; pretest and posttest responses by leveldid differ significantly for the middle group, with df 4, χ2 5 61.09, p ,.001, and for the bottom group, with df 4, χ2 5 13.58, p , .01. Table 3shows these results.

For the middle and bottom group, post hoc analyses were used to deter-mine whether pretest and posttest scores at each level differed significantly.The normal-curve approximation of binomial values was calculated, usingthe formula provided by Runyon and Haber (1991). A significant changewas determined when the resulting number exceeded the critical value(z 5 . 2.56, p 5 .01). As Table 3 shows, for the middle group, there weresignificantly fewer level 1 responses on the posttest than the pretest andsignificantly more level 3 and 4 responses on the posttest than the pretest;for the bottom group, there were significantly more level 2 responses on theposttest.

Discussion

The results of the study show significant improvement in the recognitionof the meaning of words used in the study of conservation of energy in a


TABLE 3Changes in Responses by Level, Pretest to

Posttest, for 4th-Grade Groups

Level Posttest Pretest z

Top third0 3 5 20.921 9 12 20.922 27 23 0.953 34 40 21.234 25 18 1.83

Middle third0 11 16 21.371 12 24 22.82*2 30 37 21.463 38 20 4.51*4 7 1 6.03*

Bottom third0 33 43 22.041 16 23 21.672 36 23 3.10*3 13 9 1.404 0 0 —

* p , .05.

5-week unit of study. As we had expected, improvement in the students’recognition of the meaning of words not related to the topic did not improvesignificantly. The students also showed deeper levels of knowledge of mean-ings of topical but not nontopical words 1 month after completion of theunit. Thus, students improved not only in their recognition of topical wordsbut also on the more demanding task of explaining word meanings. As Shef-elbine (1990) had found in a reading study, we found a significant relation-ship between breadth of word knowledge and performance on the word inter-view, pretest and posttest. However, breadth of vocabulary did not explainthe students’ improvement in knowledge of topical words.

Depth of understanding was assessed by a scoring system with four levels,moving from no knowledge (level 0) to an explanation of the word meaningthat showed a grasp of underlying concepts and processes (level 4), as shownin the Appendix. With this system, a 4th-grader who explained the meaningof ‘‘recycle’’ by referring to plastic bins into which they put cans and bottlesreceived a lower level score than one who explained that reusing bottles andcans meant saving natural resources that would otherwise be used to makenew bottles and cans. We reasoned that, if the students benefited from expo-sure to words used in the context of a unit of science, their explanations of

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topical word meanings would shift from simple associations or experientialknowledge to understanding of meanings that reflected the word meaningsand conceptual framework of the unit of science. The following explanationof ‘‘conservation’’ (pretest and posttest) provides an example of improve-ment in depth of knowledge; this student progressed from no knowledge ofthe word to a reasonable grasp of meanings and uses of the word appropriatefor the unit, albeit delivered in a nonfluent manner:

(Pretest)Interviewer: What does the word ‘‘conservation’’ mean?Student: Um.Interviewer: Have you ever heard that word before?Student: Yeah, I’ve heard it but I don’t know what it means.Interviewer: Is there anything you can tell me about it?Student: It might mean like, it might mean kind of like you observe something. Idon’t know.

(Posttest) Interviewer: What does the word conservation mean?Student: Um, it means helping thin[gs] . . . helping nature and trying to conservenature, trying to keep it going and keep it alive.Interviewer: OK.Student: Like if somebody is planting a tree or something, it can—they can . . .they are usually doing conservation work or. . . .Interviewer: OK, you said that it’s trying to conserve nature. What does conservemean when you use that way?Student: Um, kind of protect or like keep it alive.Interviewer: OK.Student: Um . . . keep it going.Interviewer: Good. OK, what else can you tell me about. . . .Student: Or help . . . helping, and it’s not only planting a tree, it’s like, like, wellif you’re trying to conserve water, you usually are not trying, if you see a drain ora drippy faucet, you turn it off or you get it fixed. You don’t leave the water running,and you don’t take too-long showers.Interviewer: OK. So when you say you want to conserve water, what does conservemean when you say that?Student: Um, save water.Interviewer: OK.

Comparison of pretest and posttest topical word knowledge showed thatthe middle-third group made significant changes on the depth-of-knowledgelevels, but the top and bottom groups did not. Further analysis showed thatthe middle group gave significantly fewer responses at level 1 and moreresponses at levels 3 and 4, as Table 3 shows. The type of dramatic growthillustrated in the explanation of ‘‘conservation’’ given above was most evi-dent for the middle group. As Table 2 shows, 38% of their pretest level 1responses and 43% of their pretest level 2 responses were level 3 responseson the posttest (level 3 indicating an accurate, clear grasp of the word’smeaning in the science unit, as the Appendix shows). Examination of theshifts in levels from pretest to posttest shown in Table 2 indicates that havingsome idea about or experience with the meaning of a topical word enhances


the likelihood that a student will acquire a meaning suitable for the scienceunit. Somewhat similarly, Shefelbine (1990) found that having an initial con-cept of a word meaning provided a basis for significant incidental word learn-ing during reading.

In contrast to the middle group, the students in the bottom third faced thedifficulty of knowing little or nothing about most of the topical words. Infact, 67% of their pretest responses were at levels 0 or 1 (showing no knowl-edge or a simple association). For them, significant growth was most evidentat level 2 (showing partial knowledge of the word meaning); a third of theirposttest responses were at this level. In fact, about 44% of the level 1 re-sponses moved up to level 2 responses on the posttest. Nonetheless, bottom-third students were seldom able to show anything beyond partial wordknowledge by the end of the unit—only 13% of their posttest responses wereat level 3 and none were at level 4. For this group, in particular, the overalllack of knowledge of topical words may have affected word learning. Thefewer topical words a student knows at the outset, the more likely it is thathe or she will have trouble inferring meaning of a particular word from dis-cussion in class.

Because our analysis of growth depended on a scoring system that rankedlevels of word knowledge, we were concerned that ceiling effects might haveled to an underestimation of the growth of the top group. Consequently, wecarried out a post hoc analysis of relative gain, following the procedure usedby Shefelbine (1990), which shows improvement in relation to the amountthe student did not know at the outset. Relative gain is defined as the differ-ence between the posttest and the pretest topical word scores divided by theamount to be learned: Rel Gain 5 (Posttest 2 Pretest)/(Total Possible PretestScore). The results of this analysis showed that the relative gain was .08 (.19SD) for the top group, .22 (.20 SD) for the middle group, and .11 (.14 SD)for the bottom group. An ANOVA showed that the three groups did notdiffer significantly in relative gain, F(2, 39) 5 2.39, p 5 .10. In interpretingthese results, it is important to remember that our scoring system involvespredetermined ranks; we have no reason to assume that the growth that isimplied by movement from one level to another is comparable in kind. Infact, the cognitive and/or linguistic challenges faced by students who alreadyknow the scientific meaning of words (level 3) but still can develop a fullunderstanding of underlying processes (level 4) may be quite different fromthe challenges faced by students who have an experiential understanding ofterms like ‘‘pollution’’ but lack understanding of the scientific meanings.

In summary, while there was significant growth for the whole class, pretestto posttest, not all students achieved a level of word knowledge that reflectedunderstanding of word meanings relevant for the unit of study they had com-pleted 1 month earlier. These results, like those of studies of incidental wordlearning during reading (e.g., Nagy et al., 1985), suggest that enriched con-

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texts facilitate word learning. However, even though the context for learningwas supportive, the bottom-third group did not benefit extensively. Havinglimited understanding of topical words at the outset, these students tended toshow only experiential knowledge or partial understanding of word meaningsafter the unit. Also striking was their inability to define words they had tounderstand to do the assigned projects. For example, many could not tell uswhat a thermostat was, even though they had completed the home projectson conservation of heat. Shefelbine (1990) and Curtis (1987) also found thatstudents with low vocabulary differed in the quality of their definitions. Cur-tis found that low-scorers defined words in specific contexts, while high-scorers tended to give more abstract, decontextualized definitions.

As we completed this study, we were struck by the difficulty of the wordinterview task. Explaining the meanings of science terms is a decontextua-lized language task which may tax the metalinguistic capabilities of many4th-graders. In many cases, they were aware of their own struggles to explainwords and often engaged in a process of constructing an explanation bypatching together whatever knowledge they could bring to bear, as Nelson(1996) suggested. Their explanations showed that meaning to them was var-ied in nature. Often it involved a specific instance of use or a personal experi-ence, and only sometimes was it presented in terms of abstract ideas andrelationships. These varied kinds of meaning that students held were reminis-cent of the view of Bloom (1992). We wondered if older students mightperform better on the word interview, particularly in explaining abstractwords, like ‘‘conservation.’’

The results of the study raised other questions which seemed importantto address in a second study. One concerned the nature of the curriculum.Would the results be different if the science curriculum was sequential, build-ing from one topic to the next, instead of based on a discrete unit? A secondquestion was whether depth of knowledge of topical words was related tostudents’ learning of the concepts and ideas central to the unit of study, asfor example in the ability to solve applied problems.

SECOND STUDY

The second study focused on 8th-graders in a unified, sequential curricu-lum in physical science; each unit built on the concepts and information thatpreceded it. For this reason, we expected the students to have recently ac-quired background knowledge and familiarity with at least some of the termsused to discuss information and ideas in the unit, the content of which wasseparation of substances. We thought it was important to determine whether,under these circumstances, there would be significant growth in topical wordknowledge over the unit of study and whether growth in word knowledgewas related to learning course content. Our questions were (a) Would stu-dents demonstrate greater improvement in their understanding of the topical


words than the nontopical words 1 month after the unit of study? (b) Towhat extent does depth of knowledge of topical words contribute to posttestperformance on applied problems, when controlled for pretest performanceon applied problems? and (c) Would students who initially had partial under-standing of the meaning of topical words show significant growth by the endof the unit, whereas students who lacked this knowledge would not?

Method

Subjects

Subjects were 45 8th-grade students, 22 males and 23 females, attending a public middleschool in a large suburb of Chicago. The school is attended predominantly by white andAfrican-American students (54 and 43% respectively). All students were members of one oftwo sections of a physical science course taught by the same teacher. Twenty-six of 28 studentsfrom a morning class and 19 of 24 students from an afternoon class participated in the project;the 7 students in these classes who did not participate were absent from school at the timeof the pretest. Students were all 13 or 14 years of age.

Stanford Achievement Test, Eighth Edition, quartiles in Reading and Mathematics wereavailable for 43 of the 45 students; the mean quartile for Reading was 2.5 (.63 SD) and forMath was 2.3 (.72 SD). The two classes did not differ significantly on either achievementsubtests or the experimental measures, p . .05.

Materials

Two tasks were used to investigate the students’ understanding of the words and scienceconcepts they would encounter in the unit of study. The first was a word interview, similarto the one used in the previous study. The second was a set of five applied problems. Thecontent and instructional activities that would be part of the unit on separation of substanceswere discussed with the science teacher in order to choose appropriate words and designapplied problems.

Word interview. The word interview consisted of 11 items, including 7 topical words (e.g.,‘‘distillation,’’ ‘‘crystallization,’’ ‘‘condensation’’) and 4 nontopical words (e.g., ‘‘conduc-tion,’’ ‘‘resonance’’). The latter were culled from units on heat and sound in junior highscience textbooks. The topical and nontopical words were randomly ordered and presentedin a different order on the pretest and posttest.

The word interviews were open-ended, each item beginning with the query, ‘‘What doesthe word mean?’’ The examiners used any of five scripted prompts as needed to helpthe student provide as complete an explanation as possible, including a follow-up queryif the student said he/she did not know the word (‘‘Have you heard that word before?’’); aquery to focus the student on an appropriate meaning (‘‘That’s one meaning; do you knowanother?’’); a request for clarification (‘‘What do you mean when you say ’’); a requestfor elaboration (‘‘Tell me more.’’); and a request for further explanation of processes (‘‘Howdoes that happen?’’ or ‘‘Why does that happen?’’). In addition, guidelines were developedto evaluate depth of knowledge for each word; these guidelines were used in selecting promptsduring administration of the word interview and in scoring the students’ responses. (See guide-lines for ‘‘condensation’’ in the Appendix.)

Applied problems. A set of five applied problems was used to assess the students’ learningof concepts, principles, and processes in the unit (e.g., methods to separate mixtures, character-istic properties as a means of identifying substances). In some cases it was necessary to use

WORD LEARNING 199

a topical word in stating the problem in order to avoid awkward wording, but the solution ofthe problem did not require the explanation of word meanings (e.g., ‘‘You have a mixture ofsand and sugar in a box. How could you separate the two?’’). The applications involvedconcrete and often everyday materials and situations.

Procedures

Test administration. Both pretests and posttests were administered individually in a smallroom by the researchers or a trained research assistant over a 2-day period. After a briefintroduction to the project, the student was asked several questions about study habits andinterest in science and then was given the word interview and the applied problems; the sessionlasted approximately 20 min. Posttests were carried out about 5 weeks after the unit wascompleted. For the posttest, the applied problems were administered before the word interviewfor 20 randomly selected subjects. The order of administration of these tasks did not signifi-cantly affect students’ performance, t (43) 5 .461, p 5 .647.

Scoring procedures. Two researchers independently scored the entire set of responses tothe word interview and applied problems. For the word interview, the guidelines used for testadministration also provided guidelines for scoring (see Appendix for criteria for ‘‘condensa-tion’’); each item was given a score on a scale of 0 to 4 points, depending on the depth ofknowledge evident in the student’s response. For the applied problems, points were earnedon the basis of the amount of accurate information given by the student; complete answersranged from 2 points on one problem to 4 points on several others, based on specific criteriafor each problem. For example, students received 1 point by saying that water could be addedto the sand and sugar mixture, so that the sugar would dissolve and the sand would be left;an additional point was given if the student could explain how to recover the sugar from thewater. Across the five problems, the total possible score was 14. For the word interviews, thecorrelation of the scores assigned by the raters was .93 for the pretest and .96 for the posttest;for the applied problems, the correlation of the raters’ scores was .90 for the pretest and .97for the posttest responses, all p , .001. All differences in scoring were resolved by discussion.

Science Classes

The teacher, who has a master’s degree and has been teaching for over 20 years, used aninquiry-based approach to teaching physical science without reliance on a textbook. He taughtstudents the scientific method by having them use it themselves; the class discussed problems,generated hypotheses, and conducted experiments in groups of two to four students. Eachstudent wrote up the results of the experiments, including sections on hypotheses, materials,procedures, results, and conclusions.

Classroom observations were conducted to document the types of activities in which stu-dents were engaged and to provide information about the teachers’ use of topical vocabulary.The unit of study on separation of substances occupied 18 class periods. A graduate researchassistant or one of the researchers attended 13 of the morning classes (73%); 8 of the afternoonclasses were also observed to confirm the teacher’s statement that the instruction did not differin the two classes. Other planned observations were canceled because the teacher used theclass period for testing or other purposes not related to this study. Classes were audiotaped,and running records were taken and transcribed.

Analysis of the transcripts showed that the teacher tended to explain processes or principlesusing topical words, often in conjunction with one another, but did not provide explicit defini-tions or require the students to learn the words. The following excerpt is offered as an exampleof his discourse style. This lesson started with discussion of graphing the results from theprevious day’s experiment on distillation:


Teacher: We’ve got to write results for this and preview the next experiments, sothere’s no time to waste. Those having trouble graphing could have stayed yesterdayto get help. I was here until around 4. [Pulls down screen in front of room and putsa graph on the overhead.] Not all graphs will be identical, but some things will besimilar. What would be common to all the experiments?Student 1: How many plateaus there are.Student 2: Boiling point.Teacher: Be more specific.Student 3: All go up and then go flat.Teacher: Yes, all have the same basic shape—flat in the beginning, then it goes up,and then it goes flat. All have two flat spots. [Draws example on chalk board.] Whyis there a flat spot and then a big jump?Student: There’s one liquid and it boils up, and then there’s another liquid and itboils.Teacher: What causes the rapid increase here? The thermometer was not in theliquid. When the liquid boils, the vapor is hitting the thermometer at the top of thetube. The important thing is you see two plateaus. What does that tell you?Student: There’s two liquids.

The teacher and students discussed the different boiling points of the liquids; he then remindedthem that when all of the first liquid had been condensed, they needed to change test tubesto collect the second liquid.

The transcripts were analyzed to determine the amount of extended discourse (defined asmore than 1 min per class) that was devoted to each topical word in the interview. This analysisshowed that all of the topical words were mentioned at least once and usually in more thanone class session. Most were used in extended discourse; the two exceptions were ‘‘crystalliza-tion’’ and ‘‘condensation.’’ We asked the teacher after the unit of study whether he had usedeach of the topical words as part of his discussion of separation of substances; he assured usthat he had had to use each of them because they were needed to convey ideas in the unit.These analyses only partially document word use in the class, not only because we did notobserve every class meeting but also because a large part of the class time was devoted toexperiments where students worked in small groups and where discussions among students(or with the teacher) were not audible. Nonetheless, they do suggest that word learning wasincidental in the sense that the students needed to infer the meaning of topical words fromthe discourse and graphic displays (e.g., diagrams).

Results

Improvement on Topical Words

Table 4 shows the 8th-graders’ performance on the word interview andthe applied problems, pretest and posttest, presented as percentage of oppor-tunity. The first question was whether the 8th-graders showed significantimprovement in performance on topical words but not on the nontopicalwords on the posttest. The results of a two-way ANOVA showed a significanteffect for word type, F(1, 44) 5 4.81, p , .05, and for time of testing, F(1,44) 5 389.18, p , .001. The interaction was significant, F(1, 44) 5 56.26,p , .001. Post hoc analyses showed that performance on the topical wordsimproved from pretest to posttest words, F(1, 44) 5 144.28, p , .001. Per-formance on the nontopical words dropped from pretest to posttest, F(1,44) 5 317.74, p , .001.

WORD LEARNING 201

TABLE 48th-Graders’ Scores on the Word Interview and

Applied Problems Tasks Expressed as Percentage ofPossible Points

Pretest Posttest

Word InterviewTopical Words 38.7 (14.3) 51.2 (15.4)Nontopical Words 17.0 (12.3) 9.4 (13.6)

Applied Problems 24.4 (14.4) 35.6 (21.0)

Note. Standard deviations are given in paren-theses.

TABLE 5Correlations of Pretest and Posttest Performances on the Word Interview (Topical) and

Applied Problems

Pretest WI Posttest WI Pretest AP Posttest AP

Pretest WI —Posttest WI .66* —Pretest AP .64* .56* —Posttest AP .60* .70* .74* —

Note. WI, Word Interview; AP, Applied Problems.* p , .001.

TABLE 6Contribution of Posttest Topical Words to Posttest Applied Problems Performance,

Accounting for the Effects of the Applied Problems Pretest

Step/variable Mult-R2 R2 Change F value p level

1. Pretest AP .540 — 50.52 .0002. Posttest Top Words .660 .120 14.85 .000

Note. AP, Applied Problems; Top, Topical.

Contribution of Depth of Word Knowledge to Applied Problems

The students’ performance on the applied problems posttest was signifi-cantly higher than on the pretest, t(44) 5 5.23, p , .001 (see Table 4). Inaddition, their performance on the applied problems was significantly relatedto their performance on the word interview, as Table 5 shows. To determinewhether depth of word knowledge contributed to achievement on the appliedproblems, a stepwise regression was carried out with the applied problemsposttest as the dependent variable; Table 6 shows these results. The pretestapplied problems, entered first to control for differences in initial perfor-


TABLE 78th-Graders’ Levels of Performance on Posttest Interview Based on Pretest Level

If Pretest Level 0 Level 1 Level 2 Level 3 Level 4

Top-third group5 0 1 (7.7%) 4 (30.8%) 2 (15.4%) 4 (30.8%) 2 (15.4%)5 1 0 (0.0%) 2 (20.0%) 4 (40.0%) 3 (30.0%) 1 (10.0%)5 2 0 (0.0%) 1 (2.0%) 32 (62.7%) 14 (27.5%) 4 (7.8%)5 3 1 (4.0%) 0 (0.0%) 9 (36.0%) 11 (44.0%) 4 (7.8%)5 4 0 (0.0%) 0 (0.0%) 1 (16.7%) 3 (50.0%) 2(33.3%)

Middle-third group5 0 4 (22.2%) 5 (27.8%) 3 (16.7%) 5 (27.8%) 1 (5.6%)5 1 1 (4.3%) 8 (34.8%) 9 (39.1%) 5 (21.7%) 0 (0.0%)5 2 3 (5.8%) 3 (5.8%) 34 (65.4%) 6 (11.5%) 6 (11.5%)5 3 0 (0.0%) 2 (16.7%) 5 (41.7%) 5 (41.7%) 0 (0.0%)5 4 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%)

Bottom-third group5 0 17 (37.0%) 8 (17.4%) 11 (23.9%) 7 (15.2%) 3 (6.5%)5 1 3 (13.6%) 7 (31.8%) 8 (36.4%) 3 (13.6%) 1 (4.5%)5 2 0 (0.0%) 5 (14.7%) 25 (73.5%) 3 (8.8%) 1 (2.9%)5 3 0 (0.0%) 0 (0.0%) 2 (66.7%) 1 (33.3%) 0 (0.0%)5 4 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%)

mance, accounted for 54% of the variance. The posttest interview (topicalwords) was then entered and accounted for an additional 12% of the variance,a significant contribution. Together these variables accounted for 66% of thevariance, F(2, 42) 5 40.82, p , .001.


The final question was whether students who initially had partial under-standing of the meaning of topical words would show significant growth bythe end of the unit, whereas students who lacked this knowledge would not.The class was divided into top-third, middle-third, and bottom-third groups(15 students in each), based on pretest performance on the word interview(topical words) and the applied problems. ANOVA and post hoc tests(Scheffe) showed that these groups differed significantly from each other onpretest topical knowledge, F(2, 42) 5 67.91, p , .001. A cross-tabulationwas constructed of responses by levels on the pretest and posttest for eachgroup (see Table 7). The results of chi-square analyses showed that, overall,pretest and posttest responses on the depth of understanding scale differedsignificantly for the top group, with df 4, χ2 5 22.55, p , .001; for themiddle group, with df 4, χ2 5 13.41, p , .01; and for the bottom group,with df 4, χ2 5 59.45, p , .001. Table 8 shows these results.

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TABLE 8Changes in Responses by Level, Pretest to

Posttest, for 8th-Grade Groups

Level Posttest Pretest z

Top third0 2 13 23.30*1 7 10 21.002 48 51 2.593 35 25 2.284 13 6 2.88*

Middle third0 8 18 22.63*1 18 23 21.182 51 52 2.143 21 12 2.81*4 7 0 —

Bottom third0 20 46 25.10*1 20 22 2.472 46 34 2.503 14 3 6.47*4 5 0 —

* p , .05.

Post hoc analyses were used to determine whether for each group observed(posttest) and expected (pretest) scores differed significantly at each level.The normal-curve approximation of binomial values was calculated (Run-yon & Haber, 1991). A significant change was determined when the resultingnumber exceeded the critical value (z 5 . 2.56, p 5 .01). As Table 8 shows,for the top group, the number of responses at level 0 decreased significantly,while the number of responses at level 4 increased significantly; for the mid-dle and bottom groups, the number of responses at level 0 decreased signifi-cantly while the number at level 3 increased significantly.

Discussion

The results of this study showed that 8th-graders who were studying sci-ence in a unified curriculum showed significant growth in their understandingof words used in a unit on separation of substances 1 month after the unitof study. In contrast, they made no progress on nontopical words. A secondfinding was that the 8th-graders’ level of knowledge of the topical wordscontributed significantly to their improvement in solving problems, usinginformation from the science unit. Their topical interview accounted for asignificant 12% of the variance of the applied problems posttest, after the


effects of the applied problems pretest were statistically controlled. Thisfinding suggests that the students’ level of word knowledge was related tothe acquisition of ideas and concepts needed to solve applied problems; itsupports the views of Nelson (1996), West and Pines (1985), and Meyersonet al. (1991), all of whom have argued that students need a sufficiently stronglanguage base to acquire domain knowledge in courses such as science.

Because of what is apparently a close connection between word learningand mastery of concepts and ideas, we examined cross-lag correlations tosee if we could determine a pattern of relationships over time. The correlationof the pretest interview (topical words) and the posttest applied problems,representing the extent to which prior word knowledge contributes to knowl-edge of concepts and ideas, was significant (r 5 .61, p , .001). So was thecorrelation of pretest applied problems and posttest topical words, represent-ing the extent to which prior conceptual knowledge contributes to growthof word knowledge (r 5 .56, p ,.001). Because both correlations were mod-erately strong and of similar magnitude, it appears that the structure andrelation of ideas and concepts and the words used to discuss them are learnedinteractively.

The close relationship of topical word learning and learning of coursecontent may be particularly relevant when we consider the relative improve-ment on the word interview made by students at different levels of topicalknowledge on the pretest. The results showed that all three groups madesignificant improvement on the depth of understanding scale over time. Allthree groups experienced a significant decrease in the number of responsesthat showed no knowledge of word meaning (level 0). The top-third groupmade significant gains in responses for which they gave a full explanation,showing understanding of word meanings as they were used in the scienceunit, along with a fairly complete understanding of underlying concepts andprocesses (level 4). The middle-third and bottom-third groups made signifi-cant improvement in responses that reflected the scientific meaning of aword, even if it was not fully understood (level 3). The influence of theparticular use (or meaning) of a word in the science course on students’ wordknowledge is illustrated by one student’s pretest and posttest explanationsof ‘‘residue’’:

(Pretest) Interviewer: What does the word residue mean?Student: Residue?Interviewer: Uh-huh.Student: Like um, smell and odor, I guess.Interviewer: Okay, can you tell me more?Student: Uh, that’s about it.Interviewer: OK.

(Posttest) Interviewer: What does the word residue mean?Student: It’s something left behind or a part that was left behind.

WORD LEARNING 205

Interviewer: Tell me more.Student: I can give you an example.Interviewer: That would be great.Student: If you have ink and you try to separate it and see what it is mixed with,you could take a filter or whatever and filter it with water or whatever you’re tryingto separate it from. Whatever you have left in your filter is your residue.Interviewer: Great. That’s very good. Do you know why it happens that way?Student: I’m not sure. Maybe it’s just left behind.Interviewer: Why would it be left behind? That’s what I’m asking.Student: I’m not sure.

For the bottom-third group, the significant growth found at level 3 needs tointerpreted cautiously, as it reflects changes in very few responses overall(specifically, 3 responses at level 3 on the pretest to 14 on the posttest, asTable 8 shows).

Although the results indicate significant growth for the top-third group,we carried out an analysis of relative growth to make sure that their improve-ment was not underestimated because of ceiling effects (Shefelbine, 1990).This procedure takes into account the amount of word knowledge that thestudents did not have at the outset. The results showed that the relative gainfor the top group was .18 (.18 SD), for the middle group was .19 (.22 SD),and for the bottom group was .23 (.17 SD). An ANOVA showed that thegroups did not differ significantly in relative growth, F(2, 42) 5 .34, p 5 .71.They made comparable progress, given different levels of word knowledgeat the outset. As noted earlier, our scoring system (ranking levels of wordknowledge) may not fairly capture the linguistic and cognitive challengesinvolved in improving word knowledge; movement from one level to anothermay involve different kinds or degrees of learning.

Even though all three groups made significant progress, analysis of pretestand posttest responses by level (shown in the cross-tabulation in Table 7)indicated that the groups differed markedly in their word knowledge. Thedifference scores that were the focus of the analyses reported above do nottell the whole story. For example, for the top group, the majority of responseson the pretest and posttest ranged from levels 2 (partial word knowledge)through 4 (complete understanding of the scientific term), whereas most re-sponses (pretest and posttest) for the bottom group ranged from levels 0(no knowledge) to 2 (partial knowledge). For the bottom group 37% of theresponses that started at level 0 remained at level 0 (as compared to 22%for the middle group and 8% for the top group). For the bottom group, only18% of the posttest responses were at levels 3 or 4, levels which reflectword meanings appropriate for the science unit (as compared to 27% of theresponses for the middle group and 46% for the top group). Thus, whilethe bottom-third group experienced growth over time, most of their posttestresponses did not show a grasp of word meanings appropriate for the scienceunit, and their limitation in word learning went hand-in-hand with difficulties


in learning to solve the applied problems. These students might have experi-enced the same kind of difficulty on the next unit of study, since each unitbuilt on the content and vocabulary of the unit that preceded it.

GENERAL DISCUSSION

Together the results of the two studies show that incidental word learningtook place in oral contexts, specifically in science classes that depended ondiscussion and activities for learning. Significant improvement in knowledgeof topical words was found for both 4th- and 8th-graders in science classesthat differed in terms of curriculum (discrete versus sequential units) andtypes of learning experiences (individual versus group projects). Two otherfindings may serve to clarify the incidental word learning in these classes.First, growth was made not only in recognition of the meanings of topicalwords but also in the quality of explanations of word meanings, a more strin-gent test of word knowledge. Second, performance on a standardized test ofrecognition vocabulary, which arguably is a measure of breadth of vocabu-lary, did not explain improvement on the topical words, even though perfor-mance on this measure was significantly related to the students’ scores onthe pretest and posttest interviews. Finally, it seems clear that the significantgrowth in word knowledge experienced by the students overall is not due toincidental word learning apart from the context of the science class becausesignificant growth was not made on words drawn from other areas of science.

The incidental word-learning process entails coming to an understandingof a word’s meaning as it is used in a particular context. Students mightlearn some words for the first time, but might also be expected to understandmore complex or abstract meanings for words they had originally learnedin their everyday lives in order to accommodate the meanings intended bythe teacher. For example, on the pretest, one 8th-grader, when asked about‘‘distillation,’’ remarked that her mother used distilled water in her iron, butshe could not explain what distilled water was. Her exposure to the word‘‘distillation’’ in the science experiments led her to a partial understandingof the process. As Tables 2 and 7 show, learning the abstract terms waschallenging, and improvement generally meant small, not dramatic changesin levels of word knowledge. Instances in which the student started with noknowledge and ended up with a full understanding of the scientist’s meaningwere rare. Of the responses that showed no knowledge of the word at pretest,only 4.7% of the 4th-graders and 8.0% of the 8th-graders demonstrated afull understanding of topical words, as they pertained to the unit of study,on the posttest word interview. It is not surprising, therefore, that studentsstarting the unit with no knowledge of many topical words usually did notend up with a sound understanding of their scientific meanings.

Unlike the students with no initial knowledge of topical words, the stu-dents who knew something about the topical words at the outset were ex-

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pected to show significant growth in word knowledge; this expectation wasbased on previous findings from studies of incidental word learning duringreading (e.g., Shefelbine, 1990). Our results partially support this expecta-tion. Results for the 4th-graders showed significant overall improvement inlevels of topical word knowledge for the middle-third and bottom-thirdgroups. However, follow-up analysis showed that the middle-third studentsgenerally started with some initial knowledge of topical words and werelikely to provide definitions that reflected scientific uses and meanings onthe posttest. In contrast, the bottom-third students usually started the unitwith little or no knowledge of topical words and were not very likely toacquire a level of understanding appropriate for the science unit. Results ofthe eighth-grade study showed that all three groups, based on pretest wordknowledge, made significant changes in levels of topical word knowledge.However, further analysis shows different patterns of performance for thethree groups. In particular, as Table 7 shows, the bottom-third group madeimprovement because they started with very poor topical word knowledgeand were able to give partial definitions of topical words by the end. Incontrast, the students in the middle- and top-third groups made significantprogress by moving from partial knowledge to fairly complete explanationsof scientific meanings.

Along with improvement in word learning, the results showed a significantrelationship between the depth of word knowledge students achieved andtheir performance on a task that required application of ideas and concepts.In fact, topical word learning contributed significantly to the improvementthat students made on the applied problems, pretest to posttest. Cross-lagcorrelations further demonstrated that growth in concepts and word knowl-edge mutually supported one another. These results suggest that acquisitionof content-area knowledge depends on the integration of word knowledgeand the concepts that organize or form the structural links among the ideaswithin the domain of knowledge.

The connection between growth in concepts and word knowledge suggestsa reason to be concerned about the science learning of students with littleor no understanding of topical words at the start of a science unit. It alsosuggests one instructional modification teachers might consider. Because formany students, incidental word learning did not result in sound knowledgeof topical terms and may have been a barrier to learning course content, it ispossible that word learning should be intentional, not just incidental. Focuseddiscussion of the meanings of key terms and a concerted effort to bridgeinitial understandings of word meanings and their scientific uses might helpstudents learn the ideas and information of the unit. One model is found ina study by Lewis and Linn (1994), who found that initial instruction builton students’ ‘‘intuitions’’ about word meanings led to improvements in theirunderstanding of the concepts about heat. A similar view is expressed by


Nagy et al. (1987) on the basis of their findings: ‘‘Complete explanationsof key concepts appear to be critical to nonexpert middle-grade students intheir acquiring vocabulary knowledge incidentally from expositions’’ (p.281).

A limitation of our studies was that we could not provide full documenta-tion of the use of language in the classrooms. Now that it is evident thatsignificant learning occurs through the oral and experiential contexts of sci-ence classes, further study is clearly needed to investigate the factors thataffect word learning in not only science but also other content-area courses.The cognitive and linguistic capabilities of students and the instructionalmethods may affect the extent of word learning. Study of the teachers’ intro-duction of and use of topical words might also be important. A key questionis why some students do not pick up on the meaning intended by the teacherand needed to acquire domain knowledge.

APPENDIX

Scoring Criteria for Word Interview, Study One

A. Definitions were scored according to the following criteria:0—None, ‘‘don’t know.’’1—Partial, very general knowledge; an accurate association.2—Accurate but limited information; fragmented, unclear and incom-

plete.3—Accurate and clear, but not complete (lacking conceptual founda-

tion).4—Accurate, clear, and complete; conceptual/semantic grasp evident.

B. Example of word-specific criteria used to score responses to ‘‘conserva-tion’’:

1—Simple association (e.g., ‘‘it has something to do with plants’’).2—Mention of helping or saving nature; no explanation (e.g., ‘‘to help

nature or something’’).3—Mention of preservation from destruction or loss, or official protec-

tion of natural resources (e.g., ‘‘to restore things and save theminstead of chopping down trees’’).

4—Clear and complete explanation of the preservation or protection ofnatural resources (e.g., ‘‘to save, like to conserve the rain forest;it’s disappearing and there’s not much left, so people want to saveit’’).

Scoring Criteria for Word Interview, Study Two

A. Definitions were scored according to the following criteria:0—No knowledge or incorrect knowledge.1—An association of the word; an example or simple episode.

WORD LEARNING 209

2—A synonym; a partial definition or explanation; experiential knowl-edge.

3—Some semantic/conceptual basis; partial explanation of the proper-ties or process.

4—A clear and integrated explanation of concept foundations and con-straints of meaning and use.

B. Guidelines for scoring ‘‘condensation’’ by levels1—Example or episode (e.g., ‘‘Like the mist on the mirror after you

take a shower’’).2—Synonym, such as dew (e.g., ‘‘It’s like water forming, I think, like

the clouds’’).3—Some explanation of properties, such as change of state (vapor to a

liquid) that is caused by temperature contrast (e.g., ‘‘That has to dowith water . . . if you have a glass and water like runs, it’s reallyhot and water runs off the glass, that’s condensation’’).

4—Clear and integrated explanation: the conversion of a substance fromthe vapor state to a denser liquid or solid state usually initiated bya reduction in temperature of the vapor (e.g., ‘‘Boil something andit becomes like a gas, and then you let it cool down until it becomesa liquid again. The cooling down becoming a liquid—the part that’scondensation. You heat something like it boils into a gas, but thenyou wait to cool it down until it gets, the temperature gets close tothe boiling point, and it turns back into a liquid.’’)

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Incidental Word Learning in Science Classes