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A Dual Coding View ofVocabulary LearningMark Sadoski aa Texas A&M University , College Station, Texas, USAPublished online: 02 Sep 2006.

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A DUAL CODING VIEW OF VOCABULARY LEARNING

Mark Sadoski

Texas A&M University, College Station, Texas, USA

A theoretical perspective on acquiring sight vocabulary and developingmeaningful vocabulary is presented. Dual Coding Theory assumes thatcognition occurs in two independent but connected codes: a verbal codefor language and a nonverbal code for mental imagery. The mixedresearch literature on using pictures in teaching sight vocabulary isbriefly reviewed, and a possible resolution suggested. The use of concrete,high-imagery words and both verbal and nonverbal contexts are found tobe important factors in teaching sight vocabulary along with word decod-ability. Effective methods of teaching meaningful vocabulary that areconsistent with Dual Coding Theory are briefly reviewed, includingself-generated imagery, the use of illustrations, the keyword method,and verbal-associative methods. Results are relevant for both normalreaders and those experiencing reading problems.

Vocabulary learning is an important goal in literacy, perhaps moreimportant than is generally acknowledged by researchers andteachers. Popular books on the subject have long extolled thevirtues of a rich vocabulary (e.g., Funk & Lewis, 1942; Nurnberg &Rosenblum, 1961). Academic volumes have proposed a central placefor vocabulary in literacy (e.g., Johnson, 2001; Johnson & Pearson,1984; Nagy, 1988; NICHD, 2000). Psychometric studies suggest thatvocabulary is a central factor in reading ability, along with other spe-cific factors such as decoding, comprehension, and rate (Carroll,1993; Davis, 1944; Rosenshine, 1980). Theoretical and conceptualarticles have explored the relationship of vocabulary to these otherfactors (e.g., Nagy & Scott, 2000; Ruddell, 1994). However, literature

Address correspondence to Mark Sadoski, Department of Teaching, Learning, and Culture,

4232 TAMU, Texas A&M University, College Station, TX 77843-4232. E-mail: msadoski@

tamu.edu

Reading & Writing Quarterly, 21: 221–238, 2005

Copyright # Taylor & Francis Inc.

ISSN: 1057-3569 print

DOI: 10.1080=10573560590949359

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reviews report a waxing and waning of the importance of vocabularyin research and teaching over the last 100 years (Blachowicz & Fisher,2000; Nagy & Scott, 2000). Whatever its current place in literacytheory, research, and practice, the subject of vocabulary is clearlyan important and enduring one. This article provides a view of therole of vocabulary in reading and reading instruction from theperspective of Dual Coding Theory (DCT).

OVERVIEW OF DCT

DCT is a general theory of cognition that accounts for both verbaland nonverbal cognition (Paivio, 1971, 1986, 1991), and has recentlybeen advanced as a general theory of literacy (for extensive treat-ments of this theory and a comparison to other theories of reading,see Sadoski & Paivio, 1994, 2001, 2004; Sadoski, Paivio, & Goetz,1991). This theory posits an important distinction between the verbalcode and the nonverbal code. The verbal code is specialized for repre-senting and processing language in all its forms, including speech andwriting, whereas the nonverbal code deals with the representation andprocessing of nonverbal objects, events, and situations (i.e., knowl-edge of the world). Mental imagery is the primary cognitive formof nonverbal representation. All knowledge, meaning, and memoryis explained by representation and processing within and betweenthe two codes in this theory. This includes knowledge of words andtheir meanings.

Words can be defined as verbal labels for concepts. Concepts thatrepresent concrete things, actions, and observable qualities or rela-tions are relatively easy to develop, whereas concepts that representabstract things, actions, qualities, or relations are acquired with morematurity (e.g., the concreteness of words and their age of acquisitionare inversely correlated, Ellis & Monaghan, 2002).

Accordingly, an important distinction in DCT is the differencebetween abstract language and concrete language. Abstract languagehas less access to nonverbal imagery (e.g., true), whereas concrete lan-guage has direct sensory referents (e.g., tree). In this theory, abstractlanguage depends primarily on a web of verbal associations for itsmeaning. The abstract word true is largely defined by other languageunits such as not false, factual, real, faithful, and exact. Concretelanguage also evokes a web of language, but it additionally evokesnonverbal images as a form of meaning. Verbal associates for theconcrete word tree might include trunk, roots, branches, and leaves,but the word also evokes referent images of trees of various kinds

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from the experience of the reader. Hence, concrete language enjoys anatural advantage over abstract language because it can be morereadily represented and processed in two codes (i.e., dual coding).

The DCT view of concepts and vocabulary can be compared toschema theory or other theories that assume a single, ‘‘deep struc-ture’’ code. In schema theory, schemata are defined as data structuresfor representing generic concepts stored in memory (Rumelhart,1980). These data structures are abstract and generic, composed ofrelations between a set of variables that can cover many specificinstances of a concept. No distinctions are made between abstractconcepts and concrete concepts in any version of schema theory, soa familiar abstract word like true is theoretically understood the sameway as a familiar concrete word such as tree—both instantiate anunderlying schemata, a single abstract code. Likewise, ‘‘deep struc-ture’’ reading theories that posit a single code make no concrete–abstract distinction (Smith, 1994). However, single-code theoriescannot easily explain the consistent finding that concrete wordsare learned more readily and recalled more easily than abstractwords matched for familiarity, meaningfulness, and other relevantvariables (for reviews see Paivio, 1971, 1986, 1991; Sadoski & Paivio,2001, 2004).

In DCT, written and spoken words are encoded separately bysense modality rather than as amodal abstractions (i.e., visual encod-ings for written language, auditory-motor encodings for spokenwords). Written word forms processed visually are associated withcorresponding auditory-motor word forms in the naming of words.Connecting newly learned written forms to already learned speechforms is typical in learning to read. These connections account forphonemic decoding made within the verbal code in DCT.

However, the specific meanings of words, and sometimes eventheir pronunciations, are determined by their connections to a rangeof other verbal and nonverbal representations. This is heavilyinfluenced by context. For example, the word ring has a grapho-phonemically regular correspondence that is readily phonemicallydecoded, but its specific meaning is determined by verbal context(e.g., wedding ring, boxing ring, burglary ring, telephone ring). In a sur-prising number of instances, an accurate phonemic decoding cannottake place without the prior processing of contextual meaning (e.g.,homographs such as minute in minute hand or minute detail). The spe-cific meaning of any word is further dependent on nonverbal worldknowledge, such what a wedding ring is, what clock hands are, plantswe call trees, or instances of the truth as determined by correspon-dence with actual events. Situational contexts beyond the printed

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word are heavily nonverbal, such as a bargain to a buyer or a seller.In short, word recoding may be a primarily verbal matter in mostcases, but word meaning is both verbal and nonverbal, especially inthe case of concrete language. The appropriate decoding and mean-ingful elaboration of language units in a given context are what read-ing vocabulary is all about.

DCT also includes provision for developmental and individual dif-ferences. Learners vary in reading skill and in their reliance on verbalthinking or imaginal thinking. Such evidence can be found in thewide variation seen on verbal ability measures such as vocabularytests, tests of spatial and imaginal abilities, or hemispheric preferencemeasures (Carroll, 1993). Neuropsychology has determined that partsof the left hemisphere of the brain are relatively more specialized forverbal tasks, whereas parts of the right hemisphere are more specia-lized for imaginal tasks (e.g., Gazzaniga, 2000; Paivio, 1986). There-fore, left hemispheric preference thinkers may be inclined to use morelanguage in thought, while right hemispheric preference thinkers maybe inclined to use more mental imagery. While seldom included invocabulary studies, such differences have affected the outcomes ofinstructional experiments, as will be seen later. Reading problemsmay be partly related to such differences as well as to instructionalfactors.

The rest of this article will review and interpret some key researchin vocabulary from a DCT perspective. The topics covered are sightvocabulary learning and meaningful vocabulary learning.

SIGHT VOCABULARY LEARNING

Learning words as wholes without grapheme-phoneme analysis is ateaching technique often referred to as the sight vocabulary methodor sight word method (Harris & Hodges, 1995). Common wordsunknown in printed form are associated with their familiar speechforms and usually their meanings through various instructionalapproaches. Both pictures and word concreteness have been shownto affect sight word learning.

Pictures in Sight Word Learning

The use of pictures in sight word learning is controversial. Learningsight words in the presence of meaningful pictures is a method that iswidely used in basal readers and patterned language books, althoughsome researchers have concluded that pictures may distract readers

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from attention to the details of the print. For example, Samuels(1970) discussed the focal attention hypothesis, suggesting that whenpictures and printed words are presented together, readers attendto whichever one helps them produce the response with the leasteffort. Because the pictures can already elicit a response, they inter-fere with the beginning reader’s attention to the details of theunknown print form. A review of the evidence for and against thishypothesis was presented by Schallert (1980).

A subsequent series of studies by Solman and his colleagues (e.g.,Saunders & Solman, 1984; Solman, Singh, & Kehoe, 1992; Wu &Solman, 1993) supported teaching sight words without pictures,although the researchers offered different possible explanations thanthe focal attention hypothesis. Other studies have reported resultsfavorable to using pictures with sight words (e.g., Arlin, Scott, &Webster, 1978–1979; Montare, Elman, & Cohen, 1977; Ollila &Olson, 1972). Reviews of picture effects indicate that the optimaluse of pictures in sight word learning is still an unresolved issue(Ceprano, 1987; Filippatou & Pumfrey, 1996), but the practice enjoyscontinuing popularity in beginning reading materials such as basalreaders.

As discussed earlier, DCT implies that building links betweenprecisely-learned visual and auditory-motor mental representationsis important in decoding words, but it also implies that building linksbetween these representations and both mental images of picturemeanings and verbal contextual meanings should promote the learn-ing of sight words. The usefulness of pictures would be influenced byseveral factors, including the concreteness value of the word, becauseit is easier to picture concrete words such as tree than abstract wordssuch as true.

Arlin et al. (1978–1979) addressed the usefulness of pictures insight word reading while controlling for methodological limitationsfound in prior research on the subject. Kindergartners were presentedwith a set of familiar concrete words that were unknown to them bysight in one of three learning conditions: a word and its picturepresented together, a word and its oral pronunciation presentedtogether, or a control condition with the word presented alone (stu-dents were left to their own strategies). The words with pictures con-dition produced sight word learning at a rate almost 80% faster thanwords with their pronunciations, and faster still than the controlcondition. A subsequent critique of this study (Singer, 1980) andresponse (Arlin, 1980) followed. Final results were mixed, possiblysuggesting that pictures may facilitate learning only when they donot distract from learning the precise printed word form.

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Saunders and Solman (1984) conducted two experiments alsoaddressing limitations of much earlier research and found that kin-dergartners learned sight words best when words were presentedwithout pictures. However, they found this even in a condition wherechildren’s attention was concentrated on the word first before the pic-ture, contradicting the focal attention hypothesis. These researcherssuggested that DCT could better account for the results in that theverbal–nonverbal connections were not being made because of inter-ference effects between the pictures and the printed words or thedevelopmental level of the young children. They also noted that theirresults applied only to the learning of sight words in isolation becauseillustrations associated with text had been found to aid comprehen-sion and learning (Schallert, 1980). A subsequent study (Wu &Solman, 1993) supported these interpretations.

The original findings Arlin et al. (1978–1979) are consistent withthe DCT principle that establishing connections between words andreferent images as well as intraverbal connections between visualand auditory representations is helpful in word learning. A key quali-fication seems to be that accurate learning of the printed word form iscritical in this process. The picture can help establish meaning, but itmust not detract from the formation of the visual mental represen-tation of the word.

A technique for learning sight words that addressed this problemhas been proposed and empirically tested (Bridge, Winograd, &Haley, 1983). Target words to be learned as sight words were firstaccompanied by pictures and verbal contexts in patterned booksand then on charts without pictures; that is, words were presentedfirst in meaningful verbal contexts with picture cues and then withoutthe picture cues to ensure attention to the word forms. This techniqueresulted in first graders learning more than twice as many target sightwords as a control group using an illustrated basal reader thatemphasized repetition. The experimental group also learned evenmore incidental sight words and reported more positive feelingsabout reading aloud than the control group when interviewed witha questionnaire. This study did not attempt to teach sight words inisolation and did not include a control group that received no illustra-tions. However, the technique produced impressive results and is con-sistent with common school practices that address comprehensionand attitude as well as decoding in beginning reading.

The DCT interpretation of this study is that rich verbal and non-verbal contexts together contributed to the comprehension and mem-ory of sight words. Although the words initially had rich semanticand syntactic contextual support in the experimental condition,

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important steps were also taken to ensure that attention was directedto the significant features of individual words and that word formswould be learned precisely. However, the exact role of pictures inlearning isolated sight words remains unresolved.

Concreteness and Context in Sight Word Learning

Word concreteness strongly effects sight word learning. Hargis andGickling (1978) taught average ability kindergartners a set of con-crete sight words and a set of abstract sight words that were matchedfor length and frequency. All the words were familiar words initiallyunknown to the children by sight and presented without pictures.During training, the children:

1. were presented the words on flash cards in random order2. heard each word pronounced3. heard each word used in a sentence4. used the word in a sentence of their own5. repeated the word.

Two days after training was completed, more than three times asmany concrete words as abstract words were correctly identified.Ten days after training, more than four times as many concrete wordswere correctly identified. These results were subsequently replicatedwith both kindergartners of normal ability and older mentallyretarded children (Gickling, Hargis, & Alexander, 1981).

This research was extended to middle-grade children with readingdifficulties by Hargis, Terhaar-Yonkers, Williams, and Reed (1988).Besides word concreteness, the experiment included manipulationsfor word decodability and word presentation either in story contextor in isolation. Results revealed that:

. concrete words were learned about 12% faster than abstractwords

. words presented in story contexts were learned about 12% fas-ter than words presented in isolation

. decodable (grapho-phonemically regular) words were learnedabout 6% faster than nondecodable (irregular) words.

Significant interactions between these factors indicated that abstractwords presented in isolation took the longest to learn regardless of

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decodability, whereas concrete decodable words were learned fastestregardless of context. The researchers concluded that concrete, high-imagery words are learned more easily, while abstract, low-imagerywords may require more exposure and use in context.

Kolker & Terwilliger (1981) taught first- and second-grade childrenconcrete and abstract sight words without pictures or verbal contexts.Words taught were initially unknown by sight but had familiar mean-ings. The examiner presented the word for one second on a flash card,pronounced it, had the child repeat the word within five seconds, andprovided correction as necessary. This continued until a learning cri-terion was met. The first graders took about 60% more trials to learnthe abstract words than the concrete words. The difference for thesecond graders was less (about 8% more trials for abstract words),but this difference was still highly significant (p < .0001). Terwilligerand Kolker (1982) replicated their results with a large sample ofbeginning first graders while varying word confusability (i.e., sameor different initial consonants). Similar results were obtained withkindergartners and beginning first graders by van der Veur(1975) and with second graders by McFalls, Schwanenflugel, andStahl (1996).

The results of these studies are very consistent with DCT. Overall,concrete words were learned faster even without the benefit of mean-ingful verbal contexts, especially if decodable. Abstract words that var-ied in decodability were learned more slowly and benefited morefrommeaningful verbal contexts. That is, sight word learning benefitedfrom decodability but even more from comprehensibility providedeither by concreteness or story context (for similar findings withword recognition by adults, see Strain, Patterson, & Seidenberg (1995)and Herdman & Strain (1999) but also Ellis & Monoghan (2002).

In summary, sight word learning appears to benefit from both ver-bal contexts and pictures that provide meaningful images for the wordas long as the word form is well learned. Concrete words are moreeasily learned even in isolation, especially if grapho-phonemicallyregular, whereas abstract words appear to be learned best in verbalcontexts whether regular or irregular. This applies to beginning read-ers or older children with reading difficulty. As many words taught assight words are abstract and irregular (e.g., the, were, there, have),these words may require the benefit of repeated exposure in context.

MEANINGFUL VOCABULARY LEARNING

DCT principles can be helpful in understanding the acquisition andteaching of meaningful vocabulary. Two main sources of meaningful

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vocabulary learning have been identified: incidental learning fromcontext and direct vocabulary instruction. DCT implies that encoun-tering and using words in various contexts establishes a rich set ofverbal and nonverbal connections. Such contexts include listening,speaking, reading, and writing. Only a little research is available onthe acquisition of vocabulary from listening, speaking, and writing(e.g., Stahl, Richek, & Vandevier, 1991). However, a meta-analysisof twenty experiments of incidental word learning during normalreading showed that students learn about 15% of the unknown wordsthey encounter there (Swanborn & de Glopper, 1999). This generalfigure is qualified by such factors as student grade level and partialvs. full word knowledge. Using direct instructional techniques inaddition to relying on contextual encounters can markedly improvevocabulary learning (Baumann, Kame’enui, & Ash, 2003; Beck andMcKeown, 1991; Blachowicz & Fisher, 2000; Stahl & Fairbanks,1986; White, Power, & White, 1989).

Imagery-based Methods

Word derivation and etymology may serve a useful role in directvocabulary instruction. Broudy (1988) maintained that a loss in gen-eral literacy occurs as the potential for imagery decreases through alack of understanding of the root meanings of words. He argued thatthe rich stores of imagery that contribute to English vocabulary forman ‘‘allusionary base’’ (p. 316), a conglomerate of sense perceptions,memories, and emotions held together by associations that serve sym-bolic functions in thought. Much of this base can be found in the rootmeanings of words, whether abstract or concrete.

For example, a penitentiary is accurately described as a prison, butthe image of doing penance is generally absent in contemporaryusage, and with it the meaningfulness of the concrete image. Mostabstractions have a concrete allusionary base. The word true, forexample, derives from the word for tree, an allusion to being as firmlyrooted as a tree—the tr in true and the tr in tree share the same morh-pheme. Lakoff and Johnson (1980, 1999) have maintained that allconceptual knowledge is basically concrete and that abstract conceptsare largely metaphorical. Many abstract terms are ‘‘dead’’ meta-phors, that is, terms that were once meant more literally. Forexample, the word cliche comes from a French word meaning a print-ing plate, and imitates the sound made when a die struck the metalplate over and over in printing. Likewise, the word sardonic comesfrom the Latin herba sardonia, a poisonous plant that twisted the faceinto a contorted grin in the death-throes (Shipley, 1945). That is, it is

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difficult to find a word whose origins are not concrete, and alllanguage may be metaphorical to a degree. The rich possibilities ofstudying the concrete historical roots of vocabulary would seem tooffer much potential for meaningful vocabulary development.Although little empirical research is available on using this technique,popular authors have published books on the interesting etymologiesof words, both common and technical. Enduring examples suitablefor school children are Isaac Asimov’s Words of Science (1959),Words from the Myths (1961), Words on the Map (1962), and Wordsfrom History (1968).

DCT principles have been directly applied to using imagery in theteaching of meaningful vocabulary in empirical studies. Bull andWittrock (1971) used pictures and mental imagery in studying threemethods for teaching definitions of eighteen nouns drawn from aseventh-grade spelling list to 87 fifth-graders. Half were relativelyconcrete words and half were relatively abstract words. The two wordsets were matched for meaningfulness and familiarity. Students wererandomly assigned to one of three conditions: verbal definition only,verbal definition plus illustration, or verbal definition plus self-discovered imagery, where the students had to draw their own illus-trations of the definitions. Testing after one week indicated retentiondid not differ between concrete and abstract words, but the self-discovered imagery group performed significantly better than thedefinitions-only group, and the difference between the definitions-only group and definition-plus-illustration group approached signifi-cance. The researchers concluded that imagery, at least whencombined with self-discovery, has practical significance in the learn-ing of definitions by children in classroom settings. They citedDCT as a theoretical explanation of their findings.

Smith, Stahl, and Neil (1987) applied nonverbal (i.e., pictorial) andverbal contexts in meaningful vocabulary learning. They had 142undergraduates learn 50 words (nouns and other word classes) thatwere unknown to them. No control for word concreteness was used,but three treatment conditions were designed to vary verbal andnonverbal contexts: definition only, definition and a sentence usingthe word in context, and the definition, a sentence using the wordin context, and a simple picture illustrating the meaning of the word.An immediate test of the definitions showed that the group receivingall three treatments scored highest, but the difference was not signifi-cantly different from the other groups. A two-week delayed test indi-cated that the scores grew progressively stronger with each treatmentadditive, but the only significant difference was between thedefinition only group and the definition-plus-sentence-plus-imagery

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group. The researchers concluded that their results were supportive ofDCT in vocabulary instruction.

These findings were extended by Smith, Miller, Grossman, andValeri-Gold (1994), who conducted two studies with a total of166 undergraduates. Students who differed on a test of hemisphericpreference in thinking were given conceptually complex nouns,verbs, and adjectives assumed to be unknown to them in one oftwo conditions: definition and a sentence using the word in context,or definition, sentence, and illustration. Word concreteness was notcontrolled. In both studies, students receiving the illustrationsscored significantly higher on both immediate and delayed teststhan those not receiving the illustrations. Nouns, verbs, and adjec-tives were learned equally well. Left-brain preference thinkers, pre-sumably less inclined to normally use imagery in their thinking,benefited significantly more than right-brain preference thinkersfrom the inclusion of the illustrations. This point is supportive ofthe DCT assumption of individual differences in verbal or imaginalthinking, as noted earlier.

Perhaps the best researched method of direct instruction invocabulary is the keyword method. The keyword method requireslearners to form an interactive mental image of the definition ofthe new vocabulary word and a familiar, concrete word that sharesa similar acoustic element. For example, learning the word potable,meaning suitable for drinking, could be accomplished by using thekeyword pot and having the learner generate an image of a pot ofcool spring water waiting for someone who has just crossed a desert(Tierney, Readence, & Dishner, 1990). When later recalling the defi-nition of potable, the learner retrieves pot through its acoustic associ-ation and then recalls the image and, hence, the meaning of potable.This method has been applied widely with positive results (Levin,1985, 1993; Pressley, Levin, & McDaniel, 1987; Stahl & Fairbanks,1986). It has also been successfully used in teaching foreign languagevocabulary (e.g., Atkinson, 1975; Avila & Sadoski, 1996; Rodriguez& Sadoski, 2000).

Levin et al. (1984) experimentally compared the keyword methodto semantic mapping and contextual analysis methods on vocabularylearning and vocabulary comprehension. Both high-ability andlower-ability middle-grade readers using the keyword method outper-formed their counterparts in the other groups on definition recallafter a day. High-ability readers using the keyword method alsooutperformed their counterparts in the contextual analysis groupon appropriateness judgments of sentences and sentence completions.The researchers concluded that the keyword method produced better

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recall of definitions and the same or better comprehension as com-pared to other common school tasks.

These results were extended by Levin, Levin, Glasman, andNordwall (1992). In four experiments with a total of 428 studentsfrom grades three to eight, keyword instruction, whether individualor small group, was consistently superior to contextual analysis orfree-study control instruction on tests of definition recall. Tests wereadministered from three days to two weeks after instruction. In threeof the four experiments, keyword instruction produced significantlysuperior results on tests of vocabulary usage in sentence and storycomprehension. The results of Levin et al. (1984) were also extendedby Williams and Konopak (1988), who found with sixth graders thatthe keyword method was superior to a free-study control conditionand that many keyword participants reported transferring the strat-egy to new learning situations a month later.

DCT suggests that combining the keyword method with contextualanalysis should be particularly effective because learning would occurin the two codes in different ways with potentially additive effects. Ina study of foreign language vocabulary learning in intact ninth-gradeclassrooms, Rodriguez and Sadoski (2000) experimentally compareda combined keyword-context method with keyword alone, contextalone, and rote memory methods. Words were concrete Englishnouns unknown to the Spanish-speaking participants. Instructionaltime was equated for all groups. Controlling for individual differ-ences in foreign language vocabulary learning ability, the combinedkeyword-context group performed as well as the other groups onimmediate retention but far better than all the other groups afterone week. These results are especially consistent with the DCTassumption that imagery and verbal processes are independent andadditive on their effects on memory.

Verbal-Associative Methods

Beyond contextual analysis, several methods on vocabulary acqui-sition based on verbal association have been developed. These techni-ques may work best when some sort of spatial arrangementmnemonic is employed (Bellaza, 1983).

For example, Stahl, Burdge, Machuga, & Stecyk (1992) found withfourth-graders that teaching words in semantically related groups(e.g., eating words: devour, gorge, glutton, obese) was no more effec-tive than randomly grouping the words in classroom vocabularyinstruction. They raised questions about the common educationalsuggestion to relate words in semantic categories for learning.

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However, when a graphic display is used with the semantically relatedvocabulary, results are usually effective. Moore and Readence (1984)reviewed research on graphic organizers that place related vocabularyin a hierarchical diagram and found that they are effective in pro-moting vocabulary growth, especially after reading. Carr andMazur-Stewart (1988) found that the Vocabulary Overview Guide, atechnique that includes a graphic display of related vocabularyinformation, was superior to the traditional method of listing andstudying definitions on both immediate and one-month delayed tests.Consistent with DCT, graphic displays presumably involve bothverbal-associative and imaginal-spatial processes in memory.

Finally, a more purely verbal-associative educational technique ismorphological analysis, in which students analyze an unfamiliarword into parts such as roots and affixes and then recombine theparts into meaningful wholes. White et al. (1989) estimated that thistechnique would nearly double the understanding of affixed wordsseen in context over the use of context alone. The technique wasrecommended for students in fourth grade and above because pri-mary grade children see far fewer affixed words and are familiar withfewer root words. Empirical results have tended to show that instruc-tion in morphological analysis produces improved results in targetword learning and transfer to new words both in and out of context(e.g., Baumann, Edwards, Font, Tereshinski, Kame’enui, & Olejnik,2002; Wysocki & Jenkins, 1987).

CONCLUSIONS

DCT can account for some of the most effective vocabulary learningstrategies that have been devised for both sight word learning and thelearning of meaningful vocabulary. There is considerable theoreticalvalue in such an accounting: knowing what works in vocabularylearning is one question, but understanding why it works is another.The answers to both these questions provide direction for future pro-gress in this important area. DCT can make a substantial contri-bution to that progress.

DCT provides a framework for understanding and potentiallyresolving some longstanding issues in sight word learning, such asthe proper roles of pictures. Pictures may have value in providingcues to word identity and meaningful elaboration in the form of non-verbal context, but written words must also be learned as visible unitsthat are readily discriminated from other such units. Pictures couldhinder the visual learning of words through focal-attention distrac-tion and visual interference, among other possible reasons. Therefore,

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pictures may be useful, but in such a way that word forms are welllearned also. Such techniques have been developed and tested withfavorable results.

Context and concreteness are theoretically important factors inDCT, and, whereas word decodability often has been treated as themain factor in word learning for beginners, these factors afford ben-efits as well. Considerable research shows that concreteness and ver-bal context may be more important than decodability in learningsight words. This implies that decodability, concreteness, and contextall should be considered in a balanced sight vocabulary program.

Meaningful vocabulary has been traditionally acquired throughcontextual analysis or by direct instruction in definitions. Using ver-bal contextual analysis alone to learn new vocabulary is a commoneducational technique that may not be potent enough to producean advanced vocabulary. Direct instructional techniques that employimagery, such as self-generated imagery, illustrations, or the keywordmethod, have proven effective in vocabulary learning. Using bothverbal contexts and imagery in the direct learning of definitionsmay be a highly effective combination. Methods that use visual dis-plays of vocabulary relationships, such as the graphic organizer, tendto produce organized vocabulary learning better than methods thatdo not. The study of words in their own right, including morphemicanalysis and the investigation of interesting word etymologies, shouldbe beneficial as well.

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