Journal of Experimental Psychology:Learning, Memory, and Cognition1995, Vol. 21, No. 5,1197-1208

Copyright 1995 by the American Psychological Association, Inc.r 0278-7393/95/S3.00

Errors in Short-Term Memory for Speech: A Developmental Study

Rebecca TreimanWayne State University

In a previous study (R. Treiman & C. Danis, 1988), adults who were presented with lists of spokenconsonant-vowel-consonant (CVC) nonsense syllables for immediate recall produced many errorsthat combined the initial consonant onset of one to-be-remembered syllable with the vowel-consonant rime of another to-be-remembered syllable. These onset-rime recombination errorswere more common than other types of recombination errors and also more common than serialposition errors. These findings suggest that nonwords are remembered in terms of smallerphonological units. To replicate the previous results and to determine whether they generalize tochildren, the author tested kindergarteners, 3rd graders, 6th graders, and adults on lists ofnonsense CVCs. Onset-rime conjunction errors were the most frequent type of recombinationerror, even among kindergarteners, suggesting that children code spoken syllables in terms of onsetand rime units from a young age.

Our ability to temporarily store and accurately recall ran-dom sequences of digits, letters, or other verbal stimuli is verylimited. Errors mount if the sequences are more than just a fewitems in length (e.g., Miller, 1956). Researchers have beeninterested in the functioning of this limited capacity short-termmemory system because it seems to be central to humanintelligence. The system is thought to underlie performance ona wide variety of cognitive tasks, including reading, vocabularylearning, and reasoning (e.g., Baddeley & Hitch, 1974; Badde-ley, Papagno, & Vallar, 1988; Gathercole & Baddeley, 1989).Consistent with this assumption, memory span is an importantpart of many intelligence tests (e.g., Wechsler, 1955).

People's errors in the short-term memory task can shed lighton the way in which they encode the stimuli. Researchers havedistinguished between order errors, or errors in which an itemfrom elsewhere in the presented sequence is reported, itemerrors, or errors in which an item not on the to-be-rememberedlist is recalled, and omission errors. With sequences of letters ordigits, the large majority of errors are order errors (e.g.,Aaronson, 1968). These order errors tend to involve adjacentitems, especially those from the middle of the stimulus list. Forexample, the sequence 2 8 7 5 3 may be misrecalled as 2 7 8 5 3.A number of models have been put forward to explain theseorder errors (e.g., Burgess & Hitch, 1992; Estes, 1972; Lee &Estes, 1977,1981; Lewandowsky & Murdock, 1989; Shiffrin &Cook, 1978). For example, Estes and his colleagues assumed

This article was prepared, in part, while I was on sabbatical at theMedical Research Council Applied Psychology Unit, Cambridge,England.

This research was supported by National Science Foundation GrantSBR 9020956, National Institutes of Health (NIH) Research CareerDevelopment Award HD 00769, and NIH Grant HD 18387. CatalinaDanis, Kathleen Straub, Robert Padgett, Andrea Zukowski, E. Day-lene Richmond-Welty, and Marie Cassar contributed in various waysto this research. Robert Crowder provided helpful comments on adraft of this article.

Correspondence concerning this article should be addressed toRebecca Treiman, Department of Psychology, Wayne State Univer-sity, 71 W. Warren Avenue, Detroit, Michigan 48202. Electronic mailmay be sent via Internet to treiman@math.wayne.edu.

that information about the position of an item within a trialbecomes perturbed as a function of time. In Burgess andHitch's network model, items are selected serially for recall bycompetitive queuing. Order errors may occur during recall as aresult of noise.

The short-term memory models have enjoyed some successin accounting for order errors in the serial recall of sequencesof letters and digits. Most of the models, however, have notbeen tested against data on recall of other types of sequences.This is a serious problem because the few studies that haveexamined short-term memory for sequences of unfamiliarstimuli have found very different results from those typicallyfound with letters or digits (Ellis, 1980; Treiman & Danis,1988). For example, college students in an experiment byTreiman and Danis heard lists of six spoken consonant-vowel-consonant (CVC) nonsense syllables on each trial. A samplelist is /ger/, /varj/, /kus/, /dasl/, /job/, /Jim/. (See theAppendix for a key to the notation). Order errors, or those inwhich a stimulus from the list was recalled in the wrongposition, constituted less than 12% of all errors. Much morecommon were item errors in which participants recalled anitem that was not on the to-be-remembered list. This patternby which item errors exceeded order errors (a pattern alsoobserved by Ellis in experiments with consonant-vowel [CV]syllables) is the opposite of that typically observed withsequences of letters or digits. Of importance, the item errorsobserved by Treiman and Danis were not random syllables.The incorrect items almost always shared the CVC phonologi-cal structure of the stimulus syllables. In addition, they usuallycontained phonemes from the presented list. For example, acommon error in recall of a list containing the sequence /kus//dael/ was /kael/. This syllable did not appear in the presentedlist but was made up of phonemes from two of the list items.Errors that did not contain any phonemes from the original listconstituted less than 1% of all errors.

The results of Treiman and Danis (1988) suggest that theway in which phonemes misorder and recombine in theshort-term recall of nonsense syllables is different from theway in which whole items fall out of position in the recall oflists of familiar stimuli. With a sequence such as 2 8 7 5 3,

1197

1198 REBECCA TREIMAN

transposition errors tend to involve adjacent items, as in theerror 2 7 8 5 3. With nonsense syllables, transpositions ofadjacent phonemes are very uncommon. For example, /kus/would rarely be reported as /uks/. The results of Treiman andDanis suggest that the most frequent type of error in the recallof a list of CVCs such as /ger/, /van/, /kus/, /dael/, /job/,/Jim/ is one like /keel/. This syllable is composed of the firstphoneme of one list item, /kus/, together with the second andthird phonemes of another list item, /dael/. The phonemes /ae/and IV are not adjacent to /k/ on the experimental list. Errorssuch as /kael/, which combined the first phoneme of one CVCand the second and third phonemes of another CVC, outnum-bered errors such as /jib/, which combined the first twophonemes of one stimulus with the final phoneme of another,or errors such as /dul/, which combined the first and thirdphonemes of one stimulus with the second phoneme ofanother. In another study in which the stimuli were consonant-consonant-vowel (CCV) syllables such as /kli/ and /tra/,Treiman and Danis found that errors tended to join the firsttwo phonemes of one stimulus with the third phoneme ofanother stimulus, as in the error /kla/.

Superficially, the results for CVC and CCV syllables arequite different. With CVCs, the most common intrusion errorscombined the first phoneme of one stimulus with the secondand third phonemes of another. With CCVs, the most commonintrusions joined the first two phonemes of one stimulus withthe third phoneme of another stimulus. Although the errorsare different superficially, they are similar at a deeper linguis-tic level. This was the level to which Treiman and Danis (1988)turned to explain their results. Many linguists (e.g., Fudge,1969, 1987, 1989; Selkirk, 1982; but see Davis, 1989, for adifferent view) have described the English syllable as beingcomposed of two primary units. The initial consonant orconsonant cluster of the syllable is called the onset. The voweland the final consonant(s), if present, make up the rime. Forexample, the onset of /kus/ is /k/, and the rime is /us/. With/kli/, the onset is /kl/ and the rime is IV. The results ofTreiman and Danis suggest that onset and rime units play animportant role in the coding of nonwords in short-termmemory. It is as if the onsets and rimes of the to-be-remembered syllables sometimes become "unglued" and re-join to form syllables that were not in the original list. Thus, thefirst phoneme or onset of /dael/ may link with the second andthird phonemes or rime of /kus/ to form the syllable /kael/.The first two phonemes of /kli/, which constitute the onset ofthis CCV syllable, may separate from their rime and join withthe rime of /tra/, forming /kla/.

People with disorders of semantic memory have also beenreported to produce onset-rime recombination errors in short-term memory tasks. Patterson, Graham, and Hodges (1994)studied three patients suffering from semantic dementia,which involves progressive deterioration of semantic knowl-edge. The patients were presented with short lists of knownwords (words that they understood) and unknown words(words that they no longer understood) for serial recall. Thepatients made a large number of phonological errors whenrecalling the lists of unknown words. A common error onmonosyllabic words was to produce the correct rime with thewrong onset, as v/hen fruit was recalled as /sut/.

The results with normal and disordered individuals indicatethat linguistic structure is intimately involved in the learningand recall of verbal materials. Models of short-term memorymust, therefore, take phonology into account. The results arealso important because much of the previous evidence for thepsychological reality of onset and rime units has come frommetalinguistic tasks, or tasks in which people deliberatelybreak syllables at various points. In a variety of such tasks,breaks at the onset-rime boundary are easier to master thanbreaks at other points (Fowler, Treiman, & Gross, 1993;Treiman, 1983, 1984, 1986, 1988; Treiman, Fowler, Gross,Berch, & Weatherston, 1995). It could be argued that theresults of these studies are not relevant to normal languageprocessing because they reflect strategies that are specific totasks that demand a high level of metalinguistic awareness.However, the results of the short-term memory studies speakagainst this argument. In the memory span task, the goal is toremember syllables as wholes rather than to subdivide them.Nevertheless, onset and rime units appear to play a role inshort-term memory tasks as they do in metalinguistic tasks.

The memory conjunction errors that occur with auditorilypresented nonsense syllables are reminiscent of the illusoryconjunction errors that occur in the visual domain, as withfaces or geometric shapes (e.g., Reinitz, Lammers, & Cochran,1992; Reinitz, Morrissey, & Demb, 1994; Treisman & Schmidt,1982). In both cases, stimuli seem to be coded in memory notas indivisible wholes but in terms of smaller units. Becausethese smaller units are phonological in the case of nonsensesyllables, the role of phonology in short-term memory can beexplored by studying the detailed characteristics of the conjunc-tion errors.

Pursuing this strategy, Treiman and Danis (1988) examinedthe effects of phonological variables on the nature of theconjunction errors. They examined the errors that occurred onsyllables with different types of consonants after the vowel—liquids (/r/ or /I/), nasals (/m/, /n/, or /n/), and obstruents(which include stops such as /b/ and /t/ and fricatives such asIB/ and HI). When all of the CVC stimuli were consideredtogether, errors that treated the vowel-consonant (VC) rimeas a unit were more common than retentions of either theinitial CV unit or the initial consonant-final consonant unit.However, the tendency to keep rimes intact appeared to bestrongest when the final consonant was a liquid, intermediatewhen the final consonant was a nasal, and weakest when thefinal consonant was an obstruent. Treiman and Danis alsoexamined errors in memory for vowel-consonant-consonant(VCC) stimuli. Here, too, the results varied according to thetype of consonant that followed the vowel. When the conso-nant was a liquid, people often joined the vowel and thefollowing liquid of one syllable with the final consonant ofanother syllable. When the postvocalic consonant was a nasalor an obstruent, such recombinations were less common.Across two different short-term memory studies, then, itappears that vowels and following liquids have a closer bondthan vowels and other types of consonants.

The idea that vowels and following liquids have a special linkconcurs with suggestions that are based on studies of spontane-ous speech errors (MacKay, 1978; Stemberger, 1983). More-over, several studies using metalinguistic tasks have reported

ERRORS IN MEMORY FOR SPEECH 1199

that people are more apt to treat vowel-liquid sequences asunits than to treat other types of VC sequences as units(Derwing & Nearey, 1990, 1991; Treiman, 1984; Treiman,Zukowski, & Richmond-Welty, 1995), although the differencesare not always significant (Fowler et al., 1993). Some linguists,too, have claimed that postvocalic sonorants (i.e., liquids andnasals) are more closely allied with the vowel than postvocalicobstruents, at least if the vowel is a short one such as III or /e/(Selkirk, 1982).

To date, few studies of short-term memory have adopted alinguistic perspective. Most researchers have used stimulichosen from small, familiar sets, and only a handful haveexamined adults' errors on other kinds of stimuli from alinguistic point of view (Ellis, 1980; Treiman & Danis, 1988;Treiman, Straub, & Lavery, 1994). Further research withunfamiliar stimuli or stimuli chosen from larger sets is impor-tant because the results so far suggest that models developedto account for short-term memory for sequences of familiaritems cannot be extended to memory for unfamiliar items, atleast without substantial modifications.

I carried out this study, in part, to replicate the findings ofTreiman and Danis (1988) with lists of CVC nonwords. Themajor question was whether onset-rime recombination errorswould again outnumber other types of recombination errorsand whether they would also outnumber order errors in whichan entire syllable was recalled in the wrong serial position. Twomore detailed linguistic questions were also asked. One waswhether differences in VC cohesiveness among postvocalicliquids, nasals, and obstruents would again be found. Thesecond was whether the results would vary according towhether the vowel of the CVC was long (as with HI or /o/) orshort (as with /i/ or Is/). This question is of interest in light ofdifferences between the treatment of long and short vowels inmany linguistic theories of syllables and syllable structure (e.g.,Clements & Keyser, 1983; Fudge, 1969,1987; Selkirk, 1982).

In addition to examining adults' short-term recall of non-sense syllables, I also examined that of children. There hasbeen a long history of short-term memory research withchildren, most of it using familiar stimuli such as letters, digits,or common words. Researchers have focused on the largeimprovement in memory span that occurs between childhoodand adulthood, with span increasing from about three words atage three to around seven words for adults (e.g., Chi, 1976).Several explanations have been offered for this increase inshort-term memory span with age (see Henry & Millar, 1993,for a review). Influenced by the working memory model ofBaddeley and Hitch (1974), some researchers have proposedthat improvements in memory span reflect increases in the ratewith which the stimuli can be articulated (e.g., Hulme, Thom-son, Muir, & Lawrence, 1984; Raine, Hulme, Chadderton, &Bailey, 1991). The more items that can be encoded andrehearsed within the decay time of the articulatory loop, thelonger the sequence that can be remembered. However,research evidence suggests that developmental increases inmemory span for spoken stimuli are not due solely to increasesin speech rate. Matching 5- and 7-year-old children on articula-tion rates for individual words in a span test does not equatespan performance (Henry & Millar, 1991). It is possible, then,that some of the differences between younger and older

children reflect differences in phonological coding. Perhapschildren are less likely than adults to use onset-rime coding inshort-term memory. To address this issue, I examined childrenas well as adults. I asked whether children at several develop-mental levels make onset-rime recombination errors in short-term memory for spoken syllables in the same way that adultshave been reported to do.

As described above, it is possible that onset-rime coding ofspeech for memory purposes is not in place by kindergartenand that an increase in the ability to code syllables in thismanner accounts for part of the increase in memory span thatoccurs with age. Consistent with this possibility, certain aspectsof phonological development are not complete by the timechildren begin school. For example, children in kindergartenand early elementary school typically perform poorly in explicitmetalinguistic tasks that tap the level of phonemes (seeAdams, 1990, for a review). Even at an implicit level, children'sphonemic representations may not always be the same as thoseof literate adults (Treiman, Cassar, & Zukowski, 1994; Treiman,Zukowski, et al., 1995). It is possible that onset-rime coding ofspeech for memory purposes also develops slowly. If so, youngchildren might not show the priority for onset-rime recombina-tion errors over other types of recombination errors that adultsdo.

Alternatively, children may make the same kinds of onset-rime recombination errors as adults. Supporting this view,children's ability to perceive and produce speech in theirnative language is well established by the time they enterschool. Although kindergarteners typically have trouble divid-ing syllables into phonemes in explicit metalinguistic tasks,many can segment syllables into onsets and rimes with littledifficulty {e.g., Treiman, 1992; Treiman & Zukowski, 1991).Thus, it might be expected that kindergarteners would codespoken syllables in terms of onsets and rimes in short-termmemory. Although memory span should increase with develop-ment, in line with previous work (e.g., Chi, 1976), the nature ofthe errors should show little or no developmental change.According to this view, children, like adults, should be morelikely to recall /kael/ given /kus/ and /dael/ than to recall /kul/or /kaes/. Such a result would suggest that onset-rime codingof syllables in short-term memory is a fundamental phenom-enon that characterizes all English speakers rather than astrategy that depends on high levels of maturity or cognitivesophistication.

To date, little research has examined the nature of chil-dren's recombination errors in short-term memory. A notableexception is a study by Brady, Shankweiler, and Mann (1983)with third graders. The participants included a group of goodreaders and a group of poor readers. All children heard lists offive monosyllabic nouns that they were to repeat back in theorder in which they were presented. The children's errorsoften combined phonological units from the original words.For example, children sometimes produced spate when recall-ing the list rain, hair, spell, fate, tree. Spate combines the /sp/ ofspell and the /et/ of fate. Most commonly, as in this example,the vowel and final consonant of one word were preserved as aunit together with the initial consonant or consonant cluster ofanother word. There was some indication, at least with lists ofwords that did not rhyme, that poor readers were worse than

1200 REBECCA TREIMAN

good readers at remembering the correct combinations ofunits within a word. These results are similar to those reportedby Treiman and Danis (1988) in the case of adults' memory fornonsense words. Brady, Mann, and Schmidt (1987), using CVnonsense syllables as stimuli with second and third graders,also reported a number of errors that combined the initialconsonant of one to-be-remembered syllable with the vowel ofanother. As in Ellis's (1980) study with adults, these itemerrors outnumbered order errors in which an entire to-be-remembered syllable was recalled in the wrong serial position.

The findings of Brady et al. (1983) suggest that onset-rimecoding of speech for memory purposes emerges by at leastthird grade. In the present study, kindergarteners, as well asthird graders and sixth graders, were tested to study thedevelopmental course of this phenomenon. This study alsoextended the pioneering study of Brady et al. by askingwhether onset-rime coding is more common for some types ofsyllables, such as those ending with liquids, than for other typesof syllables, such as those ending with obstruents.

The participants in the present study were kindergarteners,third graders, sixth graders, and adults. The stimuli were CVCnonsense syllables, as in the first experiment of Treiman andDanis (1988). The CVC stimuli varied in the type of finalconsonant (liquid, nasal, or obstruent) and in the nature of thevowel (long or short). List length was adjusted for each gradelevel in an attempt to equate overall level of performanceacross grade levels. Lists ranged from three items for kindergar-teners to six items for adults. The interest was not so much inthe level of performance at each grade level as in the nature ofthe errors. For ease of exposition, the methods and results foreach developmental level are separately presented.

Kindergarteners

Method

Participants. The original sample contained 67 kindergartenersfrom a public school in a middle-class suburb of Detroit. Eight childrenwere eliminated from the final sample because their speech was verysoft or unclear on the tape, making transcription difficult. Anotherchild moved out of the school district before testing was completed.The final sample contained 58 children. The children's mean age was 5years, 9 months (range: 5 years, 1 month-6 years, 3 months). All of theparticipants at this and the other age levels were native speakers ofAmerican English.

Stimuli. The lists were formed from 120 CVC nonsense syllables.The first consonants of the syllables were chosen from among /d/, /g/,/h/, /s/, /v/, and /z/. Each of the possible initial consonants was usedequally often. The rime was created by pairing a short vowel (/a/, III,lei, / » / , hi, Ivl, or /A/) or a long vowel {I'll, le/, /u/, lot, /au/, /ai/,or /oil) with a final liquid (IT/ or /I/), nasal (/m/ or In/), or obstruent(/b/ or Id^l). With two types of vowels and three types of finalconsonants, there were six ditferent types of rimes. Twenty syllableswere constructed with each rime type.

The syllables were arranged into 40 lists of three syllables each.These lists are shown in the Appendix. Each list contained one syllablewith each of the three types of final consonant, either two syllables witha long vowel and one syllable with a short vowel or the reverse. The 40lists were divided into two sets of 20 lists each, balanced with respect torime type.

Procedure. Each trial began with a familiarization phase. Theexperimenter pronounced each syllable and the child repeated it. Anymispronunciations were corrected, with children being given up tothree chances to repeat the syllable correctly.

After familiarization, the experimenter spoke the complete list at arate of one syllable per second. The child was asked to repeat thesyllables in the order in which they had been presented as soon as theexperimenter had finished saying the third syllable. Responses werephonetically transcribed by the experimenter and also tape recorded.A list was repeated if the child could not recall any syllables. Theinterrater reliability for two experimenters transcribing a sample ofpilot data was 97%.

Each child was individually tested in two sessions of about 15 mineach. One set of 20 lists was presented during each session. The orderof the two sets was balanced across children. The two sessions per childwere typically completed within 1 week.

Results and Discussion

For this and the other age groups, a response syllable wasscored as correct if it was reported as presented by theexperimenter and if it was in the correct position of the list. (If,as infrequently happened, a child still mispronounced asyllable after the third attempt to repeat it, the child's finalpronunciation was scored as correct if it was produced atrecall.) Errors provide the primary information in thesestudies.

The kindergarteners' mean error rate was 30%. In Table 1,the kindergarteners' incorrect responses are categorized bythe number of phonemes that they contained. The majority ofthe kindergarteners' errors, 79% or 1,633/2,080, containedthree phonemes, as did the CVC stimulus syllables. The next

Table 1Types of Errors (Number of and Percentage of Total) Produced by Participants at Each Developmental Level

Kindergarteners Third graders Sixth graders Adults

Error type

Omitted-syllableOne-phoneme syllableTwo-phoneme syllableThree-phoneme syllableFour-phoneme syllableFive-phoneme syllable

Total errors

Error rate

No.

300

2751,633

1375

2,080

%

1.40.0

13.278.5

6.60.2

29.9

No.

923

1841,930

1203

2,332

%

3.90.17.9

82.85.10.1

49.8

No.

2730

1652,922

12914

3,503

%

7.80.04.7

83.43.70.4

63.5

No.

1761

331,346

511

1,608

%

10.90.02.0

83.73.20.1

55.8

ERRORS IN MEMORY FOR SPEECH 1201

most common type of error, constituting 13% of all errors(275/2,080), contained two phonemes, or one less than thenumber of phonemes in the stimuli.

Because two-phoneme errors were second only in frequencyto three-phoneme errors, they were analyzed in some detail.The vast majority (97% or 267/275) of two-phoneme errorswere CV syllables. Most of the CV errors (70% or 186/267)involved the deletion of the final consonant of a stimulussyllable. For example, one child recalled /vi/ when the listcontained /vib/. These final-consonant omission errors wereanalyzed with respect to the rime type of the syllable thatserved as the source. Analyses of variance (ANOVAs), withthe variables of vowel length (short or long) and consonanttype (liquid, nasal, or obstruent), showed a main effect ofvowel length, F(l, 57) = 20.2, MSE = 0.5, p < .001, a maineffect of final-consonant type, F{2, 114) = 13.0, MSE = 0.8,p < .001, and an interaction between these two variables, F(2,114) = 16.6, MSE = 0.5, p < .001. Omissions of a finalconsonant were most frequent for syllables with long vowelsand final obstruents, with 41% (76/186) of the final-consonantomission errors occurring on these kinds of syllables. The otherfive types of syllables were statistically indistinguishable in thefrequency of final-consonant omissions according to a Scheffetest.

Children may have omitted the final consonant more oftenwith long-vowel syllables than with short-vowel syllables be-cause CV syllables with short vowels are illegal in English.Thus, words such as /vi/ and /be/ do not occur in the Englishlanguage, whereas words such as /bo/ do. The observeddifference between syllables with final obstruents and thosewith final liquids and nasals may reflect the tighter bondbetween vowels and following sonorants than between vowelsand following obstruents. As discussed earlier, vowels andfollowing sonorants appear to form stronger units than vowels

and following obstruents, especially if the sonorant is a liquid(Derwing & Nearey, 1990, 1991; MacKay, 1978; Stemberger,1983; Treiman, 1984; Treiman, Zukowski, et al., 1995).

Although the kindergarteners produced some CV errors,the majority of their errors (79% or 1,633/2,080) containedthree phonemes, thus matching the to-be-remembered stimuliin length. Table 2 provides further information about thesethree-phoneme errors. In the table, subscripts to each pho-neme indicate the syllable to which the phoneme belonged inthe to-be-remembered list. Phonemes that are assigned thesame subscript originated from the same syllable, whereasphonemes that are assigned different subscripts originatedfrom different syllables. The particular letters in the subscriptsare arbitrary; what matters is whether the subscripts forvarious phonemes are the same or different. For example, /sil/produced during recall of the list /deel/, /vib/, /sem/ would beassigned the description CaVbCc. The use of the three differentsubscripts, a, b, and c, means that each phoneme in theresponse syllable belonged to a different syllable in theto-be-remembered list, with /s/ coming from one syllable(/sem/), HI coming from another syllable (/vib/), and HIcoming from yet a third syllable (/dasl/). As another example,/sib/ produced during recall of the same list was coded asCbVaCa. The subscripts mean that /s/ came from one to-be-remembered item, whereas both HI and /b/ came fromanother item. In this coding scheme, the position of a phonemein the response syllable must be the same as its position in thestimulus syllable. Responses in which the position of a pho-neme was not maintained (e.g., /siv/ in the recall of the listindicated above, in which hi was the final phoneme in theresponse syllable but the first phoneme in the to-be-remem-bered syllable /vib/) are classified as "other" errors in Table 2.There were relatively few such errors, as Brady et al. (1983),Ellis (1980), and Treiman and Danis (1988) also observed.

Table 2Types of Three-Phoneme Errors (Number of and Percentage of Total Three-Phenome Errors) Produced byParticipants at Each Developmental Level

Error type

CaVaCa

CaVaQCaVbCaQVaCaCaVaQC,VxCa

QVaCaCaVbCcCaVbCxC.V.Q,QVaQ,QVxCaQVaC,CaViQ,CxVxQ

Other

Kindergarteners

No.

5325066

37619195

240243568403530219

100

%

3.215.34.0

23.011.75.8

14.71.52.14.22.42.11.81.30.66.1

Third graders

No.

14620881

4451421612214857

132546031482076

%

7.610.84.2

23.17.48.3

11.42.53.06.82.83.11.62.51.03.9

Sixth graders

No.

3312951498041222622277859

24265

10622

1054510

%

11.310.15.1

27.54.29.07.82.72.08.32.23.60.83.61.50.3

No.

27612396

30533

1391142320

1082334

726118

Adults

%

20.59.17.1

22.72.5

10.38.51.71.58.01.72.50.51.90.80.6

Note. Subscripts to each phoneme indicate the syllable to which the phoneme belonged in the to-be-remembered list. Phonemes that are assignedthe same subscript originated from the same syllable, whereas phonemes that are assigned different subscripts originated from different syllables.Phonemes in the response syllable that did not appear in any of the stimulus syllables for that trial receive the subscript x. CVC = consonant-vowel-consonant.

1202 REBECCA TREIMAN

Phonemes in the response syllable that did not appear in any ofthe stimulus syllables for that trial received the subscript x. Forexample, /vaedg/ produced during recall of the list /dael/,/vib/, /sem/ was coded as a CaVbQ[ error because /v/ and /as/came from different list items and /d^/ did not appear in thelist. Syllables that were correctly recalled but in the wrongserial position, or order errors, were assigned the descriptionCaVaCa. The three identical subscripts mean that all threephonemes originated from the same to-be-remembered item.

The vast majority of the kindergarteners' three-phonemeerrors (97% or 1,580/1,633) were novel CVC syllables, or itemerrors, rather than syllables from the to-be-remembered listthat were recalled in the wrong serial position, or order errors.Moreover, the item errors were related in a systematic mannerto the list items. Most of these novel CVCs (77% or 1,218/1,580) contained two phonemes from one stimulus, theirpositions the same as in the original stimulus, together with asingle phoneme from a second stimulus or a single phonemethat had not appeared on the list. These errors varied amongthemselves in the nature of the retained unit: QV (the firstconsonant and vowel), VC2 (the vowel and final consonant), orC1C2 (the two consonants). They also varied in the source ofthe third phoneme: a phoneme from the to-be-rememberedlist or a phoneme from outside the list. Errors in which allphonemes were from the original list are most likely to be trueconjunction errors in which children incorrectly combinephonemes from one remembered syllable with phonemes fromanother remembered syllable. Errors with a phoneme fromoutside the list may arise when children misrecall a singlephoneme of a CVC.

To study the nature of the children's recombination errors, Icarried out an ANOVA with the variables of type of retainedunit (CiV, VC2, or CiC2) and source of the third phoneme(inside list or outside list). This analysis showed a main effectof source of the third phoneme, F(l, 57) = 14.3, MSE = 6.4,p < .001. Errors in which all phonemes were from the stimuluslist outnumbered errors that included a phoneme from outsidethe list. There was also an effect of type of retained unit, F(2,114) = 46.1, MSE = 9.6,p < .001, and an interaction betweentype of unit and source, F(2,114) = 9.4, MSE = 5.1,p < .001.In view of the interaction, errors with all phonemes from thelist and errors with one phoneme from outside the list wereseparately analyzed. When all phonemes were from the list,VC2 units were retained significantly more often than QVunits according to a Scheffe test. C{V units were in turnretained more often than QC2 units. Another way of describ-ing these results is that CbVaCa errors reliably outnumberedCaVaCb errors, which in turn outnumbered CaVbCa errors.When one phoneme was from outside the list, the pattern wasthe same, but the advantage for VC2 units over QV units didnot reach significance (p = .09). Thus, kindergarteners oftenmaintained the rime of one stimulus syllable and combined itwith the wrong onset, frequently an onset from a differentto-be-remembered item.

To determine whether these onset-rime recombinationerrors were more common for some syllables than for others, Iexamined the source of the Q and VC2 units in the clearonset-rime recombination errors (i.e., those coded as CbVaCa

in Table 2). For the Q units, an ANOVA, with the variables of

type of final consonant of the origin syllable (liquid, nasal, orobstruent) and type of vowel of the origin syllable (short orlong), showed no significant effects. For VC2 units, however,there was a main effect of final-consonant sonority, F(2,114) = 4.1, MSE = 0.7,p < .025. The VC2 unit was more likelyto originate from a syllable with a postvocalic liquid than asyllable with a postvocalic nasal or obstruent. As in severalprevious studies with adults and children (Derwing & Nearey,1990, 1991; MacKay, 1978; Stemberger, 1983; Treiman, 1984;Treiman, Zukowski, et al., 1995), a vowel and a final liquidappeared to form an especially cohesive unit.

The most important result of this experiment is that kinder-garteners, like older children and adults in previous studies(Brady et al., 1983,1987; Ellis, 1980; Treiman & Danis, 1988),often joined the onset of one to-be-remembered stimulus withthe rime of another to-be-remembered stimulus to produce asyllable that was not in the original list. Such conjunctionerrors, which formed 23% (376/1,633) of the kindergarteners'three-phoneme errors, significantly outnumbered errors inwhich the initial consonant and vowel of one stimulus syllablejoined with the final consonant of another (15% of three-phoneme errors or 250/1,633) and errors in which the twoconsonants of one stimulus syllable joined with the vowel ofanother (4% of three-phoneme errors or 66/1,633). These resultsindicate that onset-rime coding of CVC syllables for memorypurposes is already in place by kindergarten.

There were hints in the kindergarten data that onset-rimecoding was particularly prevalent for syllables with finalliquids. The phonological rime was especially likely to beretained as a unit and combined with another onset when therime's final consonant was a liquid. Also, children were lesslikely to drop the final consonants of stimuli with final liquidsand nasals than of stimuli with final obstruents.

The results for third graders are presented next. I expectedthat the third graders, like those studied by Brady et al. (1983),would show many onset-rime recombination errors in theshort-term memory task.

Third Graders

Method

Participants. The third graders were from the same school as thekindergarteners. The data of 2 children were not analyzed becausetheir speech was unclear on the tape recording. The final sample of 39third graders had a mean age of 8 years, 7 months (range: 7 years, 9months-9 years, 11 months).

Stimuli. The same lists of nonsense syllables that were preparedfor the kindergarteners were used for the third graders. To accommo-date the third graders' greater memory spans, I added either one ortwo digits to each list. The digits were added to the beginning of thelist, the end of the list, or both. Each of the digits 1-9 was usedapproximately equally often across lists, and the same digit neverappeared more than once per list.

Procedure. All third graders began the experiment with lists ofthree syllables and one digit. If after 10 lists the child's error rate forsyllables was less than 25%, the child was switched to lists thatincluded two digits. If over the next 10 lists the child continued to makeless than 25% errors on the syllables of the five-item lists, five-item listswere used in the second session as well. If not, the child began thesecond session with four-item lists and moved to five-item lists if he or

ERRORS IN MEMORY FOR SPEECH 1203

she met the performance criterion after 10 lists. In all other respects,the procedure was like that for kindergarteners.

Results and Discussion

Because the lists for the third graders contained bothnonsense CVC syllables and digits, a first question is whetherthe children treated the digits and syllables as belonging todifferent categories. It appeared that they did, as responsesthat combined a digit name with all or part of a nonsensesyllable were rare. One such response is /naind3/, when thedigit 9 and the syllable /zaid3/ had appeared on the to-be-remembered list. Recombination errors involving digits andnonsense syllables were also very infrequent for the sixthgraders and the adults.

The third graders' error rate was 50%, somewhat higherthan the kindergarteners'. As the results in Table 1 show, thethird graders' most common type of error (83% of all errors or1,930/2,332) contained three phonemes. The percentage oftwo-phoneme responses, at 8% of the errors (184/2,332), wassmaller than it was for kindergarteners. Slightly over 40% ofthese two-phoneme errors appeared to reflect the omission ofthe final consonant of a stimulus syllable. Because thesefinal-consonant omissions were less common than they werefor kindergarteners, they were not analyzed further.

The results in Table 2 show that most of the third graders'three-phoneme errors (92% or 1,784/1,930) were item errors,or new CVC syllables that had not appeared on the originallist, rather than order errors, or syllables from the original listthat were recalled in the wrong position. The majority of thesenew CVCs (71% or 1,258/1,784) contained two phonemesfrom one stimulus syllable together with a single phonemefrom another stimulus or a single phoneme from outside thelist. These errors were analyzed by using the variables ofretained unit type (C{V, VC2, or CiC2) and source of the thirdphoneme (inside list or outside list). There was a significanteffect of phoneme source, F(l, 38) = 15.1, MSE = 12.4,/? <.001. More errors had the single phoneme from inside the listthan outside the list. Also, there was an effect of unit type, F(2,76) = 63.9, MSE = 9.8, p < .001, and an interaction betweenunit type and phoneme source, F(2, 76) = 52.2, MSE = 5.6,p < .001. In view of the interaction, separate analyses wereperformed for each value of phoneme source. In both analyses,VC2 units were recalled significantly more frequently than thetwo other types of two-phoneme units according to Scheffetests. The interaction was due to there being a three-waydifference (VQ > QV > CiC2) for syllables in which thesingle phoneme was from the list but only a two-way difference(VC2 > CjV = QC2) for syllables in which the single pho-neme was from outside the list. In summary, the results of thisanalysis indicate that the third graders' most frequent type oferror combined the rime of a stimulus syllable with a single-consonant onset.

To determine whether onset-rime recombination errorswere more frequent for some kinds of stimuli than for others, Iperformed additional analyses to examine the source of the Qand the VC2 in the Q,VaCa recombination errors. For initialconsonants, there was an interaction between the sonority ofthe final consonant of the stimulus syllable and vowel length,

F(2, 76) = 3.6, MSE = 1.5, p < .05. Initial consonants weremost likely to originate from CVCs with long vowels and finalliquids. For rime units, there was a main effect of final-consonant sonority, F(2,76) = 5.4, MSE = 1.4,p < .01, and aninteraction between sonority and vowel length, F(2, 76) =10.3, MSE = 1.4,p < .001. VC2 units, like Q units, were mostlikely to originate from syllables with long vowels and finalliquids. These results suggest that syllables with long vowelsand final liquids are especially likely to become unglued intoonset and rime units.

The most important result of this study is that the thirdgraders had a tendency to retain the rime of one to-be-remembered syllable, combining it with the onset of anothersyllable. This is the same pattern of results that Brady et al.(1983) found for third graders in the case of real words. Bothwith real words and nonwords, then, third graders showevidence of onset-rime coding of auditorily presented stimuliin short-term memory.

Sixth Graders

Method

Participants. Children were selected from a middle school in thesame school district as the school attended by the kindergarteners andthird graders. There were 46 children with a mean age of 11 years, 8months (range: 10 years, 4 months-12 years, 10 months).

Stimuli. The lists of nonsense syllables were the same as those usedwith the other age groups. However, list length was tailored to eachchild's memory span by adding digits to the three-syllable lists. Eithertwo or three digits were added to each list, depending on the child'sperformance, as described below.

Procedure. All children began the experiment with two five-itempractice lists. If the child recalled both practice lists perfectly, the childbegan the experiment with six-item lists. Then the same rule for increasingand decreasing list length was applied as with the third graders. Theprocedure was otherwise the same as that for the younger children.

Results and Discussion

The sixth graders' error rate was 61%, higher than that forthe kindergarteners and third graders. The difference meansthat the present study was not altogether successful in itsattempt to equate overall level of performance across agegroups. As for the younger children, the most common type oferror contained three phonemes (see Table 1). Becausetwo-phoneme errors were less frequent than they were forkindergarteners and third graders (just 5% of the sixth graders'errors contained two phonemes), only three-phoneme errorswere analyzed in depth.

The composition of the sixth graders' three-phoneme errorsis detailed in Table 2. Most of the three-phoneme errors (89%or 2,591/2,922) were item errors, or CVC syllables that werenot presented, rather than order errors, or items from theoriginal list that were output in the wrong order. Moreover, theitem errors were related in a systematic manner to theto-be-remembered stimuli. The majority of them (72% or1,859/2,591) contained two phonemes from one to-be-remembered syllable together with a single phoneme fromanother stimulus or a single phoneme from outside the list.The errors were analyzed by using the variables of retained

1204 REBECCA TREIMAN

unit type (Q V, VC2, or QC2) and source of the third phoneme(inside list or outside list). There was a significant effect ofphoneme source, F{\, 45) = 91.3, MSE = 16.2, p < .001. Asfor the younger children, more of the error syllables had thesingle phoneme from inside the list than outside the list. Alsosignificant was the effect of unit type, F(2, 90) = 91.0, MSE =15.5, p < .001, and the interaction of unit type and phonemesource, F(2, 90) = 130.3, MSE = 10.2, p < .001. When thesingle consonant was from the list, Scheffe tests showed thatVC2 units were retained significantly more frequently thanCiV units, which were in turn retained more frequently thanQ Q units. When the single consonant was from outside the list,the difference between VQ units and Q Q units was not reliable,but both of these units were retained more often than Q V units.

Analyses were carried out to examine the type of syllablefrom which the retained Q and VC2 units originated. Forinitial consonants, neither the type of vowel nor the type offinal consonant in the stimulus syllable had a significant effect.For VC2 units, however, there was a main effect of final-consonant sonority, F(2, 90) = 8.8, MSE = 1.9,p < .001, andan interaction between final-consonant sonority and vowellength, F(2, 90) = 22.0, MSE = 3.2,p < .001. VC2 units weremost likely to originate from syllables with long vowels andfinal liquids, as observed for the third graders. Rimes with finalliquids appeared to be especially cohesive when they containedlong vowels. This result is somewhat puzzling. Selkirk's (1982)theory suggests that it is short vowels that cohere most closely withthe following consonant (at least when the consonant is a sono-rant), and there is a limited amount of psycholinguistic evidence forthis suggestion (Fowler et al., 1993; Derwing & Nearey, 1990).

Despite this one puzzling finding, the main results for thesixth graders are clear. The sixth graders showed the same generalpattern as that observed for the younger children: more onset-rimerecombination errors than other types of recombination errors andmore onset-rime recombination errors than order errors.

Adults

Method

Participants. The participants were 24 students enrolled in psychol-ogy classes at Wayne State University in Detroit. Participants receivedcourse credit in exchange for taking part in the experiment.

Stimuli. Three digits were added to each list of three nonsensesyllables to construct the lists for the adult participants. For half of thelists, there were two digits at the beginning and one at the end; for theother half of the lists, the pattern was reversed.

Procedure. The procedure used with the children was changed intwo ways. First, the lists were tape recorded by a female speaker nativeto Detroit at a rate of one item per second. Tapes were recorded in asound-attenuated booth by using a Uher 4200 tape recorder, whichwas also used to present the stimuli to participants. A second changewas that the entire experiment was run in one session of about 45 min.There was a short break between the two sets of stimuli.

Results and Discussion

The adults' error rate was 56%. Their most common type oferror contained three phonemes (see Table 1). Becausetwo-phoneme errors were quite uncommon, constituting only2% of all errors, they were not analyzed further.

Table 2 details the composition of the adults' three-phoneme errors. As with the children, the majority of theerrors (80% or 1,070/1,346) were item errors, or syllables thatdid not appear in the original list, rather than order errors, orsyllables that were recalled in the wrong position. Of thethree-phoneme intrusion errors, the majority (76% or 810/1,070) contained two phonemes from a to-be-rememberedstimulus. An analysis, with the variables of retained unit type(QV, VC2, or QC2) and source of the third phoneme (insidelist or outside list), showed a significant effect of source, F(l,23) = 42.0, MSE = 9.4, p < .001. More syllables had the singlephoneme from the list than from outside the list, the samepattern that was observed with the children. There was also aneffect of unit type, F(2,46) = 36.2, MSE = 10.5,p < .001, andan interaction of unit type and source, F(2,46) = 40.2, MSE =7.1, p < .001. When the single consonant was from the list,VC2 units were retained more frequently than QV and QC2

units, which did not differ significantly from one anotheraccording to a Scheffe test. When the single consonant was notfrom the list, VC2 and QC2 segments were recalled atequivalent rates and both more frequently than C{V units.

When the source of the Q,VaCa errors was analyzed, nosignificant effects were found for the vowel length and final-consonant sonority of the source syllable. That is, the initialconsonant and rime unit involved in the recombination errors wereno more likely to come from one type of syllable than another.

The results of this study are largely similar to those ofTreiman and Danis (1988). In this study, as in the Treiman andDanis study, item errors that combined the onset of oneto-be-remembered CVC with the rime of another CVC werethe single most common type of error. Order errors weresecond in frequency in both studies. Indeed, for the 15 types oferrors in Table 2 that were tallied in both studies (i.e., all butthe errors classified in the other category), there was acorrelation of .85 (p < .001, one-tailed) between the numberof errors that was made in the present study and the number oferrors that was made in the Treiman and Danis study.

One discrepancy between the present study and that ofTreiman and Danis (1988) is that in the earlier study VC2

retentions were especially common relative to the other typesof two-phoneme retentions for syllables ending in liquids. VC2

retentions appeared to be intermediate in frequency forvowel-nasal rimes and least frequent for vowel-obstruentrimes. Such a trend was not found with the adults tested here,although there were some effects of final-consonant type forthe children. The results of Treiman and Danis may have beenbiased by the unequal numbers of final liquids, nasals, andobstruents in that study. There were 2 possible final liquids, 3nasals, and 13 obstruents in the earlier study. Suppose that aparticipant was attempting to recall a CVC with a final liquid,and that information about the final consonant had faded tothe point that the participant knew that the consonant was aliquid but did not know its identity. The participant couldguess the correct liquid half the time. Guesses would be muchless successful with obstruents. Thus, the number of apparentretentions of the VC2 unit may have artificially been elevatedfor liquids. This should not have been a problem in the presentstudy as there were two final phonemes of each type.

ERRORS IN MEMORY FOR SPEECH 1205

Despite this point of disagreement, the findings of the twoadult studies are broadly similar. Given a list of CVC nonwordsto recall, normal adults often combine the rime of one to-be-remembered syllable with the onset of another syllable. Theseonset-rime recombination errors are more frequent than othertypes of item errors and are also more frequent than order errors.

Combined Analyses

Several analyses were done to compare the results at thefour developmental levels. A first analysis was performed onthe percentage of correct responses. The results showed asignificant effect of developmental level, F(2, 163) = 46.3,MSE = 345.4, p < .001. Scheffe tests revealed that kindergar-teners performed better than the other three groups and thatthird graders performed better than sixth graders. Thus, thisstudy was not wholly successful in equating performance acrossthe four developmental levels. Because the results of mostinterest concerned the types of errors, though, this is not aserious problem.

A second analysis compared the three types of clear recom-bination errors: CbVaCa (onset-rime), CaVbCa, and CaVaCb.There was a main effect of grade, F(3, 163) = 38.5, MSE =17.5, p < .001, and a main effect of error type, F(3, 164) =274.7, MSE = 12.9, p < .001, as well as an interaction betweenthese two variables, F(3, 163) = 18.6, MSE = 12.9, p < .001.As described earlier, Q,VaCa recombinations were significantlymore common than either of the other two types of recombina-tions at each developmental level. The magnitude of thedifference did vary across the four developmental levels. Forkindergarteners, CbVaCa recombinations formed 54% of thetotal of CbVaCa, CaVbCa, and CaVaCb recombinations. Forthird graders the figure was 61%, for sixth graders 65%, andfor adults 58%. Looked at in this way, the priority of onset-rime recombinations over other types of recombination errorswas somewhat less for kindergarteners than it was for olderchildren and adults, but not substantially so. The most impor-tant point is that onset-rime recombinations formed well overone third of the total at each level. Were any two phonemes ina CVC equally likely to behave as a unit, CbVaCb errors shouldhave made up one third of the total of CbVaCa, CaVbCa, andCaVaCb recombinations. Even for kindergarteners, then, thevowel and the final consonant of a CVC have a special bond.

General Discussion

The results of this study show that phenomena that occur inshort-term serial memory for verbal materials do not necessar-ily occur in short-term serial memory for nonwords. Withletters and digits, errors in which a to-be-remembered item isrecalled in the wrong serial position outnumber errors in whicha recalled item was not on the original list (e.g., Aaronson,1968). With nonsense syllables, in contrast, item errors outnum-ber order errors. Even more important, the item errors arelinguistically related to the to-be-remembered items. The itemerrors usually match the stimuli in terms of number ofphonemes and sequence of consonants and vowels. In addi-tion, the incorrect items typically contain phonemes or groupsof phonemes from the to-be-remembered syllables. With the

CVC syllables studied here and by Treiman and Danis (1988),the most common item error joined the initial consonant oronset of one to-be-remembered syllable with the vowel andfinal consonant or rime of another to-be-remembered syllableto form a syllable that was not on the original list.

These phonological recombination errors suggest that memo-ries for spoken syllables, like memories for visually presentedwords and faces (e.g., Reinitz et al., 1992,1994), are not storedand retrieved as single, indivisible units. Moreover, the fea-tures that play a role in memory for speech do not behave asindependent units. Some phonemes tend to function as groupsin short-term recall, whereas other phonemes are separatelytreated. The vowel and final consonant of a CVC syllable oftenbehave as a unit, the initial consonant being relatively indepen-dent. Thus, the vowel and final consonant of one syllable mayblend with the initial consonant of another syllable to yield aCVC syllable that was not on the original list. This dependenceamong phonemes contrasts with the independence that is observedfor experimenter-defined "chunks" of letters and digits in tradi-tional short-term memory studies (Lee & Estes, 1981).

The memory conjunction errors suggest that linguistic struc-ture plays an important role in short-term memory for speech.Specifically, the onset and rime units of many linguistictheories of the English syllable (e.g., Fudge, 1969,1987,1989;Selkirk, 1982) also appear to be units of language processing.Previous studies (see Treiman, 1989, 1992, for reviews) indi-cated that onset and rime units play a role in the performanceof metalinguistic tasks. They are also involved in speechproduction and in the perception of printed words. Thepresent results show, in addition, that the phonological units ofonset and rime are important in short-term memory.

Although the present results provide strong support for theonset-rime division of the English syllable, they are lessconclusive with regard to differences among various types ofrimes. For children, there was some evidence that vowels andliquids are especially cohesive, especially (in the third-gradeand sixth-grade data) if the vowels are long. For adults, no suchdifferences were observed. The question of whether sometypes of rimes form stronger units than others in short-termmemory requires further study.

Another open question concerns the degree to which thecohesiveness between vowels and final consonants that isobserved in short-term memory reflects the coarticulation thatoccurs in speech. Perhaps vowels and final consonants areremembered together because the pronunciation of the vowelis affected by the final consonant, and vice versa. At least inCatalan, the identity of the first vowel in a VCV sequence has alarger effect on the pronunciation of the consonant than doesthe identity of the second vowel (Recasens, 1984). This resultcould be interpreted to mean that a vowel and a followingconsonant form a unit from an articulatory point of view.However, MacNeilage and DeClerk (1969) argued that thevowel of a CVC syllable exerts a stronger effect on the initialconsonant than the final consonant does on the vowel. Theysuggested, on the basis of this result, that the CV is a morecohesive or interdependent portion of the syllable than theVC. I know of no studies comparing coarticulatory effects oflong and short vowels. There are some data suggesting thatfricatives resist coarticulation more than stops (Fowler, 1994),

1206 REBECCA TREIMAN

but I know of no data comparing the degree of coarticulationfor liquids, nasals, and obstruents.

To assess the degree to which children's grouping ofphonemes in memory reflects coarticulation, it would beimportant to know about the coarticulation that occurs in theirspeech. The few studies on this topic have yielded mixedresults. Turnbaugh, Hoffman, Daniloff, and Absher (1985)reported no significant differences among 3-year-olds, 5-year-olds, and adults in terms of stop-vowel coarticulation. Nit-trouer, Studdert-Kennedy, and McGowan (1989) found thatchildren seem to coarticulate fricative-vowel syllables morethan adults, whereas Sereno and Lieberman (1987) reportedthat at least some children coarticulate less. Sereno, Baum,Marean, and Lieberman (1987) also found more variability inchildren than in adults. Obviously, further empirical studies ofchildren and adults are needed to examine the issue ofcoarticulation and how it is related to the chunking ofphonemes in short-term memory.

Despite the unanswered questions, it is clear that models ofshort-term memory for speech must give serious considerationto linguistic structure. Most existing models do not do this.Models that have been developed to account for recall of listsof digits and letters are fairly successful at explaining misorder-ings of whole items (e.g., Burgess & Hitch, 1992; Estes, 1972;Lee & Estes, 1977, 1981; Lewandowsky & Murdock, 1989;Shiffrin & Cook, 1978). However, these models fail to explainthe kinds of errors observed here in which phonemes from onelist item combine with nonadjacent phonemes from anotheritem. One recent model that does attempt to incorporateeffects of phonological structure is that of Hartley and Hough-ton (in press). This connectionist model of short-term memoryfor unfamiliar phonological forms extends the Burgess andHitch model by including a syllabic template intended tocapture constraints on the order of phonemes with a syllable.The model also includes representations of the onset and rimeparts of the syllable. The Hartley and Houghton model, likethe participants in the Treiman and Danis (1988) study andthis study, produces a large number of item errors that involvephonemes from the to-be-remembered list. As in the humandata, the most common type of recombination error joins theonset of one presented syllable and the rime of another.Future modeling work will need to build on the successes ofthe Hartley and Houghton model and to fully explain theeffects of linguistic structure.

The present study goes beyond previous work by examiningthe development of phonological coding in short-term memory.The results show that onset-rime coding is well in place by thetime that children are in kindergarten, about 5- to 6-years-old.For kindergarteners, errors that combined the onset of oneto-be-remembered stimulus and the rime of another signifi-cantly outnumbered any other single type of recombinationerror. They also outnumbered order errors in which an entireto-be-remembered syllable was recalled in the wrong serialposition. The same was true for third graders, sixth graders,and college students. Thus, the use of linguistic structure formemory purposes is a robust phenomenon that does notdepend on high levels of literacy or cognitive skill. Rather thanbeing a deliberate strategy that requires a good deal ofcognitive sophistication, it appears to be a basic characteristic

of human memory. The results imply that the increase inmemory span that occurs between the ages of five and six andadulthood does not reflect a fundamental change in phonologi-cal organization or ability to exploit this organization formemory purposes. It will be necessary to look elsewhere toexplain the improvement in memory span that occurs with age.

Previous research shows that linguistic structure affectschildren's performance on explicit metalinguistic tasks. Evenbefore they learn to read, some children can segment spokensyllables into onset and rime units. For example, they can judgewhether two words rhyme or whether they share an onset (e.g.,Treiman & Zukowski, 1991). When children begin to read andwrite, they search for orthographic units that correspond to thephonological units of onsets and rimes (e.g., Goswami, 1993;Treiman, 1992). They take advantage of the relatively stableway in which rimes are spelled in the English writing system(Treiman, Mullennix, Bijeljac-Babic, & Richmond-Welty, 1995).The present results show that children's use of phonologicalstructure is not confined to metalinguistic tasks and reading.English-speaking children, like adults, use the onset-rime organiza-tion of the syllable in remembering and recalling speech.

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{Appendix follows on next page)

1208 REBECCA TREIMAN

Appendix

The 40 Three-Syllable Lists

Key to notation: lal as in hot, 111 as in bit, /e/ as in bet, Is. I as in bat, hi as in bought, /u/ as in book, I si as in but, HI as in beet, /e/ as in bait, /u/ asin boot, lol as in boat, /au/ as in bout, /ai/ as in bite, /oi/ as in boy, /[/ as in j/iut, /nY as in song, /d$l as in yet, / j / as in yet, and /B/ as in rting.

1. /dael/, /vib/, Istml 24. /vem/,/dar/,2. /daum/,/sub/,/gar/ 25. /sul/, /dom/, /gaib/3. Izxnl, /gil/, /hAd3/ 26. /did3/, /hul/, /sim/4. /gid3/, /vaur/, /zen/ 27. /vol/, /zaid3/, /gen/5. /don/,/vaeb/,/zail/ 28. /gom/, /ser/, /did3/6. /ssd3/, Ml/,/gin/ 29. /zam/, Md3/, /hul/7. /sar/,/gim/,/heb/ 30. /doil/,/hain/,/zud3/8. /gAb,/son/,/hoil/ 31. /hoid3/, /zel/, /vim/9. /hur/,/zaum/,/daed3/ 32. /vaid3/,/dun/,/saul/

10. /hin/,/gul/,/soib/ 33. /zun/,/gal/,/vub/11. /zol/, /vaem/, /hub/ 34. /gon/,/saeb/,/voil/12. /zob/,/dum/, M>1/ 35. /gel/, /doib/, /z/vn/13. /gaen/,/sail/,/dob/ 36. /gam/,/hob/,/sul/14. Mil/, /tan/, /saud3/ 37. /vum/, /goil/, /zid3/15. /gaim/,/haed3/,/zaul/ 38. /daud3/,/ZAI/,/hen/16. /sal/, /houn/, /veb/ 39. /dub/,/var/,/som/17. /VAI/,/haid3/,/zom/ 40. /sum/,/ded3/,/har/18. /zib/, /gair/, /von/19. /hal/, /d£d3/, Izitnl20. /gud3/,/doim/,/SAI/ , . . . „ „ .21. /dur/, /han/, / K b / Received March 14,199422. /soin/, /jeb/, /gaul/ Revision received September 16,199423. /za;l/, /vim/, /dob/ Accepted October 6,1994