Phonological encoding in speech production: Comments on ...

2 Willem J. M. LeveltIntroduc<strong>in</strong>g this use of the term to denote the speaker's phonologicalpreparation of the utterance was by no means <strong>in</strong>troduc<strong>in</strong>g thestudy of this process. Clearly, the study of phonological <strong>encod<strong>in</strong>g</strong>has its roots <strong>in</strong> <strong>speech</strong> error analysis, go<strong>in</strong>g back as far as Mer<strong>in</strong>gerand Mayer's (1895) careful analysis of form errors <strong>in</strong> spontaneous<strong>speech</strong>. They dist<strong>in</strong>guished between mean<strong>in</strong>g-based substitutions(such as Ihre for me<strong>in</strong>e) and form-based substitutions (such as Studienfor Stunden), which suggested the existence of two levels ofprocess<strong>in</strong>g <strong>in</strong> <strong>speech</strong> <strong>production</strong>, one of which concerns form <strong>encod<strong>in</strong>g</strong>.This notion was elaborated <strong>in</strong> much detail by Garrett(1975). He discovered that word exchanges (such as he left it andforgot it beh<strong>in</strong>d) can be between phrases or clauses, but preservesgrammatical category and grammatical function. By contrast,sound exchanges (such as rack pat for pack rat) mostly happenbetween juxtaposed or close-by words, which can differ <strong>in</strong> grammaticalcategory and function. Apparently two levels of process<strong>in</strong>gare <strong>in</strong>volved <strong>in</strong> utterance generation, which Garrett called the'functional' and 'positional' levels. The latter <strong>in</strong>volves morphologicalprocesses such as affixation and all further phonological(though not phonetic) process<strong>in</strong>g. Except for details of phoneticpreparation this level of process<strong>in</strong>g co<strong>in</strong>cides with 'phonological<strong>encod<strong>in</strong>g</strong>' as outl<strong>in</strong>ed above.A landmark development <strong>in</strong> model<strong>in</strong>g the process of phonological<strong>encod<strong>in</strong>g</strong> was Shattuck-Hufnagel's (1979) Scan-Copier Model,with its slots-and-filler mechanism of word form <strong>encod<strong>in</strong>g</strong> <strong>in</strong> utterancecontext. The review of phonological <strong>encod<strong>in</strong>g</strong> <strong>in</strong> Levelt (1989)is largely <strong>in</strong>spired by this model<strong>in</strong>g effort. The Scan-Copier Modelwas based on both a detailed corpus analysis of phonological<strong>speech</strong> errors and on the results of systematic error-<strong>in</strong>duc<strong>in</strong>g experiments,an important methodological <strong>in</strong>novation, which br<strong>in</strong>gsus to laboratory phonology.In retrospect, the laboratory study of phonological <strong>encod<strong>in</strong>g</strong>was quite late to develop. Whereas the experimental study of<strong>speech</strong> perception was a long established field by 1975, the laboratorystudy of <strong>speech</strong> <strong>production</strong> was either articulatory phonetics,the study of the vocal tract's <strong>production</strong> of <strong>speech</strong> sounds, or read<strong>in</strong>g-basedstudy of prosody. There existed a tacit but quite general

<strong>Phonological</strong> <strong>encod<strong>in</strong>g</strong> 3disbelief that one would ever be able to ga<strong>in</strong> experimental outputcontrol over a speaker's natural utterance <strong>production</strong>, <strong>in</strong>clud<strong>in</strong>gphonological <strong>encod<strong>in</strong>g</strong>.This has drastically changed. A range of experimental paradigmshave been <strong>in</strong>vented over the past quarter century that doprovide for that type of output control. Among them are theabove-mentioned error-<strong>in</strong>duction paradigms, <strong>in</strong>troduced by Baarset al. (1975). But more importantly, there are the chronometricnam<strong>in</strong>g paradigms stemm<strong>in</strong>g from an old tradition <strong>in</strong> studies ofread<strong>in</strong>g and picture nam<strong>in</strong>g (cf. Levelt, 1999 for a review). Thattradition first touched issues of phonological <strong>encod<strong>in</strong>g</strong> whenLupker (1982) discovered that the latency of nam<strong>in</strong>g a picture wasreduced when simultaneously with the picture a visual distractorword was presented that rhymed with the target picture name (ascompared to a situation where a non-related distractor word waspresented). This 'orthographic' facilitation is really phonologicalfacilitation. It is also obta<strong>in</strong>ed when the distractor word is presentedauditorily. Any segmental phonological correspondence betweendistractor and target can <strong>in</strong>duce facilitation (Schriefers etal., 1990; Meyer & Schriefers, 1991). The contribution of Schilleret al. <strong>in</strong> the present section uses orthographic picture/word <strong>in</strong>terferenceto study, cross-l<strong>in</strong>guistically, whether syllable prim<strong>in</strong>g exists<strong>in</strong> phonological <strong>encod<strong>in</strong>g</strong>.Together with picture/word <strong>in</strong>terference, a range of other chronometricparadigms were developed to study phonological <strong>encod<strong>in</strong>g</strong>(see Levelt 1999 for review), among them the 'implicit prim<strong>in</strong>gparadigm' (Meyer, 1990). If subjects are <strong>in</strong>duced to produce ablock of words that are word-<strong>in</strong>itially phonologically identical(such as loner, local, lotus - 'homogeneous' block), word onsetlatencies are shorter than when the same words are produced <strong>in</strong>'heterogeneous' blocks (e.g. the word loner among beacon and major).The shared word onset <strong>in</strong> a homogeneous block is an 'implicit'phonological prime. The method has been profitably used to studyvarious issues of phonological <strong>encod<strong>in</strong>g</strong>, among them: Is phonological<strong>encod<strong>in</strong>g</strong> an <strong>in</strong>cremental procedure? The clear answer is'yes'. Only word <strong>in</strong>itial primes are effective. Shar<strong>in</strong>g word f<strong>in</strong>alphonology (as <strong>in</strong> deed, feed, seed) is entirely <strong>in</strong>effective. This

<strong>Phonological</strong> <strong>encod<strong>in</strong>g</strong> 5et al. 1999), English and Dutch speakers do more than 80% oftheir talk<strong>in</strong>g with no more than 500 different syllables. My roughestimation is that, on average, we have used each of these syllablesalmost 100.000 times at reach<strong>in</strong>g adulthood, i.e., some 13 timesevery s<strong>in</strong>gle day 2 .Many of these syllables are themselves high-frequency wordsand there is no reason why even multisyllabic high-frequencywords (such as about or really) wouldn't be similarly stored <strong>in</strong> this<strong>speech</strong> motor repository. Levelt et al. (1999) suggest a mechanismby which these high-frequency target syllables are <strong>in</strong>crementallyselected, as phonological syllabification proceeds. This cannot bethe full story, of course. Speakers are also able to phoneticallyencode low-frequency and even new syllables. In addition, phonetic<strong>encod<strong>in</strong>g</strong> <strong>in</strong>volves the further coarticulatory <strong>in</strong>tegration ofsuccessive articulatory syllables.The three papers discussed here address different aspects ofphonological <strong>encod<strong>in</strong>g</strong>. Jurafsky et al. focus on the issue of modularity<strong>in</strong> phonological <strong>encod<strong>in</strong>g</strong>: do homophonous words behavesimilarly <strong>in</strong> phonetic <strong>encod<strong>in</strong>g</strong>, as the above theory predicts, or istheir phonetics co-determ<strong>in</strong>ed by their specific lexical frequency?As mentioned, Schiller et al. consider whether access<strong>in</strong>g the phonologicalcode already <strong>in</strong>volves access<strong>in</strong>g syllable structure. Van Heuvenet al., f<strong>in</strong>ally, address higher levels of phonological <strong>encod<strong>in</strong>g</strong>and decod<strong>in</strong>g, relat<strong>in</strong>g to <strong>in</strong>tonational accentuation <strong>in</strong> statementsversus questions. I will now consider these contributions <strong>in</strong> turn.2. CommentaryThe empirical basis of the staged model of phonological <strong>encod<strong>in</strong>g</strong>,summarized above, is formed by chronometric laboratory data,mostly response latencies <strong>in</strong> word and phrase <strong>production</strong> experiments.In their article, Jurafsky et al. managed to test aspects ofthat theory aga<strong>in</strong>st the wider empirical doma<strong>in</strong> of naturalistic<strong>speech</strong> data. If homophones, such as the pronoun that and thecomplementizer that, share their phonological code but not theirlemma, as Levelt et al. (1999) claim to be the case, could one still

6 Willem J. M. Leveltobserves articulatory differences between them <strong>in</strong> natural connected<strong>speech</strong>? Strictly speak<strong>in</strong>g, the theory and <strong>in</strong> particular Roelofs's(1997) computational model WEAVER++, predict only thatthere will be no difference <strong>in</strong> latency. Latency differences, however,are exactly what is hard to observe <strong>in</strong> naturalistic data; one has nonatural anchor po<strong>in</strong>t for word onset latency. Jurafsky et al.checked <strong>in</strong>stead how the word is realized, its duration, its vowelquality, its coda. It conforms to the nature of the theory to predictthat homophones are phonetically realized <strong>in</strong> the same way (butsee below for a qualification). In particular, the frequency of thelemma should be irrelevant. If not, one has a so-called 'lemmaeffect'. Of course, one should correct for confound<strong>in</strong>g factors, suchas position of the word <strong>in</strong> the utterance, etc. My read<strong>in</strong>g of Jurafskyet al.'s data is that, after apply<strong>in</strong>g a range of careful controls,there are by and large no lemma effects left. This certa<strong>in</strong>ly reflectsthe spirit of our theory. Still, there are some effects. In particular,there is less coda reduction <strong>in</strong> partitive of than <strong>in</strong> genitive andcomplement of. Also, determ<strong>in</strong>er that never showed vowel reductionas the other that lemmas do, and pronom<strong>in</strong>al that tends to belonger than the other thats. Is there a left-over confound<strong>in</strong>g factor<strong>in</strong>volved? My only hunch is that these differences may relate to theprosodic structure of the word's immediate environment. The database did not allow for the mark<strong>in</strong>g of stress and accent, but itcould certa<strong>in</strong>ly have been the case <strong>in</strong> this corpus that the determ<strong>in</strong>erthat is more often accented, <strong>in</strong> particular contrastively, thanfor <strong>in</strong>stance the relative that. This needs further test<strong>in</strong>g.The analysis raises a further theoretical issue worth consider<strong>in</strong>g.How does onset latency (the strict empirical doma<strong>in</strong> of the theory<strong>in</strong> Levelt et al., 1999) relate to articulatory realization, <strong>in</strong> particularword duration? Is the realization of the articulatory gesture, <strong>in</strong>particular its duration,affected by the flow of activation at higher levels of process<strong>in</strong>g?How modular is articulation? Kello et al. (2000) argue aga<strong>in</strong>st fullmodularity. In their experiments they used a Stroop task, <strong>in</strong> whichthe subject names the color of a pr<strong>in</strong>ted word. If the word happensto be the name of a different color (e.g. the word GREEN pr<strong>in</strong>ted<strong>in</strong> red) color nam<strong>in</strong>g latency is substantially slower than when the

<strong>Phonological</strong> <strong>encod<strong>in</strong>g</strong> 7word is the name of the color (e.g. the word RED pr<strong>in</strong>ted <strong>in</strong> red)or a neutral word (e.g. the word CHAIR pr<strong>in</strong>ted <strong>in</strong> red). This iscalled 'Stroop <strong>in</strong>terference'. In Kello et al.'s experimental resultsthis difference <strong>in</strong> latencies had no counterpart <strong>in</strong> the articulatorydurations of the color word response ('red'). So far, articulationseemed to be modular with respect to higher level <strong>in</strong>terference.However, when the authors applied a response deadl<strong>in</strong>e, requir<strong>in</strong>ga speeded response, they found some evidence for prolonged articulatoryduration under Stroop <strong>in</strong>terference. Kello et al. concludedthat a modular system can change its architecture to a cascad<strong>in</strong>gone, dependent on the specific task demands. I will call this 'restrictedmodularity'. However, they obta<strong>in</strong>ed this effect <strong>in</strong> only oneof their experiments, precisely the one <strong>in</strong> which 25 % of the datahad to be removed for various reasons.Damian (2001) took up this topic <strong>in</strong> two carefully controlledexperiments. The first one was a picture/word <strong>in</strong>terference task.Here he obta<strong>in</strong>ed the usual phonological facilitation effect whenthe name of the auditory distractor word was phonologically relatedto the name of the target picture. This facilitation <strong>in</strong> nam<strong>in</strong>glatencies did not 'spill over' to articulatory durations, just as therewas no spill over <strong>in</strong> Kello et al.'s orig<strong>in</strong>al Stroop experiment. However,even when Damian applied a deadl<strong>in</strong>e, which speeded up theresponses, aga<strong>in</strong> not the slightest effect of phonological relatednessshowed up <strong>in</strong> the response durations. In a second experimentDamian affected response latencies by way of a semantic manipulation.A block of pictures to be named was either homogeneous<strong>in</strong> semantic category (e.g., all vehicles, or all vegetables) or heterogeneous(a mix of vehicle, vegetable, etc.). Semantic homogeneityleads to substantial <strong>in</strong>terference, i.e., longer response latencies(Kroll and Stewart, 1994; Damian et al. 2001). In agreement withthe orig<strong>in</strong>al Kello et al. data and with the previous picture/word<strong>in</strong>terference data, there was no concomitant effect on articulatorydurations. But such an effect was also not obta<strong>in</strong>ed when Damianapplied a deadl<strong>in</strong>e, which led to generally shorter nam<strong>in</strong>g latencies.In other words, <strong>in</strong> carefully controlled experiments, no 'spill<strong>in</strong>gover' or cascad<strong>in</strong>g under time pressure could be demonstrated.Thus, so far there is no good evidence aga<strong>in</strong>st the modularity of

8 Willem J. M. Leveltarticulation. This, however, may have theoretical repercussions foranalyses such as those reported by Jurafsky et al. Assume that alemma effect does exist. It should show up <strong>in</strong> response latencies.But if articulation is <strong>in</strong>deed modular, the lemma effect will notaffect articulatory duration. Worse, if Kello et al. were to be rightafter all, there will not be a spill-over at normal, non-speeded articulationrates. Under both theoretical cases, therefore, a null effect<strong>in</strong> Jurafsky et al.'s data does not guarantee the absence of a lemmaeffect. Still, if an even more detailed analysis of these durationdata showed a lemma effect, then both theoretical positions (fulland restricted modularity) would be <strong>in</strong> trouble.Let me now turn to Schiller et al's contribution on syllableprim<strong>in</strong>g. Syllable prim<strong>in</strong>g has never been a happy topic. In a mostcareful dissertation, Baumann (1995) showed that, whatever onedoes experimentally, it is impossible to obta<strong>in</strong> a syllabic prim<strong>in</strong>geffect by way of auditorily presented syllable primes. Of course,one always f<strong>in</strong>ds auditory prim<strong>in</strong>g, but it is irrelevant whether theprime corresponds exactly to a syllable of the target word. Theonly th<strong>in</strong>g that matters is the number of phonological segmentsshared between prime and target. We call this the segmental prim<strong>in</strong>geffect: the more shared segments, the more effective the primeis. This work was done on Dutch and German and one shouldn'texclude the possibility that specific syllabic prim<strong>in</strong>g (beyond segmentalprim<strong>in</strong>g) would be possible for other languages, for <strong>in</strong>stancesyllable timed languages. In their paper Schiller et al. provideconv<strong>in</strong>c<strong>in</strong>g evidence aga<strong>in</strong>st syllable prim<strong>in</strong>g <strong>in</strong> Dutch, English,Spanish, and with a slight hedge, also <strong>in</strong> French, even thoughSpanish and French are clearly syllable-timed.It is theoretically important to observe that the non-existenceof syllable prim<strong>in</strong>g is <strong>in</strong> fact predicted by the WEAVER+ + modelof phonological <strong>encod<strong>in</strong>g</strong> (Roelofs 1997, see also Levelt et al.,1999). As mentioned <strong>in</strong> the <strong>in</strong>troduction, auditory and orthographicprim<strong>in</strong>g affect the level of phonological code retrieval. Thecode is, however, not a syllabified structure. A syllable prime hasno special status <strong>in</strong> code retrieval. Could it affect syllabification?In the theory each auditory or orthographic <strong>in</strong>put segment canprime all related gestural scores <strong>in</strong> the syllabary. But aga<strong>in</strong>, the

<strong>Phonological</strong> <strong>encod<strong>in</strong>g</strong> 9syllabic status of the prime is irrelevant. If the first syllable of atarget word is of the type CVC, then a correspond<strong>in</strong>g CV primewill prime it partially, a correspond<strong>in</strong>g CVC prime will prime itfully, and a correspond<strong>in</strong>g CVCC prime will prime it fully and thenext syllable partially. The total amount of prim<strong>in</strong>g, therefore, issimply a function of the number of segments, not of syllable structure.In short, WEAVER++ predicts prime length effects, but nosyllable effects.It is essentially for the same reason that WEAVER++ predictsa number-of-segments effect <strong>in</strong> phonological word <strong>encod<strong>in</strong>g</strong>, butno number-of-syllables effect. This was recently challenged by Santiagoet al. ( 2000) on the basis of MacKay's Node Structure Theory(NST). They claimed to have obta<strong>in</strong>ed a number-of-syllableseffect but no (<strong>in</strong>dependent) length effect. However, the authorshad not fully controlled for word length <strong>in</strong> their experiments. Areanalysis by Roelofs (2001) shows that there is only a length effect<strong>in</strong> the reported data, no <strong>in</strong>dependent number-of-syllables effect.However, the total absence of syllable prim<strong>in</strong>g and syllablestructure effects <strong>in</strong> latency measurements of phonological <strong>encod<strong>in</strong>g</strong>does mean at all that syllables are not essential plann<strong>in</strong>g units<strong>in</strong> <strong>speech</strong> <strong>production</strong>. Syllables are among the earliest acquiredand most frequently produced motor programs <strong>in</strong> our repertoire.They are, <strong>in</strong> fact, so heavily overused, that it would be impossiblenot to store them. Of course, one can construct new ones, but thatis an exceed<strong>in</strong>gly rare event. In our theory, phonetic, articulatorysyllables are major, ultimate targets of form <strong>encod<strong>in</strong>g</strong>. It should beadded that these gestural scores may well have <strong>in</strong>ternal hierarchicalstructure not unlike the syllabic structures proposed <strong>in</strong> NST. Motorprim<strong>in</strong>g experiments by Sevald, Dell, and Cole (1995) showthat such phonetic syllabic structure is <strong>in</strong>dependent of phonemiccontent.The paper by van Heuven and Haan, f<strong>in</strong>ally, moves us beyondphonological word <strong>encod<strong>in</strong>g</strong>. It addresses an important issue <strong>in</strong>higher, supra-word level phonological <strong>encod<strong>in</strong>g</strong>. From the po<strong>in</strong>tof view of <strong>encod<strong>in</strong>g</strong>, the ma<strong>in</strong> data reported are the measured sentencemelodies of statements versus declarative questions. In thesemeasurements the syntax was kept constant; we are gett<strong>in</strong>g a pure

10 Willem J. M. Leveltview of <strong>in</strong>tonational differences between the two sentence moods.Clearly and expectedly, the two melodies differ markedly <strong>in</strong> theirboundary tones. But the more <strong>in</strong>terest<strong>in</strong>g f<strong>in</strong>d<strong>in</strong>g is that they alsodiffer <strong>in</strong> other respects. Apparently, speakers give away the modeof their utterance long before they generate the boundary tone.There is, <strong>in</strong> particular, a difference <strong>in</strong> the balance of the two pitchaccents <strong>in</strong> the sentence melody. To the best of my knowledge, thisphenomenon has not been reported before. The authors argue conv<strong>in</strong>c<strong>in</strong>glythat this difference results from an amalgamate of several<strong>encod<strong>in</strong>g</strong> processes. It is not the case that the speaker decides tomake an <strong>in</strong>terrogative statement and then <strong>in</strong>crementally <strong>in</strong>stallsthese melodic features. Rather, each feature is <strong>in</strong>stalled for its ownreason. In particular, if the speaker wants to <strong>in</strong>vite the <strong>in</strong>terlocutor'sconfirmation that a particular referent was <strong>in</strong>volved <strong>in</strong> somestate of affairs, the speaker will focus that referent by pitch accent.In itself, this has noth<strong>in</strong>g to do with <strong>in</strong>terrogation, but it doescause the characteristic imbalance of pitch accents. It should notbe too complicated to elaborate this decompositional approach,and test it <strong>in</strong> the laboratory.One advantage of this theory of <strong>in</strong>tonational <strong>encod<strong>in</strong>g</strong> is thatit allows for a limited plann<strong>in</strong>g w<strong>in</strong>dow. Speakers are often underso much time pressure that they cannot afford much 'look ahead'<strong>in</strong> their conceptual, grammatical and phonological <strong>encod<strong>in</strong>g</strong>. Thearchitecture of <strong>speech</strong> <strong>encod<strong>in</strong>g</strong> must allow for piecemeal, <strong>in</strong>crementalplann<strong>in</strong>g (Levelt, 1989). A decompositional stepwise <strong>encod<strong>in</strong>g</strong>of question <strong>in</strong>tonation relieves the speaker of attentionallyload<strong>in</strong>g long-term plann<strong>in</strong>g, but still, the outcome will be a naturalpitch contour. I am not claim<strong>in</strong>g that speakers always operate atsuch a m<strong>in</strong>imal look ahead level. When there is no particular timepressure, or when the speak<strong>in</strong>g situation is a more formal one,<strong>in</strong>cremental <strong>encod<strong>in</strong>g</strong> units can become larger, especially forskilled speakers.It should not go unnoticed that the ma<strong>in</strong> experimental contributionof van Heuven and Haan's paper is their f<strong>in</strong>d<strong>in</strong>g that listenerscan, by and large, pick up the characteristic pre-boundarypitch cues. However, that moves us beyond phonological <strong>encod<strong>in</strong>g</strong>.

<strong>Phonological</strong> <strong>encod<strong>in</strong>g</strong> 11The studies discussed <strong>in</strong> this section support a general view ofphonological <strong>encod<strong>in</strong>g</strong> as a multilevel, <strong>in</strong>cremental process. Thelevels of <strong>encod<strong>in</strong>g</strong>, from <strong>in</strong>tonational to syllabic, <strong>in</strong>volve dedicatedand rather modular operations. Incrementality is achieved by m<strong>in</strong>imiz<strong>in</strong>g'look ahead' at all levels of process<strong>in</strong>g.Notes1 Glossary 'Learn<strong>in</strong>g to read ... read<strong>in</strong>g to learn' of the National Center toImprove the Tools of Educators. http://ldonl<strong>in</strong>e.com/ld_<strong>in</strong>depth/read<strong>in</strong>g/ltrcec/ltr7-cec.html2 Assum<strong>in</strong>g 45 talk<strong>in</strong>g m<strong>in</strong>utes a day, two words per second, 1.5 syllable wordlength.ReferencesBaars, B. J., Motley, M. T., and MacKay, D1975 Output edit<strong>in</strong>g for lexical status from artificially elicited slips of thetongue. Journal of Verbal Learn<strong>in</strong>g and Verbal Behavior, 14, 382—391.Baumann, M.1995 The <strong>production</strong> of syllables <strong>in</strong> connected <strong>speech</strong>. Unpublished doctoraldissertation. Nijmegen University.Crompton, A.1982 Syllables and segments <strong>in</strong> <strong>speech</strong> <strong>production</strong>. In: A. Cutler (ed.),Slips of the tongue and language <strong>production</strong>. The Hague: Mouton.Damian, M. F.2001 Articulatory duration <strong>in</strong> s<strong>in</strong>gle word <strong>speech</strong> <strong>production</strong>: Evidencefor modularity.Damian, M. F., Vigliocco, G., & Levelt, W. J. M.2001 Effects of semantic context <strong>in</strong> the nam<strong>in</strong>g of pictures and words.Cognition, 00, 00-00Garrett, M. F.1975 The analysis of sentence <strong>production</strong>. In G.H. Bower (ed.). Thepsychology of learn<strong>in</strong>g and motivation: Vol. 9. New York: AcademicPress.Kello, C. T., Plaut, D. C, & MacWh<strong>in</strong>ney, B.2000 The task-dependence of staged vs. cascaded process<strong>in</strong>g: An empiricaland computational study of Stroop <strong>in</strong>terference <strong>in</strong> <strong>speech</strong> <strong>production</strong>.Journal of Experimental Psychology: General, 129, 340—361.

12 Willem J. M. LeveltKroll, J. & Stewart, E.1994 Category <strong>in</strong>terference <strong>in</strong> translation and picture nam<strong>in</strong>g: Evidencefor asymmetric connections between bil<strong>in</strong>gual memory representations.Journal of Memory and Language, 33, 149-174.Levelt, W. J. M.1989 Speak<strong>in</strong>g. From <strong>in</strong>tention to articulation. Cambridge MA: MITPress.Levelt, W. J. M.1992 Access<strong>in</strong>g words <strong>in</strong> <strong>speech</strong> <strong>production</strong>. Stages, processes, and representations.Cognition, 42, 1-22.Levelt, W. J. M.1999 Models of word <strong>production</strong>. Trends <strong>in</strong> Cognitive Sciences, 3,223-232.Levelt, W. J. M. & Wheeldon, L.1994 Do speakers have access to a mental syllabary? Cognition, 50,239-269.Levelt, W. J. M., Roelofs, A., & Meyer, A. S.1999 A theory of lexical access <strong>in</strong> <strong>speech</strong> <strong>production</strong>. Behavioral andBra<strong>in</strong> Sciences, 22, 1 —38.Lupker, S. J.1982 The role of phonetic and orthographic similarity <strong>in</strong> picture-word<strong>in</strong>terference. Canadian Journal of Psychology, 36, 349-367.Mer<strong>in</strong>ger, R. and Mayer, K.1895 Versprechen und Verlesen. Stuttgart: Goschensche Verlag. (Re-issued,with <strong>in</strong>troductory essay by A. Cutler and D. A. Fay (1978).Amsterdam: Benjam<strong>in</strong>s.)Meyer, A. S.1990 The time course of phonological <strong>encod<strong>in</strong>g</strong> <strong>in</strong> language <strong>production</strong>:The <strong>encod<strong>in</strong>g</strong> of successive syllables of a word. Journal of Memoryand Language, 29, 524 - 545.Meyer A. S. & Schriefers H.1991 <strong>Phonological</strong> facilitation <strong>in</strong> picture-word <strong>in</strong>terference experiments:Effects of stimulus onset asynchrony and types of <strong>in</strong>terfer<strong>in</strong>g stimuli.Journal of Experimental Psychology: Learn<strong>in</strong>g, Memory Cognition,17, 1146-1160.Roelofs, A.1997 The WEAVER model of word-form <strong>encod<strong>in</strong>g</strong> <strong>in</strong> <strong>speech</strong> <strong>production</strong>.Cognition, 64, 249-284.Roelofs, A.1999 <strong>Phonological</strong> segments and features as plann<strong>in</strong>g units <strong>in</strong> <strong>speech</strong> <strong>production</strong>.Language and Cognitive Processes, 14, 173-200.Roelofs, A.2001 Syllable structure effects turn out to be word length effects: <strong>Comments</strong>on Santiago et al. (2000). Language and Cognitive Processes,00,00-00

<strong>Phonological</strong> <strong>encod<strong>in</strong>g</strong> 13Santiago, J., MacKay, D. G., Palma, A., & Rho, C.2000 Sequential activation processes <strong>in</strong> produc<strong>in</strong>g words and syllables:Evidence from picture nam<strong>in</strong>g. Language and Cognitive Processes,15, 1-44.Schriefers, H., Meyer, A. S. & Levelt, W. J. M.1990 Explor<strong>in</strong>g the time course of lexical access <strong>in</strong> <strong>speech</strong> <strong>production</strong>:Picture-word <strong>in</strong>terference studies. Journal of Memory and Language,29,86-102.Sevald, C. A., Dell, G. S. & Cole, J. S.1995 Syllable structure <strong>in</strong> <strong>speech</strong> <strong>production</strong>: Are syllables chunks orschemas? Journal of Memory and Language, 34, 807-820.Shattuck-Hufnagel, S.1979 Speech errors as evidence for a serial-order<strong>in</strong>g mechanism <strong>in</strong> sentence<strong>production</strong>. In W.E. Cooper & E. C. T. Walker (eds.). Sentenceprocess<strong>in</strong>g: Psychol<strong>in</strong>guistic studies presented to Merrill Garrett.Hillsdale, NJ: Erlbaum.