10.1177_17470218211053244
research-article2021

QJP0010.1177/17470218211053244Quarterly Journal of Experimental PsychologyVerdonschot et al.

Original Article

Phonological encoding in Vietnamese:
An experimental investigation
Rinus G Verdonschot1 , Hoàng Thị Lan Phương2and Katsuo Tamaoka2

Quarterly Journal of Experimental
Psychology
﻿1­–12© Experimental Psychology Society 2021
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https://doi.org/10.1177/17470218211053244
DOI: 10.1177/17470218211053244
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Abstract
In English, Dutch, and other Germanic languages the initial phonological unit used in word production has been shown
to be the phoneme; conversely, others have revealed that in Chinese this is the atonal syllable and in Japanese the mora.
The current paper is, to our knowledge, the first to report chronometric data on Vietnamese phonological encoding.
Vietnamese, a tonal language, is of interest as, despite its Austroasiatic roots, it has clear similarities with Chinese
through extended contact over a prolonged period. Four experiments (i.e., masked priming, phonological Stroop,
picture naming with written distractors, picture naming with auditory distractors) have been conducted to investigate
Vietnamese phonological encoding. Results show that in all four experiments both onset effects as well as whole syllable
effects emerge. This indicates that the fundamental phonological encoding unit during Vietnamese language production is
the phoneme despite its apparent similarities to Chinese. This result might have emerged due to tone assignment being
a qualitatively different process in Vietnamese compared to Chinese.
Keywords
Language production; Vietnamese; phonological Stroop; priming; prosodification; phonological encoding
Received: 14 June 2021; revised: 26 July 2021; accepted: 16 September 2021

Speaking is one of the most remarkable abilities humans
perform daily. Seemingly effortlessly we go from theselection of concepts in our head to moving a large varietyof articulators in rapid succession to produce speech. Thisability has generated a lot of interest among psycholinguists and experimental psychologists and several theoretical models, supported by experimental and otherevidence, have emerged to describe how we accomplish
this feat. Most models agree that there is a broad distinction between accessing the meaning of a word and assembling its pronunciation (e.g., Caramazza, 1997; Dell, 1986;
Levelt et al., 1999; Roelofs, 2015).
One of the most detailed theoretical accounts of word
production can be found in Levelt et al. (1999). In theirmodel after a concept has being selected, and its semantic
and syntactic properties have been selected, phonologicalencoding commences. It is this process that has generated
quite some interest in recent years and there is now accumulating evidence that the size of the initial phonologicalunit selected during this stage is different between languages. The original Levelt et al. (1999) model has been
mainly based on Germanic languages (such as Dutch,
German, and English) and suggests that two pieces of

information are initially necessary. Particularly, spelled
out segments of a word and a word’s metrical informationneed to be retrieved. For example, to say the word “believe”
one must retrieve (from memory) its phonemic segments,
e.g., /b/, /ɪ/, /l/, /i/, /v/ and its metrical structure (i.e., disyllabic with stress on the second syllable). These pieces of
information will then be combined to form the word/bɪˈliv/. One reason that the latter (prosodified) pattern cannot simply be stored, at least in Germanic languages, isthat in these languages words often re-syllabify (e.g., the/v/ in “believe it” would attach itself to the next syllable:/bɪˈli/ + /vɪt/).
Different paradigms have been devised to investigate
how phonological encoding takes place. For example, theimplicit priming paradigm (Meyer, 1990, 1991) in which aperson needs to first remember several prompt-response
1

Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands
Graduate School of Humanities, Nagoya University, Nagoya, Japan

2

Corresponding author:
Rinus G Verdonschot, Max Planck Institute for Psycholinguistics, P.O.
Box 310, 6500 AH Nijmegen, The Netherlands.
Email: rinusverdonschot@gmail.com

2pairs (e.g., dog—bark) and then after being shown aprompt (e.g., dog) needs to respond with the learned
response (e.g., bark). The crucial manipulation in this paradigm is the creation of groups which are either overlapping in a certain feature (e.g., same onset: bark, bill, boot)or not (e.g., bark, dull, main). It has been shown that initial
overlap is necessary to facilitate naming latencies and asingle phonemic onset (e.g., /b/) is sufficient. However,this seems to be different in Chinese (e.g., Chen et al.,
2002; O’Seaghdha et al., 2010) and Japanese (Kureta
et al., 2006). In those languages, the pattern is also incremental but a minimal overlap of an atonal syllable in
Chinese (e.g., /fei/ in /fei1dan4/ “missile,” /fei2zao4/“soap,” /fei4bu4/ “lung”) or a mora in Japanese (e.g., /ka/in /ka.ts.ura/ “wig,” /ka.fu.n/ “pollen,” /ka.bu.ki/ “Japanesetheatre”) are necessary for facilitation effects to appear.
Similar results have been obtained with the masked priming word naming paradigm in which a prime is quickly(e.g., 50 ms) presented before a to-be-named target word.
For example, if the word “pear” is preceded by a prime
word such as “pole” it will be pronounced quicker than if
it is preceded by the prime “take” (e.g., Forster & Davis,
1991). As with the implicit priming paradigm, in Chinese(e.g., You et al., 2012) and Japanese (e.g., Ida et al., 2015;
Verdonschot et al., 2011) again the syllable and mora,respectively, are found to be the relevant unit to put into a
tonal/pitch frame (see Roelofs, 2015) and not a phonemic
segment.
For other languages, such as Cantonese Chinese, thepicture seems to be more complicated. For example, Wongand Chen (2008) using a picture-word interference paradigm obtained significant facilitation effects for the syllable overlap condition (Example picture: 箭 /zin3/ “arrow”
with distractor: 氈 /zin1/ “felt”) but also found significant
facilitation effects for shared rhyme (淺 /cin2/ “shallow”).
Effects were absent when only the onset was shared (滯/zai6/ “stagnation”). This suggests that sub-syllabic units
might be involved in the initial phonological planning in
Cantonese. The idea that sub-syllabic units are the appropriate planning units in Cantonese was further confirmed
through use of the implicit priming task (i.e., Wong et al.,2012) and seems to be a robust finding (though see Wonget al., 2018 who suggested that syllable retrieval still may
come before sub-syllabic encoding even in Cantonese spoken word production).
One issue which has been put forward with the experiments mentioned earlier is the use of script. Some havesuggested that if a certain script type is used in an experiment (e.g., Japanese kana or Chinese hanzi) this might
influence the results as different script types may activate
different underlying units. That is, in alphabetic script eachletter (or letter cluster) maps onto a phoneme, but Japanesekana (e.g., すし /su.shi/ “sushi”) reflect mora; and Chinese
hanzi (e.g., 菜单 /cai4dan1/ “menu”) maps onto morphosyllables. However, there is currently mixed evidence on

Quarterly Journal of Experimental Psychology 00(0)the role of script in this matter. For example, Wong andChen (2008) found sub-syllabic effects using Chinese (syllabic) distractor words and Verdonschot et al. (2011) used
Romanized Japanese (i.e., alphabetic) to investigate
whether script type could play a role, only found mora
effects; therefore, both did not find a significant role ofscript. However, recently, Yoshihara et al. (2017) found,using masked priming, that only when the whole pronunciation of a prime and target were overlapping (e.g., 迫害/ha.ku-ga.i/ - 博物 /ha.ku-bu.tsu/) significant facilitation
effects occurred (i.e., so a prime as 灰皿 /ha.i-za.ra/ would
be ineffective as it does not encompass the whole first syllable /ha.ku/). If stimuli were transcribed into kana (e.g., は
くがい /ha.ku-ga.i/), then moraic effects appeared again.
This “whole kanji” effect might, however, not apply to alltasks as Verdonschot and Kinoshita (2018) pointed out.
They argued that when the task “does not necessarily
involve reading” (like in Yoshihara et al., 2017) it might
not exert an influence and they consequently used a Stroop
colour naming task in which both moraic hiragana (e.g., み
せ /mi.se/) and morphemic kanji (e.g., 店 /mi.se/ “shop”)
overlapped with a to-be-named colour (e.g., /midori/“green”) and facilitatory mora effects appeared both forkatakana and kanji words. However, Yoshihara et al.
(2021) recently showed that using romaji (i.e., RomanizedJapanese) naming responses were also faster when the initial phoneme was shared between the colour name and the
distractor (e.g., the “k” in “kasa” [umbrella] significantly
speeded up naming yellow “kiiro” in Japanese) indicating
an effect of phonological grain size a particular distractor
maps onto. One thing which the results from Verdonschot
and Kinoshita (2018) and Yoshihara et al. (2017, 2021)
make clear is that it is worthwhile to investigate language/
script combinations in which the script does not reflect thesize of the underlying fundamental phonological unit (i.e.,such as Japanese kanji which reflect morpho-syllables
instead of moras). However, such combinations are
extremely rare as typically the script which coexists with alanguage naturally reflects the size of the fundamental
underlying phonological unit.
In this paper we would like to draw attention to theVietnamese language. Vietnamese is a syllabic tonal language which ostensibly has many commonalities with
Chinese (further explained below) but only comparatively
recently has started using the Latin (alphabetic) script.
Vietnamese is the official language of Vietnam. It uses
tones to distinguish between lexical items and it has a relatively simple syllabic structure which resembles Chinese.
For example, like Chinese, Vietnamese syllables arephono-tactically constrained. They consist of an (optional)
onset consonant, followed (optionally) by a bilabial consonant glide, followed by an obligatory vowel (carrying oneof six tones), followed optionally by a single coda consonant (cf. Pham & Baayen (2015), p. 1077; also see Pham &Baayen, 2015 for all list of all possible Vietnamese syllable

Verdonschot et al.
types). Vietnamese syllables are also all single morphemes,
and all morphemes are monosyllabic (cf. Pham & Baayen,
2015, p. 3). Words are not inflected for person, number,case, tense, gender, etc. and novel words can only beformed using compounding or reduplication. Vietnamese
has been heavily influenced by Chinese during a thousand
years in which Vietnam belonged to the Chinese empire.
Its vocabulary therefore has many borrowings from
Chinese through colonisation as well as prolonged culturaland economic interactions. McWhorter (2000) estimatesthat as much as 33% of the entire Vietnamese vocabulary
consists of Chinese words. Vietnamese has been proposed
to be a syllable-timed language (e.g., Mixdorff & Ingram,2009; Nguyễn et al., 2008) in which each syllable has a
specification for a lexical tone. Note that a language thathas syllable timing does not have to constitute a phonological unit of that size per se. For example, French is syllable-timed but significant onset effects have been foundin this language (Carreiras et al., 2006; Grainger &Ferrand, 1996). However, though many syllable-timed
languages display variable degrees of durational variability, in Vietnamese, systematic variances for vowel qualityor the duration among syllables are relatively uncommon(Nguyễn & Ingram, 2005). This might be the result fromthe prolonged presence and influence of China (and theChinese language) in Vietnam. In addition, though simply
having syllabic timing may not be enough, according toCholin et al. (2004) the main argument why phonologicalencoding needs a segment-to-frame association process isthat, during speech, syllable boundaries are different fromthe stored representations in the lexicon. In Dutch, forexample, re-syllabification is estimated to occur in around
17% of all words in connected speech (i.e., Schiller et al.,1996). Importantly, for Chinese, Cholin et al. (2004) put
forward that, as Mandarin Chinese does not have re-syllabification, syllabic units may be represented earlier inthe phonological encoding process (p. 59). This fits with
Chen et al.’s (2002) finding that atonal syllables are thesole units which showed significant priming as further
down the road (i.e., after phonological encoding finishes)
the tone would always have to be specified. It is probablethat as Vietnamese is a tonal syllabic-timed language (withno re-syllabification) it will behave similarly to Mandarin
Chinese with respect to the prosodification process (e.g.,
the syllable and not the phoneme would be used as thefundamental phonological unit to insert in a tonal frame).
The similarities between Vietnamese and Chinese are also
discussed in Sidwell (2008) who points out that Vietnamese(though it is officially an Austroasiatic language) has completely lost the rich morphological system proto-Austroasiatic (also called proto Mon–Khmer) languages had. To
illustrate this claim, Sidwell (2008) mentions the example
of compounding which has replaced affixation over time
as a new word forming mechanism in Vietnamese due toboth the fact that syllables became increasingly simple

3
over time (through Vietnam’s extended contact with
Chinese, a compounding language). In this respect, morphological encoding in modern Vietnamese is very similar
to that of Chinese and deviates significantly from its protoAustroasiatic roots.
Official documents in Vietnam were written in classicalChinese until roughly early 20th century while the more
popular literature was written using the “chữ nôm” script,
which are Chinese characters especially adapted to suit theVietnamese vocabulary. That is, each Vietnamese word
could be written using one character per syllable, some ofwhich originated from China, but also many characters
were invented in Vietnam. The main point here is that allthese scripts were morpho-syllabic (like Chinese) witheach character corresponding to a single syllable (e.g., 越南 Việt Nam “Vietnam”) which corresponded well withthe syllabic Vietnamese language. However, through the
influence of French colonisation the Latin alphabet rather
abruptly and mandatorily replaced the older scripts in official documents and popular literature. Consequently, fromthe beginning of the 20th century (until now) modern
Vietnamese is written using “chữ quốc ngữ” (lit: National
Language Script; originally invented by Portuguese missionaries in the 17th century) which is an alphabetic (latin)
script using diacritics to denote the tones (e.g., tháng“month”) as well as to distinguish certain letters whichhave slightly different sounds (e.g., vườn “garden”). The
new Vietnamese orthography is transparent, having astrong grapheme-to-phoneme match, though syllables ofcompound words are still separated by a space (e.g., theword xe lửa “train” is not written as xelửa) effectively creating syllable blocks throughout Vietnamese text.
Though linguists have issued theoretical accounts forvarious aspects of the Vietnamese language there is analmost complete lack of chronometric data. That is, contrasting Indo-European, Chinese, and Japanese languages,
few studies have used an experimental approach to measure naming latencies and/or accuracy on Vietnamese language production. The question is whether the initialphonological encoding unit in Vietnamese is the syllable(i.e., like Chinese as they are both syllabic-tonal languages
and both without re-syllabification and inflections) orwhether another unit, such as the phoneme, is initiallyselected (perhaps influenced by introduction of an alphabetic script; see Kureta et al., 2015). The notion that phonemes might be selected during the initial phase in
Vietnamese phonological encoding (despite its similarities
to Chinese) can be seen in Vietnamese language games
like nói lái (or “speaking backwards”) in which tones canbe switched between word pairs, but, interestingly, also
between the initial consonant and rime (see Macken &Nguyễn, 2006). For example, cá đối “grey mullet” may
become cối đá “stone mortar” in this game. This contrasts
with comparable games played in Chinese (文字接龙) andJapanese (shiritori) in which phonemic constituents can

4never be switched and either syllables or moras need to beexchanged.
As it is unclear whether Vietnamese uses the phoneme,mora, or syllable as the initial fundamental unit of language production the current paper aims to investigate
Vietnamese language production by employing a varietyof frequently used paradigms. Specifically, a masked priming paradigm (Experiment 1) manipulating overlap status(C, CV and Full) between masked word prime and target,a Phonological Stroop task (Experiment 2) using the same
manipulation between colour name and non-word distractor and two picture-word naming tasks (Experiment 3 and4) using the same manipulation (with written and auditory
distractors respectively). If Vietnamese shows sub-syllabic
or phonemic onset priming in all experiments, it is likelythat the initial unit in the phonological encoding process isthe phoneme (like Germanic languages). However, if onlysyllabic effects are found then Vietnamese phonologicalencoding would be like Mandarin Chinese. If there a difference is observed between experiments more involved inreading (e.g., Experiment 1) or not then script may play arole.

Experiment 1—word priming taskusing Vietnamese

Quarterly Journal of Experimental Psychology 00(0)distractors in our experiment. Due to the lack of reliable
corpus information in Vietnamese (e.g., frequency, familiarity, neighbourhood size) we decided that instead of one
control condition each overlap condition would be reshuffled to form its own control. In this way any differences
between Overlap and Control would not be due to inadequate matching characteristics. Online Supplementary
Material A displays an overview of all stimuli used in thisexperiment. The experiment was divided into 6 blocks of
24 items, in total 144 items were obtained per participant.
Block order was randomised via a Latin square design andstimuli within blocks were randomised per participant.

Apparatus and procedure
E-Prime 2.0 was used to administer the experiment. First,
a fixation (+) was shown for 750 ms, which was thenreplaced by a forward mask (###) for 500 ms. Subsequently,
the prime was shown for 50 ms after which the target
appeared and disappeared when it was named (or after
maximally 2,500 ms). After this the experimenter judged
whether the trial was correctly named or whether a voice
key error (e.g., couching, mis-triggering) or genuine error(e.g., wrong word) had occurred before the next trial
started.

Participants

Results1

Thirty students, native speakers of Vietnamese, from Ho
Chi Min University of Pedagogy (age: 21 ± 2; Female: 22,
Male: 8) took part in this experiment for monetary compensation. All had normal or corrected-to-normal vision.
Participants took the LexTale test (Lemhöfer & Broersma,
2012; range: 0–100) and scored on average: 46 ± 7.1 indicating very low proficiency in English. Their self-assessment values (range: 0–100; reading: 46 ± 8.1; writing: 43± 7.7; listening: 43 ± 6.7; speaking: 44 ± 5.4) reflectedsimilar low-proficiency and experience in using English as
an L2. No abilities in other languages were reported.

About 2.0% of the remaining RTs were discarded due to(1) a failure to respond, (2) stuttering or repairing a
response, (3) triggering the voice key using a non-verbal
response (e.g., coughing), and (4) or a failure to trigger thevoice key. In addition, there were 0.6% errors (e.g., naming a wrong word) across the board.
The treatment of correct RT data for this analysis was asfollows. First, we excluded trials (3.4%), which werequicker than 300 or slower than 1,500 ms. This left 4060
data points for further analysis, see Table 1 for RTs andaccuracy information. A comparison of raw RTs, log-transformed RTs, and inverse-transformed RTs (i.e., -1,000/RT)
revealed that log-transformed RTs were closest to normality and were therefore used in subsequent analyses. Error
data was not further analysed as there were few errors
which were distributed equally among conditions.
Response latencies were analysed with a linear mixed
effects model with participants and items as crossed random effects (e.g., Baayen, 2008) using the “lme4” package(Bates et al., 2013) implemented in R 3.0.3 (R Development
Core Team, 2014) to analyse RT for correct trials and error
rates. The “lmerTest” package in R was used to calculate
the p-values using Satterthwaite’s approximation for the
degrees of freedom (Kuznetsova et al., 2014).
In all experiments we opted to use an incremental
modelling approach (Matuschek et al., 2017) to establish
the most optimal statistical model for our data. We

Materials and design
Twenty-four to-be-named target words were selected (e.g.,BẠN “friend”) with six conditions, C-Overlap (e.g., beo“leopard”), C-Control (e.g., nấm “mushroom”),
CV-Overlap (e.g., bát “bowl”), CV-Control (e.g., nốt“note”), Full-Overlap (e.g., bàn “table”), Full-Control(e.g., nôi, “baby crib”). The tone did not overlap between
target and distractor in the overlap conditions (and most of
the control conditions); therefore, the full-overlap condition involved the atonal syllable with the target (see Chenet al., 2002; O’Seaghdha et al., 2010 who showed that theatonal syllable was the relevant proximate unit in Chinese).
Another advantage is that there was no visual overlap of
the Vietnamese tone diacritics between target andVerdonschot et al.

5

Table 1. RTs and accuracy information for Experiment 1.
Target (e.g., NỒI ‘pot’)

RT (SD)E(in %)

EffectC-overlap (e.g., nấm—‘mushroom’)
C-control (e.g., beo—‘leopard’)CV-Overlap (e.g., nón—‘hat’)
CV-Control (e.g., mục—‘catalogue’)
Full-Overlap (e.g., nôi—‘crib’)
Full-Control (e.g., bàn—‘table’)427 (59)443 (60)425 (58)438 (59)418 (58)437 (55)

0.3
0.7
0.3
0.6
1.0
0.7

16
13
19

SD: standard deviation, RT: reaction times, E: error.

Table 2. Coefficients of the main effects of the final model,
together with the standard error, t-values and p-values(Experiment 1).
Estimate
Intercept
Trial (centred)
Congruency(Overlap)
OverlapSize (CV)OverlapSize (FULL)
Congruency:
OverlapSize (CV)Congruency:
OverlapSize (FULL)SE

t-valuep-value

6.064074 0.015248 397.695 <.001−0.008303 0.001683 −4.932 <.001−0.034068 0.006163 −5.528 <.001−0.006958 0.004114−0.017560 0.004128
0.002758 0.008227−1.691 0.0908−4.254 <.001
0.335 0.7375−0.011033 0.008255−1.3370.1814

SE: standard error.

considered the following variables: “Trial” which
denotes how far a participant had progressed in theexperiment, “Congruency” with two levels (i.e., overlap,
control) and “OverlapSize” with three levels (i.e., Onset,
CV, and Full). The factor Congruency was deviationcontrast-coded (-.5, .5). The final model was log (RT) ~Trial + Congruency * OverlapSize + (1 + OverlapSize|P
articipant) + (1|Item). See Table 2 for more details. As
the global interaction between congruency (overlap ornot) and size of overlap (C, CV, Full) was not significant, pairwise comparisons are not warranted.

Discussion
We found equal priming for C, CV, and Full overlap conditions (evidenced by the absence of an interaction between
Congruency and OverlapSize). Therefore, it seems that,like Germanic languages, Vietnamese uses the phoneme as
the initial unit in the prosodification process. However, we
presented the primes and targets in chữ quốc ngữ (standard
Vietnamese script). Therefore, both masked primes andtargets in this experiment were alphabetic and the task
(i.e., reading aloud) might have made the experiment’s
focus more on written word naming rather than about phonological encoding. Note that it may also seem puzzling

why full overlap priming would show identical RT benefits compared to onset priming, however, these combinations do not constitute identity primes. That is, prime:nôi—‘crib’—target: NỒI “pot” are not identical words as
they do not carry the same tone (and therefore meaning),
which is an important factor in Vietnamese. Furthermore,
the absence of the interaction might be because masked
primes may not have been fully processed. For example,
only the initial letter might have been processed without
full prime processing, and it has been shown in Englishthat additional overlap does not necessarily creates benefits during priming (e.g., Kinoshita, 2000; Nakayama
et al., 2016).
Therefore, to further investigate phonological encoding
in Vietnamese we also employed a Phonological Stroop
paradigm. It has been argued earlier (Verdonschot &Kinoshita, 2018; but see Yoshihara et al., 2021 for a different view) that there are two (not mutually contradictory)
possibilities. The first is that, through prolonged experience, the script’s grain size, which is used to write the language (i.e., whether each character maps onto a phoneme,mora, or syllable), affects the phonological unit employedby the language user. The second is whether specific spoken word-production tasks are sensitive to certain orthographic influences. In other words, the first issue refers to
the language-user’s phonological representation itself andthe latter relates to the mechanism of the task which produces the overlap benefit. Verdonschot and Kinoshita(2018) administered a task that did not require reading
aloud a written word stimulus but rather naming of a colour (or picture name) which was deemed to be more suitable to investigate phonological encoding (as thepronunciation of a colour, or picture, name would not haveto be assembled in a step-by-step fashion, as compared toa reading aloud task).
If initial phonological encoding in Vietnamese is indeed
phoneme based, then we expect a similar pattern of results
as in Experiment 1 (though there might be increased benefits for CV and Full overlap due to task differences). If
somehow the mechanism of the task in Experiment 1(word naming) produces the overlap benefit for the phoneme and the phonological encoding process would, infact, be syllabic (or CV) for Vietnamese then we expect
significant effects for the Full Overlap (or CV) conditions
but not for the onset overlap condition in Experiment 2.

Experiment 2—phonological Stroop
task using Vietnamese
MethodParticipants. Same participants as in Experiment 1.
Materials and design. Five colours (hồng “pink,” tím “purple,” đen “black,” ‘xanh’ blue and trắng “white”) wereselected. Each colour (e.g., hồng) could be printed in a

6

Quarterly Journal of Experimental Psychology 00(0)Table 3. RTs and accuracy information for Experiment 2.
Target (ex. XANH, ‘blue’)RT (SD)E (in %)

EffectTable 4. Coefficients of the main effects of the final model,
together with the standard error, t-values and p-values(Experiment 2).

C-overlap (e.g., XỈM)C-control (e.g., PỈM)CV-Overlap (e.g., XÁU)CV-Control (e.g., PÁU)Full-Overlap (e.g., XÀNH)Full-Control (e.g., QÀNH)546 (108)579 (121)
504 (91)553 (111)484 (79)536 (102)

0.8
0.9
0.4
0.8
0.5
0.8

33

EstimateSEt-valuep-value−1.84706−0.10202−0.11272−0.17407−0.07063

0.033420.024890.01758
0.01756
0.03515−55.276−4.098−6.413−9.914−2.009

<.001
<.001
<.001
<.001
<.05

−0.09180 0.03512 −2.614

<.01

49
52

SD: standard deviation, RT: reaction times, E: error.

C-congruent non-word (e.g., hếp) or its control (e.g., gếp)a CV-congruent non-word (e.g., hỗt) or its control (e.g.,gỗt) or a full-overlap (atonal syllable) non-word (e.g.,hống) or its control (e.g., pống). The tones were different
between the target colour name and the non-words (butsimilar between overlap and controls). Colour names wererepeated for 5 times with different distractors yielding 150
experimental items per person. Stimulus order per block
was pseudo-randomised using Mix (van Casteren & Davis,
2006) with two constraints: (a) two colours could neverfollow each other and (b) two identical conditions could
never follow each other. Block order was distributed using
a latin-square design among participants.
Apparatus and procedure. E-Prime 2.0 was used toadminister the experiment. First, a fixation (+) was
shown for 750 ms. Subsequently, the target (a non-wordprinted in any of the five colours on a grey background)appeared and disappeared when it was named (or after
maximally 2,500 ms). After this the experimenter judged
whether the trial was correctly named or whether avoicekey error (e.g., couching, mistriggering) or genuine
error (e.g., wrong word) had occurred before the next
trial started.
Results. About 3.2% of the RTs were discarded due to (1)a failure to respond, (2) stuttering or repairing a response,(3) triggering the voice key using a non-verbal response(e.g., coughing), and (4) or a failure to trigger the voice
key. In addition, there were very few errors (0.7%; e.g.,naming a wrong colour or the non-word) across the board
which were equally distributed among conditions andtherefore not analysed.
The treatment of correct RT data for this analysis was
as follows. First, we excluded 55 trials (1.2%), whichwere faster than 300 or slower than 1,500 ms. This left
4,269 data points for further analysis, see Table 3 for RTs
and accuracy information. A comparison of raw RTs, logtransformed RTs, and inverse-transformed RTs (i.e.,-1,000/RT) revealed that inverse-transformed RTs wereclosest to normality and were therefore used in subsequent analyses.

Intercept
Congruency (Overlap)
OverlapSize (CV)OverlapSize (FULL)
Congruency:
OverlapSize (CV)Congruency:
OverlapSize (FULL)
SE: standard error.

The factor Congruency was deviation-contrast-coded(-.5, .5). The optimal model was (invRT ~ Congruency *OverlapSize + [1|Participant] + [1|Item]). See Table 4 formore information.
Pairwise comparisons showed that for each of the overlap sizes (C, CV and Full) the congruency effect was present, C: t(48) = -3.75; p < .001; CV: t(48) = -6.08, p < .001;
Full t(48) = -11.3; p < .001 with the C condition eliciting
less facilitation than the CV and Full conditions (whichwere comparable with each other). These results indicate
that, like Experiment 1, Vietnamese language production
seems to use the phoneme as the fundamental phonological unit during the prosodification process (Levelt et al.,1999). The interaction indicates that this effect increases
themorephonologicalinformation
overlaps(C < CV = FULL).
Although it was pointed out earlier that Verdonschot
and Kinoshita (2018) advocated the phonological Stroop
task as a viable alternative for masked priming as there
was “no intention to read the word” others have questioned
this task’s suitability (Yoshihara et al., 2021). Particularly,
in Verdonschot & Kinoshita’s work the script was moraic(katakana) or morphemic (kanji) and never alphabetic likein the current experiment (see onset effects for Japanesewritten in alphabetic romaji in Yoshihara et al., 2021). In
addition, although no participant mentioned noticing this,
it is still possible that our colour names may have beencued by the onset (and/or the following segments) of thevisible nonwords enabling faster retrieval of the congruent
colour names. This might have become evident to participants as most of the unrelated distractor onsets were notone of the five potential colour response options (except
for DẶNG for the colour ĐEN/black). We therefore opted
to run two additional picture-word interference experiments (i.e., thereby greatly increasing the response options
averting a potential cueing problem), one (Experiment 3)
with written distractors and one (Experiment 4) with auditory distractors.

Verdonschot et al.

7

Experiment 3—Vietnamese PWI taskusing written distractors

Table 5. RTs and accuracy information for Experiment 3(picture naming with visual distractors).

MethodTarget (ex. CUA, ‘crab’)

RT (SD)E (in %)

EffectC-overlap (e.g., CÓT)C-control (e.g., VÓT)Full-Overlap (e.g., CỤA)Full-Control (e.g., VỤA)664 (141)
680 (146)
567 (98)
639 (139)

1.3
1.4
0.6
0.7

16

Participants. Twenty-four participants (Age: 19.2 ± 1.5; 14
females, 10 males) either studying at Ho Chi Minh City
Open University, Saigon University, The University of
Medicine and Pharmacy at Ho Chi Minh City, or Industrial
University of Ho Chi Minh City participated in this experiment for monetary compensation. None of these participants had taken part in Experiments 1 and 2. All had
normal or corrected-to-normal vision. Participants took
the LexTale test (Lemhöfer & Broersma, 2012; range:
0–100) and scored on average: 46 ± 7.1 indicating very
low proficiency in English. Also, their self-assessment
values (range: 0–100; reading: 46 ± 8.1; writing: 43 ±7.7; listening: 43 ± 6.7, speaking: 35 ± 12.5) reflected
low-proficiency and experience in using English as an L2.
No abilities in other languages were reported.
Materials and design. Forty target words were selected(e.g., CUA “crab”) with four non-word conditions,
C-Overlap (e.g., CÓT), C-Control (e.g., VÓT), Full-Overlap (e.g., CỤA), Full-Control (e.g., VỤA). C-Control andFull-Control always had the same rime and tone as theirrespective overlap condition. For each target word a blackline-drawing (400 x 400 pixels) was selected from either
the Snodgrass and Vanderwart (1980) dataset or if not present in this set created by the authors themselves.
Apparatus and procedure. E-Prime 3.0 was used to administer the experiment. First, a fixation (+) was shown for
1,000 ms. After that, the target (a picture) with distractor
on it (SOA = 0) appeared and disappeared when it wasnamed (or after maximally 2,500 ms). After this the experimenter judged whether the trial was correctly named orwhether a voicekey error (e.g., couching, mis-triggering)or genuine error (e.g., wrong word) had occurred before
the next trial started.
Results. About 2.8% of the RTs were discarded due to (1) afailure to respond, (2) stuttering or repairing a response, (3)triggering the voice key using a non-verbal response (e.g.,coughing), and(4) or a failure to trigger the voice key. In
addition, there were very few errors (1.0%; e.g., naming awrong picture name) across the board which were equallydistributed among conditions and therefore not analysed.
The treatment of correct RT data for this analysis was asfollows. First, we excluded 5 trials (0.1%), which were
faster than 300 or slower than 1,500 ms. This left 3687 data
points for further analysis, see Table 5 for RTs and accuracy information. A comparison of raw RTs, log-transformed RTs, and inverse-transformed RTs (i.e., -1,000/RT)
revealed that inverse-transformed RTs were closest to normality and were therefore used in subsequent analyses.

72

SD: standard deviation, RT: reaction times, E: error.

Table 6. Coefficients of the main effects of the final model,
together with the standard error, t-values and p-values(Experiment 3).

Intercept
Trial
Congruency(Overlap vs. Control)
OverlapSize(C vs. FULL)
Congruency:
OverlapSize (FULL)

EstimateSEt-value p-value−1.52397−0.07179−0.03583

0.03097
0.003690.01053−49.21 <.001−19.42 <.001−3.402 <.001−0.104519 0.010500 −9.955 <.001−0.147736 0.014778 −9.997 <.01

SE: standard error.

We considered the following predictors: “Trial” which
denoted how far a participant had progressed in the experiment, “Congruency” with two levels (i.e., phonologicaloverlap, control) and “OverlapSize” with two levels (i.e.,
Onset and Full). The factor Congruency was deviationcontrast-coded (-.5, .5). The final model was (invRT ~Congruency * OverlapSize + [1|Participant] + [1|Item]).
See Table 6 for more information.
Pairwise comparisons showed that for each of the overlap sizes (C and Full) the congruency effect was present,
C: t(1,750) = -3.60; p < .001; Full t(1,807) = -17.97;
p < .001 with the C condition (though significantly different from control) eliciting much less facilitation (16 ms)
than the Full overlap condition (72 ms), z = -9.96, p < .001.

Experiment 4—Vietnamese PWI taskusing auditory distractors
MethodParticipants. Twenty-four participants (Age: 19.4 ± 1.5; 14
females 10 male) either studying at Ho Chi Minh City
Open University, Saigon University, The University of
Medicine and Pharmacy at Ho Chi Minh City, or Industrial
University of Ho Chi Minh City participated in this experiment for monetary compensation. None of these participants had taken part in any of the previous experiments.
All had normal or corrected-to-normal vision. Participants
took the LexTale test (Lemhöfer & Broersma, 2012; range:

8

Quarterly Journal of Experimental Psychology 00(0)0–100) and scored on average: 52 ± 7.0 indicating very
low proficiency in English. Also, their self-assessment
values (range: 0–100; reading: 53 ± 11.9; writing: 47 ±14.6; listening: 40 ± 18.5, speaking: 53 ± 11.9) reflectedsimilar low-proficiency and experience in using English as
an L2. No abilities in other languages were reported.
Materials and design. Identical to Experiment 3. However,
all non-word distractors were now recorded sound files
instead of written words. Care was taken to create auditory
distractors of approximately equal duration (~486 ms on
average). Auditory distractors coincided with the picture
target (SOA = 0).
Apparatus and procedure. E-Prime 3.0 was used to administer the experiment. First, a fixation (+) was shown for1000 ms. After that, the target (a picture) appeared and disappeared when it was named (or after maximally 2500 ms).
After this the experimenter judged whether the trial was
correctly named or whether a voicekey error (e.g., couching, mistriggering) or genuine error (e.g., wrong word) had
occurred before the next trial started.
Results. About 2.3% of the RTs were discarded due to (1)a failure to respond, (2) stuttering or repairing a response,(3) triggering the voice key using a non-verbal response(e.g., coughing), and (4) or a failure to trigger the voice
key. In addition, there were reasonably few errors (3.3%;
e.g., naming a wrong picture name) and therefore notanalysed.
The treatment of correct RT data for this analysis was asfollows. First, we excluded 20 trials (0.5%), which wereTable 7. RTs and accuracy information for Experiment 4(picture naming with auditory distractors).
Target (ex. CUA, ‘crab’)

RT (SD)E (in %)

EffectC-overlap (e.g., CÓT)C-control (e.g., VÓT)Full-Overlap (e.g., CỤA)Full-Control (e.g., VỤA)684 (146)
692 (138)
638 (110)688 (133)

1.3
1.4
0.6
0.7

8
50

SD: standard deviation.

faster than 300 or slower than 1,500 ms. This left 3605 data
points for further analysis, see Table 7 for RTs and accuracy information. A comparison of raw RTs, log-transformed RTs and inverse-transformed RTs (i.e., -1,000/RT)
revealed that inverse-transformed RTs were closest to normality and were therefore used in subsequent analyses.
The final model was (invRT ~ Congruency * Overlap+ [1|Participant] + [1|Item]). Any random slopes enteredin the participant or item random effect structure resulted
in statistical models which either did not converge orwere not significantly better. See Table 8 for more
information.
Pairwise comparisons showed that for each of the overlap sizes (C and Full) the congruency effect was present,
C: t(1,704) = -2.2; p < .05; Full: t(1,775) = -10.96, p < .001;
with the C condition eliciting less facilitation than the Fullconditions. These results indicate that, although the effectis rather small for the C-Overlap condition (8 ms), like theother experiments, Vietnamese language production uses
the phoneme as the initial phonological unit during the
prosodification process (Levelt et al., 1999).

General discussion
This study set out to investigate the fundamental phonological unit of language production in Vietnamese, a language which has similar properties to Chinese such as asyllable-timing, the absence of re-syllabification andinflection; but uses an alphabetic script which is written
using breaks between syllables (note: even syllables incompound words are separated by a space). There wereseveral clear indications to investigate whether the syllable
would be at the base of the phonological encoding process
in this language. If so, then that would have constituted aunique combination of a language having a syllabic fundamental phonological unit though written using an alphabetic script. To study phonological encoding in Vietnamese,
we administered four experimental paradigms: (1) amasked priming word naming experiment, (2) a phonological Stroop task, (3) a PWI experiment with written distractors, and (4) a PWI experiment with auditory
distractors. Experiment 1 obtained significant onset priming (e.g., target: HOA “flower” with prime: heo “pig” vs.

Table 8. Coefficients of the main effects of the final model, together with the standard error, t-values and p-values (Experiment 4).

Intercept
Trial
Congruency (Overlap vs. Control)
OverlapSize (C vs. FULL)
Congruency: OverlapSize (FULL)
SE: standard error.

EstimateSEt-valuep-value−1.5425723
0.0020525−0.0675846−0.0050432−0.0860832

0.0277469
0.0003183
0.0073300
0.0104391
0.0146613−55.594
6.449−9.220−0.483−5.871

<.001
<.001
<.001
.629
<.001

Verdonschot et al.
súng “gun”) as well as significant CV priming (hộp “box”)
and full overlap priming (e.g., hoả “fire”). In addition, thesecond Experiment (phonological Stroop task) also
obtained facilitation of naming latencies when the first
segment between colour and non-word were overlapping(e.g., xỉm for the colour xanh “blue”) and additional benefits (i.e., more facilitation) was obtained when more segments were overlapping (e.g., xáu and xành). Both PWI
experiments obtained facilitatory onset as well as syllable
effects (although the size was rather small for the auditory
onset effect).
One result pattern which differed between Experiment
1 (masked priming) and Experiment 2 (phonological
Stroop) is that the effect sizes were similar between theconditions (C, CV, Full) in Experiment 1, but they weredifferent for Experiment 2 with C showing less facilitation
than CV and Full (which were similar). As stated in thediscussion of Experiment 1, ordinarily identity conditions
show greater priming effects than, for example, onset conditions. However, in Experiment 1 the full condition was
not an identity condition as the (orthographically marked)
tone and therefore the meaning was different (e.g., target:MỰC “ink” and prime: mức “level,” the tone is clearly differentially marked: ự [i.e., low dropping pitch marked by
the dot below the letter] / ứ [i.e., high rising pitch marked
by the acute accent]).
Also, in our experiments a distinction can be madebetween tasks that involve reading aloud words(Experiment 1) versus the naming of objects (i.e., colours,
pictures; Experiments 2–4). In other words, whether the
to-be-named target is written or presented as a picture or acolour. Production of a picture name or colour name istypically not assembled in a piece-by-piece fashion as inwhen a letter/character string is read aloud. For Experiment
1 (masked priming) the fact that the benefit due toCV-overlap (and even the CVC overlap) was statisticallynot greater than the benefit due to C-overlap might indicate that this task was more involved with reading aloud awritten word and/or the prime may not have been fully
processed. There are several reports which show that additional overlap between prime and target do not necessarily
evoke larger priming (e.g., Kinoshita, 2000; Nakayama
et al., 2016).
One possible reason why there was a distinction
between the C and the CV/Full conditions in Experiment 2
might be that RTs for the second experiment were about
100 ms longer (Experiment 1: 431 ± 58; Experiment 2:
533 ± 102) and had a larger variability in general compared to the first experiment. However, as pointed out inthe discussion of Experiment 2 it is also possible that ourcolour names might have been cued by the onset (and thefollowing segments) of the visible nonwords enabling
faster retrieval of the congruent colour names.
Experiments 3 and 4 were PWI experiments and greatly
increased the response options averting the potential

9cueing problem of Experiment 2 (especially Experiments
4 which used auditory distractors). Both PWI experiments
showed significant onset effects and full-overlap effects
although the latter were much more pronounced than theonset effects (compared to the results of Experiments 1
and 2).
Overall, the general pattern from these results is thateven though Vietnamese on the surface seems to have
many surface characteristics of Chinese (e.g., tonal language, syllabic-timing, no re-syllabification, no inflections), at the core of how phonology is constructed it
behaves similarly to Germanic languages (e.g., English,
Dutch, German). That means that the phoneme is likely tobe the initial phonological unit selected in the prosodification process.
This is an interesting finding as many of the arguments
laid out in previous papers as to why Chinese does nothave onset priming (e.g., Chen et al., 2002; O’Seaghdha
et al., 2010; You et al., 2012) also hold for Vietnamese. In
Vietnamese word form construction depends primarily onsyllabic units, which are simple in structure (like Chinese).
Syllables in Vietnamese are typically CV(C), in which
specification of tone is required (the onset, as well as thecoda consonant, however, are optional) and the language
does not have re-syllabification, nor does it haveinflections.
One parsimonious explanation for our data is that,
despite any (apparent) similarities to Chinese, the basic
phonological unit to be used in the prosodification process is simply the phoneme. Though Sidwell (2008)
pointed out that many aspects of the morphological system of Vietnamese seems to be like Chinese, this does notguarantee it must behave in a similar way with respect tophonological encoding. For example, one important argument for the presence of onset effects during phonologicalencoding may be that Vietnamese tones are distinct from
Chinese tones in that they do not solely rely on pitch contour. In other words, some Vietnamese tones are characterised by attributes other than pitch; therefore, in
Vietnamese the tonal frame might entail more than simply
assigning tonal pitch contour to the syllable (A. H. Pham,
2001; A. H. Pham & Horn, 2004). For example, theVietnamese sắc tone starts in the middle and subsequently
rises. The ngã tone also starts in the middle (though typically higher than the sắc tone for some dialects) and rises
but for many speakers induces a glottal stop (/ʔ/) in the
middle of the vowel. A. H. Pham (2001) clearly illustrates
this by showing a discontinuous portion in the tone’s pitch
curve (Figure 7a; p 94). Another example is the huyền
tone which starts low-mid and falls subsequently. This
tone is akin to the nặng tone which follows the same pattern, but it swiftly falls in pitch. However, the latter (nặng)tone has a short “creaky” vowel, as opposed to a long
“breathy” vowel in the first (huyền) tone. Vietnamese isalso sometimes called a pitch register language in which

10

Figure 1. Illustration (following Roelofs, 2015) of theVietnamese (compound) word cá mập “shark” during the
prosodification stage of the Levelt et al. (1999) model(o = onset, n = nucleus, c = coda). The words sắc and nặngabove the tonal frame indicate the Vietnamese tone names,
the numbers 1–3 indicate the position of the segments in therespective morphemes.

different features combine and (e.g., vowel length andquality, tone, glottalization) all have an interplay witheach other (A. H. Pham, 2001). This might make
Vietnamese tone-to-syllable assignment considerably
more intricate than it is for Chinese (see Roelofs, 2015)
and consequently segments might need to be initiallyavailable in Vietnamese to be able to assign the correct
combination of features to the to be uttered word. For
example, A. H. Pham (2001) argues that the critical portion in a syllable for distinguishing Vietnamese tones isdifferent depending on the tone (i.e., the middle point in aword in hỏi and ngã, but the endpoint for some other tones
like sắc).
Here, we outline a tentative proposal for Vietnamese
phonological encoding in Figure 1 (using a similar schematic as used in Roelofs, 2015).
We assume the existence of lexemes, tonal frames, segments, and syllable motor programmes in the Vietnamese
form network. The tones in the model are denoted by theirnames (i.e., ngang, huyền, sắc, nặng, hỏi, and ngã). Duringform encoding tonal frame nodes as well as their associated segments are selected, and the segments will be incrementally combined with the tonal nodes. We propose theinitial involvement (i.e., proximate unit; O’Seaghdha
et al., 2010) of segments, and not atonal syllables as inChinese, due to the persistent onset effects across all our
experiments which could be due to the intricate assignment of tone (for which the argument has been laid out inthe previous paragraph). Ultimately, phonological encoding will result in a phonological word representation,
which has specified the segments grouped into syllables
using the appropriate pattern for the associated tone. The
example in Figure 1 denotes a di-syllabic (the most common word structure in Vietnamese) compound word cámập (“shark” in Vietnamese). This word consists of two
separate morphemes (i.e., cá means fish, and mập meansfat) which in turn activate their associated tone as well as

Quarterly Journal of Experimental Psychology 00(0)their individual constituents (denoted with numbers) andwill be prosodified into [kaː sắc] [məp̚ nặng].
However, another possibility which may account for
our results, already mentioned in the introduction, is thateven if the language portrays many similar syllabic characteristics to Chinese, it could be that by using the modern
Vietnamese alphabetic script (i.e., chữ quốc ngữ) imposedby the French in the early 1900’s, Vietnamese people may
have developed a deep grained awareness of phonemes.
The participants in our study were all young university students who did not have any mastery of Chinese script andgrew up with an alphabetic script to read and write theirlanguage. So, it might be the case that the grain size of thescript used to write Vietnamese has shaped Vietnamese
phonological encoding. There is evidence from Japanese(Inagaki et al., 2000) showing that pre-school Japanesechildren did not necessarily show mora-related segmentation for aurally presented words. That is, about half of thechildren segmented words into syllables. However, after
they learned Kana characters almost all of them showed a
mora-based segmentation, indicating a change in awareness due to acquiring literacy. One example to the contrary, although somewhat anecdotal, is the observation thatnói lái (Vietnamese Spoonerisms) such as bí mật “secret”(noun) > bật mí “to reveal a secret” (verb) is already a very
old phenomenon, which has been recorded even before thealphabetic script was introduced into Vietnam. As Macken
and Nguyễn (2006, p. 54) point out:
the fact that nói lái was used and valued highly for centuries
by Vietnamese speakers who could not read means that thephonological units of nói lái are accessed and used
independently of the writing system and independently oflearning to read a written language.

In any event, this possibility needs to be further investigated in future endeavours.
To conclude, as far as we know, this study is the firststudy to report chronometric data (i.e., RTs) on Vietnamese
phonological encoding. Our data show that prosodificationin Vietnamese proceeds similarly to Germanic languages(like Dutch, English, and German). In other words, thephoneme is the fundamental phonological unit in this language (O’Seaghdha et al., 2010; Roelofs, 2015), despite
Vietnamese having many apparent resemblances toChinese. We believe that this is a genuine phenomenon of
the phonological encoding system itself, possibly due tothe unique assignment of tone in Vietnamese, though wecannot rule out that the alphabetic grain size of the chữquốc ngữ script used to write the language has not shaped
the phonological unit used Vietnamese language users.
Acknowledgements
The authors would like to thank Sachiko Kinoshita as well as ananonymous reviewer for their constructive comments on thismanuscript.

Verdonschot et al.

11

Declaration of conflicting interests
The author(s) declared no potential conflicts of interest withrespect to the research, authorship, and/or publication of thisarticle.

Funding
The author(s) received no financial support for the research,authorship, and/or publication of this article.

ORCID iD
Rinus G Verdonschothttps://orcid.org/0000-0002-7124-4091

Supplementary material
The Supplementary Material is available at: qjep.sagepub.com

Note
1.

All data and analysis methods are available from first author
upon request.

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