1138770
research-article2022

QJP0010.1177/17470218221138770Quarterly Journal of Experimental PsychologyTamaoka et al.

Original Article

Phonological encoding in Tongan: An
experimental investigation

Quarterly Journal of Experimental
Psychology
﻿1­–6© Experimental Psychology Society 2022
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https://doi.org/10.1177/17470218221138770
DOI: 10.1177/17470218221138770
qjep.sagepub.com

Katsuo Tamaoka1,2, Jingyi Zhang3, Masatoshi Koizumi4
and Rinus G Verdonschot5

Abstract
This study is the first to report chronometric evidence on Tongan language production. It has been speculated thatthe mora plays an important role during Tongan phonological encoding. A mora follows the (C)V form, so /a/ and /ka/(but not /k/) denote a mora in Tongan. Using a picture–word naming paradigm, Tongan native speakers named picturescontaining superimposed non-word distractors. This task has been used before in Japanese, Korean, and Vietnamese toinvestigate the initially selected unit during phonological encoding (IPU). Compared with control distractors, both onset
and mora overlapping distractors resulted in faster naming latencies. Several alternative explanations for the patternof results—proficiency in English, knowledge of Latin script, and downstream effects—are discussed. However, weconclude that Tongan phonological encoding likely natively uses the phoneme, and not the mora, as the IPU.
Keywords
Language production; Tongan; picture–word naming; prosodification; phonological encoding
Received: 14 April 2022; revised: 20 October 2022; accepted: 21 October 2022

Speaking is a complex ability, yet it is carried out quickly
and with few errors (Levelt, 1989). Most theoretical models agree that the production of speech can be divided
between accessing the meaning of a word on one hand andthe construction of its pronunciation on the other (e.g.,
Caramazza, 1997; Dell, 1986; Levelt et al., 1999; Roelofs,
2015). In the formation of the pronunciation of a word(e.g., “cymbal”) it has been suggested that three pieces of
information are accessed (Levelt et al., 1999). Specifically(1) its morphemic make-up (e.g., < cymbal > is a freestanding singular morpheme), which in turn activates (2)its metrical information (e.g., ω = σ’σ meaning that theword [ω] is bi-syllabic [σσ] with stress [‘] on the first syllable), and (3) its constituent segments (e.g., /s/ /ɪ/ /m/ /b//ə/ /l/). The segments are then combined with the metricalframe to form syllabified representations [‘sɪm] [bəl]. One
reason for such an elaborate process involves the phenomenon of re-syllabification. This phenomenon occurs when
one segment is assigned to a different adjoining syllable.
For example, in the English sentence “I said it” ([aɪ] [se][dit]) the /d/ in “said” [sed] would be assigned to the last
syllable [it] to form [dit]. However, in languages such as
Mandarin Chinese, which does not employ re-syllabification, this phenomenon does not occur, hence the assignment of phonological information into a metrical structure
might be dissimilar.

There has been an upsurge in the literature indicatingthat the “units” and “frames” used in constructing a phonological word are indeed different among languages. For
example, O’Séaghdha et al. (2010), You et al. (2012), Wanget al. (2018), and Zhang and Damian (2019) all showed thatsyllables are the initial phonological unit (hereafter, IPU)
selected during Mandarin Chinese phonological encoding(but see Qu et al., 2020; Verdonschot et al., 2015). Similarly,
Kureta et al. (2006), Verdonschot et al. (2011), and Ida et al.
(2015) showed that in Japanese, the mora rather than thephoneme is the IPU. For Cantonese it has been proposedthat both syllabic and sub-syllabic units (e.g., the rhyme:
Wong & Chen, 2008, 2009; and the word-initial body:
Wong et al., 2012), but never the onset by itself, can be
activated in the early stages of phonological encoding.

1

School of Foreign Languages, Hunan University, Changsha, China
Graduate School of Humanities, Nagoya University, Nagoya, Japan
3
Center for Language and Cultural Studies, University of Miyazaki,
Miyazaki, Japan
4
Graduate School of Arts and Letters, Tohoku University, Sendai, Japan
5
Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands
2

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

2
Recent studies, however, using both behavioural (Wonget al., 2018) and event-related potential (ERP) measures(Wong et al., 2019) have shown that effects related to syllable priming occur earlier than those of body-related priming indicating that the first selected phonological unit in
Cantonese might be the syllable.
For Korean, the picture is less clear with mixed findings including evidence for the phoneme (e.g., Han &Verdonschot, 2019; Witzel et al., 2013), the syllable body
(Li et al., 2021), and the full syllable as the IPU(Verdonschot et al., 2021). The notion that the IPU might
be different for various languages has also found support
in neurocorrelational electroencephalogram (EEG) studies (e.g., Mandarin: Qu et al., 2020; Wang et al., 2017;
Japanese: Cantonese: Wong et al., 2019; Verdonschot
et al., 2019) showing task-correlated brain activation
only for particular IPUs for these respective languages.
See Alderete and O’Séaghdha (2022) for a recent overview and cross-linguistic perspective on phonologicalencoding.
One interesting related tangent is the question of howbilinguals initially construct phonology when their two
languages differ in their IPUs. Here, it has been found thatproficiency level may strongly matter. For example,
Nakayama et al. (2016) showed in an L2 speech production task that low-proficiency Japanese–English bilinguals
rely heavily on their Japanese L1 (mora) IPU when speaking in their L2 while highly proficient bilinguals develop a
more “native-like” phonemic IPU in their L2. Thus, theysuggested that extensive exposure to L2 phonology could
be important in developing a native-like IPU.
One consequence of having a non-native IPU as in thecase of low-proficiency Japanese-English bilinguals is that
L2-pronunciation may be affected. For example,
Verdonschot and Masuda (2020) showed that when analysing the acoustic wave forms of low- and high-proficiency Japanese-English bilinguals significantly morecases of epenthesis occurred for the low-proficiency group(e.g., “scar” would have been pronounced as “sukaa” or“sukaru”) resulting in the L2 conforming to the IPU of L1.
The current article is concerned with phonologicalencoding during speech production in Tongan, a Polynesianlanguage spoken in the South Pacific Kingdom of Tonga.
The island nation of Tonga recently attracted global media
attention due to the January 2022 eruption of a submarine
volcano and its resulting tsunami.
Tongan phonological encoding is of interest as there areindications that, as in Japanese, the mora may be the initialphonological unit selected during production. Hayes(1995) considers the basic rhythmic unit in Tongan to be a
combination of moras with a strong first and a weak second mora. The Tongan language has a rather limited inventory of twelve consonants (p, m, f, v, t, s, n, k, l, ŋ, ʔ, andh) and five vowels (i, e, a, u, o; cf. Garellek & White,2015). It has a rigid syllabic structure and permits only (C)Quarterly Journal of Experimental Psychology 00(0)V syllables (Anderson & Otsuka, 2006) and therefore cannot manifest re-syllabification. Mono-moraic words in
Tongan typically serve a grammatical function (e.g., “ki”
meaning “to/towards,” “pe” meaning “or”) as opposed towords carrying meaning (e.g., “kolo” meaning “town”)
which have more than one mora. A simple rule to determine the number of moras in a Tongan word is to simply“count the vowels.” For example, “feke” meaning “octopus” has two vowels, therefore two moras (/fe/+/ke/).
Another example is “fua” (/fu/+/a/) meaning “fruits.” Aphrase such as “mālō e lelei” (meaning “hello” in Tongan)
is transcribed as /ma/+/a/+/lo/+/o/+/e/+/le/+/le/+/i/and has eight moras (note: the macron — in mā and lō indicates a long vowel, and has a duration of two moras).
According to Taumoefolau (2002) and Anderson andOtsuka (2006), it is also possible to determine the numberof syllables by simply counting the vowels, therefore thenumber of moras and syllables are suggested to be coextensive in Tongan (Anderson & Otsuka, 2006, p. 41).
Tongan is a stress language and the primary stress almost
always falls on the penultimate mora of a word (Garellek& Tabain, 2020). For example, the word mā (“/ma/+/a/)‘bread” is stressed on the first mora (/ma/) although there
are exceptions such as when a word is followed by a clitic(e.g., “ni” meaning “that”) as in “that bread” – “mā ni” (/ma/+‘/a/+/ni/) which would have stress on the second
mora /a/.
English loanwords in Tongan often show epenthesis orconsonant deletion to adhere to Tongan phonotactics (likeJapanese; see Verdonschot & Masuda, 2020). For instance,
Schutz (1970) mentions several examples such as: “plastic” → “palasitiki” and “horse” → “hoosi.” Zuraw et al.
(2019) mention similar examples such as “kangaroo” → /kaŋikaluu/ and “monogram” → /monokalame/.
In all, it seems that Tongan has several important traits
in common with Japanese including its phonologicalencoding system which ostensibly uses the mora (or syllable) as the initial unit to create a word (Roelofs, 2015;
Verdonschot et al., 2011). However, several other factors
might be of relevance here; the first one being that both
Tongan and English are official languages of the Kingdom.
This situation has arisen from the fact that, although it wasnever formally colonised, Tonga was a former British protectorate from 1900 until 1970 after which time it became
an independent nation within the British Commonwealth.
Consequently, most Tongan speakers have enjoyed a comparatively high-level of education and are therefore relatively fluent in English as well. This is important as it has
been argued for Chinese-English bilinguals that increased
proficiency in an L2 (English) may lead to sub-syllabic
priming effects even in their L1 (Chinese: Verdonschot
et al., 2013). In other words, the answer to whether Tongan
is moraic or not, may potentially be obscured by their highL2 (English) proficiency. A second important factor is that
Tongan is written using the Latin script (unlike JapaneseTamaoka et al.
which is written using a combination of moraic and logographic scripts). Consequently, Tongan orthography
denotes individual phonemes which may perhaps haveinstilled phonemic awareness into native speakers.
To investigate whether the phoneme or the mora is thefirst unit selected during phonological encoding in Tongan
we conducted a picture–word naming experiment in which
participants named pictures onto which non-word distractors were superimposed. Most language production models agree that there are connections between the perception
and production networks for speech and that visual word
recognition also involves phonological activation. Levelt
et al. (1999) further assume that active phonological units
in the perceptual network can directly affect the corresponding IPUs in the production lexicon (Levelt et al.
1999, p. 7 “assumption 2”). Therefore, we have chosen
non-words as distractors as they are proposed to directly
activate IPUs in the production network while reducing
lexical influences. Employing PWIs with non-word distractors has been carried out several times before (seeVerdonschot et al., 2019 for a similar experiments inJapanese; Verdonschot et al., 2021 for Vietnamese; andVerdonschot et al., 2022 for Korean) although it should be
noted that task might be susceptible to orthographic
confounds
In our experiment the non-word distractors were either
onset- or mora-related. If the initial phonological unit
selected in Tongan is the mora we expect facilitation only
for the mora-overlap condition and not for the onset-overlap condition. If, however, the initial phonological unit
selected in Tongan is the phoneme, then facilitation is
expected for both conditions. As far as we know, there iscurrently no chronometric data on Tongan language production available, therefore this article informs theories oflanguage production through insights from rarely studied
languages, such as Tongan, providing a broader cross-language perspective (see also Alderete & O’Séaghdha, 2022
who similarly argue to move beyond Indo-European
languages).

Experiment—picture–word naming
using Tongan non-word distractors
MethodParticipants. Twenty-four native Tongan speakers from the
Tonga Institute of Education in Nuku’alofa, Tonga (14female; age 22.3 ± 5 years) took part in this experimentand were compensated for their participation. All spoke
English as their L2. Participants self-rated four aspects of
their English ability on a 1 (no-proficiency) to 6 (nativeproficiency) scale as speaking (4.4 ± 0.9), listening(4.6 ± 1.1), reading (4.8 ± 1), writing (4.6 ± 1.1) and also
marked their daily Tongan/English use as a percentage(average: 77 ± 12% Tongan vs. 23 ± 12% English).

3
Informed consent was obtained from all participants andthe experiment was carried out in accordance with the
Declaration of Helsinki.
Materials and design. Forty picturable bi-moraic words
were selected (see online Supplementary Material), eachaccompanied by four non-word distractors and theirrespective controls, totaling 160 stimuli per participant.
For example, the Tongan word “feke” meaning “octopus”
had the onset /f/ overlapping with the non-word distractor“folu” (with non-word control “solu”), and the mora /fe/with the non-word distractor “felu” (with non-word control “selu”). All stimuli were created by a native Tongan
speaker. We opted to use non-words as distractors as there
are currently no lexical characteristics databases available
for Tongan and non-words have been shown to be effectivein eliciting responses (e.g., Verdonschot et al., 2019, 2021,2022).
Apparatus and procedure. Participants were seated in aquiet room in front of a computer screen. E-Prime 3.0 wasused to present stimulus materials and record naming
latencies (RTs) and errors (Spapé et al., 2019). Participants
first saw a fixation cross for 1,000 ms followed by the picture which they were asked to name. The picture wasremoved once a response was given. If there was no
response within 2,500 ms, the picture disappeared from thescreen. For each trial the experimenter (native Tongan
speaker) judged whether the response was accurate, contained an error (e.g., saying cat instead of dog), or contained a voice key error (e.g., non-speech sounds triggering
the voice key). Between each trial there was a blank 500ms interval. Participants were asked to name targets in four
blocks. Target words were shown only once per block.
Block order was counterbalanced using a Latin-square
design. For each participant individually randomised lists
were created per block such that successive targets were
not be semantically or phonologically related. For example, targets such as owl “veka” could not directly precedeor follow targets such as dove “lupe”; also, targets such as
kite “lofa” or window “luva” could not directly precede orfollow targets such as dove “lupe.”
Results. About 2.6% of the RTs were discarded due to (1)a failure to respond, (2) stuttering or correcting a response,(3) triggering the voice key using a non-verbal response(e.g., coughing), or (4) a failure to trigger the voice key.
Furthermore, there were 1.4% errors (e.g., wrong words).
The treatment of correct RT data for this analysis was asfollows: First, trials which exceeded 2.5 SD (3.2%) were
excluded. The remaining 3,564 data points were used forfurther analysis (see Table 1 for RTs and accuracy information). A comparison of raw RTs, log-transformed RTs, andinverse-transformed RTs (i.e., –1,000/RT) revealed that
inverse-transformed RTs were closest to normality and4Quarterly Journal of Experimental Psychology 00(0)Table 1. RTs and standard deviation (SD) in ms.
Target “feke”

C-Distractor RT (SD)—example%E

CV-Distractor RT (SD)—example%E

RelatedControl
Effect780 (220)—“folu”
800 (228)—“solu”
20 ms

.5
.4

749 (200)—“felu”
777 (210)—“selu”
28 ms

.2
.3

%E = percentage errors (within condition); RT = reaction time, C = consonant, V = vowel.

Table 2. Experimental results.
Fixed Effects

EstimateSEdft-value

Pr > (|t|)(intercept)
Trialcentred
Congruency

–1.37
–0.07
–0.05

0.03
0.01
0.02

28.8
3476.0156.8–48.785–14.824–2.322

0.001
0.001
0.023

SE: standard error.

were therefore used in subsequent analyses. Error data was
not further analysed as there were few errors which wereequally distributed 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., 2015) implemented in R 4.0.3 (R Core Team, 2021). The “lmerTest”
package in R was used to calculate the p-values using Satterthwaite’s approximation for the degrees of freedom
Kuznetsova et al., 2017). In the experiment we opted touse an incremental modelling approach (Matuschek et al.,2017) to establish the most optimal statistical model forour data.
We considered the following variables: “Trial” (centred) denoting how far a participant had progressed in theexperiment, “Congruency” with two levels (i.e., overlap,
control) and “OverlapSize” with two levels (i.e., Onset,
CV). The factor Congruency was deviation contrastcoded (–.5, .5). The final model using the incremental
modelling approach was invRT ~ Trialcentered + Congruency+ (1|Participant) + (1|Item). See Table 2 for more details.
Although approaching significance, there was no significant main effect of OverlapSize (t = –1.831; p = .06). The
model including OverlapSize was also not significantly
better (χ2 = 3.36) than the model without. The interaction
between Congruency (overlap or not) and OverlapSize (Cand CV) was far from significant (t = –0.346; p = .73), and amodel including the interaction also did not provide a better
fit to the data (χ2 = 0.12) and was therefore not included.
Discussion. This article set out to investigate whether
native Tongan speakers, a language which displays moraic
qualities has an initially selected mora-based phonologicalunit (like Japanese) or a phoneme-based (like English).
When participants named pictures it was found that both
onset overlapping distractors, and mora overlapping distractors facilitated naming latencies. Therefore, it seems

most likely that the phoneme is the initially selected unit
during Tongan phonological encoding.
However, there are some alternative explanations forthe appearance of onset effects. First, participants might
have been sufficiently proficient in L2-English for an
onset effect to appear in their L1 (see Verdonschot et al.,2013 for a similar reasoning with highly-proficiency
Chinese-English bilinguals). To further investigate this,we used participants’ English self-ratings and English
usage scores as variables in the model. However, no significant effects of these variables appeared (all ts <= 1).
Second, it may have been that the use of the Latin script
has made Tongan native speakers aware of phonemes in
the language. For example, for Japanese, Inagaki, Hatano& Otake (2000) showed that pre-literate Japanese children
used a syllabic unit during word segmentation prior tolearning hiragana (a moraic script). Children were shown
pictures and a series of empty circles while holding a dollin their hands. Their task was to say the name of the pictureand “jump the doll” in the circles at the same time matching the name of the picture. So, the number of circles they
jumped indicated how the child segmentated the word during production. For example, saying /kani/ (crab) caused
two jumps (both for literate/illiterate children). However,saying paNda (three mora, /pa/ /N/ /da/ but two syllables /paN/ /da/) caused two jumps for illiterate children which isthe number of syllables but three jumps for literate children, which is the number of mora, as clearly represented
by the script パンダ). Whether or not script indeed instils
phonemic awareness was not specifically assessed in thecurrent experiment. However, some the language games
played by pre-literate Tongan children, such as“matetupu’a,” a riddle game in which a “thing” isdescribed, for example: “I am a fruit” and “I hang on atree,” and “I start with the letter S” does anecdotally inform
us that Tongan children are at least aware of individualphonemes in their language even if they could not yet read.

Tamaoka et al.
Naturally, games may involve manipulations that are notpart of typical encoding procedures therefore they do notprovide strong, and only anecdotal, information.
Third, one could postulate that our onset effect in fact
takes place downstream as syllables can be decomposed
further into segmental units in later speech production
stages.1 In other words, our onset effect is not a genuine
IPU effect, though the CV effect is. Although this cannot
be ruled out, it seems puzzling then why other languages
such as Japanese, Cantonese, and Mandarin which also
have downstream processes (e.g., O’Séaghdha et al., 2010)
have been investigated with similar (PWI) tasks and no
onset effects have been reported for these languages.
In all, it might simply be the case that Tongan, despite
any presumed moraic qualities, uses the phoneme as theinitially selected unit during language production. Tongan
speech errors, for example, do involve single phoneme
manipulations (e.g., one might erroneously say: “lekefahi*” instead of “feke lahi” “big octopus”). This contrasts with Japanese which mostly displays moraic and notphonemic speech errors (e.g., Kubozono, 1989). Note thatthe existence of phoneme errors in a language in itself
should be taken with caution. In Dutch, for example, there
are indeed many phoneme errors when compared withsyllabic errors. However, Alderete (2022) has shown thatphoneme slips are also relatively frequent in Chinese(e.g., additions such as /uk55/ → luk55 “house”), yet, significant numbers of syllable errors also exist in Cantonese1.
However, the existence of phoneme slips in Cantonese
does not mean that the Cantonese IPU is the phoneme (asfar as we know no significant onset effects are found in
Cantonese experiments investigating the IPU). As no
database on speech errors for Tongan exists it remains
unclear what the precise distribution between phoneme
and moraic errors in Tongan is and a speech error corpus
needs to be created to allow for a more comprehensive
view on what speech errors can tell us about Tongan language production.
For now, our data do seem to point towards the phoneme as the initially selected unit during Tongan phonological encoding, irrespective of L2 proficiency or script.
However, to investigate alternative explanations such as
the ones mentioned earlier, replication and extension of
our findings preferentially with additional paradigms (e.g.,form priming) is warranted.
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) disclosed receipt of the following financial support
for the research, authorship, and/or publication of this article:
This work was funded by a Grant-In-Aid (S)—19H05589—from
the Japanese Society for the Promotion of Science (JSPS).

5
ORCID iD
Rinus G Verdonschothttps://orcid.org/0000-0002-7124-4091

Supplementary material
The supplementary material is available at qjep.sagepub.com

Note
1.

We would like to thank an anonymous reviewer for pointing
this out.

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