1.1 The prosodic hierarchy in Korean

We adopt Jun’s analysis of the prosodic structure (Jun, 1996a, 1998, 2000, 2005, 2006, 2012), which is currently the most widely used model for prosodic analysis in Korean. Jun’s model is based on the Prosodic Hierarchy (Selkirk, 1984, 1986; Nespor & Vogel, 1986), and represents intonation with L and H targets following the Autosegmental-Metrical theory (Ladd, 2008). In addition, Jun (1996a, 1998, 2000, 2005, 2006, 2012) classifies Korean as a language without any head prominence related to lexical stress, pitch accent or tone, but a language with edge prominence. Four levels above the lowest unit, the syllable, are defined in the Prosodic Hierarchy: The Phonological Word (PW), the Accentual Phrase (AP), the Intermediate Phrase (ip), and the Intonational Phrase (IP). Although the ip was added in a later revision (Jun, 2006), demarcating ips in speech data is not straightforward and therefore the ip is excluded in the following discussion.²

In Jun’s model (1996a, 1998, 2000, 2005), the PW does not have any prosodic specification and the AP is the basic unit for prosodic analysis. The AP is a word-sized unit defined with particular reference to the pitch contour (see Schafer & Jun, 2002; Jun & Kim, 2004).³ An AP tends to have 3–4 syllables and 1.14–1.2 content words on average (Kim, 2004; Kim, 2009). Jun (1996a, 1998, 2006) proposes that the AP has the underlying tonal pattern THLH, where the realization of the initial tone (T) tends to depend on the laryngeal configuration of the phrase initial segment. When the initial segment is a fortis (/p*, t*, k*, ts*/) or aspirated (/pʰ, tʰ, kʰ, tsʰ/) consonant, /s/ or /h/, the initial tone tends to be H, but otherwise it is L. Segments triggering AP-initial H and segments triggering AP-initial L (i.e., lenis consonants, nasals, semivowels, and vowels) will hereafter be referred to respectively as strong segments and weak segments. The association between the type of segment and the tonal target (L vs. H) in AP-initial position is considered phonologized in Korean (Jun, 1996a, 1998), although the AP-initial tones are not always predictable (e.g., Jun, 2000; Kim, 2004). Jun (1998) states that all four tones are realized when there are four or more syllables in an AP, but if there are fewer than four syllables, some of the tones are not realized. There are 14 pitch contours of the AP reported in Jun (2000) (i.e., LH, LHH, LLH, HLH, HH, HL, LHL, HHL, HLL, LL, HHLH, LHLH, LHLL, and HHLL) and the last tone, either L or H, is associated with the AP-final syllable. The AP and IP are differentiated by the size of the perceivable disjuncture at the phrase boundary. For instance, the IP is often marked by boundary tones (e.g., L%, H%, LH%, LHL%, etc.) and significant final lengthening. Unlike the AP, boundary tones can consist of two or more tones which can be realized on the IP-final syllable.

The causes of intonational variation in Korean have not been investigated much so far. What is known is that there is a tendency referred to as the see-saw effect in Jun (1996b), which avoids the same type of tones occurring adjacent to each other, that speaking style affects the shape of the pitch contour (Kim, 2004; Kim, 2009; Kim et al., 2007), and that there is a strong preference for the AP-final H (Kim, 2004 and references therein).

1.2 Prosodic marking of narrow focus across languages

Across languages, the constituent under focus tends to involve hyper-articulation of a kind consistent with the Effort Code (Gussenhoven, 2002; Gussenhoven, 2004) and the focus can affect the phonetic shape of the following constituent in the utterance (as in post-focus compression; see below). There are multiple ways of signalling narrow focus prosodically including, for example, an increase in segmental duration or F₀ span (e.g., Xu, 1999; Chen, 2006 for Standard Chinese; Eady & Cooper, 1986; Xu & Xu, 2005 for American English; Baumann et al., 2006 for German; Peters et al., 2014 for varieties in Dutch, Frisian, or German); varying the alignment of F₀ turning points (e.g., Xu & Xu, 2005 for American English; Peters et al., 2014 for varieties in Dutch, Frisian, or German); creating prosodic breaks by phrasing (e.g., Féry, 2001 for French); using boundary tones (e.g., Venditti et al., 2008 for Japanese); varying pitch accent types (e.g., Baumann et al., 2006 for German); and compressing the pitch range, duration, and/or intensity of the constituent preceding or following the focused constituent (e.g., Eady et al., 1986; Xu & Xu, 2005 for American English; Chen et al., 2009 for Taiwanese and Mandarin; Lee & Xu, 2012 for Japanese).

In West Germanic languages such as English, German, and Dutch, the marking of narrow focus is often discussed in relation to the placement and acoustic salience of a pitch accent, which are respectively interpreted to be phonological (i.e., categorical) and phonetic (i.e., showing gradient variation within a category). The common view is that the focused word receives a pitch accent while the defocused counterpart is de-accented (e.g., Beckman & Pierrehumbert, 1986) especially if following the focused item. Alternatively, the type of pitch accent employed may differ between focused and defocused constituents (e.g., Baumann et al., 2006 for German). The type of pitch accent may also be determined by the distinction between narrow focus and broad focus, though this distinction is not always clearly marked (e.g., Baumann et al., 2006; Kügler, 2008; Féry & Kügler, 2008 for German). The gradience is related to duration (e.g., Baumann et al., 2006 for German) and scaling or alignment in F₀ (e.g., earlier peak in narrow focus in American English, Xu & Xu, 2005; Baumann et al., 2006 for Standard German).

In languages without clear lexical stress such as French and Japanese, prosodic phrasing is often referred to as a phonological marker to focus. In French, the focused constituent is generally realized in a separate phrase with its own tonal structure and with optional dephrasing of the following constituents, and sometimes with short breaks before and/or after the phrase boundaries (e.g., Jun & Fougeron, 2000)⁴. Phonetic markers of narrow (or contrastive) focus include the raising of the phrase-initial pitch and a higher F₀ peak in the prosodic phrase (Féry, 2001). In Japanese, which has lexical pitch accent, dephrasing or prosodic subordination seems to occur in relation to focal structure (e.g., Beckman & Pierrehumbert, 1986; Gussehnhoven, 2004). For instance, Venditti et al. (2008) discuss a variety of intonational means to mark focus in Japanese, including pitch range expansion, F₀ reset at the left edge of the focused constituent which may co-occur with the insertion of the IP boundary at the beginning of the focused constituent, dephrasing (i.e., post-focal prosodic subordination), and boundary pitch movement (H%, HL%). Prosodic subordination (dephrasing) is considered the most crucial way of focus marking in Japanese, and the rest are optional (Venditti et al., 2008 and references therein).

Narrow focus affects the phonetic shape of the out-of-focus constituent in some languages. Xu et al. (2012) classify languages into those with or without post-focus compression (PFC) in F₀ span, intensity, and/or duration, while the pre-focus constituent generally does not show systematic variation. PFC occurs independently of whether lexical tone, pitch accent, or lexical stress is present in a language. Languages such as English (Eady & Cooper, 1986; Xu & Xu, 2005), Japanese (Lee & Xu, 2012), and Beijing Mandarin (Chen et al., 2009) show PFC.

In summary, the focused constituent tends to be associated across languages with an increase in articulatory effort. In general, studies of West Germanic languages suggest a strong link between lexical stress and the prosodic manifestation of the focus, while the manifestation of focal structure in languages without lexical stress seems to be best described in terms of prosodic phrasing and phonetic events near prosodic boundaries. The presence of post-focus compression is known to be independent of the presence of lexical tone or stress in a language.

1.3 Previous studies on prosodic marking of focus in Korean

Previous studies show that narrow focus in Korean is signalled by phrasing together with other phonetic markers.⁵ A focused constituent initiates a new prosodic phrase and tends to be longer than neutral or post-focus counterparts, and the lengthening tends to be greater in magnitude at the edges of the focused constituent; furthermore, the lengthening at the left edge seems to be more consistent than that at the right edge (e.g., Chung & Kenstowicz, 1997; Jun & Lee, 1998; Jun & Kim, 2007). Jun and Lee (1998) show that the phrase-initial lengthening under focus is mainly due to extra articulatory strengthening of the phrase-initial segment, although Cho et al. (2011) found significant lengthening of the second syllable of focused words. The focused constituent also tends to be spoken more loudly than neutral or post-focus words (Lee & Xu, 2010; Cho et al., 2011) and shows an increased F₀ excursion, while the F₀ peak of the post-focus words tends to be compressed (Chung & Kenstowicz, 1997; Jun & Kim, 2007; Lee & Xu, 2010). Jun and Lee (1998) show that the F₀ peak in the post-focus constituent may not necessarily be lower than that of the neutral counterpart, although it tends to be lower than that of the focused constituent within the utterance.

An important phonological marker seems to be that the focused constituent always begins a new prosodic phrase. In previous studies, the phrase headed by a focused constituent has the status minimally of an Accentual Phrase (AP) (Jun & Lee, 1998) or of an Intonational Phrase (IP) (Jun & Kim, 2007). When the new phrase is headed by a focused constituent, the post-focal constituent, which would have been produced as an AP with acoustic disjuncture at both edges in the neutrally spoken utterance, may be realized without the perceivable acoustic disjuncture at its left edge. That is, the prosodic boundary following the focused constituent may be deleted, but such dephrasing is optional in Korean (Jun & Kim, 2007; Lee & Xu, 2010).⁶

The findings on the out-of-focus constituents are inconsistent. Although Lee and Xu (2010) report PFC in Korean, Jun and Lee (1998) and Yang et al. (2015) offer only inconsistent evidence of the F₀ span compression or shortening of the syllable duration in pre- or post-focus constituents. Jun and Lee (1998) report mixed results; only 3 speakers out of 5 reduced the F₀ peak height compared to neutral speech, while the defocused constituents tended to be shorter than the neutral counterpart. In Yang et al. (2015), F₀ span was wider in focused words than in defocused words when the defocused words were pre-focus but not post-focus, although the opposite trend would be expected from the findings in other languages in which PFC has been demonstrated. Yang et al. (2015) also report an interaction between the size of the focused constituent and the prosodic marking of focus; the focus effect was shown when the target word had four syllables but not with disyllabic words.

1.4 Aims and hypotheses

We explore the prosodic variation associated with information structure. In particular, we investigate prosodic marking of narrow focus not only at the level of the AP but potentially at a larger domain, and, complementarily, the prosodic properties of defocused constituents. The prosodic characteristics of Korean lead us to expect that focus marking in Korean may exploit cues similar to those reported in French and Japanese (see Section 1.2). Our expectation follows from shared features of the three languages: They lack lexical stress, and the smallest prosodic unit—the AP in Korean, for instance—is demarcated by the F₀ contour (see e.g., Welby, 2006 for French; Venditti, 2005 for Japanese; Jun, 2005 for Korean; note, however, that the AP in Japanese may include a lexical pitch accent). In both French and Korean the lack of lexical stress means there is no culminative prominence marking focus; rather, it is phrasal structure that fulfils the role, with support from overall adjustment of the F₀ span of APs. In addition, the frequent use of a complex pitch movement at the right edge of the IP, which contributes to pragmatic interpretation of the utterance in Japanese (Venditti, 2005; Venditti et al., 2008), seems to resemble that in Korean (e.g., Jun, 2005; Park, 2012).

In the experiment, we focus on examining the following specific hypotheses formulated based on the previous findings in Korean and other languages. First, there would be lengthening of the focused constituent and the linguistic units therein, and there would be shortening of the defocused constituent. We expect lengthening spreading over the focused constituent but a larger magnitude of lengthening near the constituent edges. Second, narrow focus would affect the formation of prosodic phrases in that the focused constituent begins a new prosodic phrase. Third, as in Japanese (e.g., Venditti et al., 2008), the focused constituent may be associated with a higher-level prosodic phrase than the AP and boundary tones with a complex pitch movement at the right edge. Fourth, the F₀ contour shapes in the AP would be affected by focal structure, and speakers’ F₀ adjustment in relation to the focal structure may interact with the segmentally-induced F₀ variation. Fifth, F₀ span would be affected by focal structure; the F₀ span would be widest in the focused constituent, whereas the F₀ span would be compressed in the defocused constituent in comparison to the focused or neutrally spoken counterpart. In addition, we expect to observe an association between the AP-initial segment type and tone in speech data as widely reported in previous studies (reviewed in Section 1.1).

2.1 Experimental materials

There were 32 targets of 5- or 7-syllable sequences of two number units (Table 1). It was assumed that each number unit is a Phonological Word (PW) corresponding to an Accentual Phrase (AP) in speech. The term PW is used to refer to the semantically coherent number unit in the reading materials henceforth (while in speech, a PW is produced without perceivable disjuncture at its edges, as discussed in Section 2.3). They were classified into 4 phrasing types (2 + 3, 3 + 2, 3 + 4, and 4 + 3, where + indicates the PW boundary), and there were two types of initial segments (weak and strong, see Section 1.1) in the second PW. The location of the strong segments was systematically controlled to have APs beginning with a low tone (L) or a high tone (H) in the dataset. Each PW was designed to include between two and four syllables, as 2-, 3-, and 4-syllable APs tend to occur frequently. It was intended to have experimental materials that were meaningful and familiar to speakers, while the possible confounding effect of the morpho-semantic structure was controlled. All constituents of the targets were monosyllabic numbers referring to, for example, 1 (/il/), 10 (/sip/), 100 (/pɛk/), 1,000 (/tsʰʌn/) or 10,000 (/man/), in Korean, which could be combined to create different numbers resembling words, depending on the location of a prosodic boundary. Targets were designed not to include diphthongs, but otherwise different types of segments and syllable structures were used.⁷

As many syllables as possible were kept identical at a given position across the targets to minimize the variance unrelated to the factors of interest. The first two syllables /i.man/ and the last syllable /o/ were identical for all 5-syllable targets. For the 7-syllable targets, the first three syllables, /i.pɛk.man/, and the last two syllables, /i.pɛk/, were identical for all targets, with two exceptions (marked with ^† in Table 1), where /man/ was used as the penultimate syllable. Since the potential target APs had a similar number of syllables, fillers were constructed to have different phrasing structure from them (e.g., 3 + 3, 2 + 2, 1 + 2 + 1, or 2 + 2 + 2) to distract speakers from producing speech with strict rhythmic regularity. Various numbers which did not appear in the targets were used for fillers, together with the numbers used in the targets. Some of the experimental materials were originally designed for an experiment in which speakers’ prosodic strategies for disambiguating two alternative phrasings (e.g., 2 + 3 vs. 3 + 2) are examined, reported in Jeon (2011, Chap. 4).

There were three Focus conditions: Neutral (read neutrally), PW1-focus (the first PW under narrow corrective focus) and PW2-focus (the second PW under narrow corrective focus). This design makes it possible to compare the same PW spoken in three different ways: Neutral, focused (PW1 in PW1-focus, PW2 in PW2-focus), and defocused (PW2 in PW1-focus, PW1 in PW2-focus). For the recording of the Neutral utterances, a list of sentences (‘neutral list’) was created as in Example (1) with the targets and fillers between two carrier phrases (meaning “the numbers for this time are [target]”)⁸.

In the written sentences, commas were placed after the first carrier phrase (/ipʌn#sutɯlɯn/) and after each PW in the target or filler.

A ‘focus list’ of sentences was prepared for the recordings of PW1-focus and PW2-focus. On the ‘focus list,’ either PW1 or PW2 was underlined and was preceded by a phrase with a “not A, B but A, C” construction in parentheses, as shown in Example (2), “([it is] not twenty thousand and one, a thousand and one), but the numbers this time are twenty thousand and one, ten thousand and five.”

This construction may appear to be a double correction in English (e.g., ‘ten thousand five’ in Example (2)) but it was intended to have completely different numbers resembling lexical units to be contrasted in the materials in Korean (/tsʰʌnil/, 1,001 vs. /mano/, 10,005). That is, the English-type single correction (e.g., “not twenty thousand and one (20,001), a thousand and one (1,001), but twenty thousand and one (20,001), a thousand and FIVE (1,005)”) in Korean would not yield the AP structure as desired because it could lead speakers to produce three APs as target, e.g., (imanil#tsʰʌnili#anila,)# imanil#tsʰʌn#o, “not 20,001, 1,001, but 20,001, 1,005” with monosyllabic APs.

The ‘neutral list’ consisted of 32 sentences with the targets and 64 sentences with the fillers between the carrier phrases. In the ‘focus list,’ there were 64 sentences with the targets and 128 sentences with the fillers. The order of the sentences on each list was randomized for each subject, and two filler sentences in a random order were inserted between two sentences with a target, so that there would always be two filler sentences separating sentences with a target.

The inherent nature of the number sequence in the form of a two-item list might lead to readings deviating from those of ordinary sentences which do not include numbers. However, the use of the number sequence did not elicit any noticeably different prosodic properties from what is reported in literature for ordinary sentences when read neutrally (see Jeon, 2011, Ch. 4). Further, the number sequences are likely to be associated with a phrase-final rising intonation which can be interpreted as signalling phrase-finality, continuation, and the organization of the successive items (Park, 2012) across all materials, and therefore tight experimental control was achieved.

2.2 Experimental procedure

Four native speakers of Seoul Korean (2 females—YH, HKL, and two males—KJ, CHJ) aged between 20 and 22 participated in the experiment. Participants were given a small payment. All recording was done in a sound-attenuated booth in the Hanyang University in Seoul, using a Tascam HD-P2 recorder and a Shure KSM 44 microphone. The sampling rate was 44.1 kHz.

Participants were given the ‘neutral list’ first. They had time to become familiar with the materials, and were allowed to practise if they wanted. They read through the ‘neutral list’ five times for recording. The ‘focus list’ reading was recorded after each speaker completed the ‘neutral list’ reading. With the ‘focus list,’ speakers were asked to imagine a situation in which their interlocutor misunderstood the sentence, and they were told they could silently read the phrase in the parentheses if they wanted to (see Jun & Lee, 1998 for a similar technique). They were asked to practise until they could read the materials naturally. The ‘focus list’ was read three times in total, and speakers took a short break after each list reading.

2.3 Data annotation and measurements

For Neutral, 640 utterances including the target (4 targets × 2 PW2-initial segment types × 4 phrasings × 5 repetitions × 4 speakers) were recorded. Fifteen utterances with hesitation or ambiguous phrasing were discarded, finally leaving 625 utterances for the analysis. Since we aimed to investigate natural intonational variation in speech data, no utterances were discarded by reason of being produced with F₀ contour shapes which are infrequently observed in Korean. In each of PW1-focus and PW2-focus, 378 and 382 utterances out of 384 utterances including the target (4 targets × 2 PW-initial segment types × 4 phrasings × 3 repetitions × 4 speakers) in each category were analyzed.

In order to examine durational variations related to the focus, boundaries of segments, syllables, and PWs in each utterance were annotated using Praat (Boersma & Weenink, 2010), following standard criteria suggested in Peterson and Lehiste (1960) and Turk et al. (2006). Glottal stops or creaky parts which often appeared at the vowel onset or offset were marked separately but included as part of a vowel. Glottal stops were marked only when there was a clear silent interval, and irregular but continuous pulses were marked as creak. When there was a sequence of consonants with a single closure (e.g., kts^h in /juk.ts^hʌn/ ‘6,000’), the closure was halved, and each half was treated as a closure of one consonant. The syllable boundary was defined as suggested in Korean orthography which reflects the morphological structure without regard to possible resyllabification, for instance, CVC.V to CV.CV (e.g., /man.il/ to /ma.nil/ ‘10,001’), for ease and consistency in the analysis. Although it was assumed that one PW in the reading materials would form an AP in speech, the targets included sequences of various syllabic compositions (e.g., /manil/ ‘10,001’ and /mansam/ ‘10,003’), and one orthographic syllable (e.g., /man/ ‘10,000’), a morphonological unit as an independent noun could form an AP. Therefore, the orthographic syllable division was used in all data. The duration of each syllable and PW was extracted using a Praat script.

In addition, the first author annotated the F₀ contour shape in the PW together with the type of prosodic boundary at the right edge of each prosodic phrase, following the criteria in Jun (2000). Annotation of the F₀ contour shape was necessary in order to investigate possible variations related to focal structure and also for analyzing F₀ span in PW. The PWs realized with a static pitch contour shape (e.g., HH) would need to be separated from those in a PW with a clear F₀ peak (e.g., LHLH).

The prosodic boundary strength before PW1, after PW1, and after PW2 was labelled as PW (with no perceivable prosodic disjuncture), AP (with perceivable prosodic disjuncture and the AP boundary tone), or IP (with significant phrase-final lengthening and an IP boundary tone). The points of F₀ maximum and minimum in each number unit (i.e., PW) were detected semi-automatically in Praat, their values were extracted using a Praat script, and they were used in calibrating F₀ span within each PW. The F₀ values were measured in semitones (ST) relative to 100 Hz. Outliers and octave jumps were manually corrected. Samples of 160 utterances in total were cross-checked by four native Korean speakers who are trained in prosodic annotation. The between-annotator agreement rate was high at 82% for F₀ contour shapes and at 93% for the prosodic boundary strength. For the F₀ contour shapes, out of the 18% of tokens where there was disagreement, 10% were caused by minor disagreement on the precise turning point of the F₀ (e.g., LH vs. LLH in multisyllabic PWs), which would not affect the result of the study. The rest of the disagreement was on the identification of the initial or final tone between L and H (e.g., LHLH vs. HHLH, LHL vs. LHLH). The cases where there was disagreement were re-examined by the first author, and a decision between the alternatives was made on the basis of the F₀ contour and the perceived pitch. For the prosodic boundary strength, annotators disagreed when the presence of the phrase-final lengthening in the target PW was not clear. The annotation of the tokens where there was disagreement was corrected so that prosodic phrases with clearly perceived final lengthening and a boundary tone would be referred to as the IP.

3.1 Duration

3.1.2 Syllable duration

The hypothesized relationship for syllable duration was focused > neutral > defocused, and it was expected that lengthening triggered by focus would be more pronounced at the focused constituent edges. Figure 1 demonstrates that all syllables in the Focused PW tended to be longer than those in its neutral or defocused counterpart. As expected, the magnitude of lengthening under focus was more pronounced at phrase edges than in phrase-medial syllables. Compared to Neutral, PW-initial syllables were lengthened under focus by 27% on average (mean = 46.53 ms, range 26.09–62.12 ms), PW-medial syllables by 14.3% on average (mean = 23.39 ms, range 15.01–35.53 ms), and PW-final syllables by 25% on average (mean = 46.88 ms, range 32.70–62.67 ms; also see larger absolute values of the estimates in Table 4 for the PW-initial syllable). However, the duration of syllables in the defocused PW tends to overlap with that in Neutral in Figure 1.

Figure 1

Mean duration of each syllable (ms) for each PHRASING averaged over all speakers. Error bars indicate one standard error, n = 8328. Neutral: solid line, PW1-focus: dotted line, PW2-focus: dotdash line.

Linear mixed-effect models were fitted to the syllable duration (ms) as a dependent variable. The initial full models were constructed for 5-syllable targets and 7-syllable targets respectively with fixed factors, Focus, Phrasing, PW-Initial Segment, and Syllable Position (1–5 in 5-syllable targets, 1–7 in 7-syllable targets). In the modelling process, the three-way interaction effect Syllable Position × Focus × Phrasing was statistically significant (5-syllable targets, χ² (8) = 113.63, p < 0.001; 7-syllable targets, χ² (12) = 132.5, p < 0.001). Further models were constructed for the syllable duration (ms) in each Syllable Position to explore the Focus × Phrasing interaction. Some syllables in the same position in the target occupy different position relative to the PW boundaries depending on the phrasing (e.g., the second syllable would be PW1-final in 2 + 3 phrasing but PW1-medial in 3 + 2 phrasing) and, therefore, it was necessary to examine the potential interaction between Focus and Phrasing in each Syllable Position. Since there was a significant Focus × Phrasing effect in the majority of cases (see Table 3 for the effects of fixed factors), the pairwise comparisons between the focus conditions were conducted within each phrasing.

Table 3

Summary of the main effects Focus and Phrasing and the Focus x Phrasing interaction in the mixed-effects model with syllable duration (ms) as a dependent variable for each syllable in 5-syllable targets and in 7-syllable targets. Significance codes * p < 0.05, ** p < 0.01, *** p < 0.001.

	5-syllable target		7-syllable target
Syll no.	χ2	df	χ2	df
Focus
1	132.89***	2	157.37***	2
2	120.11***		112.95***
3	118.02***		148.8***
4	226.15***		65.524***
5	219.60***		243.45***
6			166.71***
7			153.68***
Phrasing
1	21.59***	1	6.81**	1
2	5.34*		17.43***
3	2.75		10.85***
4	18.30***		2.60
5	0.16		6.46*
6			0
7			0.67
Focus x Phrasing
1	10.40*	2	1.14	2
2	28.52***		3.63
3	145.26***		30.62***
4	31.51***		140.87***
5	3.99		16.81***
6			2.04
7			1.03

The pairwise comparisons in each phrasing showing statistically significant differences are the following (see Table 4): for 2 + 3, syllables 1 (PW1-initial) and 2 (PW1-final) were significantly longer in PW1-focus than PW2-focus or Neutral, whereas there was no statistically significant difference between Neutral and PW2-focus. Syllable 3 (PW2-initial) was significantly longer in the order PW2-focus > PW1-focus > Neutral. Syllables 4 and 5 were significantly longer in PW2-focus than Neutral and PW1-focus, whereas there was no significant difference between Neutral and PW1-focus.

Table 4

The output of a Tukey contrast test for syllable duration. A positive estimate indicates that the first level in the comparison has a higher group mean. 5-syllable targets, 2 + 3, n = 346; 3 + 2, n = 341; 7-syllable targets, 3 + 4, n = 350; 4 + 3, n = 349. Significance codes * p < 0.05, ** p < 0.01, *** p < 0.001.

	5-syllable targets				7-syllable targets
		Estimate	SE	Z		Estimate	SE	z
1	2+3.PW1-f vs. 2+3.N	46.03	4.49	10.25***	3+4.PW1-f vs. 3+4.N	38.92	4.28	9.10***
	2+3.PW2-f vs. 2+3.N	1.46	4.51	0.32	3+4.PW2-f vs. 3+4.N	5.10	4.28	1.19
	2+3.PW2‑f vs. 2+3.PW1‑f	–44.57	5.00	–8.91***	3+4.PW2‑f vs. 3+4.PW1‑f	–33.82	4.77	–7.09***
	3+2.PW1-f vs. 3+2.N	25.94	4.56	5.69***	4+3.PW1-f vs. 4+3.N	37.14	4.29	8.67***
	3+2.PW2-f vs. 3+2.N	–1.47	4.50	–0.33	4+3.PW2-f vs. 4+3.N	–1.34	4.29	–0.31
	3+2.PW2-f vs. 3+2.PW1-f	–27.41	5.05	–5.43***	4+3.PW2-f vs. 4+3.PW1-f	–38.48	4.80	–8.02***
2	2+3.PW1-f vs. 2+3.N	43.16	3.72	11.61***	3+4.PW1-f vs. 3+4.N	21.08	2.31	9.13***
	2+3.PW2-f vs. 2+3.N	4.56	3.73	1.22	3+4.PW2-f vs. 3+4.N	5.37	2.31	2.33
	2+3.PW2-f vs. 2+3.PW1-f	–38.60	4.14	–9.32***	3+4.PW2-f vs. 3+4.PW1-f	–15.71	2.58	–6.10***
	3+2.PW1-f vs. 3+2.N	15.12	3.78	4.00***	4+3.PW1-f vs. 4+3.N	14.99	2.31	6.48***
	3+2.PW2-f vs. 3+2.N	–0.81	3.73	–0.22	4+3.PW2-f vs. 4+3.N	4.27	2.31	1.85
	3+2.PW2-f vs. 3+2.PW1-f	–15.94	4.18	–3.82**	4+3.PW2-f vs. 4+3.PW1-f	–10.71	2.59	–4.14***
3	2+3.PW1-f vs. 2+3.N	16.56	4.47	3.70**	3+4.PW1-f vs. 3+4.N	41.88	3.71	11.28***
	2+3.PW2-f vs. 2+3.N	45.60	4.49	10.16***	3+4.PW2-f vs. 3+4.N	–8.27	3.71	–2.23
	2+3.PW2-f vs. 2+3.PW1-f	29.04	4.98	5.83***	3+4.PW2-f vs. 3+4.PW1-f	–50.15	4.14	–12.11***
	3+2.PW1-f vs. 3+2.N	62.94	4.55	13.85***	4+3.PW1-f vs. 4+3.N	15.75	3.72	4.23***
	3+2.PW2-f vs. 3+2.N	1.86	4.48	0.42	4+3.PW2-f vs. 4+3.N	–5.56	3.72	–1.49
	3+2.PW2-f vs. 3+2.PW1-f	–61.08	5.02	–12.16***	4+3.PW2-f vs. 4+3.PW1-f	–21.31	4.16	–5.12***
4	2+3.PW1-f vs. 2+3.N	–1.435	4.022	–0.357	3+4.PW1-f vs. 3+4.N	10.59	5.09	2.08
	2+3.PW2-f vs. 2+3.N	29.70	4.04	7.36***	3+4.PW2-f vs. 3+4.N	50.71	5.09	9.97***
	2+3.PW2-f vs. 2+3.PW1-f	31.14	4.48	6.95***	3+4.PW2-f vs. 3+4.PW1-f	40.13	5.68	7.07***
	3+2.PW1-f vs. 3+2.N	11.38	4.09	2.79	4+3.PW1-f vs. 4+3.N	52.37	5.10	10.27***
	3+2.PW2-f vs. 3+2.N	62.10	4.03	15.40***	4+3.PW2-f vs. 4+3.N	–7.56	5.10	–1.48
	3+2.PW2-f vs. 3+2.PW1-f	50.72	4.52	11.23***	4+3.PW2-f vs. 4+3.PW1-f	–59.93	5.71	–10.51***
5	2+3.PW1-f vs. 2+3.N	–12.19	5.36	–2.28	3+4.PW1-f vs. 3+4.N	–12.31	4.33	–2.84*
	2+3.PW2-f vs. 2+3.N	50.05	5.38	9.31***	3+4.PW2-f vs. 3+4.N	35.39	4.33	8.18***
	2+3.PW2-f vs. 2+3.PW1-f	62.25	5.97	10.42***	3+4.PW2-f vs. 3+4.PW1-f	47.69	4.83	9.88***
	3+2.PW1-f vs. 3+2.N	2.50	5.45	0.46	4+3.PW1-f vs. 4+3.N	3.80	4.34	0.88
	3+2.PW2-f vs. 3+2.N	59.50	5.37	11.07***	4+3.PW2-f vs. 4+3.N	59.49	4.34	13.72***
	3+2.PW2-f vs. 3+2.PW1-f	57.00	6.02	9.47***	4+3.PW2-f vs. 4+3.PW1-f	55.70	4.85	11.48***
6					3+4.PW1-f vs. 3+4.N	–7.92	3.54	–2.24
					3+4.PW2-f vs. 3+4.N	24.71	3.54	6.99***
					3+4.PW2-f vs. 3+4.PW1-f	32.62	3.94	8.27***
					4+3.PW1-f vs. 4+3.N	–10.34	3.54	–2.92*
					4+3.PW2-f vs. 4+3.N	30.03	3.54	8.47***
					4+3.PW2-f vs. 4+3.PW1-f	40.37	3.96	10.18***
7					3+4.PW1-f vs. 3+4.N	–7.84	4.44	–1.77
					3+4.PW2-f vs. 3+4.N	32.91	4.44	7.42***
					3+4.PW2-f vs. 3+4.PW1-f	40.75	4.95	8.23***
					4+3.PW1-f vs. 4+3.N	–13.80	4.45	–3.10*
					4+3.PW2-f vs. 4+3.N	32.74	4.45	7.36***
					4+3.PW2-f vs. 4+3.PW1-f	46.54	4.98	9.35***

For 3 + 2, syllables 1 (PW1-initial), 2 (PW1-medial), and 3 (PW1-final) were longer in PW1-focus than in Neutral or PW2-focus, whereas there was no significant difference between Neutral and PW2-focus. Syllables 4 (PW2-initial) and 5 (PW2-final) were longer in PW2-focus than in Neutral or PW1-focus. The duration of syllables 4 and 5 did not show a significant difference between Neutral and PW1-focus.

For 3 + 4, syllables 1 (PW1-initial), 2 (PW1-medial), and 3 (PW1-final) were significantly longer in PW1-focus than in Neutral or PW2-focus, whereas there was no significant difference between Neutral and PW2-focus. Syllables 4 (PW2-initial), 6 (PW2-medial), and 7 (PW2-final) were significantly longer in PW2-focus than in Neutral or PW1-focus, and no statistically significant difference was found between Neutral and PW1-focus. Syllable 5 (PW2-medial) showed the order PW2-focus > Neutral > PW1-focus.

For 4 + 3, syllables 1 (PW1-initial), 2 (PW1-medial), 3 (PW1-medial), and 4 (PW1-final) were significantly longer in PW1-focus than in Neutral or PW2-focus, whereas the difference between Neutral and PW2-focus did not reach significance for all comparisons. Syllables 5 (PW2-initial) was also significantly lengthened in PW2-focus than in Neutral or PW1-focus, and the difference between PW2-focus and Neutral did not reach significance. Syllables 6 (PW2-medial) and 7 (PW2-final) showed the order PW2-focus > Neutral > PW1-focus.

3.2 Focus and the prosodic boundary type

It was hypothesized that the focused constituent begins a new prosodic phrase. As hypothesized, the PWs under narrow focus always initiated a new prosodic phrase, either the AP or the IP. Figure 2 shows that there was no PW-sized disjuncture (meaning there was always a perceivable prosodic disjuncture) before the focused constituent (i.e., Pre-PW1 for PW1 under focus and Post-PW1 for PW2 under focus). The hypothesis that focused PWs would be associated with a larger prosodic boundary than neutrally spoken or defocused PWs was supported in some contexts. Figure 2 shows that the most frequent prosodic boundary type was IP between the carrier phrase and the PW1 (Pre-PW1) and also after the PW2 (Post-PW2) in all Focus conditions. For Post-PW1, although AP was more common for Neutral or PW2-focus, when PW1 was under focus, the most frequent type boundary type was IP.

Figure 2

The frequency (percentage) of each boundary type between the carrier phrase and PW1 (Pre-PW1), after PW1 (Post-PW1) and after PW2 (Post-PW2). Neutral, n = 626; PW1-focus, n = 378; PW2-focus, n = 382.

The probability of an IP boundary occurrence as opposed to an AP boundary was modelled by mixed effects logistic regression (e.g., Pinheiro & Bates, 2000; Baayen et al., 2008). The initial full model included fixed factors, Focus, Phrasing, Location, and PW-Initial Segment. All two-way interaction effects were statistically significant (Focus × Phrasing, χ² (6) = 12.76, p < 0.05; Phrasing × Location, χ² (6) = 88.05, p < 0.001; Focus × Location, χ² (4) = 219.99), although the Focus × Phrasing × Location interaction was not (χ² (12) = 17.44, ns). Due to the interdependence between the three fixed factors, data were split by Location (Pre-PW1, Post-PW1, and Post-PW2) in order to explore how the PW in different positions in the utterance was affected by Focus. There were significant Focus and Phrasing effects for Pre-PW1 (Focus, χ² (2) = 31.49, p < 0.001; Phrasing, χ² (2) = 15.71, p < 0.01), Post-PW1 (Focus, χ² (2) = 315.17, p < 0.001; Phrasing χ² (3) = 37.66, p < 0.001) and Post-PW2 (Focus, χ² (2) = 25.48, p < 0.001; Phrasing χ² (3) = 10.51, p < 0.05). For Post-PW2, the Focus × Phrasing interaction was also significant (χ² (6) = 21.33, p < 0.01).

The result of the contrast test (Table 5) demonstrates the effect of Focus for Pre-PW1 and Post-PW1. For both Pre-PW1 and Post-PW1, more IP boundaries were likely to occur in PW1-focus than in Neutral or PW2-focus. Phrasing affected the likelihood of the IP boundary presence in some cases. For Pre-PW1, the target in 2 + 3 phrasing was more likely to be preceded by the IP boundary than other phrasing types. For Post-PW1, the IP boundary was more likely observed when PW1 had more syllables than PW2. For Post-PW2, a statistically significant difference in the contrast test was observed in only a few comparisons; for 3 + 2, the IP boundary was more likely to be present in PW2-focus than in Neutral or PW1-focus. For 3 + 4, more IP boundaries were present for Neutral than for PW1-focus.

3.3 F₀

3.3.1 F₀ contour shapes over the PW

It was hypothesized that the F₀ contour shapes in the PW would be affected by focal structure and speakers’ F₀ adjustment would interact with the segmentally-induced F₀ variation. First, the analysis of the annotated F₀ contour shapes revealed that when the PW was realized as an AP, the most common F₀ contour shapes were LH, HH, HLH, LHLH, and HLHL. These five types accounted for 79.25% of the total APs. Further details are not provided since the variations in the F₀ contour shapes within the AP were not related to Focus in contrast to the hypothesis, although some cases with static pitch contours (LL and HH) are presented below. The assumption that one PW in the reading materials would be realized as one AP was met in general; there were only 23 cases of the PW boundary percept (i.e., no marked prosodic disjuncture), and 9 cases out of 23 were observed in Post-PW2 when PW2 was under focus indicating post-focus dephrasing. The AP-final H frequently appeared as expected (84.33% of total APs) and the AP-initial tone tended to be determined by the type (weak/strong) of its initial segment. However, there were exceptions; Table 6 shows that not all PW2s beginning with a strong segment were realized with a phrase-initial H and there were cases of association of H with a PW-initial weak segment. In Neutral, 2% of PW1s (which all began with a weak segment) and 23% of PW2s with a weak initial segment began with H. This is likely to be an artefact related to the composition of the experimental materials. The PW2 of 2 + 3 and 3 + 4 often begins with /il/ (‘one’); some Korean speakers raise AP-initial pitch for /il/ (‘one’) in order to distinguish the two numbers /il/ (‘one’) and /i/ (‘two’) which could sound similar to each other (Jun & Cha, 2011, 2015).

Table 6

Frequency of PW-initial H (percentage) in PW1 and PW2 for each the type of the PW2-initial segment for Neutral, PW1-focus, and PW2-focus.

	Weak		Strong
PW1	Neutral (n = 626)	2%
	PW1-focus (n = 378)	8%
	PW2-focus (n = 382)	5%
PW2	Neutral (n = 314)	23%	Neutral (n = 312)	92%
	PW1-focus (n = 189)	20%	PW1-focus (n = 189)	88%
	PW2-focus (n = 190)	28%	PW2-focus (n = 192)	97%

Second, a final rise (H% and LH%) occurred frequently when the PW was aligned to the right edge of the IP. The frequency statistics in Table 7 suggests that in Neutral, H% was the most common IP boundary tone and the frequency of LH% increased when the PW was focused. The probability of the bitonal IP boundary tone (LH%, HL%) being present was modelled using mixed effects logistic regression with the fixed factors Focus, Location, and Phrasing. Since the Focus × Phrasing × Location effect was statistically significant (χ² (6) = 21.28, p < 0.01), the data were split by Location (PW1, PW2). The effect of Focus was significant for both PW1 (χ² (2) = 30.67, p < 0.001) and PW2 (χ² (2) = 222.31, p < 0.001). However, the Phrasing effect (χ² (3) = 25.69, p < 0.001) and the Focus × Phrasing interaction (χ² (6) = 37.13, p < 0.001) were significant only for PW2. A Tukey contrast test revealed that for PW1, the bitonal IP boundary tones were more likely to occur for PW1-focus than in PW2-focus, while there was no significant difference between Neutral and either of PW1-focus or PW2-focus (Table 8). For PW2, although no statistically significant differences between the Focus levels were revealed for 4 + 3, the bitonal IP boundary tones were more likely to occur when PW2 was under focus in other phrasings in comparison to Neutral or PW1-focus.

Table 7

Frequency of IP boundary tones (percentage) in Neutral, PW1-focus, and PW2-focus.

	PW1			PW2
	Neutral (n = 147)	PW1-focus (n = 274)	PW2-focus (n = 96)	Neutral (n = 410)	PW1-focus (n = 223)	PW2-focus (n = 277)
H%	96	56	67	94	78	47
L%		18	17	1	1	2
LH%	2	23	2	5	21	52
HL%	2	4	15

Table 8

The output of the post-hoc Tukey contrast test for the IP boundary tone type (monotonal vs. bitonal). A positive estimate indicates that the first level in the comparison has a higher group mean. Significance codes * p < 0.05, ** p < 0.01, *** p < 0.001.

PW1				PW2
	Estimate	SE	z		Estimate	SE	z
PW1-f vs. N	5.95	17.18	0.35	2+3.PW1-f vs. 2+3.N	–0.35	0.45	–0.77
PW2-f vs. N	7.70	17.19	0.45	2+3.PW2-f vs. 2+3.N	2.69	0.40	6.75***
PW2-f vs. PW1-f	1.75	0.24	7.23***	2+3.PW2-f vs. 2+3.PW1-f	3.04	0.47	6.43***
				3+2.PW1-f vs. 3+2.N	3.19	0.68	4.70***
				3+2.PW2-f vs. 3+2.N	4.55	0.67	6.82***
				3+2.PW2-f vs. 3+2.PW1-f	1.35	0.42	3.22*
				3+4.PW1-f vs. 3+4.N	3.18	1.08	2.96
				3+4.PW2-f vs. 3+4.N	4.25	1.05	4.06**
				3+4.PW2-f vs. 3+4.PW1-f	1.07	0.49	2.18
				4+3.PW1-f vs. 4+3.N	18.48	209.03	0.09
				4+3.PW2-f vs. 4+3.N	20.04	209.03	0.10
				4+3.PW2-f vs. 4+3.PW1-f	1.56	0.49	3.18

Further analyses of the APs produced with the static pitch contour such as LL or HH were carried out. There were no APs with LL in the data, but the APs produced with HH in Neutral could be identified (23 utterances from YH, 1 utterance from HKL, 24 utterances from KJ, and 20 utterances from CHJ). The data showed that some speakers (e.g., YH and HKL in Figure 3) consistently produced LH% on the final syllable of the focused PW in all cases whereas the two male speakers preferred raising overall pitch for the HH (e.g., KJ and CHJ in Figure 4). Statistical analysis was not carried out since there were insufficient data points.

Figure 3

Neutral (left) and PW2-focus (right), produced by YH (female).

Figure 4

Neutral (left) and PW2-focus (right), produced by KJ (male).

4.1 Prosodic marking of narrow focus in Seoul Korean

Overall, the results show that Korean speakers actively adjust the prosodic organization of the utterance in response to its focal structure. Although an exact analogue of the culminative pitch accent in West Germanic languages is not apparent in Korean due to the lack of lexical stress, similar prominence-lending acoustic properties are employed and the focus-marking phonetic events are concentrated at phrase boundaries. The speakers’ focus marking strategies are in line with general cross-linguistic trends showing an increase in the articulatory effort in the element under narrow focus, e.g., lengthening, more pitch movements, pitch raising, and wider pitch excursions (see Gussenhoven, 2004).

In the experiment, speakers were under pressure to convey emphasis in the reading materials verbatim and they were not allowed to use any of the alternative non-phonetic strategies such as changing the word order. The reading materials were sentences of two PWs that were numbers between carrier phrases, and speakers produced one or the other, or neither, of the PWs under corrective focus. The type of PW-initial segment in the target included both weak segments and strong segments.

The hypothesis that the focused constituent and syllables therein would be lengthened in comparison to the neutrally spoken or defocused constituent was supported, since the durational marking of the focused constituent was robust in the data. Duration of the target PWs was affected by Focus; the PW-initial and PW-final syllables were lengthened more (on average 27% and 25%, respectively, compared to Neutral) than phrase-medial syllables (14.3%), although the lengthening could spread over the focused constituent. Unlike the West Germanic languages in which a pitch-accented lexically-stressed syllable undergoes the greatest amount of lengthening under focus (e.g., Cambier-Langeveld & Turk, 1999), Korean speakers lengthen syllables at the phrase edges to the greatest magnitude. Although both edges of the prosodic phrase under focus are subject to lengthening in Korean, its motivation seems to be different between the left and the right edges. This study did not examine segmental duration, but previous studies reveal that the lengthening of the phrase-initial syllable is partly due to articulatory strengthening (Jun & Lee, 1998; Cho & Keating, 2001; Cho et al., 2011). On the other hand, the lengthening at the right edge is probably caused by speakers’ attempt to produce the IP boundary tones, as discussed further below.

As hypothesized, the focal structure affects the formation of prosodic phrases in that the focused constituent always initiated a new AP or IP. The interpretation that the boundary strength varies between the AP and the IP may appear to be inconsistent but it is justifiable. Following the K-ToBI criteria (Jun, 2000), at the right edge of the focused constituent there may be a simple pitch rise or fall with no perceived final lengthening (AP) or an IP-type boundary tone with significant final lengthening (IP); or there may not be a prosodic disjuncture. What is of importance is that the focused constituent is preceded by prosodic disjuncture.

The focused constituent was more likely to form an IP than an AP and it was associated with more pitch movements near the phrase boundary in comparison to its neutrally spoken or defocused counterpart. In the present experiment, in which speakers’ intonational choice was not constrained, they seemed to enjoy the freedom to manipulate the pitch movement at the right edge of the prosodic phrase by employing monotonal (H%, L%) or bitonal (HL%, LH%) IP boundary tones. For example, the constituent that carried LHLH in the AP in Neutral was realized with a bitonal boundary IP tone LH% (LH LH%) under narrow focus (see Figure 5). The bitonal LH% was used by two speakers when the Neutral PW2 had a high-static pitch (HH) (see Figure 3), while the other two speakers seemed to raise the overall level of HH (see Figure 4). When an IP was formed in the utterance, the most frequent boundary tone was a rise: 91% of the IP boundary tones were H% or LH% on average, and specifically for PW2 99% of the IP boundary tones were either H% or LH% regardless of the focus condition. This would be partly due to the nature of the reading materials, which included a two-item list, but speakers’ choice of IP boundary tone was affected by Focus and Phrasing. In general, the IP boundary was commonly observed between the first carrier phrase and PW1 (Pre-PW1) and then between PW2 and the final carrier phrase (Post-PW2), as shown in Example (3), “([it is] not twenty thousand and one, a thousand and one), but the numbers this time are twenty thousand and one, ten thousand and five.”

Figure 5

Speaker HKL (female), Neutral (left) and PW1-focus (right).

The right edge of the PW2 corresponded to the end of the target phrase, and speakers seemed to have produced the IP boundaries to separate the target phrase from the surrounding carrier phrases.

PW1 and PW2 were affected by Focus in a different way. PW1 was frequently realized as an AP when neutrally spoken or defocused (i.e., when PW2 was focused), but focused PW1 was more likely to be realized as an IP. In addition, focus on PW1 seemed to affect the magnitude of its preceding prosodic boundary together with Phrasing; the first carrier phrase was more likely to form the IP when PW1 was focused and also when the target was 2 + 3. The Focus effect was reliable for Pre-PW1 (right edge of the first carrier phrase) and Post-PW1 (right edge of PW1). In particular, PW1 under focus was more likely to have a bitonal IP boundary tone (LH% or HL%) than a monotonal boundary tone (H%, L%) regardless of Phrasing. The same tendency was observed at the right edge of PW2. However, the Focus effect was less clear, and the statistically significant Focus × Phrasing interaction suggests that the prosodic boundary strength after PW2 was more likely to be affected by other factors such as the number of syllables in the prosodic phrase (see Section 3.2).

The effect of narrow focus on prosodic structuring in Korean shares similarities to that in French (e.g., Féry, 2001) and Japanese (e.g., Beckman & Pirrehumbert, 1986; Venditti et al., 2008). One difference is that the focused constituent is aligned to the right in the prosodic phrase in French (Féry, 2013) but to the left in Japanese and Korean. In addition, Japanese speakers use a salient rise (H) or a rise-fall (LHL) pitch movement at the final syllable of the focused word (Venditti et al., 2008, sect. 3.4.2). These seem similar to Korean speakers’ use of the IP boundary tones (e.g., H%, L%, LH%, HL%) observed in the present study.

The occurrences of IP boundary tones in relation to focal structure may not be surprising in that in Korean, complex IP boundary tones are commonly used to deliver pragmatic meaning (Jun, 2000; Park, 2012). Although K-ToBI suggests nine boundary tones (i.e., L%, H%, LH%, HL%, LHL%, HLH%, LHLH%, HLHL% and LHLHL%; see Jun, 2000), even more complex pitch movement such as HLHLHLHLHL% is observed in spontaneous speech (Park, 2012). Yet there is little research investigating the complex pitch movement that seems to be accompanied by substantial phrase-final lengthening, and the use of the IP boundary tones in relation to focal structure has not been previously reported in Korean. This is probably because the experimental materials in previous studies were generally in the form of pairs of a simple WH-question and an answer, and also unexpected F₀ contours were discarded in order to investigate phonetic variations within one type of F₀ contour shape.

The IP boundary tone is a potentially important cue to information structure for listeners. Speakers seem to highlight the focused constituent by increasing its prosodic boundary strength and separating it from adjacent constituents. The adjustment of duration or pitch (e.g., the use of complex pitch movements) at the right edge seems to be exploited when speakers make a semantic or pragmatic change from a neutral reading. These strategies would complement the consistent marker of narrow focus—the prosodic disjuncture occurring at the left edge of the focused constituent—since the disjunctural cue may not be a sufficient marker to information structure. Although the strength of the left edge is enhanced under narrow focus by F₀ raising in some cases and lengthening, these cues would be ambiguous with respect to the domain of the focus. When listeners perceive a large magnitude of prosodic disjuncture or complex pitch movements, they would be able to confirm that the preceding part of the utterance carried informational prominence. However, it should be noted that the rise on the phrase-final syllable (H% or LH%) does not exclusively signal narrow focus or emphasis in the corrective sense. For example, LH% is associated with questions, continuation rises, explanatory endings, annoyance, irritation, or disbelief (Jun, 2000) and also surprise, incredulity, or confirmation (Park, 2012). It is possible that the use of narrow corrective focus in conversation is linked to a negative speaker attitude such as irritation or disbelief.

One of the aims of the present study was to investigate whether focal structure affects the F₀ contour shapes in the utterance. The result is that narrow focus affects the presence or the type of boundary tones in the IP as discussed above, but not within the AP. In Korean, the distribution of the F₀ turning points is less predictable than in West Germanic languages. In West Germanic languages, the turning point is likely to be associated with the lexically stressed syllable (see Chen, 2012 and references therein), and its distribution within an utterance is considered phonologically motivated (Ladd, 2008). In this case, the conventionalized phonetic cues include the height and scaling of the F₀ turning points, which systematically vary depending on the focal structure (e.g., Hanssen et al., 2008). On the other hand, in Korean, the F₀ turning point locations are strongly affected by phrasing as often signalled by boundary tones, and also partly determined by the number of syllables in the AP and the type of phrase-initial segment. The distribution of pitch turning points apart from the IP boundary tones at the right edge does not seem to be what native Korean speakers directly manipulate in relation to the focal structure.

In the design of the experimental materials, the type of AP-initial segment, which is known to affect the AP-initial tone (L vs. H), was taken into account, since it was expected to interact with focus-related variations in F₀. However, the statistical analysis results regarding temporal adjustment and also F₀ show that the AP-initial segment type does not significantly affect the way speakers adjust the phonetic parameters under narrow focus (one exception is the treatment of F₀ span in defocused constituents, discussed in Section 4.2).

When the target PWs were realized as APs, the expectation about their phonetic shape was generally met, in that the majority of the APs (79.25%) showed previously reported frequent F₀ contour shapes such as LH, HH, HLH, LHLH and HLHL and the AP-final H was commonly observed in the data (84.33% of total APs). The phonologized association between the type of segment and the AP-initial tone (see Section 1.1) was observed in general in the dataset, although there were some exceptions (see Table 6). The main cause of this exception seems to be that /il/ ‘one,’ which tends to trigger AP-initial H in young people’s speech, often appeared in the reading materials (Jun & Cha, 2011, 2015). Although /il/ ‘one’ begins with a vowel, which is commonly associated with an AP-initial L tone as an initial segment, Korean speakers often produce the word with a H tone. Jun and Cha (2011, 2015) suggest that the H tone associated with /il/ ‘one’ probably originates from a need to distinguish it from /i/ ‘two,’ since the two numbers can be confused in communication.

An expansion in the F₀ span under narrow focus was observed in the data as hypothesized (e.g., Jun & Lee, 1998; Lee & Xu, 2010), similarly to the increase in the F₀ excursion size of the pitch accent in West Germanic languages. In addition, Cho et al. (2011) showed that speakers enhance the consonantally-induced F₀ perturbations at high-information sites in prosodically important positions in Korean; F₀ was higher in the vowels of focused words with HH than in those of defocused words. Although the data in the present study were not sufficient to determine corrective focus as a factor conditioning the F₀ variation in the phrase-initial syllable, there were some cases where the focus was cued by boosted F₀ when the neutral target had HH (Figure 4).

We conclude that the focused constituent is always preceded by a prosodic boundary and also signalled by lengthening in Korean, since these effects are consistently observed across studies (e.g., Jun & Lee, 1998; Jun & Kim, 2007; Lee & Xu, 2010; Cho et al., 2011). As hypothesized, the focused constituent could be aligned to a higher-level prosodic domain than the AP. As demonstrated in Figure 2, although each PW is likely to be realized as an AP in neutral reading, the target PW1 under focus, or the right edge of PW2 in any experimental condition, was frequently perceived as an IP. The IPs under focus were more likely to be associated with a bitonal boundary tone (e.g., LH%) than a monotonal one in comparison to neutral or defocused readings. However, there seem be restrictions on the environment in which the IP is formed; for example, IP formation seemed to be affected by the location of the focused constituent within a sentence and also the number of syllables in the target. The results also suggest that post-focal dephrasing, i.e., deletion of the prosodic boundary as reported in some speakers’ speech in Jun and Lee (1998), is not likely to occur when the utterance includes an itemized list; and in addition they confirm that dephrasing is only optional (see Jun & Lee, 1998 and Lee & Xu, 2010 for similar findings). In the present analysis, there were only a few cases that were marked as having merely PW-sized disjuncture (i.e., no perceivable prosodic disjucture) between PW2 and the following carrier phrase.

These prosodic structural cues to narrow focus can be accompanied by the expansion in F₀ span and/or the boundary pitch movement at the right edge. The focus-related increase in acoustic parameters interacts with other factors such as the size of the prosodic unit and the morphosyntactic construction of the utterance. The prosodic markers of focus tend to be concentrated near the phrase edges. Probably due to the lack of lexical prominence, the syllables at the phrase edges seem to serve as the anchoring site of the adjustments in Korean.

It is possible that there are non-prosodic constraints on the phonetic manifestations of focal structure. One potential area for further research is the relationship between morphosyntactic and prosodic marking of narrow focus, particularly the effect of the position of the focused constituent and the omission of the defocused constituent, which is a common strategy for signalling focal structure in Korean. Although native Korean speakers’ tendency to place the focused constituent utterance-initially is noted (Sohn, 1999), the phonetic properties of the utterance-initial focused constituent are not well understood.

4.2 Defocusing in Seoul Korean

The experimental evidence does not fully support the hypothesis that systematic reduction in duration and F₀ span would be observed in defocused constituents in comparison to neutrally spoken counterparts. Syllable duration was statistically significantly shorter in defocused PWs only for syllable 5 in 3 + 4 and for syllables 6 and 7 in 4 + 3 than in Neutral. There was no evidence showing F₀ span reduction in defocused constituents; when the PW-initial segment was a weak consonant (for all PW1s and part of PW2s), the F₀ span measurement showed the order focused > defocused > neutral. With the PW-initial strong segment in PW2, F₀ span did not show a statistically significant difference between defocused and neutrally spoken PWs, although it was wider in the focused PWs.

In the present study, the defocused constituent was either pre-focus (PW1 in PW2-focus) or post-focus (PW2 in PW1-focus). Our finding seems to be in contrast to Lee and Xu (2010), who found post-focus reduction in prosodic parameters. In fact, there are possible reasons for the inconsistency across the studies: First, different F₀ properties were measured in different studies. For example, Lee and Xu (2010) report the mean and maximum F₀ values in their target materials; the focused constituent had higher values than neutral, while these values were lower in the post-focus constituent. These measurements compare the F₀ level rather than the span, which is the difference between the maximum and the minimum F₀ values, measured in the present study. Second, the experimental tasks differed across studies. In Lee and Xu (2010), speakers answered prompt WH-questions (A: “What did you say Minswu eats?” and B: “Minswu eats potstickers”). In contrast, in this study and in Jun and Lee (1998), listeners were explicitly asked to emphasize the target constituent as a correction of what was previously said. These differences may be related to different focus types. The experimental techniques in the present study would elicit corrective focus (also in Jun & Lee, 1998), unlike those in Lee and Xu (2010) which may correspond to presentational (Gussenhoven, 2007) or informational focus (Féry, 2013). Third, the differences in the structure of the experimental materials may have led to different results. For instance, in Lee and Xu (2010), the target word seemed to be either utterance-initial as a subject of the sentence or utterance-penultimate as a direct object of the final predicate, although the full materials were not provided. However, in the present study, the defocused constituent was within the target between carrier phrases forming a number sequence with the preceding focused constituent and the target was never utterance-initial or -penultimate. Lee and Xu (2010) actually found a statistically significant effect of the position of the constituent (utterance initial vs. medial), and it is possible that the post-focus compression effect is more easily observed towards the end of the utterance. All in all, there is no strong evidence showing the reduction in prosodic parameters in defocused constituents in comparison to the neutrally spoken counterpart in Korean.