The [n]→[l] onset merger represents a prototypical case of contrast loss. These syllable-initial phonemes, described by Zee (1999b) as an apico-laminal denti-alveolar nasal and apical (denti-)lateral approximant, historically differed in both nasality and tongue blade involvement. There is also an asymmetry in frequency: [l]-onsets occur more often than [n] by both measures of type frequency (approximately double) and token frequency (approximately six times; Leung, Law, & Fung, 2004).

Since the 1940s or earlier (Wong, 1941 as cited by To et al., 2015; see also Bourgerie, 1990), [n] has been documented to be steadily merging towards [l] in progressively younger generations (Hashimoto, 1972; Yeung, 1980; Bourgerie, 1990; Zee, 1999a). Most recently, To et al. (2015) reported that nearly all of their participants, regardless of age group and gender, produced the innovative form [l] in place of the historical /n/ (94.2% of children versus 94.6% of adults). All available evidence thus points to (near-)completion of the merger by the start of the 21^st century.

Because the innovative [l] has become so prevalent, Chen (2018) notes that this merger appears to be comparatively less stigmatized than other pairs such that “most users do not consider them wrong” (p. 7). Nevertheless, hypercorrection from historical [l] to [n] has been described—albeit with some debate—in the literature. In support, Pan (1981) reports [n] realizations of historical /l/ in a word list reading task. Zee (1999a) also notes that there are “hypercorrective individuals” who may use [n]. In contrast, Bourgerie (1990) impressionistically found little evidence of hypercorrection in sociolinguistic interviews, further claiming that no other studies had reported the [l] to [n] direction of change and that “most observers believe that this hypercorrection does not occur” (p. 46). Later studies only investigate historical /n/ items, leaving unknown the degree to which hypercorrection of [l] to [n] is present in HKC.

It has further been specifically noted that [n]→[l] varies by speech register such that [n] is associated with formality (Pan, 1981) and careful speech (Zee, 1999a). This is supported by production data, as Bourgerie (1990) found that impromptu, conversational speech included the most [l] realizations (80.5%), trailed by interview speech (58.2%) and public speech (38.6%). Thus, even while casual speech may mostly comprise innovative variants, HKC speakers also have access and exposure to speech registers that include the conservative [n] variant. The presence of stylistic variation complicates the interpretation of merger completion in this speech community across sporadic research reports with varying methodologies.

The [ŋ̩]→[m̩] merger involves two historical phonemes, the syllabic velar and bilabial nasal consonants, that were largely non-contrastive. [ŋ̩] historically occurred in relatively few lexical items, limited to the three low tones. Of these, Bauer (1982a) contends that only four occur with any frequency in spoken HKC: two common words (五 ng5 ‘five,’ 午 ng5 ‘noon’) and two surnames (吳 ng4 and 伍 ng5). On the other hand, [m̩] historically occurred only as a single—albeit highly frequent—morpheme: the negation marker 唔 m4 ‘no, not.’ Both categories therefore contained few types but still maintained a phonemic contrast. The single morpheme for /m̩/ combined with the rather limited inventory of /ŋ̩/ words suggests that contrastiveness has been largely uncompromised over the course of the merger.

Though this merger was first documented in the 1980s (Bauer, 1982a; 1982b), evidence suggests that the [ŋ̩]→[m̩] change was well underway by the late 1970s and likely initiated around the 1940s from labial assimilation for the highly frequent word ‘five’ (Bauer, 1986). Since then, To et al. (2015) reported that nearly all children (born 1993-1994) and adults (born 1960-1987) produce the innovative [m̩]. Specifically, 98.6% of children and 95.5% of adults used [m̩] for the word ‘five.’ Given that this study collected data only for the most frequently occurring historical /ŋ̩/ word, the generalizability of these results to other words of this category is unknown. At face value, however, the [ŋ̩]→[m̩] merger appears to be near completion at the community level, and possibly complete for a great many individual speakers.

Some early sources demonstrate general or public awareness of the [ŋ̩]→[m̩] merger: Newspapers mentioned homophony of the negative morpheme m4 and the surname ng4 in 1980 and 1981, while a Chinese dictionary listed ‘five’ with both velar and bilabial pronunciations (Lau, 1977, cited by Bauer, 1982a). As one of the mergers identified by proper pronunciation campaigns, it can be assumed that awareness has been maintained, though the degree of salience or stigmatization of this particular merger is uncertain. Finally, like [n]→[l], the conservative [ŋ̩] is associated with formality and can occur in style-shifting (e.g., [m̩] is produced more often during spontaneous speech than story or word list reading; Bauer, 1982a).

Unlike the former two mergers, the [ŋ]↔Ø merger—involving the syllable-initial velar nasal and its null-initial (Ø) counterpart (also referred to as zero-initial, phonetically either a vowel or glottal stop onset; Bourgerie, 1990; Chen, 2018)—is described as historically allophonic, such that [ŋ] onset occurred with low tones while null-initial occurred with high tones. While this merger is not technically a merger of phonemic categories, it is a merger of lexical classes and is discussed as a merger within the Cantonese literature (e.g., To et al., 2015). To complicate matters, this merger has also undergone a reversal in direction over time, leading to a loss of the historical pattern of complementary distribution.

Since the start of the 20th century, both historical [ŋ] and Ø have shown evidence of merging towards the other (note some exceptions of [ŋ] onset occurring with mid to high tones; Ball, 1907 as cited in To et al., 2015). Specifically, reports suggest that Ø→[ŋ] took place in the first half of the century (Wong, 1941 as cited in To et al., 2015), which was subsequently supplanted by a [ŋ]→Ø change in the second half (Yeung, 1980; Bourgerie, 1990). Along with the change in merger direction, younger speakers (roughly born since the 1960s–70s) used null-initial more often than not for both historical /ŋ/ and Ø (Young, 1980; Bourgerie, 1990; Zee, 1999a). Likewise, the children in To et al. (2015) produced more null-initial variants for both historical /ŋ/ (65.0%) and historical Ø (94.2%), in contrast to the adult proportions of Ø production for historical /ŋ/ (37.5%) and historical Ø (68.7%). However, both groups differentiated historical /ŋ/ and Ø historical categories, using null-initial more for historically Ø items. Thus, in spite of the bidirectional merger and variation in both historical classes, the two categories remain distinct to a degree from a community standpoint, although the original tone-based complementary distribution does appear to be lost.

A further complexity arises when we compare the results of To et al.’s (2015) survey to Bourgerie (1990). In To et al. (2015), children, as compared to adults, produced significantly more Ø for /ŋ/ (65.0% versus 37.5%) and significantly less [ŋ] for Ø (5.8% versus 31.3%). These group values are conspicuously similar to Bourgerie’s (1990) children and young adult group values of Ø for [ŋ] (66.2% versus 36.7%) and [ŋ] for Ø (0% versus 25.4%), despite the fact that Bourgerie’s child speakers (born 1970s–80s) correspond roughly to the adult cohort of To et al.’s study (born 1960–87). Since the methodologies of these two studies were quite different, direct comparisons may not be appropriate; however, taken at face value, there appears to have been no progression of the sound changes at the community level between the 1980s to the 2000s.1

One potential explanation is that stigmatization of the null-initial as ‘lazy’ led to age-based patterning across the community, such that adult populations tend to produce the more ‘proper’ and ‘prestigious’ [ŋ] variant for both historical classes. Indeed, according to Chen (2018), this merger is more socially stigmatized compared to mergers like [n]→[l], perhaps due to its relative rarity. As with the other mergers, style-shifting is reported to occur for [ŋ]→Ø (Bourgerie, 1990) such that impromptu speech featured the highest rate of null-initials for historical [ŋ] words (35.6%), followed by interview (21.8%) and public speech (8.7%). Further investigation, particularly of speakers born in the 1990s in more recent years, is necessary before coming to a conclusion about the status of the [ŋ]↔Ø variation.

Production stimuli consisted of 64 Cantonese words presented visually in Chinese orthography2 accompanied by an English translation (full word list in Appendix). Each target historical onset (/l/, /n/, /ŋ/, Ø) appeared in four words while each target historical syllabic nasal (/ŋ̩/, /m̩/) appeared in three, totalling 22 target words. The remaining 42 consisted of filler word pairs with non-target Cantonese contrasts, including onset stop aspiration (/ts/-/tsʰ/, /t/-/tʰ/, /k/-/kʰ/) and other merging consonants (onset /k/-/kʷ/; coda /n/-/ŋ/, /t/-/k/).

Perception stimuli consisted of three 13-step continua generated between Cantonese real-word minimal pairs, one per merger as listed in Table 4. To create these continua, the target minimal pairs were produced by a 33-year-old Cantonese speaker and trained linguist who grew up in Hong Kong. Stimuli were digitally recorded at a sample frequency of 44.1 kHz in a sound-attenuated booth using an AKG C520 headset mic with a USBPre 2 Pre-Amp. The speaker read from transcriptions of each target word, accompanied by the Chinese orthography, to elicit maximally contrastive pronunciations. She was asked to produce each pair naturally but as similarly as she could (aside from the target contrast) to facilitate more natural-sounding synthesis. Each target word was produced at least three times. The clearest and most similar recorded pairs were selected for synthesis. Decisions were based on duration, pitch, and intonation similarity assessed by the first author via auditory and spectral analysis in Praat (Version 5.4.08, Boersma & Weenink, 2015).

These six natural productions were then used as endpoints to create three word-pair continua using tandem-straight in Matlab (Kawahara et al., 2008). The entire word forms were used as the endpoints, which, given tandem-straight’s global synthesis methods involving acoustic decomposition and generation, allows for natural-sounding resynthesis that retains redundant co-variation. Twenty-five acoustically-equidistant steps were synthesized between the duration of the target words, with each pair time-aligned at acoustic landmarks (e.g., phone boundaries) to facilitate morphing. From these, every odd-numbered step was selected to result in thirteen equidistant steps. The resulting continuum steps gradually morph from one endpoint token to the other, thus including in the synthesis an array of phonetic differences across the tokens. The natural endpoints were carefully selected to be as similar as possible in terms of non-contrastive elements. As such, the main perceptible change across continua is between the target sounds in each pair. The continua are available at https://osf.io/mk2v4/?view_only=51cfc7a974f345678e226944023dcb39. Figure 1 illustrates the transition between the initial sound in the aak1-ngaak1 continuum (i.e., the beginning of the vowel [aː] and the entire duration of [ŋ]) with waveforms and spectrograms of the midpoint and endpoint recordings. Judgments from the first author and two other Cantonese-speaking colleagues were used to select the most natural-sounding continuum per merger. In all, the 13 variants from each continuum totalled 39 tokens.

Participants completed the Bilingual Language Profile (BLP; Birdsong, Gertken & Amengual, 2012), which was used to quantify Cantonese-English language dominance scores. A small number of modifications were made to better reflect the language experiences of the population (e.g., accounting for the education system in Hong Kong and the role of Mandarin in Hong Kong, alongside Cantonese and English). Additional questions about biographical information, language background, and language experiences were included to adjudicate participant inclusion criteria. Scores were calculated from the BLP portion of the questionnaire. The BLP is bound between –218 to +218. Zero indicates balanced dominance between the two languages while negative and positive scores represent relative Cantonese and English dominance, respectively. The range was negative (–165, –2), indicating Cantonese dominance for all speakers. Mean values and standard deviation for the four demographic groups are reported in Table 2. An analysis of variance with the BLP dominance score as the dependent measure and Age and Gender as independent variables revealed no significant effects. This confirms the uniform Cantonese dominance in the sample, and BLP scores are not considered further.

An exit interview was administered to examine metalinguistic awareness about the mergers in the participant’s own speech and experiences. The interview was conducted in English or Mandarin, supplemented by Cantonese when necessary to ensure comprehension.3 Participants were presented with a list of minimal or near-minimal word pairs designed to historically contrast the target sounds. For each pair, they were asked to say the words as they would in casual speech, explain any differences between their productions, and name the prescribed pronunciation if they were aware of any. At the end, participants were asked if they were familiar with the term 懶音 laan5 jam1 ‘lazy pronunciation,’ what they thought it meant, and whether they believe (or have been told by others) that they use it in their own speech.

Participants were seated alone at a computer in a sound-attenuated booth where they were presented with the production task followed by the perception task. Instructions were provided visually in English on the screen. Upon completion, the experimenter returned to the room to answer any questions while participants filled out the language questionnaire, then conducted the exit interview. To reduce the chance that participants would change their speech behaviour due to realizing the purpose of the experiment (i.e., our interest in the target sounds), the production task, which included fillers, was ordered prior to the perception task, which involved only the target sounds.

In the self-paced production task, Chinese characters and the English translation were visually presented using E-Prime 2.0 software (Schneider, Eschman, & Zuccolotto, 2007) in three randomized blocks, where each word appeared once per block (192 trials in total). Participants were asked to read the Chinese characters out loud. Productions were digitally recorded using an AKG C520 headset microphone connected to a UR22MKII interface. Participants pressed the zero key on the keyboard to begin a two-second recording for each trial. They were allowed to re-record as many times as they wished before moving on to the next word by pressing the spacebar. Participants spent approximately 20–30 minutes on this task.

Perception stimuli were auditorily presented in a two-alternative forced choice lexical identification task. To reduce influences of explicit knowledge about ‘proper’ pronunciation, participants were instructed to respond as quickly as possible and not overthink their response. Using E-Prime 2.0, the synthesized Cantonese words were played over AKG K77 Perception headphones at a comfortable listening level, accompanied by a visual display of the appropriate minimal pair words in Cantonese orthography and the English translation. For each trial, participants heard the audio stimulus once and saw two word choices labelled with ‘1’ or ‘5’ (on the left or right side of the screen). They were asked to press the button on the button box (i.e., ‘1’ or ‘5’) that corresponded to the word they heard. If no response was registered within three seconds, the next trial began automatically. Each token was repeated three times throughout the experiment, randomly presented over three blocks (117 trials in total).

To assess production, two phonetically-trained Cantonese speakers who grew up in Hong Kong coded the onset of each item, or in the case of the syllabic nasals, the sole segment comprising the word. Items were blocked by talker, randomized, and presented to the coders blind, without knowledge of the intended lexical items. Coders categorized the onset from a closed set, presented orthographically as six options: ‘l,’ ‘m,’ ‘n,’ ‘ng,’ ‘a vowel,’ or ‘other.’ The 204 items identified by both transcribers as ‘other’ were coded by the first author. These items either did not include a usable production (e.g., recording errors where the word was cut off or missing) or included a mispronounced production (e.g., saam1 ‘clothing’ instead of lau1 ‘coat’).

The coders agreed on 4933 trials. Inter-rater reliability for the two coders was calculated in R (R Core Team, 2020) using the Kappa statistic for two raters unweighted using the kappa2() method from irr() (Gamer, Lemon, Fellows, & Singh, 2019) from the perspective of whether there was agreement on the transcription of each item’s coded onset. These data from the two coders are reported in Table 5. Kappa scores ranged from values that are in the range described as near perfect agreement for historical /l/ and /n/-initial words to moderate agreement scores for the historical syllabic nasals. To resolve disagreement, all items (n = 725) on which the two coders disagreed were presented in a similar format to the first author: blinded as to their lexical identity and organized by talker. Sixteen of these disagreement items were removed due to recording errors or mispronunciations. The ultimate coding for each item was then determined as whichever category two out of the three coders agreed.

Data for the [n]→[l] merger (n = 1158) were analyzed in a logistic mixed effects regression model with the probability of [l] productions ([l] = 1, [n] = 0) as the dependent measure. All categorical variables were sum coded (Historical Pattern: /l/ = 1, /n/ = –1; Talker Age: Older = 1, Younger = –1; Talker Gender: Male = 1, Female = –1) and entered as possible main effects and interactions. There were random intercepts for Subject and Item, with Historical Pattern as a by-subject random slope.4

The model output is summarized in Table 6. There was a significant intercept, and a significant effect of Historical Pattern. These results indicate that [l] productions are overall more likely, and that [l] productions are even more likely on words that are historically pronounced with /l/. These results are visualized in Figure 2, separated by the non-significant factors of Talker Age and Gender in order to transparently present the individual variation that is present. The figures present a barplot to indicate the group patterns, along with individual data points for each individual; these individual data points are somewhat transparent so that individual overlap is observable. Lines connect an individual’s data points for the two word classes. While the group averages indicate that both historically /l/ and /n/ words are usually pronounced with [l], Figure 2 illustrates how there is both group-level separation between historical categories (confirming the model result) and considerable variation on the individual level.

To better visualize the individual-level data, we also present each individual’s mean proportion of the innovative variant for the two historical categories as a scatter plot in Figure 3. Here, the bottom right quadrant represents conservative contrastive productions ([n] for /n/ and [l] for /l/), the top right quadrant represents innovative merged productions ([l] for /n/, [l] for /l/), the bottom left represents hypercorrective merged productions ([n] for /n/, [n] for /l/), and the top left represents a fully flipped contrastive production ([l] for /n/, [n] for /l/). Most participants are clustered in the top right quadrant, realizing /n/ as [l] the majority (or all) of the time, though there is considerable variation ranging to fully historically contrastive for a small number of participants in the bottom right corner. Participants who lean conservative include a mix of older and younger individuals. Five participants who are mainly younger (two younger men, two younger women, and one older woman) appear relatively merged in the hypercorrective direction, realizing a majority of both /n/ and /l/ words as [n]. As expected, none are contrastive in the opposite-to-historical direction. This visual inspection of the individual variation further supports the non-significance of age and gender as a predictor of innovative variant productions.

Data for the [ŋ̩]→[m̩] merger (n = 872) were analyzed with a logistic mixed effects regression model in an identical fashion to those for the [n]→[l] merger, with the variant-specific variables coded analogously (i.e., dependent variable as the probability of [m̩] productions: [m̩] = 1, [ŋ̩] = 0; Historical Pattern: /m̩/ = 1, /ŋ̩/ = –1).

The model output is summarized in Table 7. There was a significant intercept, along with significant effects of Historical Pattern, Age Group, and Gender. There were no significant interactions. The results are visualized in Figure 4 separated by Historical Pattern, Age Group, and Gender with the bars showing the group pattern, overlaid with individual results. These visualizations corroborate the statistical output. Overall, talkers are more likely to use [m̩] for both historical word classes, but the effect of Historical Pattern confirms that [m̩] is more likely for historically /m̩/ words. In addition, older speakers are more likely to show the innovative pattern, using higher rates of [m̩], while male participants are significantly more likely to use [m̩] than female participants.

Figure 5 presents the individual proportion scatterplot for [ŋ̩]→[m̩], as described for [n]→[l]. The vast majority of participants are located in the top right quadrant, representing innovative productions where both /m̩/ and /ŋ̩/ are realized as [m̩] the majority of the time. Many individuals are fully merged, clustering in the top right corner. There is some variation in proportions of [m̩] productions, though no participants produce flipped categories, and two younger women produce a hypercorrective pattern (majority [ŋ̩] for both /ŋ̩/ and /m̩/). Overall, this visualization makes clear that the individuals who produce variable, conservative, or hypercorrective patterns are overwhelmingly younger women (along with some older women and younger men), confirming the model Age and Gender effects where women and younger participants skew towards producing [ŋ̩].

Data for the [ŋ]↔Ø merger (n = 1023) were analyzed similarly to the two previous mergers with a logistic mixed effects regression model. The variant-specific variables were coded with null-initial assumed as the innovative variant (i.e., dependent variable as the probability of vowel-initial productions: Ø = 1, [ŋ] = 0; Historical Pattern: Ø = 1, [ŋ] = –1).

The model output is summarized in Table 8. There was a significant intercept, and a significant effect of Historical Pattern. The results are visualized in Figure 6 separated by Historical Pattern, along with the nonsignificant effects of Age Group and Gender. Again, the bars demonstrate the group pattern and individuals’ results are presented as a top layer. Participants are more likely to use [ŋ] for all of these lexical items, with the effect of Historical Pattern indicating that vowel initial productions are more likely on historically vowel initial words, but these are still, overall, unlikely. Some clearly prefer vowel-initial onsets, however; individuals from three of the four demographic groups use vowel-initial onsets 100% of the time for both historically vowel-initial and [ŋ]-initial word classes.

These results can be seen more clearly in the individual scatterplot (Figure 7). Unlike the other two mergers, the vast majority of participants are located in the bottom left quadrant, representing merged productions where both historical null and [ŋ] are overwhelmingly realized as [ŋ]-initial, including many individuals who are fully merged (clustering in the bottom left corner). Although no age effect was detected in the model, visual inspection of the individual data provides some insight into trends of variation. Specifically, the few participants who show a comparatively conservative pattern (lower right quadrant) are all older while all but one of the participants who show merging towards null (top right quadrant) are younger.

Group-level production results indicate that all three Hong Kong Cantonese merger pairs maintain some form of community-wide contrast, as indicated by a statistically significant effect of historical category. However, underlying these community averages was a wide variety of merging patterns at the individual level. For [n]→[l], speakers ranged from maximally merged to maximally contrastive, while for [ŋ̩]→[m̩] and [ŋ]↔Ø, the majority of speakers were either fully merged or demonstrated an intermediate contrast. There was also a subset of individuals who were ‘hypercorrective’ such that they produced mainly conservative variants for both historical categories (e.g., [n] for both /n/ and /l/). Although degree of contrastiveness varied substantially across individuals, in none of the three mergers is it predicted by demographic factors like age or gender (i.e., no significant interactions were found), which suggests that these mergers should not be characterized as changes-in-progress.

Null responses were removed, accounting for just over 1.5% of the data. The remaining data (n = 3265) were fit to a logistic mixed effects regression model predicting the likelihood of a historical /l/ word response (/l/ = 1, /n/ = 0). Continuum step was centered and scaled, and Talker Age and Gender were sum coded (Age: Older = 1, Younger = –1; Talker Gender: Male = 1, Female = –1). Subject was a random effect with Step as a by-subject random slope.5

The model output is reported in Table 9, and the results are visualized in Figure 8. There was a significant intercept, indicating that /l/ word responses were more likely, and main effects of Step and Age. The interaction between Step and Age was also significant. While, overall, participant response functions varied predictably by continuum step with more [n]-like realizations receiving more /n/ word responses, younger listeners present comparatively more extreme responses at the continuum endpoints, resulting in a steeper response function.

To explore the individual differences in the discreteness of these lexical items, individual values were quantified using the by-subject contrast coefficient slope (CCS), following the methods provided by Casillas (2021). This value, which can be taken as a measure of category ‘crispness’ (Morrison, 2007; Casillas & Simonet, 2016), is an estimate of the slope of each individual’s sigmoid at its steepest point. More extreme values indicate more crisp or discrete perceptual categories, while values closer to zero are taken to indicate a less discrete contrast, which we interpret as evidence of a merger in this case. As a concept, this crispness value acknowledges that phonological categories can exist on a gradient in terms of their categorical contrasts (see, for example, Hall, 2013). These category crispness values were estimated by fitting new logistic regression models with continuum Step (centered and scaled) as the only fixed effect. The left panel in Figure 9 shows the individual values for the [n] and [l] contrast. There are two extreme outliers with crispness values below –5; both of these individuals had nearly discrete response functions such that the first six steps of the continuum were categorized 100% of the time as /l/ and the last six steps of the continuum was categorized 100% of the time as /n/. This contrasts with the majority of participants who had more gradient sigmoid functions. The central tendency of the value was negative (Mean = –0.35, Median = –0.10) and the range was substantial (–5.33, 0.09).6 These data, visualized in more fine-grained detail in Figure 10, suggest that at the individual level, the degree of category crispness varied considerably. Younger women represent the most variable demographic group, demonstrating a very flat distribution and including comparatively many individuals with crisper categorization; younger men show a similar pattern which is notably flatter than both older groups.

To analyze the [ŋ̩]→[m̩] merger, null responses were removed, accounting for just over 2% of the data. The remaining data (n = 3248) were fit to a logistic mixed effects regression model predicting the likelihood of a historical /m/ word response (/m̩/ = 1, /ŋ̩/ =0). All other model specifications were the same as [n]→[l].

The model output is reported in Table 10, and results are visualized in Figure 11. There was a significant intercept, indicating that /m̩/ responses were more likely, and there were main effects of Step, a two-way interaction between Age and Gender, and a three-way interaction between Step, Age, and Gender. Older men (M = 0.64) and younger women (M = 0.62) were more likely than younger men (M = 0.54) and older women (M = 0.49) to categorize the continuum as /m̩/. These demographic variables interact with step, and Figure 11 makes clear that the perceptual changes by step are much smaller than those for the [n]→[l] merger. The word categorization functions suggest that all listener groups are quite advanced in the merger, with younger women presenting the biggest distinction between /m̩/ and /ŋ̩/.

Individual differences in recognition performance for [ŋ̩]→[m̩] were also analyzed in terms of category crispness. The middle panel in Figure 9 presents the distribution of these values. The range of values is attenuated compared to [n]→[l] (–0.23, 0.08), and the measures of central tendency are lower (Mean = –0.03, Median = –0.014), indicating that the contrast is overall less crisp for /ŋ̩/ and /m̩/. Figure 12 additionally reveals that while most demographic groups accordingly present distributions sharply peaking near zero, younger women as a group present a flatter distribution with increased variability towards higher crispness values. The majority of values are negative, however, indicating consistency in the direction of the category distinction that does exist.

Lastly, the responses to the [ŋ]↔Ø continua were analyzed in a similar manner. Null responses were removed, accounting for just over 1% of the data. The remaining data (n = 3277) were fit to a logistic mixed effects regression model predicting the likelihood of a historical vowel-initial word response (Ø = 1, /ŋ/ =0). All other model specifications were the same as above.

The model output is reported in Table 11, and the results are visualized in Figure 13. There was a significant intercept, indicating that [ŋ] responses were more likely, and there was a main effect of Step. As the two-way interaction between Step and Age (p = 0.05912) approached the threshold for statistical significance, we include it in Figure 13 for consideration. Younger listeners trended towards more categoricity in their response patterns.

Individual differences for [ŋ]↔Ø were also quantified in terms of category crispness. While the mean (Mean = 0.029) and median (Median = 0.009) both are positive, the range of values (–0.22, 0.31) spans 0 to a greater degree than those for the previous two continua. Individuals’ data for these continua are shown in the right panel of Figure 9. Not only do the values for [ŋ]↔Ø indicate that listeners are not at all crisp in their category boundary, the varying signs of the crispness value indicates that individuals differ in the direction of their categorization of these items. That is, individuals have different mappings of which lexical item is vowel-initial and which is [ŋ]-initial. Figure 14 indicates that younger women again stand out with more distributed scores, particularly including a slight skew towards crisper positive values. While younger men show a strongly peaked distribution centered on zero, there were also a few individuals who look rather different in showing relatively crisp categorization.

Group-level perceptual results indicate that each merger is characterized by different patterns, but unlike production, age appears to be a relevant factor. Simplifying slightly, younger listeners were generally more categorical: significantly so for [n]→[l], a trending effect for [ŋ]↔Ø, and a case where younger women alone appear more categorical for [ŋ̩]→[m̩]. In other words, younger listeners were often less merged in recognition than older participants. Individual category crispness values further demonstrate that individuals varied from no differentiation between lexical items (present for all mergers) to fully categorical (for /n/ and /l/). Across mergers, the /n/ and /l/ categories were the most discrete, followed by /m̩/ and /ŋ̩/. The [ŋ] and null-initial lexical items elicited the least discrete patterns, and the +/– signs of the crispness values further indicate that listeners categorize these items in opposing directions.

Production-perception analyses, which correlate an individual’s degree of merger in production to their degree of merger in perception, reveal a mixed bag of results. We find moderate production-perception correlations for [n]→[l] and [ŋ̩]→[m̩] despite different degrees of overall mergedness, but no correlation for [ŋ]↔Ø. At the same time, while all mergers reveal a similar overall trend of misalignment such that if not aligned, production remains more contrastive than perception, [n]→[l] and [ŋ]↔Ø show an additional pattern where individuals with merged production show contrast in perception despite little to none in production. Finally, age-based trends suggest that younger individuals are less misaligned than older individuals in the direction of production contrast but more misaligned in the direction of perception contrast.

Several factors could plausibly lead to the discrepancies between current results and prior predictions about the trajectory of these consonant mergers. We consider here four possible sources: methodological differences, style-shifting, age-grading, and community-wide change.

In terms of methodology, we used several words per merger pair as opposed to the single word used in To et al. (2015). Rather than representing a true difference in norms over time, the larger set of lexical items could have simply provided a more accurate depiction of variant usage across the lexicon. However, by-word examination of the current results rules out this explanation: Production of the same words used in To et al. (2015) demonstrates consistently lower rates of [l], [m̩], and null-initial.12 Specifically, the group rates of [l] for naam4 ‘male’ are similar to the aggregate values, ranging from 35.9% for young women to 74.1% for older men (compared to 94%). Similarly, rates of [m̩] for ng5 ‘five’ range from 51.2% to 88.9% (compared to 95–98%) while rates of null-initial for ngau4 ‘cow’ range from 2.8% to 22.2% (compared to 37–65%).

Another methodological difference between our study and the previous offers the possibility that speakers may have been style-shifting to a formal register in the current data given our lab-based reading task, but would have produced more innovative variants in a more casual setting without the influence of orthography (e.g., the picture naming task in To et al., 2015). This interpretation could be congruent with the across-the-board increases in [n] and [ŋ]. Given the prescriptivist norms in the local context, task-based style-shifting is plausible and cannot be ruled out as an explanation for our diverging results (a point we return to below).

A third possible scenario is that of age-grading13 due to linguistic marketplace pressure, wherein individuals change their production patterns over different life stages, linked to the social value of ‘standard’ variants (for reviews of age-grading and lifespan changes, see Wagner, 2012; Cheshire, 2006). If age-preferential language use were the explanation in the current data, the generation studied in To et al. (2015) as children may have begun to use more of the ‘formal’ prestige variants, namely [n] and [ŋ], now that they are young adults and likely in more professional settings. Like style-shifting, this could explain the increase in conservative variants in the younger generation across all three mergers. On the other hand, interpretation of the results as age-grading is less clearly motivated for older adults based on these data. For one, the adult group in To et al. (2015) cannot be directly matched to our older adult sample, and two, it is not fully clear what an age-grading explanation would predict for this generation, which spans middle-aged to retirement-aged individuals. Future data collection specifically targeting age-grading will be necessary to adjudicate such an interpretation.

Lastly, production norms may have changed due to reversal of the phonological merger in younger generations. Given that older men appear to be merging [ŋ̩]→[m̩] at a similar rate as previously reported, the current results could be consistent with an incipient reversal. For [l]→[n] and [ŋ]↔Ø, however, younger speakers did not make a larger contrast relative to the older generation. Perhaps these age-undifferentiated results reflect a community-wide change of language ideologies due to increase in awareness of the ‘proper’ social meaning of [n] and [ŋ] since the advent of the ‘proper pronunciation’ campaigns in the late 2000s. Notably these events occurred after To et al. (2015) conducted their study. This social shift may have led to more prestige-related style-shifting in the present day as compared to the past.14

If changes in production were indeed driven by an ideological shift, the age-related results for [ŋ̩]→[m̩] could be seen as representing an effect of register that is particularly pronounced in younger speakers; that is, the social association of [ŋ̩] with ‘properness’ may not exist as strongly for older speakers (or, alternatively, older speakers may be less invested in abiding to newer social norms). Moreover, women were more likely to use high rates of [ŋ̩] for both categories, including historical /m̩/. Given that women have been suggested to (a) be more aware of social stigma and (b) use more prestige variants (e.g., Labov, 1990), this is compatible with the interpretation that prestige motivates the maintenance of contrast or overall increased use of the conservative variant. The sharp shift in [ŋ]↔Ø norms from majority null-initial in To et al. (2015) to majority [ŋ] in the current study could also stem from drastically increased salience of the social meaning of [ŋ] as ‘proper,’ aligning with Chen’s (2018) assertion that null-initial is particularly stigmatized as ‘lazy.’

It is clear that, to fully understand the patterns found in these data, speech style and attitudes must be accounted for. Thus, limitations of the current study include a lack of consideration for multiple registers in the production task and attitudes about ‘lazy pronunciation.’ Accounting for variable styles would have allowed for more conclusive interpretation of descriptive results, especially in comparison to previous literature. At the same time, while we were limited in our methodological choices due to constraints of the stimuli, the formal style elicited in our task does not invalidate our findings, including those of the production-perception analyses. Speakers have a repertoire at their disposal, and we tapped into a particular style of production, which may well have been influenced by our methodological choices; regardless, we need to account for the linguistic knowledge presented to us. Moreover, our choice of an isolated, context-free, single word production task accompanied by orthography is well matched with the perception task, which is characterized by all those features as well. This well-matched formality allows for interpretable (mis)alignment patterns across production and perception.

With respect to ‘lazy pronunciation,’ although the exit interviews confirm that all participants knew what ‘lazy pronunciation’ was, we did not assess awareness or attitudes for each particular merger. Attitudes can vary substantially, potentially influencing patterns of both production and perception. For example, although many participants characterized the mergers as ‘incorrect’ and ‘lazy,’ one young man expressed more neutral or positive sentiments, describing the pronunciations as ‘more convenient’ (see also Lin, Yao, & Luo, 2021 on both positive and negative attitudes about the younger generation’s accent). Knowledge of the degree of stigmatization for each merger, along with individual attitudes towards the stigmatization, could help contextualize variation across individuals as well as any potential community-level reversals that are motivated by group orientation towards or away from the existing social meanings of the merger variants (see, e.g., Labov, Rosenfelder, & Fruehwald, 2013; Tamminga, 2019). Continued research is needed to document whether merger reversals eventually emerge in production across the Hong Kong community; this work would benefit from comparison of multiple speech styles, including more naturalistic speech, as well as inclusion of awareness and attitude assessments to form a clearer picture of production norms across both age and context.