## 3 Results
### Perceptual Evaluation  
The perceptual evaluation showed that the native group exhibited notably high accuracy in tone production, with an average of 82.22% (ranging from 59.44% to 99.72%). By contrast, the immigrant group displayed an average accuracy of 52.98% (ranging from 8.91% to 93.13%). Figure 2 presents the results of tone production accuracy as perceptually evaluated by native listeners, with Figure 2A showing the matrix from native speakers and Figure 2B illustrating the matrix from immigrants. The vertical \(y\)-axis and the horizontal \(x\)-axis represent the target tone and the response tone, respectively. For instance, Row 1 from Figure 2A lists the production of T1 by native speakers, with each cell from Row 1 depicting the percentage of the T1 production being perceived as pronounced as a certain tone (from T1 to T6). It can be seen that 99.2% of the T1 tokens were perceived as T1, and 0.8% of the T1 tokens were perceived as T3. The grey cells correspond to the production accuracy, and the pink cells highlight the incorrectly perceived tones with a percentage higher than 10%, i.e., the common errors. As shown in Figure 2, the order of tone production accuracy from highest to lowest was T4 \(>\) T1 \(>\) T2 \(>\) T3 \(>\) T6 \(>\) T5 for the native group and T1 \(>\) T2 \(>\) T4 \(>\) T6 \(>\) T3 \(>\) T5 for the immigrant group. The native speakers' T1, T2 and T4 were perceived as the expected tone with near-perfect accuracy (>95%), and their T3 also showed substantial accuracy (about 80%). However, the accuracy of T6 and T5 produced by native speakers was only slightly above 50%. For the immigrants, only T1 and T2 yielded ideal results (>80%), and the remaining four tones generally failed to achieve 50% accuracy.  
Next, GLMMs were fitted to examine the effects of predictors on listeners' responses. The GLMMs revealed significant main effects of _group_ [\(\chi^{2}\)(1) = 59.390, \(p\) < 0.001] and _tone_ [\(\chi^{2}\)(5) = 767.108, \(p\) < 0.001], as well as a two-way interaction between _group_ and _tone_ [\(\chi^{2}\)(5) = 151.541, \(p\) < 0.001]. These results confirmed the observations above: the performances of the native speakers were significantly better than those of the immigrants, and the accuracy of some of the tones was significantly higher than was the accuracy of others. In addition, the pairwise comparisons showed that the native speakers' accuracy was significantly higher than that of the immigrants for each tone at the 0.001 level, except for T6, for which the significance level was 0.05. With regard to the random effects, the speaker explained 49.37% of the variance and 70.26% of the standard deviation, implying considerable variability in tone production across individuals; the listener explained 0.26% of the variance and 5.07% of the standard deviation, suggesting consistent judgements amongst the listeners.  
Regarding the confusions of each type of tone, the native speakers' main confused tones were T3 \(\rightarrow\) T6 (T3 was identified as T6), T5 \(\rightarrow\) T2 and T6 \(\rightarrow\) T3. These confusions heavily influenced the intelligibility of Cantonese tones, and the accuracy rate for native speakers for T3, T5 and T6 would have exceeded 90% if these confusions had been eliminated. In comparison, it was not surprising that the same confusions occurred for tones produced by the immigrants, whose notable tone confusions were T3 \(\rightarrow\) T4, T4 \(\rightarrow\) T6, T5 \(\rightarrow\) T3, T5 \(\rightarrow\) T6, and T6 \(\rightarrow\) T4, all of which occurred at higher rates (by at least 15%) compared to their native counterparts' productions. From the perspective of the perceptual evaluation, tone confusion within the immigrant group was predominantly observed between T3 and T6.