## 4 Discussion
### Pedagogical Implications  
Our results indicate that tonal contour is not a problem for L1-dominant Polish speakers learning Mandarin (L2), but tonal register is. These results contrast with previous findings, such as those by [39], which indicated that L1-dominant Polish speakers learning Mandarin (L2) typically have a smaller tonal range compared to Taiwanese Mandarin speakers. This suggests that the group of L1-dominant Polish speakers learning Mandarin (L2) in our study has already overcome the issue of tonal range. On the other hand, ref. [49] proposes methods for Cantonese and English learners acquiring Mandarin Chinese, emphasizing the need for learners to recognize potential errors in intonation, prosody, and stress patterns in Mandarin Chinese due to the phonetic features of their respective native languages, known as language transfer effects. Based on these findings, targeted instructional strategies are recommended to provide Mandarin Chinese models and practice opportunities. Thus, the minimal difference between L1-dominant Polish speakers learning Mandarin (L2) and TM natives in T3 and T4 within disyllabic words implies that acquiring a low-ending tone is easier or occurs earlier for learners compared to the high-ending tones T1 and T2. Given the historical adoption of different habitual pitch ranges in Mandarin Chinese and Polish languages, and the potential for low register tones to stabilize disyllabic word production, the pedagogical implications are as follows:  
(a) L1-dominant Polish speakers learning Mandarin (L2) have appropriately expanded their tonal range. Therefore, more attention should be devoted to practicing the ending high-register tones. It is important to note that the difficulty in producing high-ending tones arises in the random sequence of tones in speech, compared to the predictable stress patterns of the Polish language. Therefore, more practice with the 16 tonal combination exercises can help L1-dominant Polish speakers learning Mandarin (L2) reduce the occurrence of unnatural production of all tones. (b) One approach to inhibit hyper-articulated T1 and T2 is to continue practicing accompanied by Tone 3. Evidence suggests that when T3 precedes T1, T1 is produced more native-like (e.g., T3T1 or T1T3). However, the inhibitory effect of T3 seems less powerful when neighboring T2 (e.g., T3T2 or T2T3). This could be because producing T2 or T3 involves not only controlling pitch within the time duration and up to the end but also reaching a proper reference point, posing a greater challenge for L1-dominant Polish speakers learning Mandarin (L2). It appears that T4 within various tonal combinations achieves the greatest success. Therefore, encouraging L1-dominant Polish speakers learning Mandarin (L2) to practice the low ending point, starting with T4, is advisable. Both T3 and T4 are suitable candidates for tonal combination practice, as T3 remains in the low register and T4 benefits from its similarity to stress in Polish. Individuals can choose the tone appropriate for their tonal development. (c) Specifically, since L1-dominant Polish speakers learning Mandarin (L2) perform better with disyllabic words that include low tone T3 or falling tone T4, and given that there is no significant difference between disyllabic words composed of T1 and T2 with T3 and T4, it is recommended that L1-dominant Polish speakers learning Mandarin (L2) start practicing with the disyllabic word combinations that they find easier. This approach is likely to help them stabilize the tonal register of T1 and T2 within disyllabic words. (d) Among the difficulties, for initial practice, despite the fact that the T1T1 disyllabic word combination shows the greatest difference from native Mandarin speakers, it is still suggested to begin with T1T1 training. This is because, once the starting point of T1T1 is correct, maintaining a consistent rate of tonal vibration will make the overall disyllabic word tone more similar to that of native Mandarin speakers.