1、 Introduction

Explored the challenges of polysemous words in second language vocabulary acquisition and pointed out that they have not received sufficient attention in second language acquisition research. Research shows that even high-level second language learners find it difficult to grasp all the meanings of polysemous words, and their ability to guess the meaning of polysemous words in context is not as good as that of non polysemous words. The meanings of polysemous words can be classified into primary and secondary, among which the prototype meaning is the most easily thought of, usually the original or high-frequency meaning of the word. The typical category theory in cognitive linguistics holds that the different meanings of polysemous words form a category, and the prototype meaning is a typical member of this category. Research has shown that providing prototype meanings helps learners guess the non prototype meanings of polysemous words and maintain their meanings in long-term memory, thereby promoting the learning of non prototype meanings. However, existing research has mostly focused on the role of prototype meaning in the process of word meaning guessing, and there is relatively little research on the impact of explicit teaching of prototype meaning on learners' learning of both prototype and non prototype meanings. This study employs a case study method to investigate the impact of teaching prototype meaning on the acquisition and retention of prototype meaning and non prototype meaning by advanced level Chinese learners.

2、 Research Methods

The research subject M is a native Portuguese speaker with advanced proficiency in Chinese, who has studied abroad in China and is currently pursuing a PhD in Sinology in Germany. The research design includes a pre-test to determine target words, followed by post tests 1 and 2 after reading articles and teaching. The target words are divided into two groups, A and B. Group A only teaches metaphorical meanings, while Group B teaches the prototype meaning first and then the metaphorical meaning. Post test 1 is conducted one week after teaching, and post test 2 is conducted four months after teaching. The tests include prototype and metaphorical meanings. The scoring criteria for the definition are 2 points for complete correctness, 1 point for partial correctness, and 0 point for incorrect. The consistency of the two authors' ratings is 85.7%, and the average is taken when there is inconsistency.

3、 Research results

This study explores the impact of prototype teaching on the acquisition of polysemous word meanings through case studies. Research has found that after teaching, subject M's knowledge of the meaning of the target word has increased, with accuracy rates of 81% and 86% for prototype and metaphorical meanings, respectively. However, after 4 months, these rates decreased to 59.5% and 68.2%, respectively. The mastery of word meanings can be divided into three types: complete mastery, partial mastery, and complete lack of mastery. After teaching, M fully mastered 71.9% of the meanings, partially mastered 28.1%, and after 4 months, the fully mastered meanings decreased to 40.6%, completely forgotten meanings accounted for only 12.5%, and nearly half of the meanings were partially mastered (46.9%). Compared to learning accompanying words, teaching can increase learners' vocabulary knowledge in a short period of time. However, the long-term effect of teaching prototype meaning is not very obvious, and the accuracy of metaphorical meaning interpretation in the group without teaching prototype meaning is higher than that in the group with teaching prototype meaning. Post test 2 showed that M was able to correctly identify the prototype or metaphorical meanings of 15 out of 16 target words, with 9 words having more prominent prototype meanings in psychological vocabulary and 6 words having more prominent metaphorical meanings. This indicates that prototype teaching has some help for subjects to master the meanings of polysemous words, but the long-term effect is limited, and the impact on the mastery of metaphorical meanings is not significant.

4、 Discussion

Research on second language vocabulary acquisition shows that learners are more effective in guessing the marginal meanings of polysemous words based on their prototype meanings. Verspoor and Lowie's (2003) study found that prototype meanings help improve English learners' ability to guess metaphorical meanings and maintain long-term memory. Zhang Jiangli's (2013) research also supports this viewpoint, that Chinese learners who provide core meanings are more helpful in understanding the character "bo" than non prototype meanings. However, in this study, it was found that the effect of teaching prototype meanings compared to acquiring metaphorical meanings was not significant, possibly due to learners' inaccurate understanding of prototype meanings, such as misunderstandings of "correspondence" and "revival"; The difference between the translated words and the Chinese prototype meaning in dominant languages, such as the mismatch between "floating" and English "fluent"; Learners have not established a connection between the prototype meaning and metaphorical meaning, such as understanding the prototype meaning and metaphorical meaning of "digestion". In addition, learners' professional background and frequent exposure to metaphorical meanings also affect their understanding of word meanings.

5、 Teaching Inspiration

Emphasis was placed on the importance of prototype and metaphorical meanings in teaching polysemy, and several teaching inspirations were proposed. Firstly, the consistency between prototype meaning and high-frequency meaning is crucial for the selection of teaching sequence, and prototype meaning should be prioritized for teaching to help learners achieve native language proficiency. Secondly, mastering the prototype meaning helps learners construct the entire semantic network, rather than just a single semantic item. In addition, teachers should provide accurate foreign language translations to avoid learners mistakenly associating target language vocabulary with words in their mother tongue or commonly used foreign languages. Meanwhile, word meaning teaching should provide appropriate typical usage and context, as learners often memorize word meanings through specific examples. These insights are of great significance for improving the effectiveness of acquiring the meaning of polysemous words.

6、 Conclusion

Explicit teaching promotes word meaning acquisition and is more effective than incidental learning; The prototype meaning in learners' psychological vocabulary is not significant, and the influence of contrastive metaphorical meaning acquisition is limited; Case studies reveal individual characteristics, and future research needs to expand the sample and consider factors related to polysemous item markers and word meaning acquisition; Further exploration is needed to compare the role of prototype meaning teaching with metaphorical meaning acquisition.