語音及視聽整合知覺在嬰兒學習語音相似詞彙上的效果

Abstract

英語嬰兒研究顯示，從14個月大開始，嬰兒已經能夠在較短的時間且只利用語音線索，學習語音差異較大的新詞，如lif 和neem；但是到了17個月大，才能夠利用精細的語音知覺表徵，學習語音差異較小的詞彙，如bih 和 dih。華語的聲調具有區辨音節詞彙意義的功能，也是嬰兒學習語言的重要目標。所以，檢視嬰兒利用精細聲調表徵以學習詞彙的發展趨勢，成為檢視華語嬰兒語言學習歷程的重要課題。另外，研究顯示2個月的嬰兒已經擁有整合視聽知覺的能力，而此能力可以幫助嬰兒區辨語音，但較少研究探索整合知覺對於嬰兒詞彙學習的影響。本研究的目的在探討語音知覺，及視聽整合知覺在嬰兒詞彙學習上的發展趨勢。本研究包含兩個實驗，實驗一以56名13(n = 15)、15(n = 13)、17(n = 15)及20(n = 13)個月大的嬰兒為參與者，透過「雙對轉換作業（two pairs switch task）」進行資料搜集，目的在瞭解嬰兒透過一聲及四聲聲調表徵學習詞彙的發展情形。研究結果發現，只有20個月的嬰兒能夠發現物體-詞彙錯誤配對的情形，而其餘三個月齡的嬰兒則無。即20個月大嬰兒呈現學習聲調最小配對詞彙的能力，而13至17個月大嬰兒尚未出現相同的詞彙學習能力。實驗二以14、17及20個月的嬰兒（各月齡n = 24）為研究對象，同樣透過雙對轉換作業進行資料搜集，希望瞭解視聽整合知覺在詞彙學習上的角色。研究檢視嬰兒是否同時看到/ga/的嘴形和聽到/ba/的聲音，會產生/da/的語音知覺（即McGurk effect）之後，又有辦法學到詞彙和物體的配對。即在後續的物體-詞彙配對的測驗中，發覺物體-詞彙配對的錯誤。研究結果顯示，嬰兒至20個月的年紀時，透過視聽整合知覺以學習詞彙仍有困難。另外，卻發現整合視聽線索和新詞彙學習對兩歲前的嬰兒來說，為兩個相互競爭的心理歷程。即當嬰兒整合視聽線索的同時，比較不容易展現新詞學習；但在無整合視聽線索時，嬰兒則能夠展現詞彙學習，此現象在14個月的嬰兒身上又更為顯著。實驗二同時也發現14個月的嬰兒，已經可以學到只有子音差異的/baba/和/gaga/兩個詞彙。另外，實驗一及實驗二的詞彙學習表現與嬰兒語言發展的相關分析發現，在此兩個實驗作業下的詞彙學習表現與其語言發展的相關程度並不高。整體而言，嬰兒無論透過聲調表徵或是子音表徵學習詞彙，皆可以在一歲半到兩歲之間達成。但欲同時整合視聽知覺並學習新詞彙，則到20個月大尚無法呈現。

English-learning infants were capable of learning phonetically dissimilar words at 14 months of age. Till 17 months of age, they were able to learn phonetically similar words. Lexical tones manifest lexical meanings of syllables in Mandarin Chinese. Thus, exploring the developmental trends of learning words of lexical-tone minimal pairs is essential to further understanding the language development process in Mandarin learning infants. Some studies showed that audiovisual perception emerged as early as 2 months of age. This perceptual ability also facilitated infants to easily discriminate speech sounds. However, no studies examined the development trend of the effect of audiovisual perception on word learning. The goal of this study was to figure out the effects of phonetic perception and audiovisual perception on learning new words. There were two experiments in our study. The first experiment examined the developmental trend of using the ability of perceiving lexical tones to learn new words. Fifty-six infants, aged 13-(n=13), 15-(n=15), 17-(n=13) and 20-months(n=15), were tested with two pairs switch task when learning lexical tone contrasts words, tone 1 vs. tone 4. The results showed that only 20-month-old infants easily using perceptual ability of lexical tones in word learning. The second experiment was also test infants with two pairs switch task. The ages of infants were 14(n=24), 17(n=24) and 20 months (n=24). This experiment tried to explore whether infants were able to learn phontically-similar words and present the audiovisual perception simultaneously. In other words, it was anticipated that infants did not only integrate audio/ba/ and visual/ga/ stimuli and form the audiovisual perception /da/ (i.e., McGurk effect), but also map phonetically-similar words with referents. The result showed that neither 14-month-old infants nor 20-month-old infants learned words during audiovisual-perception processing. However, infants either showed audiovisual perception or learned new words, this pattern was clearer in 14–month-old infants. In addition, both of the experiments didn’t find any significant correlations between infants’ word learning performance and language abilities. In conclusion, infants are able to learn phonetic similar word after 18 months of age, but they were difficult to perform the ability of audiovisual intermodal perception and learning phonetically-similar words at the same time.