以瞳孔反應探討嬰兒的跨情境詞彙學習發展

Abstract

嬰兒詞彙學習研究的重要研究問題為：兒童如何從許多新詞和指稱物的配對可能性中，理解當下聽到的詞彙的指稱物？早期研究多著重於兒童如何利用先天或後天習得的偏好來限縮當下情境中可能的指稱物，減少詞彙與指稱物的可能配對數量，來決定新詞真正的意義。跨情境學習為近來新的研究方向。不同於先前理論，跨情境學習機制認為兒童藉由多次觀察詞彙與可能指稱物共同出現的機率，最終能藉由統計機率來決定詞彙的指稱物。本研究檢驗嬰兒是否能進行跨情境學習，以習得詞彙。實驗一利用兒童瞳孔反應，來評估嬰兒能否配對熟悉字和指稱物，而實驗二探討嬰兒能否使用跨情境學習機制，來學習新詞。實驗一的參與者為33位12個月嬰兒和21位17個月嬰兒。實驗一的結果顯示，在使用熟悉字的情況下，12個月和17個月嬰兒都能習得詞彙與指稱物之配對。實驗二的參與者為27位12個月嬰兒和18位17個月嬰兒。實驗二的結果顯示，只有詞彙能力相對較好的17個月嬰兒能藉由跨情境學習機制習得新詞，詞彙能力相對較差的17個月嬰兒與12個月大之嬰兒並無法藉由跨情境學習機制習得新詞。此研究結果指出跨情境學習機制受兒童的語言能力影響，兒童可能需要具有一定的詞彙能力後才能藉由此機制習得新詞。此外，實驗結果發現，相較於注視時間分析，瞳孔反應對於兒童的認知歷程變化更敏感；且兒童於進行詞彙學習實驗時的瞳孔大小變化，能反應出其語言發展程度上的差異。簡言之，本研究顯示瞳孔反應能作為嬰兒詞彙學習研究表現之依變項，且17個月大語言能力較好的嬰兒開始出現跨情境學習。

Cross-situational learning was proposed to explain how novice learners learn from noisy data. It states that over time and exposures, the co-occurrence between a word and its referent will increase and the co-occurrence between the word and other potential referents will decrease. As a result, the learners are able to converge on the correct word-referent pairings. The current study included two experiments to examine 12- and 17-month-old infants’ word learning. Thirty-three 12-month-old and 21 17-month-old infants participated in Experiment 1.The results of Experiment 1 showed that both 12- and 17-month-old infants were able to learn word-referent pairings given unambiguous parings using familiar words. Twenty-seven 12-month-old and 18 17-month-old infants participated in Experiment 2. The results of Experiment 2 indicated the developmental changes in cross-situational learning: only 17-month-old infants with relatively larger vocabulary size are able to learn from cross-situational statistics, while 17-month-old infants with relatively smaller vocabulary size and 12-month-old infants are unable to achieve cross-situational learning. The present study recorded and analyzed infants’ pupil diameters in the experiments to extend the current understanding of pupillometry in infant studies with two findings: 1) the measure of pupil diameter is more sensitive to the hidden cognitive activities than the measure of looking time and 2) pupil responses can reflect individual differences in infants’ word learning. To sum up, the current study showed that pupil responses can serve as the dependent variables in studies on early word learning and that 17-month-old infants with relatively larger vocabulary size are able to achieve cross-situational learning.