我們人類到底是如何學會說話的？在語言發展的研究領域，學者們長久以來便很有興趣試圖解釋小孩子是怎樣學會說話的。「先天決定」(the innatist)和「社會互動」(the social interactionist)理論是試著解釋此一現象立論最針鋒相對的兩大學派，這種先天抑是後天決定人類語言習得的爭論在於我們是要把焦點放在個人本身或是外在環境，先天決定論者提出了諸如「語言習得裝置」(language acquisition device)和「關鍵時期假設」(critical period hypothesis)等的觀念來力陳語言能力是人類特有的天賦才能；而社會互動論者則提出了如「大人看護小孩時之童言童語」(child-directed speech)等的現象來力倡語言發展是受到兒童所處生活環境和他們語言及認知能力的交互作用極深地影響。本文將試著探討雙方所主張立論之差異所在，然後並進一步討論此兩學說對學校學習暨表現的啓示。 How and why can young children acquire language so very successfully and seemingly effortlessly? In the field of language development, theorists have long tried to explain why children say what they do, and most importantly, why they eventually speak like adults. Innatist and social interactionist theories can be considered two of the most competing approaches proposed for addressing these issues, with the 'nature' formulations of innatists on the one end of the continuum and the 'nurture' theses of social interactionists on the other. This kind of nature-nurture controversy is a matter of whether in the process of language acquisition special emphasis should be laid either on children themselves or the outside learning environment. The innatist, who puts forward such ideas as the 'language acquisition device' and 'critical period hypothesis', maintains that language is a species-specific phenomenon unique only to human beings, whereas the interactionist, who brings forth ideas like 'child-directed speech', submits that the course of development is greatly affected by the interplay between children's social language environment as well as their linguistic and cognitive capacities. The aim of this paper is to discuss the key concepts by which these two camps 'debate has been formulated and then to further address the possible implications of both sides' accounts on academic learning and/or achievement. Through the discussion in the present paper, it seems clear that children's success of learning language apparently depends upon some kind of innate mechanisms that make acquisition possible in humans but not in any other species, and above all, upon the input from competent speakers in their surrounding environment. Judging from the innatist and social interactionist positions, we can notice that the eclectic nature of the social interactive approach is one of its great strengths that makes it seem to hold the most promise for us in the future to account for how we humans learn to speak.