語言和生命時程

Language and Life Timelines

比起其它靈長類，人類壽命除了明顯較長外，還多了一個有助學習的「童年期」，兩者皆是文化演化的產物。大腦在我們誕生後的頭兩年內有爆炸性成長，重量增長三倍，以吸收外在世界以及周遭文化的大量訊息。語言是一套既獨立又彼此相關的繁複技巧，在不同時程內習得，能夠達到不同的熟練度，習得結果存在大量的個別差異。學說任何語言都須習得一整套的感知敏感度，才能辨別該語言裡重要的語音區別，還得要協調及精細控制幾百條與呼吸、發聲和發音有關的肌肉。雖然越早開始越能輕鬆學會說新語言所需的運動技能，但語言的認知成分，而非其運動成分，可以在年紀很大了才掌握，如詞彙和語法。語言和行為的許多其它方面的不同時程，都在基因與環境的互動下有其源頭，若干的遺傳性病變是在幼兒期或人生的遲暮之年才浮現。儘管許多人能健康安享晚年，有些人卻飽受不同型態的神經退化折磨，如阿茲海默症。隨著世界漸趨高齡化，語言失調的挑戰在規模上快速增長，病徵也漸趨多樣複雜。希望未來的研究更應考量構成人類社會的生物多樣性和文化多樣性。 Compared with other primates, humans have an extended lifespan and are blessed with the additional stage of ＂childhood＂ for learning, both of which are products of cultural evolution. Our brains grow at an explosive rate during our first two years, tripling its weight at birth, soaking up an astonishing amount of information about the physical world as well as the culture into which we are born. Language is a complex set of independent but interrelated skills, acquired at different timelines to different degrees of proficiency, with a great deal of variation across individuals. Speaking any language well requires the acquisition of a full set of perceptual sensitivities to the phonetic distinctions significant for that language. It also requires the coordination and fine control of several hundred muscles for respiration, phonation, and articulation. Although the motor skills for speaking a new language come much more easily to the young, the cognitive components of language, not its motoric components, can be mastered quite late in life, such as its vocabulary and grammar. The various timelines for language and many other aspects of behavior have their sources in the interaction of genes with environment. Several genetic pathologies surface either in infancy, or in the sunset years. While many of us live out the newly available years in good health, some suffer from various types of neuro-degeneration, and foremost among these is a severe form of dementia called the Alzheimer's disease. The challenge of language disorders has mushroomed in size and become manifold more complex with the world aging so fast. Hopefully due consideration in this area of research will be given to the biological and cultural diversity that comprise our entire humanity.