我們每天一張開眼睛接觸到外界的光線,大腦就開始不斷地處理知覺到的各種刺激,辨識所看到的物體、符號及文字等,根據當時的情境及需求,做出必要的行為反應。其中眼睛所擔負的重要任務,就是在第一時間在視網膜把外界光線能量的變化,轉變成神經電位的變化,藉由視覺系統將外界刺激傳導至大腦做進一步的處理。然而,由於視網膜神經接受細胞分佈的特性,視網膜上不同區域的視覺敏銳度並不相同,在網膜的中央小窩附近區域才能接收最清楚的影像,因此眼睛必須經常的移動,才能看清楚外在的世界。眼球移動的特性,使得研究者有機會藉由眼球的凝視位置及停留時間,來探討與認知歷程的關係。在本文中,將先簡介視覺系統基本的傳導通道,特別是視網膜的生理特性,如何造成眼球移動的必要性;其次將介紹眼動的基本特性,以及測量眼球凝視位置的方法;最後則以閱讀歷程為例,說明研究者如何運用眼球移動的行為來探討認知歷程的運作。
When we open our eyes and perceive the light, the brain starts processing data transmitted via our perceptual system. The brain has to first recognize all stimuli, including objects, images or linguistic signs, then respond to them according to the demands of different situations. In this process, the role of the eyes is to transform the light stimulation on the retina into neural electricity immediately, then relay the to the brain for further processing via the optical neural system. Yet, the physiological restriction of the retina, that visual acuity decreases as the location moves away from the fovea, makes it necessary for the eyes to move back and forth in order to perceive information. The gaze location and pause duration allow researchers to explore the underlying mechanism of different cognitive functions. This article first introduces the optical-neurological system and the physiological features of the retina, and it moves on to explain the measurement of eye movement and gaze locations, then, reviews researches which investigate the correlations between eye movement and Chinese reading.