Research on eye movement control during first language (L1) reading has long since established that (i) words are read most efficiently when the first saccade into the word lands near its center, (ii) words are refixated more often when landing positions deviate from the center of the word, and (iii) relatively proficient readers' saccades land closer to this center position. Eye-tracking studies of second language (L2) reading tend to compare participant groups based on their language background (L1 vs L2) rather than L2 proficiency. As of yet, there has been no comparison of these approaches. This study reports a comparative analysis of the Multilingual Eye-movement COrpus (MECO), which contains data on English text reading and its component skills from 543 participants representing 12 different L1s. Analyses of the distributions of initial landing positions and refixation probabilities establish that the gradient measure of proficiency in English (as L1 or L2) has a greater explanatory power than categorical contrasts between language backgrounds. We also found that English proficiency has a gradient effect on efficiency of saccadic targeting: more proficient readers landed their initial saccades closer to the word's center. However, more proficient readers of English were also less accurate in their saccadic targeting, showing greater dispersion of initial landing positions. We link this puzzling finding to the observation that landing in a suboptimal position comes with a much higher processing cost (refixation probability) for less proficient readers. This study discusses theoretical and methodological implications of the novel findings for reading research. / Thesis / Master of Science (MSc) / When we read text, we do not continuously move our eyes across it, but we make a series of rapid eye fixations on different parts of the text. Scientists know that if we fixate our eyes on a center of a word rather than on its beginning or end, we will understand that word the fastest. Highly skilled readers make the first fixation on any word in a more optimal place compared to less skilled readers. Making such optimal fixations allows highly skilled readers to understand each word they encounter faster, which makes them better readers and leads to more successful outcomes later in life. In this research project we were interested in how reader's proficiency in reading related skills affects the efficiency of their eye-movements during reading English as a first and second language. The results found that more proficient readers were found to have a lighter penalty to the speed of their reading when fixating their eyes farther away from the optimal position in words. Additionally, the results demonstrated that proficiency in reading related skills is a better indicator of the efficient eye-movement behavior than native language of the reader.

探討閱讀時視覺與語言因素之研究指出眼球移動位置的決定主要受到低階視覺特徵的影響。有些研究也認為此一涉及計算眼跳目標的決策發生在執行眼球移動之前。為了檢視中文詞彙內的視覺複雜度分佈是否影響眼跳目標決定機制 、我們提出了視覺複雜度分佈指標 (visual complexity distribution index, VCD index) 來代表中文雙字詞內的複雜度分佈情形。依據視覺複雜度分佈指標 、本研究挑選出三組不同視覺複雜度分佈的詞彙 (左偏移、右偏移以及無偏移) 、並將這些詞彙箝入於句子中。紀錄中文讀者閱讀這些句子的眼球運動軌跡 、以比較三組實驗情境下的初次觸接凝視時間 (first-pass duration) 、落點位置 (landing position) 以及眼跳機率指標 (probability measures) 差異。使用線性混合模型 (Linear mixed model, LMM) 估計實驗組別效果 、以探討視覺複雜度分佈指標如何影響決定停留時間與眼跳位置的機制。結果發現右偏移組落點位置都落在其他兩組的右側 、而兩組偏移組的凝視時間都較不偏移組短。進一步分析顯示上述結果需在眼跳目標為中文詞彙才可觀察到。這指出由視覺複雜度分佈指標所反映出的中文雙字詞明視度型態 (luminance pattern) 、會在該詞彙被凝視之前影響眼跳位置的決定 、並依落點位置差異而調節了該詞彙被凝視時的處理。 / Previous studies about the visual and linguistic factors that influence the decision about where to move the eyes next in reading suggest a strong influence from low-level features; some studies also assume that this decision involves the computation of a saccade target before the oculomotor program is executed. In order to test whether the distribution of visual components within Chinese words influence the saccade targeting mechanism, we devised a new parameter that reflects the distribution of visual information along 2-character words’ area: the Visual Complexity Distribution (VCD) index. Three groups of words with a marked VCD index (i.e. Left-Bias, Right-Bias and Non-Bias) were identified and embedded in natural sentences; the eye movement of Chinese native speakers was recorded while they read this material in order to contrast first-pass duration, landing position and probability eye movement measures between conditions. The experimental effects were estimated through contrast between conditions using Linear Mixed Models, thus providing evidence about the VCD index’s influence on both, the decision about the when and where to move the eyes next. The analyses on initial fixation position indicate a rightwards shift when sending the eyes towards words with Right-Bias in comparison to the other conditions and shorter fixation durations when biased words are fixated in comparison to the Non-Bias words. Further analyses demonstrated that the results above can only be observed when specifying saccade targets from Chinese words. These results indicate that the luminance patterns within 2-character Chinese words, as reflected by the VCD index, can influence the specification of a saccade target when those words are about to be fixated as well as modulate the fovea load when those words are currently fixated.