台灣東部原住民佔當地人口的四分之一，成為東部原漢關係中一項重要的結構性制約條件。本文參考國外有關族群人口比例以及權力威脅論的研究，依據歷年人口統計，以及「台灣地區社會意向調查」問卷訪問資料，分析東部原漢互動關係背後的人口結構肇因與社會心理機制。研究發現東部漢人對原住民明顯的抱持著負面意象。跟其他漢人比起來，東部漢人贊同天生的種族優劣觀，並且認為山地話粗俗、原住民懶惰。負面族群意象所反映出來東部原漢關係的緊張，跟原住民「顯著少數」人口比例所加諸的結構制約力量，密切呼應。本文揭示這種人口比例跟族群意象之間的可能關聯，並以政治、經濟、教育種種不同情境為例，說明東部漢人跟原住民之間的種種競爭，都是奠基於「原住民人口佔有顯著比例」這項結構事實，才益發突顯。原住民優惠政策固然引起原漢關係緊張，可是正因為東部原住民人口比例相對的突出，才能強化這項觸媒的效應。不論族群互動的情境內涵是什麼，都很難擺脫人口結構的基本制約力量；而這種原漢關係的社會心理基礎，得以透過負面的族群意象充分展現。

Despite its disadvantaged status as a token minority, the Taiwan aborigines account for one fourth of the population in Eastern Taiwan. Such a unique proportion has become a critical structural factor in conditioning the Han-aborigine relationships in the east. This study examines what social-psychological consequences this unique condition causes. It draws from the literature on "group proportion" and "power threat" hypotheses, then analyzes two data sets collected in "The Taiwan Social Image Survey". The analyses confirm that the eastern Han hold negative images toward the aborigines in terms of inferiority in inherent traits, language, and characters. According to the literature, such negative ethnic images closely correspond to the fact that the aborigines compose more than a token minority in the east. Based on these findings, the paper explains the relationships between group proportions and ethnic images. It further explores alternative factors situated in political, economic, and educational spheres. Although eastern Han and aborigines compete with each other in these substantive areas, competition becomes severe only under the circumstances of a significant minority. The inter-ethnic tension is also contributed to other factors such as aborigine welfare policy, but again such a policy arouses the unease from the Han only when the aborigine population accounts for a significant proportion in the region. The Han-aborigine relationships may change over various contents and situations. These changes, however, are often subject to the peculiar proportions of the ethnic groups involved. It is by means of such connections and mechanisms that this study explicates how the eastern Han envision the aborigines.