Language Learning ISSN 0023-8333 On Crosslinguistic Variations in Imperfective Aspect: The Case of L2 Korean EunHee Lee University at Buffalo Hae-Young Kim Duke University This article examines the acquisition of Korean imperfective markers, the progressive -ko iss- and the resultative -a iss-, with a view to understanding how tense/aspect mor- phology expands beyond prototype associations with inherent aspects of the verbs. We hypothesized that -a iss- will develop later than -ko iss-, but that the development of -a iss- will precede or coincide with the expansion of -ko iss- marking for result state meaning. Cross-sectional data were collected from 120 learners of second language Korean using a sentence interpretation task and a guided picture description task. The results support our hypothesized acquisition route of imperfective markers, establishing dynamic durativity as the prototypical meaning of the Korean imperfective -ko iss- and suggesting individual variation in expanding the prototype. Keywords Korean tense and aspect; L2 tense and aspect; imperfective markers; cross- linguistic variation; prototype account; congruence principle; input distribution and frequency; one-to-one principle; individual variation Tense and Aspect Morphology in Interlanguage Perfective versus imperfective is a fundamental grammatical aspectual contrast made in many languages. The perfective aspect provides an external perspective to a situation, whereas the imperfective aspect presents an internal perspective. Perfective views a situation as a total bounded whole, including the beginning point and the end point of the situation (Comrie, 1976; Smith, 1991). Imper- fective views a situation from within, disregarding its beginning or final points. Perfective and imperfective aspect marking varies with languages. English does Correspondence concerning this article should be addressed to EunHee Lee, University at Buffalo, The State University of New York, Department of Linguistics, 623 Baldy Hall, Buffalo, NY 14260-1030. Internet: ehlee@buffalo.edu Language Learning 57:4, December 2007, pp. 651–685 651 C  2007 Language Learning Research Club, University of Michigan