This paper describes an application of INDSCAL to the analysis of item response data for the Test of English as a Foreign Language. The TOEFL is a test of English proficiency that is taken by foreign students planning to attend school in America. The test has several kinds of items, grouped into three separately scored sections: Listening Comprehension, Structure and Written Expression, and Reading Comprehension and Vocabulary. Substantively, this study was concerned with delineating differences in test performance associated with native language and level of English proficiency. From a linguistic perspective, the language group differences bear on the issue of whether examinees make "contrastive" errors attributable to specific contrasts between their language and English (Lado, 1957) or "developmental" errors typical of anyone at a particular stage in learning English (Corder, 1967). From a psychometric perspective, these differences are relevant to the question of whether the test measures the same constructs for the various language groups.
